Effects of endurance training on energy substrate partitioning during exercise in postmenopausal women

PURPOSE: To examine the effects of endurance training on changes in energy substrate partitioning during exercise in sedentary, but otherwise healthy, postmenopausal women. METHODS: Ten postmenopausal women (aged 55±1 yr) completed 12 weeks of endurance exercise training [5 days/wk, 1 h/day, 65% peak oxygen consumption (VO 2 peak)]. Whole‐body energy substrate partitioning was determined by indirect calorimetry during 60 min cycle ergometer exercise in one pre‐training exercise trial [65% VO 2 peak, PRE] and two post‐training exercise trials [65% pre‐training VO 2 peak (ABT) and 65% post‐training VO 2 peak (RLT)]. RESULTS: Endurance training increased VO 2 peak by ∼16% (1.69±0.08 to 1.95±0.08 l/min, P <0.01). Compared to PRE (0.96±0.02), respiratory exchange ratio was reduced during exercise at ABT (0.93±0.01, P =0.01 vs. PRE), but not RLT (0.95±0.01). Accordingly, endurance training reduced the %energy from carbohydrate and increased the % energy from lipid during exercise at ABT (both P <0.05 vs. PRE), but not RLT. CONCLUSION: In sedentary, healthy postmenopausal women, endurance training increased peak aerobic capacity and lipid utilization during endurance exercise at a given absolute workload. Supported by NIH grant AR42906.