Effects of a higher acute protein intake post muscle-damaging exercise on muscle recovery in older female endurance runners

Abstract

Masters endurance athletes who train and compete in organised competitive endurance events, appear to take longer to recover after muscle-damaging exercise than younger athletes. A reduced sensitivity to increase skeletal muscle protein synthesis (MPS) in response to the anabolic stimuli of protein and exercise may be contributing to the slower repair and remodelling of muscle fibres. This decreased stimulus for MPS negatively affects recovery in this older cohort of athletes, although evidence supports the notion that the ingestion of a higher dose of protein than the current recommendation of 20 grams, post muscle-damaging exercise, demonstrates improvements in muscle function of male masters triathletes. However, the efficacy for a higher protein intake in female masters endurance athletes has not been established. Chapter 2 investigates the effects of ingesting a higher acute dose of protein (40 g) compared to the current recommended dose (20 g) on muscle recovery following exercise-induced muscle damage in older female (≥48 y) endurance runners. The study assessed muscle recovery by measuring isometric maximal voluntary contraction of the knee extensors, peak countermovement jump height, perceived muscle soreness, and flexibility prior to, and at 3 and 24 hours following a downhill running protocol, used to elicit muscle damage. The study recruited six well trained female endurance runners, 48 years of age and older (mean ± SD: age; 52 ± 5.6 y, body mass; 61.4 ± 6.2 kg) to take part in three downhill running trials, each separated by one week. Participants consumed one of three energy matched (1190 kJ) recovery beverages immediately following the run. Beverage composition was either a 70 g carbohydrate placebo or one of two protein supplements; 20 g of protein and 50 g of carbohydrate, or 40 g of protein and 30 g of carbohydrate. The 40 g of protein had a likely small beneficial effect compared to the placebo (ES = 0.24 ± 0.5) and 20 g of protein (ES = 0.25 ± 0.29) for improving maximum voluntary contraction from baseline to 24 hours. The 40 g of protein had a likely small beneficial effect for improving countermovement jump height compared to 20 g of protein from baseline to 3 hours (ES = 2.9 ± 4.9), and to 24 hours compared to the placebo (ES = 0.32 ± 0.39) and 20 g of protein (ES = 0.27 ± 0.19). The 40 g of protein had an unclear effect on muscle soreness and flexibility. The findings of this current study suggest that the acute ingestion of 40 grams of whey protein isolate following muscle-damaging exercise, had a small beneficial effect on improving muscle function within 24 hours, in masters female runners.