Physiological Determinants of Ultramarathon Trail-Running Performance

Context : The physiological determinants of ultramarathon success have rarely been assessed and likely differ in their contributions to performance as race distance increases. Purpose : To examine predictors of performance in athletes who completed either a 50-, 80-, or 160-km trail race over a 20-km loop course on the same day. Methods : Measures of running history, aerobic fitness, running economy, body mass loss, hematocrit alterations, age, and cardiovascular health were examined in relation to race-day performance. Performance was defined as the percentage difference from the winning time at a given race distance, with 0% representing the fastest possible time. Results : In the 50-km race, training volumes, cardiovascular health, aerobic fitness, and a greater loss of body mass during the race were all related to better performance (all P < .05). Using multiple linear regression, peak velocity achieved in the maximal oxygen uptake test ( β = −11.7, P = .002) and baseline blood pressure ( β = 3.1, P = .007) were the best performance predictors for the men’s 50-km race ( r = .98, r 2 = .96, P < .001), while peak velocity achieved in the maximal oxygen uptake test ( β = −13.6, P = .001) and loss of body mass ( β = 12.8, P = .03) were the best predictors for women ( r = .94, r 2 = .87, P = .001). In the 80-km race, only peak velocity achieved in the maximal oxygen uptake test predicted performance ( β = −20.3, r = .88, r 2 = .78, P < .001). In the 160-km race, there were no significant performance determinants. Conclusions : While classic determinants of running performance, including cardiovascular health and running fitness, predict 50-km trail-running success, performance in longer-distance races appears to be less influenced by such physiological parameters.