AUTHOR=Tiller Nicholas B. , Chiesa Scott T. , Roberts Justin D. , Turner Louise A. , Jones Siana , Romer Lee M. 

TITLE=Physiological and Pathophysiological Consequences of a 25-Day Ultra-Endurance Exercise Challenge

JOURNAL=Frontiers in Physiology

VOLUME=10

YEAR=2019

URL=https://www.frontiersin.org/journals/physiology/articles/10.3389/fphys.2019.00589

DOI=10.3389/fphys.2019.00589

ISSN=1664-042X

ABSTRACT=<p><bold>Background:</bold> This case-report characterized the respiratory, cardiovascular, and nutritional/gastrointestinal (GI) responses of a trained individual to a novel ultra-endurance exercise challenge.</p><p><bold>Case Presentation:</bold> A male athlete (age 45 years; <inline-formula><mml:math id="M1" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mover accent="true"><mml:mo>V</mml:mo><mml:mo>˙</mml:mo></mml:mover></mml:math></inline-formula>O<sub>2</sub>max 54.0 mL⋅kg<sup>-1</sup>⋅min<sup>-1</sup>) summited 100 mountains on foot in 25 consecutive days (all elevations &gt;600 m).</p><p><bold>Measures:</bold> Laboratory measures of pulmonary function (spirometry, whole-body plethysmography, and single-breath rebreathe), respiratory muscle function (maximum static mouth-pressures), and cardiovascular structure and function (echocardiography, electrocardiography, large vessel ultrasound, and flow-mediated dilatation) were made at baseline and 48 h post-challenge. Dietary intake (four-day food diary), self-reported GI symptoms and plasma endotoxin concentrations were assessed at baseline, pre/post mid-point, pre/post end-point, and 48 h post-challenge.</p><p><bold>Results:</bold> The challenge was completed in a total exercise time of 142 h (5.3 ± 2.8 h⋅d<sup>-1</sup>), with a distance of 1141 km (42.3 ± 43.9 km⋅d<sup>-1</sup>), and energy expenditure of 80460 kcal (2980 ± 1451 kcal⋅d<sup>-1</sup>). Relative to baseline, there were post-challenge decreases in pulmonary capacities and expiratory flows (≤34%), maximum expiratory mouth-pressure (19%), and maximum voluntary ventilation (29%). Heart rate variability deteriorated, manifesting as a 48% decrease in the root mean square of successive differences and a 70% increase in the low-frequency/high-frequency ratio. Pre- to post-challenge endotoxin concentrations were elevated by 60%, with a maximum increase of 130% after a given stage, congruent with an increased frequency and severity of GI symptoms.</p><p><bold>Conclusion:</bold> The challenge resulted in pulmonary and autonomic dysfunction, endotoxaemia, and GI distress. The findings extend our understanding of the limits of physiological function and may inform medical best-practice for personnel supporting ultra-endurance events.</p>