Broad Spectrum Polyphenol Supplementation from Tart Cherry Extract on Markers of Recovery from Intense Resistance Exercise

BACKGROUND: Tart cherry supplementation has been shown to enhance recovery from strenuous exercise due to its antioxidant properties. The majority of these studies used tart cherry juice, with a significant calorie content. The primary purpose of this study was to assess whether powdered tart cherry extract with minimal calorie content reduces oxidative stress and enhances recovery following intense resistance exercise. METHODS: Thirteen men (mean age: 26.2 ± 5.3 years; height: 184.3 ± 8.2 cm; weight: 92.9 ± 15.6 kg) performed a demanding resistance exercise protocol consisting of 6 sets of 10 repetitions of barbell back squat with 80% 1RM. The protocol was performed once following 7 days of 500 mg of tart cherry extract and once following placebo. Serum protein carbonyl (PC) content, creatine kinase activity (CK) and creatine kinase myocardial band content (CK-MB) were used to assess oxidative stress, skeletal and cardiac muscle damage respectively. Muscle soreness was assessed by visual analog scale. Physical performance was measured by countermovement jump power and handgrip dynamometer strength. RESULTS: There was a significant increase in PC in the placebo (PL) condition when compared to the Tart Cherry (TC) condition at Immediate Post (IP) (PL: 0.4 ± 0.3 vs. TC: − 0.4 ± 0.2 nmol∙mg(− 1); p < 0.001), 1 h (PL: 0.3 ± 0.3 vs. TC: − 0.7 ± 0.3 nmol∙mg(− 1); p < 0.001) and 24 h (PL: 0.1 ± 0.4 vs. TC: − 0.3 ± 0.5 nmol∙mg(− 1); p = 0.010). There was a significant increase in CK activity in PL when compared to the TC at IP (PL: 491.1 ± 280 vs. TC: 296.3 ± 178 U∙L(− 1); p = 0.008) and 3 h (PL: − 87 ± 123 vs. TC: 43.1 ± 105.3 U∙L(− 1); p = 0.006). There was a significant (p = 0.003) increase in CKMB concentration in PL when compared to the TC (PL: 21.6 ± 12.4 vs. TC: − 0.3 ± 11.8 ng∙ml(− 1); p = 0.006) at 1 h post. There was a significant increase in handgrip strength in TC when compared to PL (PL: − 2 ± 5.1 vs. TC: 1.7 ± 3 kg; p = 0.017) at 24 h post. CONCLUSIONS: This study demonstrated that tart cherry extract reduced oxidative stress and markers of muscle and cardiac damage following intense resistance exercise. This occurred along with a prevention of the decrease in handgrip strength seen following the intense exercise protocol, indicating a potential reduction in central fatigue. These benefits were seen with minimal energy intake.