Volume of exercise and fitness nonresponse in sedentary, postmenopausal women.
Level 2 - randomized trial
Secondary analysis of a randomized controlled dose-response trial
PubMed 19204597 · doi:10.1249/MSS.0b013e3181896c4e
What was done
A secondary analysis of the Dose Response to Exercise in Women (DREW) randomized controlled trial examined predictors of maximal aerobic fitness (VO2max) nonresponse. Sedentary postmenopausal women aged 45-75 years were randomized to one of three exercise training doses for 6 months: 4, 8, or 12 kcal x kg(-1) x wk(-1), exercising 3-4 days per week at 50% VO2max. The control group was excluded, leaving 310 women for analysis. Logistic regression evaluated age, BMI, baseline VO2max, ethnicity, and treatment dose group as predictors of nonresponse, which was defined as a change in VO2max <= 0 L x min(-1).
What was found
Nonresponders comprised 44.9% of the 4-, 23.8% of the 8-, and 19.3% of the 12-kcal x kg(-1) x wk(-1) treatment groups (P < 0.0001). Significant predictors of nonresponse were treatment group (P = 0.0003), baseline VO2max (P < 0.0001), and age (P < 0.05). Odds ratios (95% CI) for nonresponse were 0.45 (0.24-0.85) for the 8- vs 4-kcal group, 0.27 (0.13-0.53) for the 12- vs 4-kcal group, 2.13 (1.53-2.95) for baseline VO2max, and 1.35 (1.00-1.83) for age. Maximal effort, BMI, age, and race significantly predicted baseline VO2max.
Why it matters
Fitness nonresponse to aerobic training is partly volume-dependent, showing that higher exercise doses substantially decrease the probability of failing to increase VO2max.
Limits
The study included only sedentary postmenopausal women aged 45-75 years, limiting generalizability to men, younger women, or other populations. Nonresponse was defined strictly by VO2max change <= 0 L x min(-1), without assessing other potential physiological or health benefits. The non-exercise control group was excluded from this analysis.
Cited by
- context Roughly 40 percent of people who engage in guideline-based moderate-intensity continuous exercise for six months do not show a measurable improvement in VO2 max.