The development of neuromuscular fatigue throughout constant power output cycling below, at, and above the maximal lactate steady state in young and healthy females and males
Date
2022-04-20
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Abstract
Exercise-induced neuromuscular fatigue development (NMF) is a transient phenomenon in which its etiology, amplitude (i.e., pre- to post-exercise changes) and time course (i.e., changes during the exercise bout) are directly affected by exercise intensity and sex of the population. It has been suggested that NMF development is related to the metabolic disturbance during the exercise, which might also underpin the increase in O2 cost of work as shown by the development of oxygen uptake slow component (V̇O2SC). However, it is currently unknown if NMF development is affected by slight manipulations in exercise intensity around the heavy and severe boundary, herein defined as the maximal lactate steady state (MLSS), thus demarcating metabolic responses that are stable (i.e., below and/or at) or unstable (i.e., above). Moreover, it is unknown if NMF development around the MLSS, and thus different metabolic responses, would be the same between females and males, and until the time to task failure (TTF). The specific objectives were to compare the effects of exercising at MLSS, as well as slightly below and above MLSS in NMF development, in females and males, regarding: (i) the total NMF amplitude after 30 min bouts of exercise and subsequent performance until TTF; (ii) the time course of NMF throughout a 30 min bout of exercise and at task failurewithin a broader range of exercise intensities around the MLSS (i.e., (i) at the MLSS, (ii) +10W and (iii) -10W, and (iv) +15% and (vi) -15%); (iii) if the relationship between the development of NMF and V̇O2SC is maintained regardless the exercise duration and intensity around the MLSS. The results are organized in three different studies, divided into chapters III, IV and V of the present thesis. The first study (chapter III), showed that the total amplitude of NMF development was exacerbated once exercising above the MLSS compared to below the MLSS, regardless the sex. The second study (chapter IV) showed that the time course of NMF was the same regardless of the exercise intensity and sex, wherein ~75% of the overall development of NMF occurred within the first 5 min of exercise. Finally, the third study (chapter V) showed that the development of both NMF and V̇O2SC were similar and correlated regardless of the exercise intensity and duration. Collectively, these findings provide a detailed characterization of the amplitude and time course of NMF development in exercise intensities around the MLSS in both females and males. As a possible explanation to these results, and highlighted in each study, was that slight change in exercise intensity around the MLSS, possibly, elicited distinct metabolic disturbance within the muscles, specially once exercising above compared to below the MLSS. Therefore, it was suggested that the development of both NMF and V̇O2SC might be related to metabolic disturbance occurring within the muscles.
Description
Keywords
neuromuscular, fatigue, sex-differences
Citation
de Almeida Azevedo, R. (2022). The development of neuromuscular fatigue throughout constant power output cycling below, at, and above the maximal lactate steady state in young and healthy females and males (Doctoral thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca.