Effects of an 8-month exercise training program on off-exercise physical activity

Abstract

Purpose: An active lifestyle is widely recognized as having a beneficial effect on cardiovascular health. However, no clear consensus exists as to whether exercise training increases overall physical activity energy expenditure (PAEE) or whether individuals participating in regular exercise compensate by reducing their off-exercise physical activity. The purpose of this study was to evaluate changes in PAEE in response to aerobic training (AT), resistance training (RT), or combined aerobic and resistance training (AT/RT).

Methods: Data are from 82 participants in the Studies of Targeted Risk Reduction Interventions through Defined Exercise-Aerobic Training versus Resistance Training study, a randomized trial of overweight (body mass index = 25-35 kg·m(-2)) adults, in which participants were randomized to receive 8 months of AT, RT, or AT/RT. All subjects completed a 4-month control period before randomization. PAEE was measured using triaxial RT3 accelerometers, which subjects wore for a 5- to 7-d period before and after the exercise intervention. Data reduction was performed with a previously published computer-based algorithm.

Results: There was no significant change in off-exercise PAEE in any of the exercise training groups. We observed a significant increase in total PAEE that included the exercise training, in both AT and AT/RT but not in RT.

Conclusions: Eight months of exercise training was not associated with a compensatory reduction in off-exercise physical activity, regardless of exercise modality. The absence of compensation is particularly notable for AT/RT subjects, who performed a larger volume of exercise than did AT or RT subjects. We believe that the extended duration of our exercise training program was the key factor in allowing subjects to reach a new steady-state level of physical activity within their daily lives.

FIGURE 1

Graphical representation of a typical day's accelerometer data.

FIGURE 2

Change score by group for total PAEE (A) and off-exercise PAEE (B). Error bars indicate SE. Although the control period (which includes the change that occurred during the run-in period in all 82 subjects) has been included in this figure for visual comparison only, there were no statistical comparisons between the control period data and the exercise groups. The only statistical comparisons were between the three independent exercise training groups. †Significant difference from RT (P < 0.05).

FIGURE 3

Total caloric expenditure per week in AT and RT. Average weekly energy expenditure from AT workouts was calculated, using our 14-kcal·kg⁻¹·wk⁻¹ target for each participant, along with the preexercise weight of each participant in our AT only and AT/RT groups (average preexercise weights of subjects in these groups were 95.4 kg for men and 84.1 kg for women). Average weekly RT energy expenditure was estimated by multiplying the average caloric expenditure from one RT workout (measured both with indirect calorimetry and RT3 accelerometer) by three, given that RT subjects were asked to complete three workouts per week.