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 (ß = -11.7, P = .002) and baseline blood pressure (ß = 3.1, P = .007) were the best performance predictors for the men's 50-km race (r = .98, r2 = .96, P < .001), while peak velocity achieved in the maximal oxygen uptake test (ß = -13.6, P = .001) and loss of body mass (ß = 12.8, P = .03) were the best predictors for women (r = .94, r2 = .87, P = .001). In the 80-km race, only peak velocity achieved in the maximal oxygen uptake test predicted performance (ß = -20.3, r = .88, r2 = .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.

Alterations in Cardiac Function Following Endurance Exercise Are Not Duration Dependent.

Cardiac function has been shown to transiently decrease following prolonged exercise, with greater durations related to increased impairment. However, the prospective assessment of exercise duration on cardiac performance is rare, and the influence of relative exercise intensity is typically not assessed in relation to these changes. The aim of this study was to determine whether progressively longer running distances over the same course would elicit greater cardiac impairment. The present investigation examined cardiac alterations in 49 athletes, following trail-running races of 25, 50, 80, and 160 km, performed on the same course on the same day. Echocardiography, including conventional and speckle tracking imaging, was performed with legs-raised to 60° to mitigate alterations in preload both pre- and post-race. Race-intensities were monitored via heart rate (HR). Following the races, mean arterial pressure (Δ-11 ± 7 mmHg, P < 0.0001), and HR (Δ19 ± 14 bpm, P < 0.0001) were altered independent of race distance. Both left and right ventricular (LV and RV) diastolic function were reduced (ΔLV E/A -0.54 ± 0.49, P < 0.0001; ΔRV A' + 0.02 ± 0.04 m/s, P = 0.01) and RV systolic function decreased (ΔTAPSE -0.25 ± 0.9 cm, P = 0.01), independent of race distance. Cardiac impairment was not apparent using speckle tracking analysis with cubic spline interpolation. While race duration was unrelated to cardiac alterations, increased racing HR was related to greater RV base dilation (r = -0.37, P = 0.03). Increased time spent at higher exercise intensities was related to reduced LV ejection fraction following 25 km (r = -0.81, P = 0.03), LV systolic strain rate following 50 km (r = 0.59, P = 0.04), and TAPSE (r = -0.81, P = 0.03) following 80 km races. Increased running duration did not affect the extent of exercise-induced cardiac fatigue, however, intensity may be a greater driver of cardiac alterations.