An analysis of the duration of non-local muscle fatigue effects

Zahiri, Ali (2023) An analysis of the duration of non-local muscle fatigue effects. Masters thesis, Memorial University of Newfoundland.

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Abstract

Introduction Non-local muscle fatigue (NLMF) refers to a transient decline in the functioning of a non-exercised muscle following the fatigue of a different muscle group. Most studies examining NLMF conducted post-tests immediately after the fatiguing protocols, leaving the duration of these effects uncertain. Purpose The aim of this study was to investigate the duration of NLMF effects by examining post-test durations of 1-, 3-, and 5-minutes as well as a Control condition, Methods In this randomized crossover study, 17 recreationally trained participants (four females) were recruited. The study aimed to investigate the acute effects of unilateral knee extensor (KE) muscle fatigue on the contralateral homologous muscle strength, activation, and fatigue resistance (endurance). The participants underwent four sessions, with a minimum 48- hour interval between visits. Each session included testing at one-, three-, or five-minutes posttest, or for a Control condition. Measurements included non-dominant KE muscle force, endurance, and electromyography (EMG) from the vastus lateralis and biceps femoris muscles. The fatigue protocol involved two sets of continuous 100-seconds maximal voluntary isometric contractions (MVIC) performed by the dominant KE, separated by 1-minute of rest. Results Non-dominant KE MVIC forces showed reductions of 15.81% (p<0.0001, d=0.72) at 1-min and 8.54% (p=0.005, d=0.30) at 3-min post-test. The KE MVIC instantaneous strength revealed a significant reduction between 1-min (p=0.021, d=1.33), and 3-min (p=0.041, d=1.13) compared with the control. In addition, EMG revealed large magnitude increases with the 1-minute versus control condition (p=0.03, d=1.10). Conclusions Recovery duration (recovery time was 5-min) plays a crucial role in the manifestation of NLMF. Moreover, the influence of factors such as familiarity with high intensity resistance training loads and the specific muscle group targeted during fatigue protocols were also highlighted.

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