Exercise tolerance during VO2max testing is a multifactorial psychobiological phenomenon

Adrian W Midgley,Keith Earle,Lars R Mcnaughton,Jason C Siegler,Peter Clough,Fiona Earle

doi:10.1080/15438627.2017.1365294

Abstract

ABSTRACTFifty-nine men completed a VO2max test and a questionnaire to establish reasons for test termination, perceived exercise reserve (difference between actual test duration and the duration the individual perceived could have been achieved if continued until physical limitation), and perception of verbal encouragement. Participants gave between 1 and 11 factors as reasons for test termination, including leg fatigue, various perceptions of physical discomfort, safety concerns, and achievement of spontaneously set goals. The two most common main reasons were leg fatigue and breathing discomfort, which were predicted by pre-to-post test changes in pulmonary function (p = 0.038) and explosive leg strength (p = 0.042; R2 = 0.40). Median (interquartile range) perceived exercise reserve, was 45 (50) s. Two-thirds of participants viewed verbal encouragement positively, whereas one-third had a neutral or negative perception. This study highlights the complexity of exercise tolerance during VO2max testing and more research should explore these novel findings.

Highlights

Hill, Long, and Lupton (1924) proposed that during the assessment of maximal oxygen uptake (VO2max) the cardiovascular system’s capacity to deliver oxygen to working muscles is reached, resulting in muscle hypoxia, a rapid increase in intramuscular lactate concentration, and muscle fatigue leading to task failure
Another issue is that leg fatigue and breathing discomfort are the most common main reasons for VO2max test termination (Hamilton et al, 1996; Myers et al, 1992; O’Donnell et al, 1998), it is currently not known whether participants who terminate the test due to leg fatigue demonstrate greater pre-topost changes in explosive leg strength than changes in pulmonary function, and vice-versa
The observation that a VO2max test is typically continued until task disengagement rather than task failure supports the proposition of a perceived exercise reserve, defined as the time difference between the actual test duration and the test duration the individual perceives could have been achieved if exercise had been continued until task failure

Summary

Introduction

Hill, Long, and Lupton (1924) proposed that during the assessment of maximal oxygen uptake (VO2max) the cardiovascular system’s capacity to deliver oxygen to working muscles is reached, resulting in muscle hypoxia, a rapid increase in intramuscular lactate concentration, and muscle fatigue leading to task failure. Empirical evidence supporting a voluntary control of effort and task disengagement during VO2max testing comes from observations that individuals typically terminate the test because of perceived pain and discomfort rather than any physical limitation (Hamilton, Killian, Summers, & Jones, 1996; Myers et al, 1992; O’Donnell, Chau, & Webb, 1998) These studies provide important insight into exercise tolerance during VO2max testing, only the main reason for task disengagement was reported, including either an option for combined leg fatigue and breathing discomfort (Hamilton et al, 1996; O’Donnell et al, 1998) or combined general and leg fatigue (Myers et al, 1992).

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