Is Metabolic Adaptation An Indicator Of Non-functional Overreaching In Older Women?

Healthy exercise adaptation balances progressive overload with adequate recovery. Since aging and menopause affect physical function, it is crucial to understand how training volume influences biomarkers of health and performance in older women. PURPOSE: Previous data has shown that high-volume weekly training adversely affects free-living physical activity in older women. In the present work, secondary analyses were performed comparing changes in resting metabolic rate (RMR), vascular biomarkers, and aerobic capacity occurring between 16 and 32 weeks of training in older women. METHODS: A subset of 42 older women (age = 65 ± 4 y; BMI = 26.6 ± 4.0 kg/m2) who completed 32 weeks of supervised exercise training were evaluated. Randomization to group assignment was based on days per week of aerobic and resistance training frequency: A [1 + 1], B [2 + 2], or C [3 + 3]. Considering prior work, training frequency A and B were pooled (n = 30) and compared to training frequency C (n = 12). Indirect calorimetry and DXA were used to measure RMR and body composition, respectively. Pulse contour analysis from the radial artery was used to measure resting blood pressure and systemic vascular resistance. A graded treadmill test was used to measure maximal aerobic capacity (V̇O2max). Regression modeling including age, fat mass, and fat-free mass were used to predict RMR. Metabolic adaptation was defined as a significantly lower measured compared to predicted RMR. Univariate analyses were performed accordingly. RESULTS: A significant time by group interaction was found, with a greater metabolic adaptation in response to training volume C compared to training volume A + B (-44 ± 101 kcal/d vs. 50 ± 130 kcal/d; p = 0.031, ηp2 = 0.11). Training volume C also exhibited a significantly increased systolic (9 ± 18 mm Hg vs. -1 ± 11 mm Hg; p = 0.030, ηp2 = 0.10) and diastolic (5 ± 7 mm Hg vs. -1 ± 6 mm Hg, p = 0.007, ηp2 = 0.15) blood pressure compared to training volume A + B. No differences were observed for systemic vascular resistance or V̇O2max. CONCLUSION: Identification of physiological biomarkers indicative of non-functional overreaching remain elusive. Nevertheless, the present work suggests that high-volume weekly training including 3 aerobic and 3 resistance sessions per week is contraindicated to maximally enhance health and performance in older women. Supported by: National Institutes of Health: R01AG027084, R01AG027084-S, and P30DK056336.