Effects of Aerobic Exercise on Muscle Strength and Physical Performance in Community‐dwelling Older People from the Hertfordshire Cohort Study: A Randomized Controlled Trial

There is considerable interest in the role of physical activity interventions to address the age-related loss of skeletal muscle mass. Resistance exercise has consistently been associated with improvement in muscle strength and physical performance (PP) in older adults, but the influence of aerobic exercise on these outcomes is less clear. Studies of the influence of aerobic exercise on muscle have typically taken place in specific patient populations and less so in older people. The effects of a fully supervised 12-week aerobic exercise intervention on muscle strength and PP were studied in the community-dwelling healthy older men and women who participated in the Hertfordshire Physical Activity Trial (HPAT),1 a substudy of the Hertfordshire Cohort Study.2 The HPAT has been described previously.1 In brief, 100 men and women (aged 67–76, 44% female) were randomized to an aerobic exercise program or a nonintervention control group; 96 attended 12-week follow-up. The exercise group participated in fully supervised 1-hour sessions on a cycle ergometer three times weekly over 12 weeks, with exercise intensity maintained using heart rate monitoring. Participants in the control group were asked to continue with their usual level of physical activity. Staff unaware of group allocation assessed muscle strength and PP at the beginning and end of the study using a Jamar dynamometer to assess grip strength3 and a PP battery including a 6-meter timed up and go (TUG) test,4 timed 3-meter walk, chair rises, and one-leg balance.5 Multilevel linear regression models were used to analyze differences in change from baseline in muscle strength and each PP measure between the exercise and control groups. The study had ethical approval from the Hertfordshire Local Research Ethics Committee (ref. 05/Q0201/23). All participants gave written informed consent. There was a 0.75-second (95% confidence interval (CI) = 0.03–1.48 seconds) greater improvement in the TUG performance in the exercise group compared with the control group (P = .04). Average TUG times decreased from 11.0 ± 2.0 seconds at baseline to 10.2 ± 1.6 seconds at follow-up in the exercise group, with no change in the control group (Table 1). The improvement in TUG performance in the exercise group was slightly greater in men (0.87 seconds; 95% CI = −0.06 to 1.81) than women (0.57 seconds; 95% CI = −0.56 to 1.70). There were no significant differences between groups in change in grip strength, 3-m walk, one-leg balance, and chair rise time over the 12-week follow-up. Restriction to the per-protocol sample of 85 participants (37 exercise, 48 controls) who completed 85% of their exercise sessions did not alter the results. The literature describing the effects of aerobic exercise on skeletal muscle function is limited. One study investigated the effect of a dance-based aerobic exercise intervention on indices of falling in older Japanese women; the exercise group showed significantly better one-leg balance, functional reach, and faster walking time around two cones than a control group but no significant changes in strength or motor processing measurements.6 Two studies compared the effect of aerobic with that of resistance exercise on muscle strength and PP in older people.7, 8 The results suggested that aerobic exercise improved measures of PP such as gait speed and balance, whereas resistance exercise was necessary to improve muscle strength. Randomized controlled trials of combined resistance and aerobic exercise interventions have demonstrated improvements in PP and muscle strength.9, 10 Previous exercise interventions have typically been conducted in specific patient populations; a strength of HPAT is that all participants were drawn from a population-based sample. A limitation of HPAT is that the recruitment rate was low (18%), possibly owing to the commitment and intensive phenotyping required from participants. Physical activity levels typically decline in later life. Effective community-based interventions to increase physical activity with a view to improving muscle strength and PP must be attractive and manageable for older people; aerobic exercise activities could constitute an important part of such interventions. Further research is required to assess the longer-term effects of different types of physical activity on muscle strength and PP outcomes in older people. The study was funded by the Medical Research Council (grant codes MC-U106179471, MC-U106179474, MC-UP-A620–1 014, and MC-UP-A620–1015). We thank the HPAT study group and the study participants for making this work possible. Conflict of Interest: The editor in chief has reviewed the conflict of interest checklist provided by the authors and has determined that the authors have no financial or any other kind of personal conflicts with this paper. Author Contributions: Finucane, Griffin, Wareham, Cooper, and Aihie Sayer: designed the study and took overall responsibility for it. Denison, Syddall, Martin, and Dodds: conducted and interpreted the statistical analysis and prepared the manuscript. All authors reviewed and approved the final manuscript. Sponsor's Role: The sponsors had no role in the design, methods, participant recruitment, data collection, analysis, or preparation of the paper.