D2O to determine muscle protein synthesis rates in response to post‐exercise nutrition in adults

Muscle protein synthesis (MPS) is acutely stimulated by either endurance exercise or protein consumption, but the long‐term and combined effects in older adults are unknown. We used deuterium oxide (D 2 O) to evaluate long‐term effects of post‐exercise nutrition and endurance training on MPS. Sedentary adults (n=16, 50±8 yrs) performed 6‐wks of endurance training and consumed either a carbohydrate (CHO) or carbohydrate and protein (PRO) drink after exercise. D 2 O (50 ml tid) was administered during the training period to maintain body water pool enrichment at 1–2%. VO 2 max was measured pre‐ and post‐training as a surrogate for mitochondrial function. MPS over the 6‐wks was determined from total percipitable protein in a 10–20 mg muscle biopsy by gas chromatography‐mass spectroscopy. Training increased (p<0.05) VO 2 max in the PRO (25.5 ± 4.2 to 28.1±3.9 ml/kg/min) but not in CHO group (31.1 ±7.1 to 32.5 ±9.1 ml/kg/min). MPS was not different between CHO and PRO groups (0.06 ± 0.004 vs. 0.05 ±0.003 %/day, p=0.23). Although MPS was not different between CHO and PRO, the VO 2 max increase with PRO suggests post‐exercise nutrition may impact aerobic training adaptations. Further analysis will evaluate long‐term mitochondrial proliferation. Our use of D 2 O provides novel insight into long‐term synthesis rates in aging humans. Funding from The Colorado Nutritional Research Unit.