The Influence of Ultra-Endurance Exercise on the Cardiovascular and Related Physiological Systems

INTRODUCTION: There is currently limited longitudinal data investigating the performance and health-related influence of ultra-endurance training and participation. Cross-sectional investigations have highlighted a potential for those performing most exercise to be at an increased risk of cardiovascular events. If such risks occur, they are likely to be due to a combination of the stress provided through training and events together. PURPOSE: To assess the development of several physiological factors associated with exercise training and to gain a greater insight regarding the changes in cardiac electrical conductance from endurance training. A sub-study sought to investigate the short and longer-term influence of an iron-distance triathlon on indirect measures of arterial stiffness. METHOD: Part 1: Seventy-six previously recreationally active participants underwent a 6 month endurance training programme in preparation for an iron-distance triathlon, consisting of a 3.86km swim, 180.25km cycle, and a 42.2km run. Multiple assessments were performed at months 0, 2, 4 and 6; including submaximal and exhaustive cycling tests, anthropometric measurements and 12-lead ECG’s. Part 2: Eleven athletes from part 1 (TRI) and 10 recreational control participants (NOTRI) were assessed on 4 occasions with identical time intervals. Arterial stiffness and cardiovascular functional parameters were obtained 7 days prior (T1) to an iron-distance triathlon, 12–18 hours post-event, 7 days post-event, and 28 days post-event. RESULTS: Part 1: Cardiorespiratory fitness and performance parameters increased over the training period, irrespective of age, with greatest improvements from month 0–2 and the least improvements from month 4–6. Additionally, a progressive increase was observed in the frequency of both training-related and training-unrelated ECG findings. Part 2: A significant difference in central arterial stiffness was found between TRI and NOTRI 12–18 hours post-event and 7 days post-event but not prior to or 28 days post-event. No differences were observed between groups for peripheral stiffness at any time-point. Additionally, no time effect was observed when the TRI group were treated separately. CONCLUSION: Training caused significant improvements to fitness related physiological factors. In a minority of individuals, endurance training induced bioelectrical patterns of what is currently referred to as abnormal criteria, which may reflect a normal change to what was previously thought of as abnormal findings or, alternatively, be pathological manifestations in previously healthy individuals. Part 2 of this study showed a delayed central arterial stiffening may occur one day and one week following a single day ultra-endurance event. Importantly, all measurements were found to be similar one month post-event; implying only a transient exercise-induced elevation to arterial stiffness