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


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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    • "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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    • "The rate at which RPE increases during opened-loop, constant-load exercises (in which exercise intensity cannot be reduced) seems to be set at the beginning of the exercise and regulated as a function of the remaining time to exhaustion [1]. Thus, the time to exhaustion during a given exercise bout can be predicted by the rate of increase of RPE [4] [5] [6] [7] [8]. It is interesting to note that some psychological manipulation techniques alter the RPE response during opened-loop exercise [9] [10]. "
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    ABSTRACT: Purpose: We examined the effects of listening to music on time to exhaustion and psychophysiological responses during moderate-intensity exercise performed in fatigued and non-fatigued conditions. Methods: Fourteen healthy men performed moderate-intensity exercise (60% Wmax) until exhaustion under four different conditions: with and without pre-fatigue (induced by 100 drop jumps) and listening and not listening to music. Results: Time to exhaustion was lower in the fatigued than the non-fatigued condition regardless listening to music. Similarly, RPE was higher in the fatigued than the non-fatigued condition, but music had no effect. On the other hand, listening to music decreased the associative thoughts regardless of fatigue status. Heart rate was not influenced by any treatment. Conclusion: These results suggest that listening to music changes attentional focus but is not able to reverse fatigue-derived alteration of performance.
    Physiology & Behavior 02/2015; 139:274-280. DOI:10.1016/j.physbeh.2014.11.048 · 2.98 Impact Factor
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    • "While race dynamics are likely to increase the variability of exercise intensity within both draft-legal and non-draft-legal races, pacing could also be influenced by other external factors such as water currents, wind conditions,35,39,85 topography,10,42,85 environmental heat, and humidity.86 For example, a higher mean power output of 192±21 W was reported during women’s world cup flat cycling races, as compared with 169±17 W observed during hilly races.87 "
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    ABSTRACT: Triathlon is a multisport event consisting of sequential swim, cycle, and run disciplines performed over a variety of distances. This complex and unique sport requires athletes to appropriately distribute their speed or energy expenditure (ie, pacing) within each discipline as well as over the entire event. As with most physical activity, the regulation of pacing in triathlon may be influenced by a multitude of intrinsic and extrinsic factors. The majority of current research focuses mainly on the Olympic distance, whilst much less literature is available on other triathlon distances such as the sprint, half-Ironman, and Ironman distances. Furthermore, little is understood regarding the specific physiological, environmental, and interdisciplinary effects on pacing. Therefore, this article discusses the pacing strategies observed in triathlon across different distances, and elucidates the possible factors influencing pacing within the three specific disciplines of a triathlon.
    Open Access Journal of Sports Medicine 09/2014; 5:223-34. DOI:10.2147/OAJSM.S44392
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