Factors predicting adherence to 9 months of supervised exercise in healthy older women.

Background: Little is known about factors affecting adherence to highly-structured and supervised exercise programs in older people.

Methods: Healthy, inactive older (≥65 y) women (N = 30) were randomized into a 1) higher- (ATH-80% VO₂peak); 2) moderate- (ATM-65% VO₂peak) intensity aerobic; or 3) lower-intensity resistance (RTL; 50% VO₂peak) group. All 3 groups exercised 4 days·week⁻¹ for an average of 45 to 70 min·session⁻¹ over 9 months. Adherence (%) was defined as the proportion of prescribed sessions (N = 144) in which subjects achieved their 1) prescribed heart rate (intensity adherence) and 2) their prescribed duration (duration adherence). Primary determinants of adherence included prescribed intensity (METs) and prescribed duration (min), as well as age, body composition, VO₂peak, and exercise self-efficacy score.

Results: Intensity adherence was nearly 100% for all 3 groups, while duration adherence was 95%, 91%, and 85% in the RTL, ATH, and ATM groups, respectively. Prescribed exercise duration was the strongest determinant of duration adherence (r = -0.72; P < .0001), independent of prescribed METs, age, VO₂peak, and body composition.

Conclusions: Due to competing lifestyle demands, exercise intensity may be less of a factor in adherence among older women than is exercise duration.