Background
Description of the condition
Muscle strength is the amount of force produced by a muscle. The loss of muscle strength in old age is a prevalent condition. Muscle strength declines with age such that, on average, the strength of people in their 80s is about 40% less than that of people in their 20s (Doherty 1993). Muscle weakness, particularly of the lower limbs, is associated with reduced walking speed (Buchner 1996), increased risk of disability (Guralnik 1995) and falls in older people (Tinetti 1986).
Description of the intervention
Progressive resistance training (PRT) is often used to increase muscle strength. During the exercise, participants exercise their muscles against some type of resistance that is progressively increased as strength improves. Common equipment used for PRT includes exercise machines, free weights, and elastic bands.
How the intervention might work
Contrary to long held beliefs, the muscles of older people (i.e. people aged 60 years and older) continue to be adaptable, even into the extremes of old age (Frontera 1988). Trials have revealed that older people can experience large improvements in their muscle strength, particularly if their muscles are significantly overloaded during training (Brown 1990; Charette 1991; Fiatarone 1994).
Why it is important to do this review
Despite evidence of benefit from PRT in terms of improving muscle strength, there is still uncertainty about how these effects translate into changes in substantive outcomes such a reduction in physical disability (Chandler 1998). Most studies have been under-powered to determine the effects of PRT on these outcomes or have included PRT as part of a complex intervention. In addition, there is uncertainty about the effects of PRT when more pragmatic, home or hospital-based programmes are used, and the safety and effectiveness of this intervention in older adults who have health problems and/or functional limitations. Finally, there is uncertainty about the relative benefits of PRT compared with other exercise programmes, or the effectiveness of varying doses of PRT (i.e. programmes of varying intensity and duration). This update of our review (Latham 2003a) has continued to assess and summarise the evidence for PRT.
Objectives
To determine the effects of progressive resistance strength training (PRT) on physical function in older adults through comparing PRT with no exercise, or another type of care or exercise (e.g. aerobic training). Comparisons of different types (e.g. intensities, frequencies, or speed) of PRT were included also. We considered these effects primarily in terms of measures of physical (dis)ability and adverse effects, and secondary measures of functional impairment (muscle strength & aerobic capacity) and limitation (e.g. gait speed).
Methods
Criteria for considering studies for this review
Types of studies
Any randomised clinical trials meeting the specifications below were included. All non-randomised controlled trials (e.g. controlled before and after studies) were excluded. Also excluded were trials for which details were provided that indicated these used quasi-randomised methods, such as allocation based on date of birth.
Types of participants
Older people, resident in institutions or at home in the community. Trials were included if the mean age of participants was 60 or over, but excluded if participants aged less than 50 were enrolled. The participants could include frail or disabled older people, people with identified diseases or health problems, or fit and healthy people.
Types of interventions
Any trial that had one group of participants who received PRT as a primary intervention was considered for inclusion. PRT was defined as a strength training programme in which the participants exercised their muscles against an external force that was set at specific intensity for each participant, and this resistance was adjusted throughout the training programme. The type of resistance used included elastic bands or tubing (i.e. therabands), cuff weights, free weights, isokinetic machines or other weight machines. This type of training could take place in individual or group exercise programmes, and in a home-based or gymnasium/clinic setting. Studies that utilised only isometric exercises were excluded. Studies that included balance, aerobic or other training as part of the exercise intervention (and not simply part of the warm-up or cool-down) were also excluded.
We found the following comparisons between groups in the trials:
- PRT versus no exercise (greatest difference between groups was expected)
- Different types of PRT: high intensity versus low intensity, high frequency versus low frequency, or higher speed (power training) versus regular speed (greatest effect expected in the higher intensity groups). Power training refers to the type of PRT that emphasizes speed.
- PRT versus regular care (including regular therapy or exercise)
- PRT versus another type of exercise (smaller difference between groups expected)
Types of outcome measures
Primary outcomes
This review assessed physical function in older adults at the level of impairment, functional limitation and disability. The primary outcome of this review was physical disability. This was assessed as a continuous variable. The outcomes were categorized based on the Nagi model of health states (Nagi 1991). In this model, disability is considered to be a limitation in performance of socially defined roles and tasks that can relate to self-care, work, family etc. In this review, the primary assessment of physical disability included the evaluation of self-reported measures of activities of daily living (ADL, i.e. the Barthel Index) and the physical domains of health-related quality of life (HRQOL, i.e. the physical function domain of the SF-36). Data from these measures were pooled for the main analysis of physical disability. However, because these two types of measures (ADL and physical domains of HRQOL) evaluate different health concepts, they were also evaluated in separate analyses. The Nagi model also includes firstly, the domain of 'functional limitations' which are limitations in performance at the level of the whole person and includes activities such as walking, climbing or reaching, and secondly, 'impairments' that are defined as anatomical or physiological abnormalities.
Since the protocol of this review was written, the International Classification of Functioning, Disability and Handicap (ICF) has been released (WHO 2001). Under this system, disability is an umbrella term for impairments, activity limitations and participation restrictions. Using the ICF, the outcome measures evaluated in this review fall under the domains of impairments, limitations in simple activities (similar to 'functional limitations' in Nagi's system) and limitations in complex activities (similar to some aspects of disability in Nagi's model).
Secondary outcomes
Measures of impairment (outcome comparisons 2 and 3)
The following secondary outcomes were assessed as continuous variables:
- muscle strength (e.g. 1 repetition maximum test, isokinetic and isometric dynamometry)
- aerobic capacity (e.g. 6 minute walk test, VO2 max: maximal oxygen uptake during exercise)
Measures of functional limitation (simple physical activities)
The following secondary outcomes were assessed as continuous variables:
- balance (e.g. Berg Balance Scale, Functional Reach Test)
- gait speed, timed walk
- timed 'up-and-go' test
- chair rise (sit to stand)
- stair climbing (added in 2008)
The balance outcome is also reviewed in a separate Cochrane review (Howe 2007).
Other outcomes
The dichotomous secondary outcomes assessed were adverse events, admission to hospital and death. The effect of PRT on falls was also evaluated, although these outcomes are considered in a separate Cochrane review (Gillespie 2003). Pain and vitality measures were evaluated as continuous outcomes, and were used to provide additional information about the potential adverse effects or benefits of PRT.
Outcomes removed after the protocol
In the original protocol for this review, measures of fear of falling and participation in social activities were also included as outcomes. However, when the size and complexity of this review became apparent, the authors decided to limit this review to assessments of physical disability as this was the prespecified primary aim of the review. Therefore, these outcomes are not included in the current review. In addition, the protocol also stated that assessments of disability using the Barthel Index and Functional Independence Measure (FIM) would be dichotomised. However, as no trials included the FIM as an outcome and only three trials used the Barthel Index, the decision was made to report these data as continuous outcomes only.
Search methods for identification of studies
Electronic searches
We searched the Cochrane Bone, Joint and Muscle Trauma Group Specialised Register (March 2007), the Cochrane Central Register of Controlled Trials (The Cochrane Library 2002, Issue 2; February 2007), MEDLINE (1966 to May 01, 2008), EMBASE (1980 to February 06, 2007), CINAHL (1982 to July 01, 2007), SPORTDiscus (1948 to February 07, 2007), PEDro - The Physiotherapy Evidence Database (accessed February 07, 2007) and Digital Dissertations (accessed February 01, 2007). No language restrictions were applied.
In MEDLINE (OVID Web) the subject specific search strategy was combined with the first two phases of the Cochrane optimal search strategy (Higgins 2006). This search strategy, along with those for EMBASE (OVID Web), The Cochrane Library (Wiley InterScience), CINAHL (OVID Web), SPORTDiscus (OVID Web) and PEDro, can be found in Appendix 1.
Searching other resources
We contacted authors and searched reference lists of identified studies, and reviews (Anonymous 2001; Buchner 1993; Chandler 1996; Fiatarone 1993; Keysor 2001; King 1998; King 2001; Mazzeo 1998; Singh 2002).
We also handsearched the following conference proceedings:
- 16th International Association of Gerontology World Congress; 1997; Adelaide (Australia).
- 17th International Association of Gerontology World Congress; 2001; Vancouver (Canada).
- Proceedings of the 13th World Congress of Physical Therapy; 1995; Washington (DC).
- Proceedings of the 14th World Congress of Physical Therapy; 1999; Japan.
- New Zealand Association of Gerontology Conferences - 1996 Dunedin, 1999 Wellington and 2002 Auckland (New Zealand).
- The 60th annual scientific meeting of the Gerontological Society of America; 2007, San Francisco, CA.
- The American Congress of Rehabilitation Medicine - American Society of Neurorehabilitation Joint Conference; 2006, Boston, MA.
Data collection and analysis
Selection of studies
For this update (Issue 3, 2009), one author (CJL) conducted the searches. Both listed authors (CJL, NL) reviewed the titles, descriptors or abstracts identified from all literature searches to identify potentially relevant trials for full review. A copy of the full text of all trials that appeared to be potentially suitable for the review was obtained. Both authors independently used previously defined inclusion criteria to select the trials. In all cases, the reviewers reached a consensus when they initially disagreed about the inclusion of a trial. Before this update, the same method of identifying and assessing studies was used, although other members of the previous review team assisted (Latham 2003a).
Data extraction and management
Two authors independently extracted the data and recorded information on a standardised paper form. They considered all primary and secondary outcomes. If the data were not reported in a form that enabled quantitative pooling, the authors were contacted for additional information. If the authors could not be contacted or if the information was no longer available, the trial was not included in the pooling for that specific outcome.
Assessment of risk of bias in included studies
The methodological quality of each trial was independently assessed by two authors (NL, CS in the first review; CJL, NL in the update) using a scoring system that was based on the Cochrane Bone, Joint and Muscle Trauma Group's former evaluation tool. The review authors were blinded to the trial authors' institution, journal that the trial was published in and the results of the trial. A third review author (CA) was consulted in the first review if a consensus about the trial quality could not be reached. No third review author was involved in the review update. The criteria for assessing internal and external validity can be found in Table 1.
Assessment of heterogeneity
The chi
Data synthesis
Where it was thought appropriate, the results from the studies were combined. Data synthesis was carried out using MetaView in Review Manager version 5.0. For continuous outcomes, mean differences (MD) and 95% confidence intervals (CI) were calculated when similar measurement units were used. To pool outcomes using different units, standardised units (i.e. standardised mean differences, SMD) were created as appropriate. We calculated risk ratios and 95% CI for dichotomous outcomes, where possible.
If minimal statistical heterogeneity (P < 0.1) existed, fixed-effect meta-analysis was performed.
For trials that compared two or more different dosages of PRT versus a control group, data from the higher or highest intensity group were used in the analyses of PRT versus control.
Subgroup analysis and investigation of heterogeneity
If substantial statistical heterogeneity existed, the review authors looked for possible explanations. Specifically, we considered differences in age and baseline disability of the study participants, the methodological quality of the trials and the intensity and duration of the interventions. If the statistical heterogeneity could be explained, we considered the possibility of presenting the results as subgroup analyses. If the statistical heterogeneity could not be explained, we considered not combining the studies at all, using a random-effects model with cautious interpretation or using both fixed-effect and random-effects models to assist in explaining the uncertainty around an analysis with heterogeneous studies.
Sensitivity analysis
Sensitivity analyses were conducted to assess the effect of differences in methodological quality. These included allocation concealment, blinding of outcome assessors, statements of intention-to-treat analysis and use of attention control.
Results
Description of studies
See: Characteristics of included studies; Characteristics of excluded studies.
Results of the search
Please see the 'Characteristics of included studies'.
One hundred and twenty-one trials with 6700 participants at entry were included in this review. Four studies were published only as abstracts and/or theses (Collier 1997; Fiatarone 1997; Moreland 2001; Newnham 1995).
Included studies
There was variation across the trials in the characteristics of the participants, the design of the PRT programmes, the interventions provided for the comparison group and the outcomes assessed. More detailed information is provided in the 'Characteristics of included studies'; however, a brief summary is provided here.
Language
All reviewed trials were published in English.
Location
Sixty-eight trials were conducted in the USA, 13 in Canada, 9 in Australia or New Zealand, and 31 in various European countries.
Study size
Most of these studies were small, with less than 40 participants in total, but 14 studies had 100 or more participants in total in a PRT group and a control group (Buchner 1997; Chandler 1998; Chin A Paw 2006; de Vos 2005; Ettinger 1997; Jette 1996; Jette 1999; Judge 1994; Latham 2003; Maurer 1999; McCartney 1995; Mikesky 2006; Moreland 2001; Segal 2003).
Participants
Health status
The participants in 59 trials were healthy older adults. In the remaining 62 trials, the participants had a health problem, functional limitation and/or were residing in a hospital or residential care. Thirty-two trials included older people with a specific medical condition, including diabetes (Brandon 2003), prostate cancer (Segal 2003), osteoarthritis (Baker 2001; Ettinger 1997; Foley 2003; Maurer 1999; Mikesky 2006; Schilke 1996; Topp 2002), osteoporosis/osteopenia (Liu-Ambrose 2005), peripheral arterial disease (Hiatt 1994; McGuigan 2001), recent stroke (Moreland 2001; Ouellette 2004), congestive heart failure (Brochu 2002; Pu 2001; Selig 2004; Tyni-Lenne 2001), chronic airflow limitation (Casaburi 2004; Kongsgaard 2004; Simpson 1992), clinical depression (Sims 2006; Singh 1997; Singh 2005), low bone-mineral density (Parkhouse 2000), hip replacement due to osteoarthritis (Suetta 2004), hip/lower limb fracture (Mangione 2005; Miller 2006), obesity (Ballor 1996), chronic renal insufficiency (Castaneda 2001; Castaneda 2004) and coronary artery bypass graft surgery three or more months before exercise training (Maiorana 1997). Nineteen other trials recruited participants who did not have a specific health problem, but were considered frail and/or to have a functional limitation (Bean 2004; Boshuizen 2005; Chandler 1998; Fiatarone 1994; Fiatarone 1997; Fielding 2002; Hennessey 2001; Jette 1999; Krebs 2007; Latham 2003; Manini 2005; McMurdo 1995; Mihalko 1996; Miszko 2003; Newnham 1995; Skelton 1996; Sullivan 2005; Topp 2005; Westhoff 2000). In nine trials, the participants resided in a rest-home or nursing home (Baum 2003; Bruunsgaard 2004; Chin A Paw 2006; Fiatarone 1994; Hruda 2003; McMurdo 1995; Mihalko 1996; Newnham 1995; Seynnes 2004). In addition, two trials included participants who were in hospital at the time the exercise programme was carried out (Donald 2000; Latham 2001). In the other trials, most or all of the participants lived in the community.
Gender
Most studies included both men and women, although 10 trials included men only (Fatouros 2002; Hagerman 2000; Haykowsky 2000; Hepple 1997; Izquierdo 2004; Katznelson 2006; Kongsgaard 2004; Maiorana 1997; Segal 2003; Sousa 2005) and 22 trials included women only (Bean 2004; Brochu 2002; Charette 1991; Damush 1999; Fahlman 2002; Flynn 1999; Frontera 2003; Haykowsky 2005; Jones 1994; Kallinen 2002; Liu-Ambrose 2005; Macaluso 2003; Madden 2006; Nelson 1994; Nichols 1993; Parkhouse 2000; Pu 2001; Rhodes 2000; Sipila 1996; Skelton 1995; Skelton 1996; Taaffe 1996).
Age
In 49 studies the mean or median age of the participants was between 60 and 69 years old; in 57 studies, the mean/median age was between 70 and 79 years old; and in 20 studies, it was 80 years old or over.
Lifestyle
Fifteen studies specifically recruited participants with a sedentary lifestyle (Ades 1996; Beneka 2005; Charette 1991; Fatouros 2002; Fatouros 2005; Frontera 2003; Kalapotharakos 2005; Katznelson 2006; Malliou 2003; Mihalko 1996; Parkhouse 2000; Pollock 1991; Rhodes 2000; Topp 1996; Tsutsumi 1997).
PRT Programmes
Settings
Most training programmes took place in gym or clinic settings with all sessions fully supervised. Ten studies were entirely home-based (Baker 2001; Chandler 1998; Fiatarone 1997; Jette 1996; Jette 1999; Katznelson 2006; Krebs 2007; Latham 2003; Mangione 2005; McMurdo 1995), while 12 additional studies carried out some of the training at home and some in gym/clinic settings (Boshuizen 2005; Ettinger 1997; Jones 1994; Mikesky 2006; Simoneau 2006; Skelton 1995; Skelton 1996; Topp 1993; Topp 1996; Topp 2002; Topp 2005; Westhoff 2000).
Intensity
The resistance training programmes in most trials (i.e. 83 trials) involved high intensity training. Most of these trials used specialized exercise machines for training. Thirty-six trials used low-intensity to moderate-intensity training, with most using elastic tubing or bands. All of the high-intensity training was carried out at least in part in gym or clinic based settings, with the exception of two published trials (Baker 2001; Latham 2003) and a trial published as an abstract (Fiatarone 1997).
Frequency and duration
The frequency of training was consistent across studies, with the exercise programme carried out two to three times a week in almost all trials. Two exceptions to this were the two trials conducted in hospital which carried out the exercises on a daily basis (Donald 2000; Latham 2001). In contrast, there was large variation in the duration of the exercise programmes and the number of exercises performed in each programme. Although most of the programmes (i.e. 71 trials) were eight to 12 weeks long, the duration ranged from two to 104 weeks. In 54 trials the exercise programme was longer than 12 weeks. The number of exercises performed also varied, from one to more than 14.
Adherence
Data about adherence to the PRT programme are reported in the 'Characteristics of included studies'. These data are difficult to interpret because different definitions for adherence or compliance were used across the trials. In most trials, adherence referred to the percentage of exercise sessions attended compared with the total number of prescribed sessions and in this case the reported adherence rate is high (i.e. greater than 75%). Many trials only included participants that completed the entire trial (i.e. excluded drop-outs), while some trials reported these data with drop-outs included.
Comparison interventions
Comparisons were conducted between a PRT group and a control group and between a PRT group and a group that received other type of intervention. In addition, comparisons between high intensity or frequency and low intensity or frequency, different sets, and different types of contraction training were also conducted. Multiple comparisons within a trial were possible when the trial included more than two groups that were relevant to the review. Twenty-eight trials had three groups. Among these trials, 14 included an aerobic training group in addition to a PRT group and a control group (Ettinger 1997; Fahlman 2002; Fatouros 2002; Haykowsky 2005; Hiatt 1994; Jubrias 2001; Kallinen 2002; Madden 2006; Malliou 2003; Mangione 2005; Pollock 1991; Sipila 1996; Topp 2005; Wood 2001), and seven included two PRT groups that exercised at different intensities in addition to a control group (de Vos 2005; Fatouros 2005; Hortobagyi 2001; Hunter 2001; Kalapotharakos 2005; Seynnes 2004; Singh 2005). One trial had a PRT group, a functional training group, and a PRT with functional training group (Manini 2005). The other six trials either had a balance training group (Judge 1994), functional training group (Chin A Paw 2006; de Vreede 2007), an endurance training group (Sipila 1996), a mobility training group (McMurdo 1995), or a power training group (Miszko 2003) in addition to a PRT group and a control group. One trial had three groups that exercised at three different frequencies in addition to a control group (Taaffe 1999).
PRT versus controls
One hundred and four trials compared PRT with a control group. The control group might receive no exercise, regular care, or attention control (i.e. the control group receives matching attention as the intervention group).
Comparisons of PRT dosage
High intensity versus low intensity
Ten studies compared PRT programmes at high intensity versus low intensity (Beneka 2005; Fatouros 2005; Harris 2004; Hortobagyi 2001; Seynnes 2004; Singh 2005; Sullivan 2005; Taaffe 1996; Tsutsumi 1997; Vincent 2002).
Different frequencies of PRT
Two trials (DiFrancisco 2007; Taaffe 1999) compared PRT performed at different frequencies (i.e. once, twice, or three times per week).
Different sets
One study compared PRT at different sets, i.e. 3-sets versus 1-set (Galvao 2005). One set of exercise means several continuous repeated movements.
Concentric versus eccentric training
One study (Symons 2005) compared PRT at two types of contraction training: concentric versus eccentric training. During concentric training, speed was added at concentric contraction phase and vise versa for eccentric training.
PRT versus aerobic training
PRT was compared with aerobic (endurance) training in 17 trials (Ballor 1996; Buchner 1997; Earles 2001; Ettinger 1997; Fatouros 2002; Hepple 1997; Hiatt 1994; Izquierdo 2004; Jubrias 2001; Kallinen 2002; Madden 2006; Malliou 2003; Mangione 2005; Pollock 1991; Sipila 1996; Topp 2005; Wood 2001).
PRT versus balance training
One study compared PRT with balance training (Judge 1994). Balance training included training on a computerized balance platform and non-platform training (i.e. balancing on different surfaces, with varying bases of support, with different perturbations). Both exercise programmes were performed in a research center three times per week for three months.
PRT versus functional training
Three studies compared PRT to functional training (Chin A Paw 2006; de Vreede 2007; Manini 2005). Functional training involves game-like activities or exercise movements in various directions. In Chin A Paw 2006, functional training involved game-like or cooperative activities; and in de Vreede 2007, functional training involved moving with a vertical or horizontal component, carrying an object, and changing position between lying, sitting, and standing.
PRT versus flexibility training
One study compared PRT with flexibility training (Barrett 2002).
Power training
Power training refers to the type of PRT that emphasizes speed. Three studies applied this type of training (de Vos 2005; Macaluso 2003; Miszko 2003).
Outcomes
A variety of outcomes were assessed in these studies: the primary outcomes of physical function and secondary outcomes of measures of impairment and functional limitation.
Excluded studies
The excluded studies and their reasons for exclusion are listed in the 'Characteristics of excluded studies'. The main reasons for exclusion were that the study was not a randomised controlled trial or that the study design caused serious threats to its internal validity (57 trials); the studies used a combination of exercise interventions (i.e. not resistance training alone) (51 trials); the strength training programme did not use a progressive resistance approach (32 trials); and some participants were not elderly (i.e. did not have a mean age of at least 60 years and/or included some participants below 50 years of age) (25 trials).
Studies awaiting assessment
Nine trials were identified on a search update to May 2008, and a further trial was added after a referee's comment.
Risk of bias in included studies
Methodological quality scores of each item for all included studies are given in Table 2. A summary of the findings of key indicators of internal validity are listed below.
Allocation concealment
Eleven studies provided some information about the method of randomisation that suggested that randomisation was probably concealed (i.e. the use of concealed envelopes or the randomisation was generated by an independent person) (Baker 2001; Chin A Paw 2006; Donald 2000; Foley 2003; Jette 1999; Latham 2001; Latham 2003; McMurdo 1995; Moreland 2001; Sims 2006; Sullivan 2005). Nineteen studies used randomisation list/table but allocation concealment was unclear (Barrett 2002; Baum 2003; Buchner 1997; de Vos 2005; de Vreede 2007; DiFrancisco 2007; Ettinger 1997; Krebs 2007; Liu-Ambrose 2005; Maurer 1999; Miller 2006; Schilke 1996; Segal 2003; Singh 1997; Singh 2005; Skelton 1995; Suetta 2004; Vincent 2002; Wieser 2007).
Loss to follow-up
Some trials had high drop-out rates, with several studies reporting more than 20% of their participants were lost to follow-up (Bruunsgaard 2004; Chin A Paw 2006; DeBeliso 2005; Donald 2000; Katznelson 2006; Kongsgaard 2004; Mangione 2005; Mikesky 2006; Topp 1996). In some studies there was clear evidence of bias associated with the deliberate exclusion of patients such as those who failed to adhere to the exercise programme (Izquierdo 2004; Madden 2006; Topp 1996; Vincent 2002) or those who had adverse responses (Hagerman 2000).
Intention-to-treat analysis
Twenty-two studies stated that they used intention-to-treat analysis (Baker 2001; Barrett 2002; Baum 2003; Buchner 1997; Chin A Paw 2006; Ettinger 1997; Fiatarone 1994; Foley 2003; Judge 1994; Katznelson 2006; Latham 2003; Liu-Ambrose 2005; Macaluso 2003; Mikesky 2006; Miller 2006; Moreland 2001; Nelson 1994; Ouellette 2004; Pu 2001; Segal 2003; Sims 2006; Sullivan 2005).
Blinded outcome assessment
Thirty-three studies stated that they used a blinded assessor for all outcome measures (Barrett 2002; Baum 2003; Bean 2004; Boshuizen 2005; Buchner 1997; Casaburi 2004; Castaneda 2004; Chin A Paw 2006; de Vreede 2007; Ettinger 1997; Foley 2003; Haykowsky 2005; Jette 1996; Jette 1999; Jones 1994; Judge 1994; Kalapotharakos 2005; Katznelson 2006; Krebs 2007; Latham 2003; Liu-Ambrose 2005; Mangione 2005; Maurer 1999; McMurdo 1995; Mikesky 2006; Miller 2006; Moreland 2001; Newnham 1995; Segal 2003; Sims 2006; Singh 2005; Sullivan 2005; Westhoff 2000).
Eight additional studies used a blinded outcome assessor for some, but not all outcome assessments (Baker 2001; Castaneda 2001; de Vos 2005; Fiatarone 1994; Ouellette 2004; Pu 2001; Singh 1997; Suetta 2004).
Blinding of participants
Blinding of participants is difficult in studies of exercise interventions. However, the use of attention control groups can help to minimise bias. Thirty-six studies used some type of attention programme for the control group (Baker 2001; Baum 2003; Bean 2004; Brochu 2002; Bruunsgaard 2004; Castaneda 2001; Castaneda 2004; Chin A Paw 2006; Damush 1999; Ettinger 1997; Fiatarone 1994; Fiatarone 1997; Foley 2003; Judge 1994; Kongsgaard 2004; Latham 2003; Liu-Ambrose 2005; Mangione 2005; Maurer 1999; McCartney 1995; McMurdo 1995; Mihalko 1996; Mikesky 2006; Miller 2006; Miszko 2003; Moreland 2001; Newnham 1995; Ouellette 2004; Pu 2001; Seynnes 2004; Simons 2006; Sims 2006; Singh 1997; Suetta 2004; Topp 1993; Topp 1996). In 10 of these studies, the control group received 'sham' exercise programmes (Bean 2004; Brochu 2002; Castaneda 2001; Castaneda 2004; Kongsgaard 2004; Liu-Ambrose 2005; Mikesky 2006; Ouellette 2004; Pu 2001; Seynnes 2004).
Duration of follow-up
Five studies continued to follow up the participants after intervention had ended (Buchner 1997; Fiatarone 1994; Moreland 2001; Newnham 1995; Sims 2006). Two of these followed up falls for more than one year (Buchner 1997; Fiatarone 1994).
Effects of interventions
Eleven studies did not report final means and standard deviations for some or all of their outcome measures but instead reported baseline mean scores and mean change in scores from baseline (Baum 2003; Bean 2004; Buchner 1997; Chandler 1998; Fiatarone 1994; Hiatt 1994; Jette 1996; Lamoureux 2003; Madden 2006; Sullivan 2005; Topp 1996). If additional data could not be obtained from the investigators, the final mean score was estimated by adding the change in score to the baseline score, and the standard deviation of the baseline score was used for the final score.
Four studies did not report standard deviations for some or all of their outcome measures but instead reported standardized errors (Ouellette 2004; Seynnes 2004; Suetta 2004; Topp 2002). The standard deviations were estimated based on reported standardized errors and sample sizes.
Eight studies did not report numerical results of outcomes of interest for the purpose of this review and additional data were not provided by the investigators (Castaneda 2004; Fielding 2002; Harris 2004; Haykowsky 2005; Krebs 2007; Miller 2006; Topp 2005; Wieser 2007).
PRT versus control
Measures of physical (dis)ability/HRQOL (complex physical activities)
The main function (disability) measures from trials that had appropriate data were pooled using the standardised mean difference (SMD) and a fixed-effect model. Because studies measured function in scales with different directions, a higher score indicates either less disability/better function or more disability/poor function, a transformation was conducted to make all the scales point in the same direction. Mean values from trials in which a higher score indicates more disability/poor function were multiplied by -1. There is a significant effect of PRT in decreasing disability (see Figure 1; Analysis 1.1: 33 trials, 2172 participants; SMD 0.14, 95% CI 0.05 to 0.22). When the physical function domain of SF-36 or SF-12 was pooled from 14 studies (n = 778) using a fixed-effect model, no difference was found ( Analysis 1.2: SMD 0.07, 95% CI -0.08 to 0.21). No difference was found from the pooled results of three trials for activity of daily living measures ( Analysis 1.3). A number of studies had function measures (i.e. measures of activity, function or HRQOL) that could not be pooled. The available data from these measures are reported in Table 3.
 | Figure 1. Forest plot of comparison: 1 PRT versus control, outcome: 1.1 Main function measure (higher score = better function). |
Measures of impairment
Strength
Many different muscle groups were tested and a number of methods were used to evaluate muscle strength in these trials. To minimise clinical heterogeneity, data were pooled from one muscle group. The leg extensor group of muscles was selected since this group was the most frequently evaluated. The effect size was calculated using standardised mean difference (SMD) to allow the pooling of data that used different units of measurement. Seventy-three studies involving 3059 participants reported the effect of resistance training on a lower-limb extensor muscle group and provided data that allowed pooling. A moderate-to-large beneficial effect was found ( Analysis 1.5: SMD 0.84, 95% CI 0.67 to 1.00, random-effects model; fixed-effect model: SMD 0.53, 95% CI 0.46 to 0.61).
Supplementary analyses
Significant statistical heterogeneity was apparent in these data (P < 0.0001). Since a large number of studies assessed this outcome, it was possible to explore this heterogeneity by stratifying the data. Differences in treatment effects due to the quality of the trials were investigated. We also explored subgroups of trials that were based on the design of the treatment programmes and the characteristics of the participants.
To explore the effect of data quality on treatment effects, data were stratified by four design features that are associated with internal validity. These are allocation concealment; blinded assessors; intention-to-treat analysis (ITT); and attention control groups. The fixed-effect model was used throughout in order to obtain the results for the test for subgroup differences. The effect was smaller in the few studies with clear allocation concealment (6 trials, 607 participants) compared with studies with unknown concealment of allocation (67 trials, 2452 participants): Analysis 10.1: test for subgroup differences: Chi² = 32.69, df = 1 (P < 0.00001). The effect was also smaller in studies that used blinded assessors (19 trials, 1523 participants) compared with studies that did not use blinded assessors (54 trials, 1536 participants): Analysis 10.2: test for subgroup differences: Chi² = 70.56, df = 1 (P < 0.00001). This was also true for studies that used intention-to-treat analysis (ITT) (12 trials, 1041 participants) versus no ITT (61 trials, 2018 participants): Analysis 10.3: test for subgroup differences: Chi² = 49.74, df = 1 (P < 0.00001). It is noticable that trials that applied better design features tend to be the larger trials. The effect was smaller when attention control groups were used (attention control: 24 studies, 1408 participants, no attention control: 49 studies, 1651 participants): Analysis 10.4: test for subgroup differences: Chi² = 25.04, df = 1 (P < 0.00001).
Subgroup analyses were conducted to explore the effect of PRT when the design of the exercise programme and the characteristics of the participants differed. The effect of differences in the exercise programme was explored by examining effect estimates in studies that used different intensity and duration. High intensity strength training was compared with low to moderate intensity training. This analysis suggests that while both training approaches are probably effective in improving strength, higher intensity training (54 trials, 2026 participants) has a larger effect on strength than low to moderate intensity training (19 trials, 1033 participants): Analysis 10.5: test for subgroup differences: Chi² = 7.24, df = 1 (P = 0.007). Longer duration programmes (i.e. greater than 12 weeks) were also compared with shorter duration programmes (less than 12 weeks). The duration of the trial appeared to have minimal effect on the strength outcome (< 12 weeks: 20 trials, 828 participants; > 12 weeks: 36 trials, 1736 participants): Analysis 10.6: test for subgroup differences: Chi² = 0.04, df = 1 (P = 0.85).
Treatment effects in older people with and without a chronic disease (or functional limitation) were also assessed. Again, resistance training appeared to be effective in improving strength in both groups of older people, but there was statistical heterogeneity in the effects. Studies that included participants who had specific health problems and/or functional limitations were compared with studies that included only healthy older people. The effect in older adults who were healthy has a larger effect size than older adults with specific health problems (healthy older adults: 46 trials, 1502 participants; older adults with specific health problems: 19 trials, 926 participants): Analysis 10.7: test for subgroup differences: Chi² = 19.85, df = 1 (P < 0.00001). In addition, PRT in studies that included older adults who had a physical disability or functional limitation appeared to be less effective than in those that included older adults who did not have functional limitations (people with functional limitations: 13 studies, 784 participants; people with no functional limitations: 41 studies, 1349 participants): Analysis 10.8: test for subgroup differences: Chi² = 29.33, df = 1 (P < 0.00001). However, this result could be confounded by the intensity of the PRT programmes, as almost all programmes that included people with functional limitations were carried out at a low to moderate intensity. There were insufficient data available to compare the results by gender (men only: 5 trials with 107 participants; women only: 15 trials with 486 participants).
Aerobic capacity
The main measure of aerobic capacity was pooled from 29 studies (n = 1138) using a random-effects model. These results suggest that PRT has a significant effect on aerobic capacity ( Analysis 1.6: SMD 0.31, 95% CI 0.09 to 0.53). Further analyses were performed for three specific measures of aerobic capacity: VO2 max (ml/kg/min), peak oxygen uptake (L/min) and the six-minute walk test (meters). A consistent significant effect was found for VO2 max ( Analysis 1.7: 18 trials, n = 710, MD 1.5 ml/kg/min, 95% CI 0.49 to 2.51). Similarly, a significant positive effect was found for the six-minute walk test ( Analysis 1.8: 11 trials, n = 325, MD 52.37 meters, 95% CI 17.38 to 87.37).
Measures of functional limitations (simple physical activities)
Balance/postural control
Results from all balance performance measures were pooled using SMD and a fixed-effect model. Data pooled from 17 studies with 996 participants showed a small but non-significant benefit (higher score indicates better balance) for balance ( Analysis 1.9: SMD 0.12 (95% CI 0.00 to 0.25).
Gait speed
Two different measures of walking speed were used: gait speed (measured in meters per second) and timed walk (i.e. time to walk a set distance, measured in seconds). A higher gait speed score indicates faster mobility, while a higher timed walk score indicates slower mobility. Because of this difference, these data were analyzed separately. Data for gait speed were available from 24 studies that included 1179 participants ( Analysis 1.11: MD 0.08 m/s, 95% CI 0.04 to 0.12, random-effects). This indicated that PRT has a modest but significant beneficial effect on gait speed. Only eight trials measured the timed walk (seconds) as an outcome measure and no evidence of an effect was found ( Analysis 1.12; 204 participants, MD -0.23 seconds, 95% CI -1.07 to 0.62, fixed-effect).
Timed up-and-go
Timed up-and-go (i.e. time to stand from a chair, walk three meters, turn, and return to sitting, measured in seconds) was analysed using a fixed-effect model. Data, available from 12 trials and a total of 691 participants, showed the PRT group took significantly less time to complete this mobility task ( Analysis 1.13: MD -0.69 seconds, 95% CI -1.11 to -0.27).
Timed chair rise
Time to stand up from a sitting position data were available in 11 studies (n = 384). Because different numbers of sit-to-stand were counted, SMD and a random-effects model was used to pool these results. These showed a significant, moderate to large effect on this task in favour of the PRT group ( Analysis 1.14: SMD -0.94, 95% CI -1.49 to -0.38).
Stair climbing
Time to climb stairs data, which were available from eight trials, also favoured PRT ( Analysis 1.15). However, these results were highly heterogenous.
Falls
Thirteen studies collected data about the effect of resistance training on falls or reported the incident of falls, but the outcomes reported did not allow pooling of the data. The available data is reported in Table 4. Three of these studies (Buchner 1997; Fiatarone 1994; Judge 1994) were part of the FICSIT trial, a prospective preplanned meta-analysis to determine the effectiveness of exercise to prevent falls in older people (Province 1995). The data were extracted from the main FICSIT paper, because papers published about the individual exercise programmes did not provide useful data about the effect of resistance training alone on falls. One additional trial investigated the effect of resistance training on falls in older people while they were in hospital (Donald 2000). Another trial also assessed the effect of PRT on frail older people following discharge from hospital (Latham 2003). There is a more comprehensive review of the effect of exercise on falls in a separate Cochrane review (Gillespie 2003).
With the exception of Latham 2003, all of these trials were small (i.e. less than 80 participants in the resistance training and control groups). Only Donald 2000 found a significant reduction in falls, but there were few fall events in this trial.
Adverse events
Adverse events are reported for all trials in the review at the end of the results section.
Vitality
The vitality (VT) domain of the SF-36 health status measure was assessed in 10 studies involving 611 participants. For this measure, a higher score indicates better health (i.e. more vitality): there was no evidence of an effect of PRT from the pooled data ( Analysis 1.17: MD 1.33 95% CI -0.89 to 3.55).
Pain
Data of bodily pain (BP) domain of the SF-36 health status measure were provided by 10 studies involving 587 participants. For this measure, a higher score indicates better health (i.e. less pain), there was no evidence that PRT had an effect on bodily pain ( Analysis 1.18: MD 0.34, 95% CI -3.44 to 4.12). In contrast, six studies with 503 participants included pain measures where a higher score indicates more pain, and found evidence to support a modest reduction in pain following PRT ( Analysis 1.19: SMD -0.30, 95% CI -0.48 to -0.13). These six studies all included participants with osteoarthritis and used pain measures designed specifically for this population, which could have increased their sensitivity to change.
Health service use, hospitalization and death
Five studies provided data about hospitalization rates, length of stay and/or outpatient visits. Donald 2000 reported that people who received PRT in addition to regular in-hospital physiotherapy had a length of stay of 27 days compared with 32 days for the control group. Latham 2003 found that 42/120 people in the PRT group were admitted to hospital over six months compared to 35/123 in the control group. The third trial by Singh 1997 reported that, over a 10 week period, people in the PRT group had mean 2.1 (SD 0.4) visits to a health professional and mean 0.24 (SD 0.2) hospital days compared to controls mean of 2.0 (SD 0.5) visits and mean 0.53 (0.4) hospital days. The fourth study by Singh 2005 reported visits to a health professional over the study (average numbers per person): high intensity group, 2 (2); low intensity group, 2 (1.8); controls, 5 (1.8). The fifth study by Miller 2006 reported participants' discharge destinations but did not specify the group: 52 participants were discharged to a rehabilitation programme, 12 were transferred to a community hospital, 16 were discharged to higher level care, and 20 returned directly to their pre-injury admission accommodation. An additional study, Buchner 1997, provided data about health service use, but only reported data that were pooled to include participants in aerobic training, combined aerobic training and PRT and PRT alone. This study found no change in hospital admissions between those in the exercise and control groups, but an increased number of outpatient visits by those in the control group. Finally, two studies stated that there was no difference in health care visits (Fiatarone 1997) or hospitalization (Pu 2001) but no specific data were provided.
Thirteen studies provided data about participant deaths that allowed pooling (Baum 2003; Boshuizen 2005; Chin A Paw 2006; Donald 2000; Ettinger 1997; Fiatarone 1994; Kallinen 2002; Latham 2003; Mangione 2005; Miller 2006; Moreland 2001; Newnham 1995; Selig 2004). The risk ratio of death in the PRT group was not significantly different from the control group ( Analysis 1.20: 20 deaths versus 21 deaths; RR = 0.89, 95% CI 0.52 to 1.54).
Comparisons of PRT dosage
Thirteen trials investigated the effects of different doses of PRT. Note that data from medium intensity were not examined in the following.
High versus low intensity PRT
Physical function, pain and vitality
Of the 10 studies comparing high versus low intensity PRT, only two (Singh 2005; Tsutsumi 1997), evaluated physical function, pain and vitality using the domains of the SF-36. No significant difference was found for physical function ( Analysis 2.1) or pain ( Analysis 2.4), but vitality scores were statistically significantly higher for high intensity ( Analysis 2.5: MD = 6.54, 95% CI 0.69 to 12.39).
Strength
Data from all nine studies (n = 219) were available to examine the effect of high versus low intensity PRT on lower limb strength (Beneka 2005; Fatouros 2005; Harris 2004; Hortobagyi 2001;Seynnes 2004; Sullivan 2005; Taaffe 1996; Tsutsumi 1997; Vincent 2002). The results indicate that high intensity training results in greater lower limb strength, as a moderate effect was seen ( Analysis 2.2: SMD = 0.48, 95% CI 0.03 to 0.93; random-effects model).
Aerobic capacity
Three studies compared the effect of high versus low intensity PRT on aerobic capacity (Fatouros 2005; Tsutsumi 1997; Vincent 2002). These studies (n = 101) did not show greater benefit from high intensity compared with low intensity training ( Analysis 2.3: MD 1.82 ml/kg/min, 95% CI -0.79 to 4.43; higher score favours high-intensity group).
High intensity versus variable intensity PRT
One trial (Hunter 2001) comparing high intensity PRT with variable intensity PRT showed no statistically significant differences for strength ( Analysis 3.1: n = 24, MD = 0.61, 95% CI -0.21 to 1.44) and aerobic capacity ( Analysis 3.2).
Frequency
Taaffe 1999 and DiFrancisco 2007 compared PRT at different frequencies, respectively three times a week versus once a week, and twice a week versus once a week. Both studies recruited few participants and applied high intensity intervention. There were no significant differences between the two exercise frequencies in muscle strength ( Analysis 4.1: MD = 0.40, 95% CI -0.44 to 1.25; MD = -0.46, 95% CI -1.40 to 0.48).
Sets
Galvao 2005 compared PRT at 3-sets versus 1-set in 28 participants. No significant differences between the two groups were found for muscle strength ( Analysis 5.1), six minute walk test ( Analysis 5.2), sit-to-stand ( Analysis 5.4) and stair climbing ( Analysis 5.5). However, participants who exercised at 3-sets walked significantly faster than those who exercised at 1-set ( Analysis 5.3: MD = -29.6 seconds, 95% -54.23 to -4.97).
PRT versus aerobic training
Physical function
Five studies evaluated the effect of PRT compared with aerobic training on physical function. Four studies (Buchner 1997; Earles 2001; Hiatt 1994; Mangione 2005) used outcomes in which a higher score indicates less disability (n = 125), and found no significant difference (see Analysis 6.1: SMD -0.21, 95% CI -0.56 to 0.15; lower score favours the aerobic training group). The other study (Ettinger 1997) (n = 237) also found no significant difference between the groups for function (see Analysis 6.2: SMD 0.05, 95% CI -0.21 to 0.30; higher score favours aerobic group).
Strength
Data on lower extremity strength were available from 10 studies (n = 487) (Ballor 1996; Buchner 1997; Earles 2001; Ettinger 1997; Fatouros 2002; Izquierdo 2004; Malliou 2003; Pollock 1991; Sipila 1996; Wood 2001). These data when pooled using a random-effects model showed that PRT had a significant benefit compared with aerobic training on strength (see Analysis 6.3: SMD 0.44, 95% CI 0.08 to 0.80; higher score favours PRT).
Aerobic capacity
Aerobic capacity was evaluated in eight studies involving 423 participants (Ballor 1996; Buchner 1997; Ettinger 1997; Hepple 1997; Hiatt 1994; Kallinen 2002; Madden 2006; Pollock 1991). This was measured using VO2 max in ml/kg/min. Using the random-effects model, aerobic training had a non-significant benefit compared to PRT for this outcome ( Analysis 6.4: MD -1.13 ml/kg/min, 95% CI -2.63 to 0.38; higher values favours PRT).
Gait speed
Mangione 2005 reported on gait speed (m/s) and found no significant difference between groups ( Analysis 6.6: MD -0.08 m/s, 95% CI -0.30 to 0.14; higher speed favours PRT group)
Pain
Ettinger 1997 found no significant difference between groups in pain ( Analysis 6.7: MD 0.12; 95% CI -0.14 to 0.37; lower score favours PRT).
PRT versus balance
One study (Judge 1994) compared PRT with balance retraining (n = 55). This study found that strength improved in the PRT group, but not in the balance training group. Chair rise time and gait speed did not improve in any group, with gait speed actually declining in the balance training group. However, balance improved in the balance training group compared with the PRT group.
PRT versus functional training
Three studies compared PRT with functional training (Chin A Paw 2006; de Vreede 2007; Manini 2005). No significant differences between the two interventions were found for the reported outcomes (see: Analysis 7.1 physical function; Analysis 7.2 strength; Analysis 7.3 timed up and go; Analysis 7.4 vitality; Analysis 7.5 pain).
PRT versus flexibility training
Barrett 2002 (n = 40) compared a group of older adults who undertook PRT with a control group who did mainly stretching for the major muscle groups (flexibility training). No statistically significant differences were found for any of the reported outcomes (see: Analysis 8.1: SF-36 physical function; Analysis 8.2: strength; Analysis 8.3: timed walk; Analysis 8.4: chair stand; Analysis 8.5: vitality; Analysis 8.6: pain).
Power training
Two studies (de Vos 2005; Miszko 2003) (n = 76) compared power training with a control group. de Vos 2005 and another study (Macaluso 2003) also compared different intensities of power training. While the data for muscle strength for de Vos 2005 favoured high intensity power training, data pooling was inappropriate given the substantial and significant heterogeneity (see Analysis 9.1).
Adverse events
Among 121 studies that were reviewed, 53 studies provided no comment at all about adverse events associated with the training programme. Of the remaining 68 studies, 25 reported no adverse events and 43 reported some adverse reaction to the exercise programme. An additional eight studies did not report adverse events as such, but it is possible that an event occurred since these studies reported drop-outs from the exercise group secondary to increasing pain or specific injuries (Chandler 1998; Charette 1991; Fiatarone 1997; Hagerman 2000; Hortobagyi 2001; Jette 1996; Maurer 1999; Topp 1993). Given that there were considerably more drop-outs from the PRT group than from the control group (see methodological quality section above), it is possible that the number of cases of adverse events reported here are an underestimate.
Only nine studies provided an a priori definition of an adverse event in the study methods or objectives (Earles 2001; Ettinger 1997; Judge 1994; Kallinen 2002; Latham 2003; Liu-Ambrose 2005; Moreland 2001; Pollock 1991; Singh 1997). Eight of these nine studies detected adverse events (Earles 2001; Ettinger 1997; Judge 1994; Kallinen 2002; Latham 2003; Liu-Ambrose 2005; Moreland 2001; Pollock 1991). However, there was little consistency in the definition that was used, with some studies only reporting serious events that the investigators thought were possibly related to the exercise programme (i.e. Ettinger 1997) while other studies reported all adverse events that occurred in each group. Most adverse events were musculoskeletal problems. Serious adverse events were rare, and none appeared to be directly related to the exercise programme. One study reported one death of myocardial information in the PRT group (Kallinen 2002). Another two studies reported one death in the PRT group but the reason of death was not reported (Baum 2003; Chin A Paw 2006). Further details about all adverse events reported in these trials can be found in Table 5.
Discussion
Summary of main results
This review identified, graded and synthesized the available literature regarding the effect of a specific exercise intervention, PRT, on a particular population, older people. To increase the generalisability of these data, the trials included participants with a range of health problems, and the dose and delivery of the PRT programmes varied. This made it possible to assess overall effects of the intervention on older people, with a potential for exploring the effects on subgroups (i.e. in different groups of older people or with different doses of PRT). Overall, this review suggests that PRT has a small but significant effect on improving physical function (complex activities), a small to moderate effect on decreasing some impairments and functional limitations, and a large effect on increasing strength. Adverse events were poorly reported in most studies, which limits the ability of this review to assess the risks associated with this intervention. Additionally, there is some preliminary evidence that suggests that PRT might reduce pain in older people with osteoarthritis. The effect of exercise on reducing pain in people with osteoarthritis is reported in another Cochrane review (Brosseau 2003). The sparse data did not allow an adequate assessment of the effect of PRT on fall risk. However, a separate Cochrane review (Gillespie 2003) has reviewed fall prevention.
Overall completeness and applicability of evidence
This review update highlights the fact that exercise training in older adults continues to be a dynamic area of research, with the number of included studies doubling in the five years since the previous review. A quick update extending the MEDLINE search to May 2008 identified nine further studies. However, the majority of the trials continue to be studies with small sample sizes.
This review deliberately used broad inclusion criteria and multiple strategies to try to identify as many studies as possible that used PRT training with older adults. Despite these efforts, given the broad coverage of our review it is inevitable that we have missed some trials. It is particularly challenging to identify unpublished trials in this area because the studies could have been presented at many different types of conferences (stoke, OA, CHD etc). We acknowledge that it was not possible to hand search all of the potential conferences where studies in this area could be presented, and it is therefore possible that we missed some studies that had negative or neutral results and are more difficult to get published. Although we attempted to contact authors when there was any uncertainty about data, it is also likely that data could also have been missed both from the excluded trials (i.e. the outcomes may have been recorded but not reported) and the included trials (i.e. data not reported and/or data not available for pooling).
Quality of the evidence
The 121 studies in this review were generally of poor methodological quality, as most of the studies did not use design features that are known to increase internal validity, such as concealed randomisation; intention-to-treat analysis, blinded outcome assessors, or attention control groups. Only 11 studies used concealed randomisation; 22 studies used intention-to-treat analysis; and 33 studies used blinded outcome assessors for all outcomes. Therefore, caution is required when drawing conclusions from these data. When data were stratified by indicators of study quality for the outcome muscle strength, results from the high quality trials continued to support the positive effect of resistance training on strength. However, these data also indicate that low quality trials, usually small studies, that comprise the majority of the studies in the review probably overestimate the effect of resistance training because of random chance effects from small studies. The long-term outcome of PRT is unclear because the majority of studies stopped following up participants once the intervention had ended.
PRT versus control
PRT shows small positive effect on measures of physical function (disability). PRT also appears to have a positive effect on aerobic capacity and most measures of functional limitations, including gait speed, timed "Up-and-Go" and, the time to stand up from a chair. All of these effects were statistically significant, although the effect sizes tended to be small to moderate, and the clinical significance of these effects is unclear. PRT appears to have a large positive effect on strength and aerobic capacity in older people. However, there was a large amount of statistical heterogeneity associated with the estimate in strength. This variation was reduced, but not eliminated, by investigating differences in outcome in different groups of participants, types of intervention and in trials that used different quality indicators. Please note that results from such exploratory analysis are tentative. In exploratory subgroup analyses, it appeared that training intensity has the greatest effect on strength (i.e. high intensity training has a greater effect on strength than lower intensity training), while the duration of the training appears to have a reduced effect. The magnitude of the effect was influenced by participants' health status or functional status. PRT in healthy participants had a greater effect than in those with a chronic disease or functional limitation. In other words, it appeared that people with a pre-existing health condition or with functional limitations had smaller gains in strength. Additionally, men had larger gains in strength than women; although there were fewer trials in men. These subgroup analyses must be interpreted with caution as the number of participants is reduced which decreases the precision of these estimates. In addition, it is possible that study size is a source of heterogeneity, as several of the largest and highest quality trials included people with function limitations and/or lower intensity training programmes, and study quality appears to reduce the effect estimates. Overall, the effect of PRT on function is positive for older adults; although the effect seems diminished when it transfers from muscle strength to functional limitations and disability.
It was not possible to pool fall data because falls were reported differently in the five studies that measured this outcome. These data might suggest a trend towards PRT reducing falls, since four of the five studies found that participants in the PRT group had fewer falls than those in the control group. However, the effect of PRT alone on falls is still not clear.
Adverse events were poorly monitored and reported in most of these trials. This makes it difficult to assess the risk of injury or other adverse events associated with resistance training. The finding that several studies reported drop-outs from the exercise programme due to pain or injury, yet failed to report any adverse events, suggests that adverse events might have been under-reported in some trials. This hypothesis is further supported by the finding that the studies with a clear definition of adverse events in their study methods were more likely to detect these events than those with no definition. The large number of drop-outs from the PRT group compared to controls also raises the possibility that people are experiencing adverse effects from PRT that are not identified in these trials. However, it is reassuring that participant's pain and vitality were not affected by PRT, and in fact PRT appeared to decrease pain in people with osteoarthritis. Furthermore, there was no evidence of increased risk of hospitalization. A few studies reported decreased use of health care services in the PRT group. Finally, there were a few reports of serious adverse events (i.e. myocardial infarction or death) in the PRT group but there was no evidence that these events were directly associated with the intervention. There was also no evidence of increased risk of death in the PRT group when compared with the control group.
Comparison of PRT dosage
There are currently few randomised data available to guide the dose and prescription of PRT. Trials investigated different aspects of this issue were all small studies and most were of poor quality. When high intensity training was compared with low intensity training, data from 10 trials show that high intensity training has a greater effect on strength than lower intensity training. Among these 10 trials, three show that high intensity training has a greater effect on aerobic capacity. Eight of the 10 trials were healthy older people who participated in highly supervised, gym-based programmes. Therefore, it is not clear if high intensity PRT is more beneficial than low intensity training in less fit or healthy older people and/or in home or hospital based programmes. Limited evidence are available for exercise frequencies and sets.
PRT versus other training
Overall, no significant differences were found between the different types of training. When PRT is compared to aerobic training, PRT tended to produced larger gains in strength than aerobic training. However, these two types of training are not different in aerobic capacity. This finding is to be expected, given that the strength outcome is more specific to PRT. There are fewer data available to determine the comparative effect of these types of training on physical disability, but the available data suggest that the two training programmes have a similar effect on this outcome. There are too few data to draw conclusions about other forms of training such as balance or mobility training compared to PRT.
Authors' conclusions
Implications for practice Doing PRT two to three times a week can improve physical function in older adults, including reducing physical disability, some functional limitations (i.e. balance, gait speed, timed walk, timed 'up-and-go', chair rise; and climbing stairs) and muscle weakness in older people. Therefore, it would appear to be an appropriate intervention for many older people to improve performance of some simple physical tasks. The training also shows a reduction in pain in people with osteoarthritis. However, some caution is warranted with this intervention as in many studies adverse effects have been poorly monitored. Nonetheless, serious adverse events appear to be rare. When used in clinical practice, clinicians should monitor for adverse effects, particularly when older people who might be at higher risk of injury (i.e. frail or recently ill older people) are undertaking PRT. Additionally, there is no information regarding how long these effects can be maintained because the majority of the studies did not follow up the effect after the training had ended. |
Implications for research We recommend that future trials investigating the effect of PRT in older people should:
Future trials should include participants and interventions that are similar to those in health care settings (i.e. frail or recently ill older people), so that, if proven to be effective, resistance training can be incorporated into routine health care services. Well-designed trials are also required to determine the most appropriate dose of PRT to use with different participants and in different settings. |
Acknowledgements
The authors would like to thank the editorial team of the Cochrane Bone, Joint and Muscle Trauma Group, particularly Lindsey Elstub, Lesley Gillespie, Joanne Elliott and Leeann Morton, for their assistance throughout the review process. In particular, thanks to Lesley and Joanne for searching the Cochrane registers and assistance with developing the search strategies. Thank you to Leeann and Lindsey for their advice and guidance about the procedures and content. We would also like to thank the Review Group's editors and the external referees, Prof John Campbell, Dr Keith Hill and Professor David Stott for their helpful comments on earlier drafts of this review.
The reviewers would like to thank Craig Anderson, Derrick Bennett, and Caroline Stretton for their contribution for the first review. The reviewers also would like to thank the National Institute of Disability and Rehabilitation Research (NIDDR) for a post-doctoral fellowship to the first author (H133P001) through Boston University and Switzer research fellowship (H133F060030) and National Institute of Aging (P30 AG031679) to the second author for supporting the review update. In addition, the second author received support for this review through a Pepper Center Trainee award from Boston Pepper Center funded by the National Institute of Aging (1P30Ag031679-01).
Data and analyses
- Top of page
- Background
- Objectives
- Methods
- Results
- Discussion
- Authors' conclusions
- Acknowledgements
- Data and analyses
- Appendices
- What's new
- History
- Contributions of authors
- Declarations of interest
- Sources of support
- Notes
- Index terms
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Appendices
Appendix 1. Search strategies
MEDLINE (OVID WEB)
1. ((strength$ or resist$ or weight$) adj3 training).tw.
2. progressive resist$.tw.
3. or/1-2
4. Exercise/
5. Exercise Therapy/
6. exercise$.tw.
7. or/4-6
8. (Resist$ training or strength$).tw.
9. and/7-8
10. or/3,9
11. limit 10 to ("all aged (65 and over)" or "aged (80 and over)")
12. (elderly or senior$).tw.
13. and/10,12
14. or/11,13
15. randomized controlled trial.pt.
16. controlled clinical trial.pt.
17. Randomized Controlled Trials/
18. Random Allocation/
19. Double Blind Method/
20. Single Blind Method/
21. or/15-20
22. Animals/ not Humans/
23. 21 not 22
24. clinical trial.pt.
25. exp Clinical Trials as topic/
26. (clinic$ adj25 trial$).tw.
27. ((singl$ or doubl$ or trebl$ or tripl$) adj25 (blind$ or mask$)).tw.
28. Placebos/
29. placebo$.tw.
30. random$.tw.
31. Research Design/
32. or/24-31
33. 32 not 22
34. 33 not 23
35. or/23,34
36. and/14,35
EMBASE (OVID WEB)
1. ((strength$ or resist$ or weight$) adj3 training).tw.
2. progressive resist$.tw.
3. or/1-2
4. Exercise/
5. Kinesiotherapy/ or Therapy Resistance/
6. exercise$.tw.
7. or/4-6
8. (resist$ or strength$).tw.
9. and/7-8
10. or/3,9
11. limit 10 to aged <65+ years>
12. (elderly or senior$).tw.
13. and/10,12
14. or/11,13
15. Clinical trial/
16. Randomized controlled trial/
17. Randomization/
18. Single blind procedure/
19. Double blind procedure/
20. Crossover procedure/
21. Placebo/
22. Randomi?ed controlled trial$.tw.
23. Rct.tw.
24. Random allocation.tw.
25. Randomly allocated.tw.
26. Allocated randomly.tw.
27. (allocated adj2 random).tw.
28. Single blind$.tw.
29. Double blind$.tw.
30. ((treble or triple) adj blind$).tw.
31. Placebo$.tw.
32. Prospective study/
33. or/15-32
34. Case study/
35. Case report.tw.
36. Abstract report/ or letter/
37. or/34-36
38. 33 not 37
39. limit 38 to human
40. and/14,39
The Cochrane Library (Wiley)
#1 ((strength* or resist* or weight*) NEAR/3 training):ti,ab,kw
#2 (progressive resist*):ti,ab,kw
#3 #1 OR #2
#4 MeSH descriptor Exercise, this term only
#5 MeSH descriptor Exercise Therapy, this term only
#6 (exercise*):ti,ab,kw
#7 (#4 OR #5 OR #6)
#8 (resist* or strength*):ti,ab,kw
#9 (#7 AND #8)
# 10(#3 OR #9)
#11 (elderly or senior*):ti,ab,kw
#12 (#10 AND #11)
CINAHL (OVID WEB)
1. ((strength$ or resist$ or weight$) adj3 training).tw.
2. progressive resist$.tw.
3. or/1-2
4. Exercise/
5. Therapeutic Exercise/
6. "Exercise therapy: ambulation (iowa nic)"/ or "Exercise therapy: balance (iowa nic)"/ or "Exercise therapy: joint mobility (iowa nic)"/ or "Exercise therapy: muscle control (iowa nic)"/ or "Teaching: prescribed activity/exercise (iowa nic)"/
7. exercise$.tw.
8. or/4-7
9. (resist$ or strength$).tw.
10. and/8-9
11. or/3,10
12. limit 11 to (aged <65 to 79 years> or "aged <80 and over>")
13. (elderly or senior$).tw.
14. and/11,13
15. or/12,14
16. exp Clinical Trials/
17. exp Evaluation Research/
18. exp Comparative Studies/
19. exp Crossover Design/
20. clinical trial.pt.
21. or/16-20
22. ((clinical or controlled or comparative or placebo or prospective or randomi#ed) adj3 (trial or study)).tw.
23. (random$ adj7 (allocat$ or allot$ or assign$ or basis$ or divid$ or order$)).tw.
24. ((singl$ or doubl$ or trebl$ or tripl$) adj7 (blind$ or mask$)).tw.
25. (cross?over$ or (cross adj1 over$)).tw.
26. ((allocat$ or allot$ or assign$ or divid$) adj3 (condition$ or experiment$ or intervention$ or treatment$ or therap$ or control$ or group$)).tw.
27. or/22-26
28. or/21,27
29. and/15,28
SPORTDiscus (OVID WEB)
1. ((strength$ or resist$ or weight$) adj3 training).tw.
2. progressive resist$.tw.
3. or/1-2
4. Exercise/
5. Exercise therapy/
6. exercise$.tw.
7. or/4-6
8. (resist$ or strength$).tw.
9. and/7-8
10. or/3,9
11. (elderly or senior$).tw.
12. and/10-11
13. exp Clinical trial/
14. exp Randomized controlled trial/
15. Placebo/
16. ((clinical or controlled or comparative or placebo or prospective or randomi#ed) adj3 (trial or study)).tw.
17. (random$ adj7 (allocat$ or allot$ or assign$ or basis$ or divid$ or order$)).tw.
18. ((singl$ or doubl$ or trebl$ or tripl$) adj7 (blind$ or mask$)).tw.
19. (cross?over$ or (cross adj1 over$)).tw.
20. ((allocat$ or allot$ or assign$ or divid$) adj3 (condition$ or experiment$ or intervention$ or treatment$ or therap$ or control$ or group$)).tw.
21. or/13-20
22. and/12,21
PEDro
Abstract and Title: "strength training", "resistance training", "progressive resistance"
Therapy: Strength training
Subdiscipline: Gerontology
Method: Clinical trial
When searching match any term "AND"
What's new
Last assessed as up-to-date: 1 December 2007.
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History
Protocol first published: Issue 4, 2000
Review first published: Issue 2, 2003
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Contributions of authors
For the first version of the review (completed 2002), Dr Nancy Latham, Dr Craig Anderson, Dr Derrick Bennett and Dr Caroline Stretton contributed to the development of the protocol, the analysis and interpretation of the data and the write-up of the review. Dr Nancy Latham took the lead in conducting the analyses and writing the protocol and review. In addition, Dr Latham and Dr Stretton conducted the searches, identified the trials, conducted the quality assessments and extracted the data. Dr Bennett provided methodological and statistical guidance for the review. Dr Anderson served as the adjudicator when a consensus about data issues could not be reached between the two reviewers, and provided guidance about the methods and interpretation of the review.
The review was substantially updated in 2009 by Dr Chiung-ju Liu and Dr Nancy Latham. Dr Liu took the lead in conducting the update, which included undertaking the searches, screening search results, organizing retrieval of papers, screening retrieved papers against inclusion criteria, appraising quality of papers, extracting data, contacting authors for additional information, entering data into RevMan, doing the analyses and writing up. The project was completed when Dr Liu was a post-doctoral research fellow at the Health and Disability Research Institute at Boston University. Dr Latham assisted in identifying the trials, conducting the quality assessments, extracting the data, interpreting the results and writing the review.
Both Dr Chiung-ju Liu and Dr Nancy Latham are guarantors for the review.
Declarations of interest
Dr. Latham is an author for two trials. The trials were rated independently by other reviewers in the first review.
Sources of support
Internal sources
- Health and Disability Research Institute, School of Public Health, Boston University, USA.
- Department of Occupational Therapy, School of Health and Rehabilitation Sciences, Inidana University at Indianapolis, USA.
External sources
- NIDRR Post-doctoral Fellowship, grant # H133P001, USA.
- NIDRR Switzer Research Fellowship, grant #H133F060030, USA.
- National Institute of Aging, grant # P30 AG031679, USA.
Notes
Substantial updates of reviews such as this one often take a considerable time to prepare and then take through the editorial process. They can therefore seem 'out of date' before publication, particularly in research active areas. However, although an updated search made in May 2008 revealed nine more potentially eligible trials (which await assessment, pending the next update), it is unlikely that the review's main findings will be substantively changed by these. [Comment by Helen Handoll, Co-ordinating Editor, May 2009]
Index terms
Medical Subject Headings (MeSH)
Activities of Daily Living; Muscle Weakness [*rehabilitation]; Randomized Controlled Trials as Topic; Recovery of Function [physiology]; Resistance Training [adverse effects; *methods]
MeSH check words
Aged; Humans
* Indicates the major publication for the study