Physiological effects of an ultra-marathon run

Autonomic functions of the body and gas exchange have been studied in one athlete (master of sports in skiing, aged 27 years, with a maximal oxygen consumption of 67 mL/(min kg)); during a 6-h indoor ultra-marathon race; at an average speed of 2.7 m/s. Continuous monitoring of the heart rate was carried out using a Polar RS 800 heart rate monitor. Gas analysis of the exhaled air and recording of the parameters of external respiration were carried out during the first hour with subsequent repetitions during 20?C30 minutes each hour, using a Metamax mobile device (Germany) mounted on the subject throughout the race. Before and after the subject passed the intervals of a distance when these parameters were measured, the blood lactate content was measured. Our data demonstrate a number of features that accompany fatigue at the final stage of the race, such as a decrease in efficiency of body functions, which is expressed by an increased heart rate and oxygen usage, an activation of anaerobic glycolysis path of energy production, and intensification of the external respiration. In addition, the methods of correlation and regression analysis revealed the changes (increase and decrease) of the relationship between the functions depending on whether muscular performance is at the stage of warming up, sustainably high performance, or in at a stage of extreme fatigue. These findings suggest interference of the effects of the central and tissue mechanisms of fatigue on the organization of oxygen transportation in the body. Apparently, in the instance of an ultra-marathon run, i.e., a prolonged performance of moderate power, autonomic functions, rather than the energy resources of the body, play the role of the main limiting factor.