Dark Chocolate and Exercise Performance in Hypoxia

Nitrate supplements (beetroot juice, pure sodium nitrate) have become common among endurance athletes because the ingestion of exogenous nitrate leads to increased levels of nitric oxide (NO) in the body. Increased NO has been shown to have various performance enhancing effects such as increased muscle contractility, increased blood flow through vasodilation, mitochondrial biogenesis, and improved glucose uptake. Supplementation with exogenous forms of nitrate has also been shown to improve cycling performance in the oxygen deprived environment of simulated altitude through increased muscular oxygenation. Further research is emerging that suggests that dark chocolate (DC) may have similar effects through flavonoids, a bioactive micronutrient that increases the synthesis of NO and reduces the rate at which NO is removed from the blood. In addition to performance enhancement, the flavonoids in DC also have anti-inflammatory and antioxidant effects, which could reduce muscle damage after a bout of exercise and increase the rate at which the muscle recovers. The purpose of this research is to investigate the effects of DC on cycling performance and recovery in cyclists at altitude. it is hypothesised that the DC condition will result in superior metabolism during exercise and increase muscular oxygenation, leading to improved performance while enhancing recovery from exercise. Methods: 12 trained cyclists will be randomized to supplement with 160g of DC or an isocaloric placebo per day for 2 weeks in a cross-over study. After the 2-weeks of supplementation participants will attend a lab session in which they will cycle 90 minutes at 60% VO2max followed immediately by a 10km time trial (TT) at a simulated altitude of 1500m (15% O2). Plasma levels of blood glucose and lactate will be measured before, throughout, and after exercise while muscular and cerebral oxygenation will be measured continuously throughout exercise. Recovery of the knee extensors will be assessed before and immediately after exercise as well as 24 and 48 hours later by determining knee extensor strength and muscle pain.