There is a wide individual heterogeneity in the maximal aerobic fitness (V x O 2max) response to exercise training.
Purpose: To examine predictors of V x O 2max nonresponse after aerobic exercise training in postmenopausal women.
Methods: The Dose Response to Exercise in Women (DREW) study was a randomized, controlled trial examining the effects of incremental training doses on sedentary postmenopausal women (45-75 yr). Participants were randomized to one of three exercise treatment groups (4, 8, or 12 kcal x kg(-1) x wk(-1)) for 6 months. Participants exercised 3-4 d x wk(-1) at 50% V x O 2max. Predictors of baseline V x O 2max were determined by ANOVA. We used a logistic regression analyses with categorical (ethnicity and treatment group) and standardized continuous variables (age, body mass index [BMI], and baseline V x O 2max) to determine predictors of nonresponse (Delta <or= 0 L x min(-1)). Our analysis included 310 women because the control group was excluded.
Results: A total of 44.9%, 23.8%, and 19.3% of the 4-, the 8-, and the 12-kcal x kg(-1) x wk(-1) treatment groups (P < 0.0001), respectively, were nonresponders. Maximal effort, BMI, age, and race significantly predicted baseline V x O 2max. Treatment group (8 and 12 kcal x kg(-1) x wk(-1) vs 4 kcal x kg(-1) x wk(-1); P = 0.0003), baseline V x O 2max (P < 0.0001), and age (P < 0.05) were significant predictors of nonresponse. Odds ratios and 95% confidence intervals were 2.13 (1.53-2.95) for baseline V x O 2max; 1.35 (1.00-1.83) for age; 0.45 (0.24-0.85) for the 8- versus the 4-kcal x kg(-1) x wk(-1) group; and 0.27 (0.13-0.53) for the 12- versus the 4-kcal x kg(-1) x wk(-1) group.
Conclusion: Women that were younger, less fit, or exercised more during the DREW trial had greater odds of improving their fitness with training. The most important finding of this study was that greater volumes of exercise were associated with a lower probability of being a nonresponder.