Browsing by Author "Coates, Kyla"

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    The Mechanisms of Fatigability from Whole-Body Exercise and its Relationship to Chronic Fatigue in People with Multiple Sclerosis
    (2018-08-09) Coates, Kyla; Millet, Guillaume Y.; Culos-Reed, Susan Nicole; Zijdewind, Inge; Jarvis, Scott E.
    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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    The short-term recovery of corticomotor responses in elbow flexors
    (2019-03-14) Aboodarda, Saied J; Fan, Selina; Coates, Kyla; Millet, Guillaume Y
    Abstract Background The recovery of neurophysiological parameters at various time intervals following fatiguing exercise has been investigated previously. However, the repetition of neuromuscular assessments during the recovery period may have interfered with the true corticomotor excitability responses. In this experiment, fatiguing contractions were combined with a single post-fatigue assessment at varying time points. Ten participants undertook 5 bouts of 60-s maximal voluntary contractions (MVC) of the elbow flexors, separated by 20 min. Before and after each 60-s fatiguing exercise (FAT), participants performed a series of 6-s contractions at 100, 75 and 50% of their MVC during which transcranial magnetic, transmastoid electrical and brachial plexus electrical stimuli were used to elicit motor evoked potentials (MEP), cervicomedullary motor evoked potentials (CMEP) and compound muscle action potentials (Mmax) in the biceps brachii muscle, respectively. Post-FAT measurements were randomly performed 0, 15, 30, 60, or 120 s after each FAT. Results MVC force declined to 65.1 ± 13.1% of baseline following FAT and then recovered to 82.7 ± 10.2% after 60 s. The MEP·Mmax−1 ratio recorded at MVC increased to 151.1 ± 45.8% and then returned to baseline within 60 s. The supraspinal excitability (MEP·CMEP−1) measured at MVC increased to 198.2 ± 47.2% and fully recovered after 30 s. The duration of post-MEP silent period recorded at MVC elongated by 23.4 ± 10.6% during FAT (all P < 0.05) but fully recovered after 15 s. Conclusions The current study represents the first accurate description of the time course and pattern of recovery for supraspinal and spinal excitability and inhibition following a short maximal fatiguing exercise in upper limb.
  • Thumbnail Image
    ItemOpen Access
    The short-term recovery of corticomotor responses in elbow flexors
    (2019-03-14) Aboodarda, Saied J; Fan, Selina; Coates, Kyla; Millet, Guillaume Y
    Abstract Background The recovery of neurophysiological parameters at various time intervals following fatiguing exercise has been investigated previously. However, the repetition of neuromuscular assessments during the recovery period may have interfered with the true corticomotor excitability responses. In this experiment, fatiguing contractions were combined with a single post-fatigue assessment at varying time points. Ten participants undertook 5 bouts of 60-s maximal voluntary contractions (MVC) of the elbow flexors, separated by 20 min. Before and after each 60-s fatiguing exercise (FAT), participants performed a series of 6-s contractions at 100, 75 and 50% of their MVC during which transcranial magnetic, transmastoid electrical and brachial plexus electrical stimuli were used to elicit motor evoked potentials (MEP), cervicomedullary motor evoked potentials (CMEP) and compound muscle action potentials (Mmax) in the biceps brachii muscle, respectively. Post-FAT measurements were randomly performed 0, 15, 30, 60, or 120 s after each FAT. Results MVC force declined to 65.1 ± 13.1% of baseline following FAT and then recovered to 82.7 ± 10.2% after 60 s. The MEP·Mmax−1 ratio recorded at MVC increased to 151.1 ± 45.8% and then returned to baseline within 60 s. The supraspinal excitability (MEP·CMEP−1) measured at MVC increased to 198.2 ± 47.2% and fully recovered after 30 s. The duration of post-MEP silent period recorded at MVC elongated by 23.4 ± 10.6% during FAT (all P < 0.05) but fully recovered after 15 s. Conclusions The current study represents the first accurate description of the time course and pattern of recovery for supraspinal and spinal excitability and inhibition following a short maximal fatiguing exercise in upper limb.