Investigating the efficacy of cocoa flavanols as an ergogenic aid for muscle recovery in males and females following exercise-induced muscle damage

Cocoa flavanols (CF) are bioactive compounds that exert antioxidant and anti-inflammatory properties and can aid overall health as a result. This PhD looked to investigate the efficacy of CF as an ergogenic aid for muscle recovery following exercise-induced muscle damage (EIMD). As strenuous exercise can elicit oxidative stress and cause the muscle to enter an inflammatory state, CF may aid recovery by blunting the overproduction of reactive oxygen species and limit the pro-inflammatory response. A systematic review of the literature was carried out, resulting in 14 studies, identifying that acute and sub-chronic consumption of CF blunts exercise-induced oxidative stress and, likely through a similar mechanism, may delay fatigue during exercise. It was identified that the most pertinent area of research related to CF and EIMD as only three studies currently existed, with evidence of the benefits unclear due to methodological issues, such as ineffective muscle damaging protocols. Not only that, but within sporting settings, optimal recovery is crucial for maintaining high levels of performance whether in training or during competition. A failure of full recovery can reduce athletic performance, e.g., reductions in force output or sprint ability, and can increase injury risk.

The first experimental study investigated the impact of an acute dose of CF (either 830mg or 1245mg) on muscle recovery following EIMD. Overall, 23 participants completed the study. Participants performed maximal voluntary isometric contractions (MVIC) of the knee flexors to assess muscle function and a visual analogue scale (VAS) and lower extremity functional scale (LEFS) to assess perceived soreness. To induce muscle damage five sets of 10 maximal concentric/eccentric hamstring curls were performed on each leg using an isokinetic dynamometer, with muscle function and soreness being measured immediately post, 24, 48 and 72 hr following EIMD. It was observed that the highest dose of CF (1245mg) may have a minimal effect on the recovery of MVIC and muscle soreness; although not statistically significant. The second experimental study was a sub-group inter and intra-sex analysis of the data gathered from the first study. Overall, no significant differences were observed between males and females for measures of muscle recovery. The third experimental study investigated the impact of daily consumption of 1245mg of CF on muscle recovery following repeated bouts of strenuous exercise, separated by 72 hours. In addition to MVIC, VAS, and LEFS, electromyography was included within the measures to assess muscle recovery. This study had 9 participants complete the seven-day protocol (one baseline and six consecutive days) ingesting 8 beverages throughout the period. No overall significant differences were observed between the groups, however at the final time point (48 hr post the second EIMD protocol) large effect sizes were observed and a statistically significant difference at that time point for MVIC data, VAS, and LEFS. The data contained within this thesis provides novel information on the potential of CF as an ergogenic aid for muscle recovery. It appears that CF does not offer a significant benefit for muscle recovery when compared to a recovery drink containing only carbohydrate and protein. However, the large effect sizes observed in all three studies imply there may be a small effect of CF on recovery, as such the data from this PhD needs to be corroborated by future research to further justify the use of CF as an ergogenic aid for recovery.