Effects of short‐term protein supplementation on muscle work efficiency in elderly adults

Abstract

ObjectiveThis study assessed the effect of increased dietary protein intake on adaptation of energy expenditure and skeletal muscle function at rest and during low‐intensity physical activity in elderly adults.MethodsUsing a randomized, crossover design, 12 adults (7 F, 5 M), aged 82 ± 7 y (mean ± SD) completed two 6‐day periods of consuming fruit‐smoothie beverages twice daily (with breakfast and lunch) containing 230 kcal and 25 g whey protein (WPro) or 25 g corn‐derived glucose polymer (CHO) (total 460 kcal/day and 50 g/day WPro or CHO).ResultsOn day 7 of each period, fasting blood urea nitrogen was 28 ± 9% higher in WPro vs. CHO (P=0.003), consistent with higher total protein intake. Fasting state energy expenditure and respiratory ratio at rest and while exercising on a stationary cycle at 1, 10, 20 watts were not different between WPro and CHO. Gross mechanical efficiency of skeletal muscle progressively increased from 1 to 10 to 20 watts, but this response was not different between WPro and CHO.ConclusionShort‐term supplementation with either whey protein or glucose polymer does not differentially influence fasting state whole body substrate utilization or skeletal muscle work efficiency in elderly adults.Support: NIH CTSI Grant # TR000006