Impact of supervised aerobic exercise training on habitual physical activity in healthy older adults: the Hertfordshire physical activity randomised controlled trial

Objectives: Physical activity is important for health, but the influence of structured, supervised aerobic exercise sessions on habitual physical activity in healthy older adults is unclear. Methods: We evaluated habitual physical activity in the Hertfordshire Physical Activity Trial, where healthy older adults were randomised to 36 supervised 1-hour gymnasium sessions on a cycle ergometer at moderate intensity over 12 weeks or to a control group with no intervention. We estimated physical activity energy expenditure (PAEE) and time spent in sedentary behaviour and light and moderate or vigorous physical activity over 7 days at three time points (before, during and immediately after the intervention) with individually calibrated combined heart rate and movement sensing. Results: Of 100 randomised participants (44% female, aged 67-76 years), 96% completed follow-up. Midway through the intervention, neither overall PAEE nor time spent at different intensities were different between groups. However, on the 3 days of the week that the structured exercise sessions occurred (Monday, Wednesday, Friday), the exercise group had a 9.1 kJ kg^-1 day^-1 ((2.5, 15.7), p=0.007) increase in PAEE, a reduction in sedentary time and increased time spent at light and moderate or vigorous physical activity, compared with the control group. Conclusions: Three 1-hour bouts per week of structured aerobic exercise increased daily physical activity on the days they occurred, but not overall physical activity across the whole week. Population-wide strategies such as better cycling and walking infrastructure may increase physical activity in healthy older adults more effectively than treatment with structured exercise programmes. Trial registration number: ISRCTN60986572.