Juvenile idiopathic arthritis (JIA) is one of the most common chronic illnesses of childhood, characterized by joint swelling, pain, stiffness, and fatigue. Despite advances in pharmacologic management of joint inflammation, research indicates that many children have persistent active disease and functional limitations that impact quality of life even as adults (1). A growing body of research documents significant impairments in aerobic fitness and muscle strength in children with JIA compared with healthy controls, presumably as a result of decreased physical activity secondary to disease symptoms (2). Although the evidence linking reduced fitness and limitations in the performance of daily activities has not been overwhelming, several studies report delays in the development of complex motor skills (running, jumping, hopping, skipping, etc.) that require speed, agility, and coordination (3, 4). The consequences of impaired exercise capacity are often insidious, resulting in limitations in higher-level physical activities, participation in sports and other extracurricular activities, and decreased overall quality of life.
Research to date leaves several questions unanswered, including: the influence of disease activity, severity, duration, and type on exercise capacity; the most effective exercise regimen to improve functional capacity and performance in activities that are important to the child; and, possibly the most important, the best strategy to improve the child's adherence to our exercise recommendations. Three reports in this issue of Arthritis Care & Research offer some answers to these questions (5–7). Studies by van Brussel et al and Lelieveld et al add important information to the discussion about exercise capacity and its relationship to functional ability in children with JIA, while the third article, a report by Feldman and colleagues, discusses the impact of adherence to medical and exercise recommendations on outcomes in children with chronic arthritis and offers valuable suggestions for clinical practice.
Van Brussel et al compare aerobic and anaerobic exercise capacity in Dutch children with JIA with matched healthy controls (5), while Lelieveld et al examine the same attributes in adolescents with arthritis attending a JIA transition outpatient clinic (6). These studies were both conducted in the same exercise laboratory using the same exercise testing protocol. The combined sample of 87 subjects with JIA, ranging in age from 6.7–18 years, is a larger cohort than in any previous single study of exercise capacity. The results of both studies demonstrated significant impairments in aerobic and anaerobic capacity in most subjects with JIA compared with healthy controls. These findings agree with previous reports, but also strengthen their conclusions in several ways that emphasize the magnitude and pervasiveness of these impairments. Van Brussel et al report that 59 (95%) of 62 subjects had impaired aerobic capacity and 54 (94%) had impaired anaerobic power, suggesting that this is an almost universal problem in children with JIA. By reporting their subjects' exercise capacity in terms of the percent of predicted values for healthy controls, the results of these studies also indicate that the magnitude of these impairments is large. Finally, by using currently approved definitions of disease activity based on the Paediatric Rheumatology International Trials Organisation (PRINTO) core set criteria (8) to classify patients, these studies provide a model that should allow comparison of outcomes across studies, something that previously has been difficult.
The fact that anaerobic capacity is reduced in children with JIA is not surprising. Work by several groups suggests that muscle atrophy and weakness are common clinical findings that occur early in the disease process, are often generalized to muscle groups far from inflamed joints (9), and may be cumulative over time as each episode of active inflammation takes its toll on the body (10, 11). The study by Lelieveld et al (6) adds to our knowledge of the relationship among physical fitness, performance of daily activities, and health-related quality of life by showing a significant and strong correlation between anaerobic capacity and functional ability, measured by the Childhood Health Assessment Questionnaire (C-HAQ) disability index (DI), as well as the visual analog scale (VAS) scores for pain and overall well-being. Simply put, subjects who were more physically fit reported feeling better and having less difficulty with daily activities. As the researchers point out, anaerobic power is necessary for activities that require short, explosive bursts of muscle force, including rising to stand from the floor, ascending steps, jumping, hopping, throwing or kicking a ball, and running short distances. Many physical activities of young children are anaerobic in nature, as their play often involves short but intense periods of high energy interspersed with longer periods of low-intensity activity. A previous study by Takken et al also found that anaerobic power correlates significantly to C-HAQ DI, as well as to scores on 5 of the 8 individual categories of the questionnaire (12). Mean power was most strongly associated with hygiene, dressing and grooming, and eating (activities that typically require short periods of energy expenditure). Scores on the activities subscale did not correlate with either aerobic or anaerobic capacity. This is most likely due to the ceiling effect of the original C-HAQ, which contains a limited number and variety of higher level and more complex motor skills. Work by Melson et al, presented at the American College of Rheumatology's Annual Scientific Meeting in 2005, reported that even children with well-controlled arthritis may demonstrate subtle biomechanical deficits that impact their ability to safely and successfully participate in sports (13).
These new studies add to the continuing discussion about the relationship between reduced fitness and disease status. The researchers found little difference in fitness levels between subjects who had active disease and were taking medications and those who were in clinical remission and not taking medications. This supports the current view that exercise capacity is not significantly related to disease status in JIA. What appear to be more important than either disease activity or duration are sex and disease type. Van Brussel et al found the largest deficits in exercise capacity in children with positive rheumatoid factor polyarticular-onset JIA, and the smallest impairments in those with persistent oligoarticular-onset JIA. Both studies reported that aerobic and especially anaerobic capacity are more impaired in girls than boys; while this mirrors the typical sex differences in healthy children, it is important to remember that girls with JIA in these studies were compared with an age-matched and sex-matched control group. The findings of significant impairments in exercise capacity in adolescents with JIA challenge any notion that children may “outgrow” their arthritis or recover their functional capacity simply by getting older. Adolescents with JIA who have impaired fitness due to a sedentary lifestyle may be at increased risk for poor fitness in the middle and later adult years, when muscle mass and strength naturally decline. Impairments in muscular power may contribute to activity limitations, poor neuromuscular performance, and decreased participation in sports among adolescent girls with JIA even when their disease is well controlled or inactive.
These studies suggest that we cannot take a one-size-fits-all approach to assessment and management in children with JIA. We must expand our thinking to understand the impact of each disease type on specific components of exercise capacity and, in turn, the effects of these impairments on children's functional performance. For example, adolescent girls with positive rheumatoid factor polyarticular-onset JIA may be at the greatest risk for reduced physical activity, impaired exercise capacity, and the activity limitations and participation restrictions that follow. Further studies must be done to determine if significantly impaired exercise capacity in young girls with polyarticular disease is an additional predictor of poor functional outcome in the adolescent and adult years.
Mounting evidence shows that children with JIA can improve their physical fitness through carefully structured and supervised aquatic or land-based physical conditioning programs with no increase in disease activity. A review of studies examining the effects of exercise training programs in children with JIA concluded that children who perform aerobic exercise for at least 30 minutes twice a week for 6 weeks actually experience a decrease in clinical signs and symptoms, including joint swelling, pain, and limited motion (2). The exercise regimens in most of these studies emphasized general, low-impact physical conditioning, although some studies included individualized resistance training. The new studies in this issue of Arthritis Care & Research suggest that anaerobic training may also be beneficial, particularly with regard to improving functional capacity and performance of both basic and more complex daily activities.
Van Brussel et al broach the question of whether anaerobic training is safe for children with arthritis because the activities involved are typically faster, at a higher intensity, and higher impact than those included in current general conditioning regimens for children with JIA (5). This is a legitimate concern and may depend to a great extent on a child's disease type and status. While children with clinically active polyarticular-onset JIA are the most likely to have significantly impaired anaerobic capacity, their risk for injury with high-impact activities is high. Those with clinically inactive disease may be able to safely participate in anaerobic training and improve their fitness and functional performance. Myer et al (14) recently published a single case report describing a program of specialized neuromuscular training to improve motor control and lower limb biomechanics in a 10-year-old girl with inactive oliogoarticular-onset JIA who wished to play competitive basketball. The training regimen included resistance exercises, core stability, agility drills, and plyometrics performed twice a week for 5 weeks. Post-training improvements included lower limb muscle strength, hamstring to quadriceps ratio, jumping technique and symmetry in landing, and postural control in single limb stance. There were no immediate adverse effects. Obviously, the results of a single case study cannot be generalized to other children, but this report should stimulate further research to understand the risks and potential benefits of anaerobic training in children with JIA.
Although most health professionals now agree on the importance of keeping children with JIA physically active and fit, this is easier said than done. These complex and chronic diseases require coordinated care among a multidisciplinary team; parents and children are integral members of this team and must buy into the management plan. Professionals and parents alike share a certain frustration in trying to get children to adhere to prescribed medication and exercise treatments that disrupt their daily life and often cause family conflict. The article in this issue by Feldman and colleagues (7) offers important insights to this problem by showing that even moderate adherence to recommendations for home exercise programs, based on reports by parents, was associated with positive short-term outcomes in children with JIA, including decreased perception of pain, improved functional ability and parent global assessment of health status, and better quality of life. This supports previous studies that reported decreased pain and disease symptoms and improved overall health status following participation in carefully structured and supervised exercise regimens (15, 16). As Feldman et al point out, many complications of childhood arthritis occur early in the disease course and more aggressive therapeutic approaches may be important to mitigate these problems; this may hold true for assessing exercise capacity, early intervention, and careful monitoring of the child's active participation in the exercise program.
Feldman and colleagues also queried parents on problems they experienced in managing their child's illness that negatively affected adherence to medical and exercise recommendations. Most of us are very familiar with the organizational problems that parents encounter, including difficulty in getting medical appointments, long waiting lists for physical or occupational therapy, and difficulty understanding or following the clinician's instructions. This later issue is particularly relevant with respect to exercise instruction. Unless the clinician provides clear verbal and written instructions, demonstrations, and illustrations of the exercises, as well as specific recommendations for the intensity and number of repetitions for each exercise, the parents and children may find it difficult to follow the home program. Most of us find it difficult to adhere to a daily exercise routine despite all of the research touting the health benefits and deleterious consequences of a sedentary lifestyle. Seeing immediate and periodic benefits, such as feeling better, having more energy, or fitting into a favorite outfit, tends to reinforce our resolve to exercise. Pediatric physical and occupational therapists know we must engage children and teens, as well as the parents of younger children, in setting goals for intervention that are important and meaningful to them. Clearly explaining how the recommended exercise regimen will help them meet those goals and providing regular incentives may improve the child's adherence.
This brings us to the last question. Where do we go from here? In regard to research, large, multicenter randomized controlled exercise trials would provide more definitive information about the benefits and risks associated with aerobic and anaerobic training in children with different types of JIA. However, in order to compare study results, it is essential to develop a standardized core set of outcome measures for rehabilitation interventions. Research on exercise capacity suggests that tests of aerobic and anaerobic fitness should be included; we must examine and validate field measures of these attributes that can be quickly and easily administered in the clinic. Some possible measures include the 50-meter run to assess anaerobic function, distance-based or time-based run/walk or walk-only tests to measure aerobic performance, and the physiologic cost index to estimate energy during submaximal exercise. Two measures in the current PRINTO core set of response variables that would be useful include the parent's global assessment of well-being and functional ability. The C-HAQ, the most frequently reported measure of physical function in JIA, is known to have a ceiling effect, especially in children with mild disease, leaving little room to show improvement with intervention. Lam et al (17) proposed several revised versions of the C-HAQ, like the VASCHAQ-38, that include additional items describing more complex and intense motor tasks and sports and allow the child to compare his or her performance with that of similar age children without JIA. These forms of the C-HAQ appear to be more sensitive in detecting functional difficulties and may be more responsive to changes following rehabilitation.
These new studies also provide some clear directions for clinical practice, including: 1) early referral to rehabilitation services to establish baseline measures of physical status and provide recommendations to the parent and child to maintain an active lifestyle; 2) assessment of exercise capacity or performance at diagnosis and periodical monitoring during periods of active and inactive disease, with extra vigilance for children with polyarticular disease; 3) identifying goals that are important to the child and parents; 4) providing specific, straightforward information on why exercise is necessary, how to exercise safely and effectively, how to recognize and manage post-exercise soreness and stiffness, and how exercise will help the child reach his or her goals.
Currently, few exercise videos are designed specifically for children with arthritis. A beginner's exercise DVD for young children with JIA funded by the Arthritis Foundation has recently been produced (information available from the author). Separate booklets for children and parents describe the effects of arthritis on different body systems, the importance of exercise, and safe exercise practices. An exercise DVD for older children with mild or inactive disease that emphasizes aerobic and muscular fitness and motor skills necessary for safe participation in sports is in development. There is a great need for additional products of this type to offer children with JIA a variety of options to stay physically fit and improve their health status. I encourage everyone involved in the care of children with arthritis to read the new articles in this issue and open a discussion with young patients about the importance of daily exercise in managing their health and achieving their personal goals.