Muscle damage and its relationship with muscle fatigue during a half-iron triathlon.

Abstract

BACKGROUND: To investigate the cause/s of muscle fatigue experienced during a half-iron distance triathlon. METHODOLOGY/PRINCIPAL FINDINGS: We recruited 25 trained triathletes (36±7 yr; 75.1±9.8 kg) for the study. Before and just after the race, jump height and leg muscle power output were measured during a countermovement jump on a force platform to determine leg muscle fatigue. Body weight, handgrip maximal force and blood and urine samples were also obtained before and after the race. Blood myoglobin and creatine kinase concentrations were determined as markers of muscle damage. RESULTS: Jump height (from 30.3±5.0 to 23.4±6.4 cm; P0.05) but significantly correlated with myoglobin concentration (r = 0.65; P<0.001) and creatine kinase concentration (r = 0.54; P<0.001). CONCLUSIONS/SIGNIFICANCE: During a half-iron distance triathlon, the capacity of leg muscles to produce force was notably diminished while arm muscle force output remained unaffected. Leg muscle fatigue was correlated with blood markers of muscle damage suggesting that muscle breakdown is one of the most relevant sources of muscle fatigue during a triathlon.