The effects of polyphenol supplementation on muscular strength, power, and soreness following eccentric exercise
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An acute bout of unaccustomed eccentric exercise causes prolonged strength loss and delayed onset muscle soreness (DOMS) for several days. Chronic dietary supplementation with polyphenols, from pomegranates, has been shown to accelerate recovery following eccentric exercise, but the optimal dose is unknown. The purpose of this study was to determine the effect of dietary supplementation with different doses of pomegranate juice concentrate (PJC) on muscular strength, power, and soreness throughout a 96-hour time period following an acute bout of eccentric exercise. Healthy recreationally active males (n=45) were assigned to one of three treatment groups: Once-daily PJC (1x), twice-daily PJC (2x), or placebo (PLA) supplementation over a period of eight days. A 1x dose of PJC provided approximately 650 mg GAE. On day four of each treatment, subjects performed downhill running intervals (-10% grade) over a 40-minute period followed by 40 repetitions of eccentric elbow flexion at 100% of concentric 1-RM. Muscle soreness of arms and legs, maximal isometric strength of the elbow flexors (EF) and knee extensors (KE), vertical jump height (VJ[subscript height]) maximal cycling power (P[subscript max]), and 10-meter sprint velocity (V[subscript 10m]) were assessed pre-exercise and 2, 24, 48, 72, 96 hours post-exercise. Additionally, maximal instantaneous power (IP[subscript max]), maximal velocity (V[subscript max]), maximal torque (T[subscript max]), and torque at 0° (T0) were assessed on the inertial load power cycle pre-exercise and 24, 48, 72, 96 hours post-exercise. Throughout the 96-hours post-exercise, isometric EF strength was significantly higher in 1x and 2x groups as compared to PLA (main treatment effect, 83.6 ± 2.7% vs. 85.6 ± 1.9% vs. 78.4 ± 1.8%, respectively; p < 0.001). Isometric KE strength was significantly higher in 1x and 2x groups as compared to PLA (main treatment effect, 93.9 ± 1.5% vs. 91.6 ± 1.5% vs. 87.1 ± 1.8%, respectively; p < 0.001). Both VJ and V10m were significantly higher in 1x compared to PLA (main treatment effect, 99.9 ± 0.9% vs. 98.0 ± 1.0%, respectively, p = 0.037; 100.0 ± 0.8% vs. 97.8 ± 0.7%, respectively, p = 0.003). Muscle soreness and Pmax, were similar at all time points between groups. We conclude that dietary supplementation with 1x or 2x PJC results in higher isometric strength values compared to placebo for EF and KE muscles during the 96-hour period after an acute bout of eccentric exercise.