The Mechanisms of Fatigability from Whole-Body Exercise and its Relationship to Chronic Fatigue in People with Multiple Sclerosis
Date
2018-08-09
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Abstract
Objectives: The present study investigated the mechanisms of neuromuscular fatigue in people with Multiple Sclerosis (PwMS) during cycling to determine whether chronic perceived fatigue is associated with motor fatigability in PwMS. Methods: Thirteen PwMS with high levels of perceived fatigue (HF), thirteen PwMS with low levels of perceived fatigue (LF), and thirteen healthy controls (CON) completed an incremental cycling task to volitional exhaustion. By employing an innovative cycle ergometer, neuromuscular evaluations (NME) were performed at baseline, every 3 minutes during cycling, and immediately after exhaustion. Maximal voluntary contractions (MVC) and electrical stimulation of the femoral nerve (PNS) were used to quantify voluntary activation (VA) and muscle contractile ability (PT) of the knee extensors during each NME. The EMG responses to PNS (Mmax) and transcranial magnetic stimulation (MEP) during 50% of MVC were used to quantify central drive (EMG-RMS/Mmax), corticospinal excitability (MEP/Mmax) and corticomotor integrity (MEP latency) in the vastus lateralis (VL) and rectus femoris (RF) muscles during each NME. Results: MVC declined to a greater extent at exhaustion in the HF group compared to the other groups (P = .032) in part due to a larger decline in PT compared to CON (P = .041). EMG-RMS/Mmax in the VL (last commonly completed stage (NME3): P = .047; exhaustion: P = .006), and MEP/Mmax amplitude in the VL (NME3: P = .042; exhaustion: P = .029) and in the RF (NME3: P < .001; exhaustion: P = .007 at exhaustion) were consistently lower in HF compared to CON while MEP latency was consistently longer in HF in the VL (NME3: P = .010; exhaustion: P = .009) and RF (NME3: P = .038; exhaustion: P = .038) compared to CON. Conclusion: Cycling results in greater neuromuscular fatigue at exhaustion in PwMS who experience chronic fatigue than in healthy controls due to central and peripheral alterations.
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Keywords
Multiple Sclerosis, exercise, Fatigue, Neuromuscular Fatigue, Motor Fatigability
Citation
Coates, K. D. (2018). The mechanisms of fatigability from whole-body exercise and its relationship to chronic fatigue in people with multiple sclerosis (Master's thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca. doi:10.11575/PRISM/32802