Volume of Exercise and Fitness Nonresponse in Sedentary, Postmenopausal Women

SISSON, S. B., P. T. KATZMARZYK, C. P. EARNEST, C. BOUCHARD, S. N. BLAIR, and T. S. CHURCH. Volume of Exercise and Fitness Nonresponse in Sedentary, Postmenopausal Women. Med. Sci. Sports Exerc., Vol. 41, No. 3, pp. 539 545, 2009. There is a wide individual heterogeneity in the maximal aerobic fitness ((V) over dot(2max)) response to exercise training. PURPOSE: To examine predictors of (V) over dot(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.kg(-1).wk(-1) for 6 months. Participants exercised 3-4 d.wk(-1) at 50% (V) over dot(2max)). Predictors of baseline (V) over dot(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) over dot(2max)) to determine predictors of nonresponse (Delta <= 0 L.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.kg(-1).wk(-1) treatment groups (P < 0.0001), respectively, were nonresponders. Maximal effort, BMI, age, and race significantly predicted baseline (V) over dot(2max)). Treatment group (8 and 12 kcal.kg(-1).wk(-1) vs 4 kcal.kg(-1).wk(-1)); P = 0.0003), baseline (V) over dot(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) over dot(2max); 1.35 (1.00-1.83) for age; 0.45 (0.24-0.85) for the 8- versus the 4-kcal.kg(-1).wk(--1) group; and 0.27 (0.13-0.53) for the 12- versus the 4-kcal.kg(-1).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.