Article

Evidence for complex system integration and dynamic neural regulation of skeletal muscle recruitment during exercise in humans

Research Unit for Exercise Science and Sports Medicine, University of Cape Town, Newlands, South Africa. <>
British Journal of Sports Medicine (Impact Factor: 5.03). 01/2005; 38(6):797-806. DOI: 10.1136/bjsm.2003.009852
Source: PubMed

ABSTRACT

A model is proposed in which the development of physical exhaustion is a relative rather than an absolute event and the sensation of fatigue is the sensory representation of the underlying neural integrative processes. Furthermore, activity is controlled as part of a pacing strategy involving active neural calculations in a "governor" region of the brain, which integrates internal sensory signals and information from the environment to produce a homoeostatically acceptable exercise intensity. The end point of the exercise bout is the controlling variable. This is an example of a complex, non-linear, dynamic system in which physiological systems interact to regulate activity before, during, and after the exercise bout.

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Available from: Timothy Noakes, Sep 03, 2014
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    • "The positive influence of sustained vocal encouragement, motivational self-talk, motivational music and video on the power output during the maximal effort exercising (St. ClairGibson and Noakes, 2004;Barwood et al., 2009Barwood et al., , 2015) suggests the involvement of motivation and effort perception in regulation of maximal force output under different environmental conditions.Evstigneeva et al. (2012)reported that the button pressing in response to the rare deviant acoustic stimuli during the fatiguing task (sustained submaximal contraction) resulted in improved motor task performance, compared to the passive listening task. Thus, the effect observed in the oddball paradigm may be associated with the interaction of motor and cognitive processes, related in this case to the discrimination between stimuli. "
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    ABSTRACT: We examined the effect of involuntary attention switching (related to mismatch negativity generation in the oddball paradigm) on fatigue development during trials of different durations. The experiment consisted of two trials, long (40 minutes) and short (15 minutes), and two experimental conditions in each trial: the simple reaction task (deviants-only paradigm) and the stimuli recognition task (oddball paradigm). In each condition, a participant responded to each target acoustic stimulus by squeezing a handgrip dynamometer. We found the significantly lower rates of fatigue development in the short-trial deviants-only paradigm compared to the long trial. The short- and the long-trial oddball paradigms differed significantly from both the short- and the long-trial deviants-only paradigms. The results demonstrated that the fatigue developed differently depending on the expected trial duration. The involuntary activation of attention broke this subconscious regulative mechanism leading to increase of the compression force during the long trial and its decrease during the short.
    Full-text · Article · Feb 2016 · Frontiers in Physiology
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    • "). No change or decreases in EMG AMP during prolonged, submaximal cycle ergometry have been attributed to a decrease in the metabolic demands of the task, reductions in conscious effort, and/or alterations in central recruitment strategies (Bull et al. 2000; St Clair Gibson and Noakes 2004). The time-related decreases in EMG AMP and PO in the present study indicated that reductions in muscle activation during the continuous 1-h rides were necessary to maintain a constant RPE. "

    Full-text · Dataset · Oct 2015
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    • "Based on the fact that the PFC is associated with cognitive tasks, motivation and decision-making, decreasing oxygenation at high exercise intensity prior to exhaustion in the PFC has been assumed to trigger centrally mediated fatigue and the decision to stop exercise in numerous former studies [3] [6] [9] [12] [13] [14] [15]. Hypoxia is proposed to accelerate cerebral deoxygenation, thus central fatigue [2] [8] [10] [11] [15] [16]. "
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    ABSTRACT: The correlation of NIRS (near-infrared spectroscopy) and EEG (electro-cortical activity) in exercise studies has never been shown. Eight sport students performed an incremental bicycle exercise test under normoxic and hypoxic (12.7% O2) conditions respectively. EEG and NIRS recordings of the prefrontal cortex (PFC, Brodmann area 10. 46) were performed synchronously to shed light on their correlation. ANOVA revealed a higher absolute workload (231.3 ± 37.2 W), and relative PFC oxygenation under normoxic conditions, whereas hypoxic conditions resulted in earlier exhaustion (200 ± 26.7 W) and reduced PFC oxygenation. NIRS parameters increased remarkably with exercise intensity (P < 0.001) and differed between conditions (O2Hb: P < 0.001; HHb: P = 0.023; tHb: P = 0.016) and hemispheres (O2Hb: P = 0.023). For EEG, higher prefrontal cortical current density during compared to pre and post exercise was revealed for both conditions (P < 0.001). No difference between conditions and hemispheres were found. In conclusion, brain cortical activity is not impaired by hypoxia. No correlation between NIRS and EEG, but a moderate correlation between EEG and cardio-vascular parameters and a moderate to high correlation between NIRS and cardio-vascular parameters were found. The results emphasize that the transfer of EEG and NIRS results need to be done with caution.
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