Kaempferol Reduces Cardiopulmonary Load and Muscular Damage in Repeated 400‐m Sprints: A Double‐Blind, Randomized, Placebo‐Controlled Trial

Plants exposed to hypoxic conditions have been suggested to produce more biologically active phytochemicals than those exposed to normal oxygen levels. Previously, we investigated 314 highland crop species and showed that the flavonoid kaempferol extracted from a highland quinoa grain markedly increased mitochondrial metabolism and ATP production in a hypoxic environment in vitro. Thus, we hypothesized that kaempferol would be effective during exercise under harsh conditions, in which anaerobic metabolism occurs. This study adopted a double-blind, placebo-controlled, crossover design to investigate the effect of a single oral dose of kaempferol (10 mg) on the athletic performance-related indicators of 13 male university athletes (20.8 ± 0.7 years) who performed two consecutive 400-m runs with the shortest 90-min interval assuming qualifying and main races. Although no significant differences were observed in the 400-m race times between the placebo and kaempferol groups, kaempferol intake markedly reduced the respiratory and heart rates during the second run (<i>p</i> < 0.05). In addition, kaempferol intake reduced the levels of muscle damage markers, myoglobin, and aspartate transaminase (<i>p</i> < 0.05). A single oral dose of kaempferol reduced the cardiopulmonary burden and muscle damage in individuals participating in 400-m runs. Kaempferol may be a useful supplement for relieving the physical load, particularly in individuals performing strenuous exercises with high oxygen demand. <b>Trial Registration:</b> UMIN Clinical Trials Registry in Japan: UMIN000049588.