The effects of unilateral dominant knee extensors fatigue on non-exercised contralateral and ipsilateral elbow and plantar flexors

Whitten, Joseph (2020) The effects of unilateral dominant knee extensors fatigue on non-exercised contralateral and ipsilateral elbow and plantar flexors. Masters thesis, Memorial University of Newfoundland.

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Abstract

The field of non-local muscle fatigue (NLMF) is a relatively young one. However, key factors and trends regarding methodologies and possible mechanisms are starting to be identified. Controlling for factors such as particular muscle groups selected, fatiguing protocols utilized, and participant factors such as age, sex, and training status are starting to illuminate the neurological, biological, biomechanical, and psychological contributions to NLMF effects. To date, this is the first investigation of ipsilateral and contralateral upper and lower body muscle groups following unilateral lower body fatigue that the investigators are aware of. The present study investigated the effects of exercise-induced knee extensor fatigue on force output and electromyography (EMG) activity of both, the ipsilateral and contralateral, non-exercised elbow and plantar flexors. Twelve participants (six females, six males) attended six testing sessions: i) fatigue-ipsilateral plantar flexor (PF), ii) control-ipsilateral PF, iii) fatigue-ipsilateral elbow flexor (EF), iv) control- ipsilateral EF, v) fatigue-contralateral PF, or vi) fatigue-contralateral EF. The non-fatigued muscle groups were assessed with maximal voluntary contractions (MVCs) and normalized electromyographic (EMG) activity prior to and immediately post the intervention as well as during a repeated MVC protocol of twelve repeated MVCs at a work to rest ratio of 5/10 s. Ipsilateral EF MVC strength and endurance decreased following dominant KE fatigue as evidenced by a decrease in both MVC force immediately post- fatigue intervention and FI across the repeated MVC protocol. There were no significant differences in PF force or EMG or EF EMG immediately post-test or during the repeated MVC protocol. This study strengthens current theories which suggest that upper body muscle groups are more susceptible to NLMF effects following lower body fatigue and postulates that fast twitch (EF) predominant muscles are more susceptible to NLMF effects than are slow twitch (PF) predominant muscles.

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