Twenty-eight young healthy male subjects with an average age of 23 ± 3.9 years (mean ±s.e.m.) participated in this study. All participants were physically active, but had not participated in a structured resistance-training protocol for at least 6 months. All subjects were normotensive (< 140/90 mmHg), not obese (Table 1) and free from chronic diseases as assessed by medical history, physical examination and blood lipid levels. The McMaster Research Ethics Board approved the experimental protocol and all participants provided written informed consent before participating in the study.
Participants completed 12 weeks (up to 60 sessions) of whole-body resistance training to induce muscle hypertrophy. Using a 3-day split routine (pushing, pulling and leg exercises), participants completed resistance-training sessions five times per week on a rotating schedule. The pull session consisted of parallel arm pull-down, seated wide grip row, seated narrow grip row, reverse fly and biceps curl. The push session included shoulder press, bench press, vertical bench press, triceps extension and chest flys. Finally, the leg session consisted of extension, curl, incline press and seated calf raises. Participants exercised based on one of the predetermined regimens, either pull, push or legs, on the first day of the week and rotated to the subsequent exercise regimen the following day. This continued throughout the 60 sessions of the overall training protocol. Training was conducted in the fitness centre on the McMaster University Campus. Sessions were held on Monday to Friday. Participants were instructed not to participate in other resistance-type exercises. Also, participants who were aerobically active (two sessions maximum per week) were asked to maintain their activity level, while those not participating in aerobic activity were instructed to abstain from such activities.
Prior to training, participants were familiarized with the resistance-training equipment. Motion-guided machines were employed due to ease of use and adjustment and to minimize potential participant injury. Each training session lasted approximately 1 h. One repetition maximum (1RM) lifts were performed on each equipment four times: prior to the initiation of training, following the 4th, 8th and the 12th week of training. The 1RM testing performed at each time point was coordinated to coincide with the appropriate day of the 3-day cycle.
Measurements of fat- and bone-free mass were obtained prior to and following the training protocol using dual photon X-ray absorbsiometry (DXA: Model QDR-1000/W, Hologic Inc., Waltham, MA, USA). Following a familiarization session, arterial compliance, intima–media thickness (IMT), heart dimensions and resting brachial BP were measured prior to the initiation of training, once during the seventh, and the twelfth week of training with the same investigator conducting all the tonometry measurements. The procedures involving BP, cardiac and arterial measurements were conducted using an identical protocol under the same control conditions at all time points. Measurements were obtained a minimum of 24 h following the last training session and at the same time of the day (within ∼2 h). Testing sessions were conducted at the same time of the day for each individual participant. Participants were asked to abstain from nicotine and caffeine for at least 12 h prior to testing and evaluations were made ∼4 h after the consumption of 237 ml of a commercial meal replacement (BOOST, Mead Johnson Nutritionals, Ottawa, ON, Canada). All measurements were obtained with participants in the supine position in a temperature-controlled room (21–24°C). Measurements of blood pressure were taken in a dimly lit room.
Upon arrival, participants were instrumented with an oscillometric automated BP measurement device (model CBM-7000, Colin Medical Instruments, San Antonio, TX, USA) and instructed to lie motionless for 10 min. Measurements of brachial systolic (SBP), diastolic (DBP), pulse pressure (PP), and calculated mean arterial pressure (MAP =⅓(PP) + DBP) were obtained in triplicate at intervals of 2 min. As described by Carter et al. (2003), the first measurement of arterial BP from the automated sphygmomanometer is consistently high. Thus, the average of the last two measures was used to determine resting brachial BP.
Central arterial compliance was assessed at the common carotid artery according to the method described by Miyachi et al. (2003). The main difference involved calibration of carotid blood pressure to arterial blood pressure measured continuously using arterial tonometry at the wrist rather than by an arm cuff. Ten measurements of arterial BP and two measurements of arterial diameter change were used to determine cross-sectional compliance. Beat-by-beat changes in BP were obtained in the radial and carotid arteries using two applanation tonometry instruments. Continuous automated radial artery BP was measured (CBM-7000, Colin Medical Instruments, San Antonio, TX, USA), while at the carotid artery a manual pen-like device containing a high-fidelity transducer (model SPT-301, Millar Instruments Inc., Houston, TX, USA) was used to obtain continuous BP waveforms. Carotid artery BP was obtained in the right carotid artery while ultrasound images were obtained simultaneously in the left carotid artery.
The pen-like arterial tonometer (Millar) is sensitive to manual hold-down pressure; thus requiring adjustment of the obtained values based on several assumptions (Kelly et al. 1989). Briefly, it was assumed that DBP and MAP are similar in all conduit arteries when an individual is in the supine position (Nichols et al. 1998) while SBP is amplified through the arterial tree. The mean and minimum BP obtained from the carotid waveform were equated to the MAP and DBP of the radial artery. The maximum BP waveform recorded in the carotid artery was then used as an extrapolation point from the calibrated MAP and DBP (Kelly et al. 1989).
Arterial and cardiac images were obtained using B-Mode Ultrasound (System FiVe, GE Medical Systems, Horten, the Netherlands). For arterial images, a 10-MHz linear array probe was positioned longitudinal to the left carotid artery and an image ∼2 cm proximal to the bifurcation that divides the vessel into the external and internal portions of the artery was obtained. Two video clips of one complete heart cycle were obtained and digitally stored at a frame rate of 12 frames/s for off-line analysis of diameter change. Participants were also instrumented with an electrocardiograph (model Cardiomatic MSC 7123, Medical Systems Corp, Miami, Fl, USA) for simultaneous recording of R–R intervals. All physiological measurements of HR and BP were input to a data acquisition board (Powerlab model ML795, ADInstruments, Colorado Springs, CO, USA) for analog to digital conversion and stored on a personal computer (IBM Netvista X86 compatible processor, White Plains, NY, USA) using available software (Chart 4.2, ADInstruments) with analog signals sampled at 200 Hz. Digital images obtained with B-mode ultrasound were converted to digital imaging and communication in medicine (DICOM)-compressed JPEG stacked image files for further analysis using automated software (AMS II, Chalmers University of Technology, Göteborg, Sweden).
During semi-automated artery analysis the arterial diameter from leading edge to leading edge was assessed for all frames of the digital video clip. A minimum of 100 measurements of vessel diameter was used to obtain a mean arterial diameter for each frame. The maximum and minimum diameters obtained during the heart cycle were then used to determine diameter change. Subsequently, the two measurements of diameter change were used to calculate cross-sectional compliance (CSC) (Miyachi et al. 2003):
where, CSC is cross-sectional compliance, PP is pulse pressure, r is the radius of the artery, d is diameter of the artery, max is the maximal value and min is the minimal value. While β-stiffness index, β was calculated as (O'Rourke et al. 2002):
IMT was determined through automated determination of the proximal aspect of the intima and the proximal interface of the adventitia based on gradient and intensity differences from pixel to pixel. The average IMT from two images of the common carotid artery were compared at each time point.
Left ventricular dimensions and functional characteristic measurements were made in a subset of 19 participants after selection of the most appropriate images available for analysis. Images obtained from nine of the participants were either improperly aligned or of insufficient quality to warrant analysis at one of the three time points. Two B-mode full heart cycle high-resolution (60 Hz) video clips obtained in the parasternal long axis were acquired while subjects were positioned in the left lateral decubitus position. One additional M-mode image was taken according to the American Society of Echocardiography guidelines when the orientation of the heart was appropriate. Digital video clips and appropriate M-mode images were subsequently transferred for off-line analysis using commercially available software (Echopac 6.4.2, GE Medical Systems, Horten, the Netherlands).
Analysis of heart images involved the use of anatomical M-mode. This feature allows B-mode digital videoclips, acquired in the parasternal long axis, to be reconstructed as M-mode images. This enables the inclusion of patients with heart orientations that are not ideal for typical M-mode acquisition. Once anatomical M-mode images were constructed, subsequent analysis was conducted (Sahn et al. 1978). Intra-observer and inter-observer coefficients of variability (CV) ranged from 4.5 to 11% and 6 to 12%, respectively, for various individual cardiac parameters (e.g. intraventricular septum during systole (IVSs)).