The limitations of the constant load and self-paced exercise models of exercise physiology

Abstract

Link to this article: http://journals.cambridge.org/abstract_S1755254012000013How to cite this article: Frank E. Marino (2010). The limitations of the constant load and self-paced exercise models of exercise physiology. AbstractThe fundamental tenets of exercise physiology are to describe energy transformations during physical work and make predictions about physical performance under different conditions. Historically, the most popular method to observe such responses during exercise has been the constant load or fixed-intensity protocol, based largely on the assumption that there is a certain threshold response of the organism under a given condition. However, constant load exercise does not fully allow for randomness or variability, as the biological system is overridden by a predetermined externally imposed load that cannot be altered. Conversely, in self-regulated (paced) exercise, there is almost an immediate reduction in power output and muscle recruitment upon commencing exercise. This observation suggests the existence of neural inhibitory command processes. This difference in regulation demonstrates the inherent importance of variability in the biological system; for in tightly controlled energy expenditure, as is the case during constant load exercise, sensory cues cannot be fully integrated to provide a more appropriate response to the given task. The collective evidence from conventional constant load versus self-regulated exercise studies suggests that energy transformations are indeed different, so that the inherent biological variability accounts for the different results achieved by the two experimental paradigms.

Caffeine increases motor output entropy and performance in 4 km cycling time trial

“…Consequently, isometric muscle task-derived results cannot provide enough to understand the MOEn in more usual forms of exercise. For example, exercises such as a cycling time trial may be insightful to understand the MOEn-fatigue relationship in strenuous whole-body self-paced exercises, as this exercise mode requires a more complex, moment-to-moment regulation when regulating pacing and exercise performance [8][9][10][11][12][13][14][15]. For example, power output fluctuations during a cycling time trial may indicate the CNS ability to deal with the central-peripheral fatigue interplay during a more natural form of exercise [8,15], thereby offering insights on the role of the neuromuscular complexity in exercise regulation and pacing strategy.…”

The Effect of Double – Blind Carbohydrate Ingestion during 60 km of Self-Paced Exercise in Warm Ambient Conditions

“…A recent study evaluating the effect of CHO (0–6%) on TTE in both cool (10°C) and warm (30°C) conditions report T c at exhaustion to be no higher than ∼38.5°C in the heat even when TTE was significantly reduced [3]. Perhaps in a self-paced trial the ability to alter moment-by-moment muscle force and power outputs, and presumably the metabolic heat production so that a maximal level of heat accumulation is never attained [29]–[31], produced similar T c responses across conditions.…”

Marathon Performance Depends on Pacing Oscillations between Non Symmetric Extreme Values

“…Even if these two paradigms of exercise (selfpace or constant-load model) have different limitations (see the Ref. [32]), the self-pace model has allowed new insights into the optimization of energy transformation (see the Ref. [33]).…”