Influence Of Aerobic Exercise On Non-exercise Physical Activity: Midwest Exercise Trial-2 (MET-2)

Introduction Compensatory changes in non-exercise physical activity (NEPA) in response to an aerobic exercise training program may impact weight loss.

Purpose To examine changes in NEPA in response to 2 levels of aerobic exercise training.

Methods Ninety-two overweight/obese (BMI 25-39.9) sedentary young adults (18-30 yrs.) completed (i.e. ≥ 90% scheduled exercise sessions) a 10-mo. trial of aerobic exercise (5 days/wk.,70-80% max heart rate, supervised ≥4 days/wk.) at either 2,000 (n = 37; 19 females) or 3,000 (n = 37; 18 females) kcal/wk. or served as non-exercise controls (n = 18, 9 females. NEPA was assessed over 7 consecutive days by accelerometer (ActiGraph Model GT1M) at baseline, 3.5, 7 and 10 mos. Mixed modeling was used to examine differences between groups (group effect), within groups (time effect) and group-by-time interaction for NEPA assessed as average counts/min, and time spent sedentary ( 5999 counts/min) intensity PA.

Results Within the exercise groups (2,000 and 3,000) N=74, there were no significant effects (all p > 0.05) of group, time, or group- by-time interactions for NEPA assessed as counts/minute, sedentary time, or time spent in light, moderate or vigorous intensity PA. However, activity counts/min were significantly higher (p < 0.001) in the 3,000 kcal/wk. group (346±141min.) vs. controls (290±106min.) at 7 mos. and significantly higher (p < 0.001) in both the 3,000 kcal/wk. (345±163min.) and 2,000 kcal/wk. groups (317±146min.) vs. controls (277±116min.) at 10 mos. Although non-significant, sedentary time increased slightly (+2.3%) in controls and decreased in both the 2,000 kcal/wk. (-6.2%) and 3,000 kcal/wk. groups (-4.3%).

Conclusions A 10-mo. aerobic exercise training program at either 2,000 or 3,000 kcal/wk. was not associated with compensatory changes in NEPA. However, the observation of significantly higher levels of NEPA (counts/min) and lower sedentary time in exercisers vs. controls suggest that, contrary to conventional wisdom, overweight and obese individuals do not become less physically active or spend more time in sedentary pursuits in response to exercise. Supported by NIH R01 DK49181