BackgroundExercise-induced muscle damage (EIMD) is accompanied by localized oxidative stress / inflammation which, in the short-term at least, is associated with impaired muscular performance. Dietary antioxidants have been shown to reduce excessive oxidative stress; however, their effectiveness in facilitating recovery following EIMD is not clear. Blueberries demonstrate antioxidant and anti-inflammatory properties. In this study we examine the effect of New Zealand blueberries on EIMD after strenuous eccentric exercise.MethodsIn a randomized cross-over design, 10 females consumed a blueberry smoothie or placebo of a similar antioxidant capacity 5 and 10 hours prior to and then immediately, 12 and 36 hours after EIMD induced by 300 strenuous eccentric contractions of the quadriceps. Absolute peak and average peak torque across the knee, during concentric, isometric, and eccentric actions were measured. Blood biomarkers of oxidative stress, antioxidant capacity, and inflammation were assessed at 12, 36 and 60 hours post exercise. Data were analyzed using a two-way ANOVA.ResultsA significant (p < 0.001) decrease in isometric, concentric and eccentric torque was observed 12 hours following exercise in both treatment groups. During the 60 hour recovery period, a significant (p = 0.047) interaction effect was seen for peak isometric tension suggesting a faster rate of recovery in the blueberry intervention group. A similar trend was observed for concentric and eccentric strength. An increase in oxidative stress and inflammatory biomarkers was also observed in both treatment groups following EIMD. Although a faster rate of decrease in oxidative stress was observed in the blueberry group, it was not significant (p < 0.05) until 36 hours post-exercise and interestingly coincided with a gradual increase in plasma antioxidant capacity, whereas biomarkers for inflammation were still elevated after 60 hours recovery.ConclusionsThis study demonstrates that the ingestion of a blueberry smoothie prior to and after EIMD accelerates recovery of muscle peak isometric strength. This effect, although independent of the beverage’s inherent antioxidant capacity, appears to involve an up-regulation of adaptive processes, i.e. endogenous antioxidant processes, activated by the combined actions of the eccentric exercise and blueberry consumption. These findings may benefit the sporting community who should consider dietary interventions that specifically target health and performance adaptation.

Endurance athletes are susceptible to cellular damage initiated by excessive levels of aerobic exercise-produced reactive oxygen species (ROS). Whilst ROS can contribute to the onset of fatigue, there is increasing evidence that they play a crucial role in exercise adaptations. The use of antioxidant supplements such as vitamin C and E in athletes is common; however, their ability to enhance performance and facilitate recovery is controversial, with many studies suggesting a blunting of training adaptations with supplementation. The up-regulation of endogenous antioxidant systems brought about by exercise training allows for greater tolerance to subsequent ROS, thus, athletes may benefit from increasing these systems through dietary thiol donors. Recent work has shown supplementation with a cysteine donor (N-acetylcysteine; NAC) improves antioxidant capacity by augmenting glutathione levels and reducing markers of oxidative stress, as well as ergogenic potential through association with delayed fatigue in numerous experimental models. However, the use of this, and other thiol donors may have adverse physiological effects. A recent discovery for the use of a thiol donor food source, keratin, to potentially enhance endogenous antioxidants may have important implications for endurance athletes hoping to enhance performance and recovery without blunting training adaptations.

Eccentric exercise is known to bring about microstructural damage to muscle, initiating an inflammatory cascade involving various reactive oxygen species. This, in turn, can significantly impair physical performance over subsequent days. Taurine, a powerful endogenous antioxidant, has previously been shown to have a beneficial effect on muscle damage markers and recovery when taken for a few days to several weeks prior to eccentric exercise. However, to date no studies have looked at the effects of supplementing over the days following eccentric exercise on performance recovery. Thus, this study aimed to determine whether supplementing with taurine over three days following eccentric exercise attenuated the rise in serum creatine kinase and improved performance recovery in males. In a blinded, randomized, crossover design, ten recreationally-fit male participants completed 60 eccentric contractions of the biceps brachii muscle at maximal effort. Following this, participants were supplemented with 0.1 g∙kg−1 body weight∙day−1 of either taurine or rice flour in capsules. Over the next three mornings participants underwent blood tests for the analysis of the muscle damage marker creatine kinase and carried out performance measures on the isokinetic dynamometer. They also continued to consume the capsules in the morning and evening. The entire protocol was repeated two weeks later on the alternate arm and supplement. Significant decreases were seen in all performance measures from pre- to 24-h post-eccentric exercise (p < 0.001) for both taurine and placebo, indicating the attainment of muscle damage. Significant treatment effects were observed only for peak eccentric torque (p < 0.05). No significant time × treatment effects were observed (all p > 0.05). Serum creatine kinase levels did not significantly differ over time for either treatments, nor between treatments (p > 0.05). These findings suggest that taurine supplementation taken twice daily for 72 h following eccentric exercise-induced muscle damage may help improve eccentric performance recovery of the biceps brachii.

This study was designed to investigate the effects of alcohol consumption on recovery of muscle force when consumed immediately postexercise in young females. Eight young women completed 300 maximal eccentric actions of the quadriceps femoris muscle on an isokinetic dynamometer on two occasions in a randomized, cross-over design after which an alcoholic beverage (0.88g ethanol/kg body weight) or an iso-caloric placebo was consumed. Maximal isokinetic (concentric and eccentric) torque and isometric tension produced across the knee were measured in both the exercised and control leg predamage, 36 hr post, and 60 hr post damage. Venous blood creatine kinase (CK) activity and muscle soreness ratings were taken before damage and once per day to 60 hr post damage. Significant differences were observed between the exercised and control leg for maximal concentric, and eccentric torque and isometric tension (p < .05). A near significant Treatment × Time interaction was observed for isometric tension (p = .077), but not for concentric or eccentric torque. No main effects of treatment (alcohol) or interactions with Time × Leg or Leg × Treatment were observed. Perceived muscle soreness during box stepping and squatting showed significant time effects (p < .05), and CK activity did not significantly change. Our results indicate that the consumption of 0.88g ethanol/kg body weight following eccentric exercise-induced muscle damage does not affect recovery in the days following damage in females.

BackgroundKeratins are structural, thiol-rich proteins, which comprise 90% of total poultry feather weight. Their favourable amino acid profile suggests the potential for use as a protein source and ergogenic aid for endurance athletes, following treatment to increase digestibility. This study investigated whether 4 weeks of soluble keratin (KER) consumption (0.8 g/kg bodyweight/day) by 15 endurance-trained males would have favourable effects on body composition, blood and cardiorespiratory variables, and cycling performance, compared to casein protein (CAS).MethodsSupplementation was randomized, blinded and balanced, with a minimum eight-week washout period between trials. An exercise test to measure oxygen consumption during submaximal and maximal cycling exercise was completed at the start at and end of each intervention. Anthropometric (DEXA) and blood measures were made prior to and following each intervention period.ResultsTotal body mass and percentage body fat did not change significantly (p > 0.05). However, a significantly greater increase in bone-free lean mass (LM) occurred with KER compared to CAS (0.88 kg vs 0.07 kg; p < 0.05). While no change in LM was evident for the trunk and arms, leg LM increased (0.45 ± 0.54 kg; p = 0.006) from baseline with KER. KER was not associated with changes in blood parameters, oxygen consumption, or exercise performance (p > 0.05).ConclusionsThese data suggest that KER is not useful as an ergogenic aid for endurance athletes but may be a suitable protein supplement for maximizing increases in lean body mass.

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