Purpose: The aim of this study was to investigate the effect of an ultra-marathon on heart rate variability (HRV) and psychometric indices in endurance runners. In addition, we aimed to determine the magnitude of change and subsequent recovery for 7 days following the race.

Methods: Recreationally trained runners (n = 13 (8M); age = 36.6 ± 7.6 years; height = 174 ± 9 cm; weight = 70.5 ± 9.3 kg) completed measures of HRV upon waking in the morning for 1 week prior to and 1 week following a 64-km running race. Profile of mood states, wellbeing, and muscular soreness were also measured throughout the study period to further contextualise recovery.

Results: An increase in heart rate accompanied by decreased LnSDNN, LnRMSSD, LnLF, LnHF, and LnLF/HF from baseline were observed 1 day post-race (p < 0.05). Indices of HRV had returned to baseline on day 2 of recovery. Perceptual fatigue and muscle soreness increased post-race (immediately following and on day 1 of recovery) (p < 0.05) and took until day 5 of recovery to return to baseline.

Conclusion: The results indicate that cardiac autonomic control is significantly altered in response to a 64 km ultra-marathon. Specifically, parasympathetic activity is suppressed. The change in autonomic control was relatively short-lived, and parasympathetic-related indices had returned to baseline 2 days after the event. Subjective measures of fatigue and wellbeing suggest that athletes were not completely recovered until day 5 post-event, with muscular soreness remaining prominent during this period. A combination of physiological and psychological parameters is important to contextualise recovery in ultra-endurance runners.