The heart of an endurance athlete: impact of and recovery after an ultra-endurance event

Abstract

Background Limited research currently exists on what the impact of an ultra-endurance mountain bike event has on the heart of an endurance athlete, and that exercise can potentially cause significant cardiac stress. Aims Our study set out to determine the stress and recovery of participation in a three-day ultra-endurance mountain biking event in the heart of athletes using HRV as an outcome measure. Methods Sixteen healthy participants (male and female) in a three-day ultra-endurance mountain biking event underwent a five-minute resting ECG recording in a supine position. Heart rate variability measurements were recorded two days before the race (baseline testing), after each race day (post-event testing) and at 24-hour recovery (recovery). Results Time-domain and frequency domain measures showed significant (p≤0.05) changes in HRV parameters after each race day. Our study found significant changes in HRV parameters all of which reflected an increase in sympathetic activity at rest after each day of the event. This data also indicates that the mean HR and RR variability variables did not returned to baseline value after 24-hours of recovery, showing ANS dysfunction and imbalances persisted up to at least 24-hours of post-event recovery. The body was under continuous sympathetic dominance during rest as well as during each day of racing, meaning that each race day can be considered as physiological stress to the body. This may, in turn, cause a disturbance in homeostasis and an increase in ANS dysfunction. Thus, recovery beyond 24-hours is needed before returning to further high intensity (greater than six metabolic equivalents) training after such an ultra-endurance event to prevent unwanted effects. Conclusion A three-day ultra-endurance mountain biking event causes ANS dysfunction which does not fully recovery 24-hours after the event. This has implications for further research and monitoring of athletes in advising a return to strenuous activity.