From catastrophe to complexity: A novel model of integrative central neural regulation of effort and fatigue during exercise in humans: Summary and conclusions

Research Unit for Exercise Science and Sports Medicine, University of Cape Town, Sports Science of South Africa, PO Box 115, Newlands 7725, South Africa.
British Journal of Sports Medicine (Impact Factor: 5.03). 03/2005; 39(2):120-4. DOI: 10.1136/bjsm.2003.010330
Source: PubMed

ABSTRACT

It is hypothesised that physical activity is controlled by a central governor in the brain and that the human body functions as a complex system during exercise. Using feed forward control in response to afferent feedback from different physiological systems, the extent of skeletal muscle recruitment is controlled as part of a continuously altering pacing strategy, with the sensation of fatigue being the conscious interpretation of these homoeostatic, central governor control mechanisms.

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Available from: Timothy Noakes, Sep 03, 2014
    • "This observation was expected and has been documented as part of a typical pacing strategy during both time-trial performances and in distance-deceived running trials in AB athletes. In these studies, it has been typically found that performance decreases significantly immediately following disclosure of deception, before a certain level of recovery and an endspurt in performance is observed, which we repeat in this study (Lambert et al., 2005; Noakes et al., 2005; Tucker, 2009; Tucker & Noakes, 2009; Noakes, 2011). In a deception trial, the central regulator, or brain, is deceived into believing it has a certain workload to complete , and regulates the allocation of resources accordingly , as pacing is highly dependent on knowledge of the exercise endpoint. "
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    ABSTRACT: This study investigated performance and physiology to understand pacing strategies in elite Paralympic athletes with cerebral palsy (CP). Six Paralympic athletes with CP and 13 able-bodied (AB) athletes performed two trials of eight sets of 10 shuttles (total 1600m). One trial was distance-deceived (DEC, 1000 m + 600 m) one trial was nondeceived (N-DEC, 1600 m). Time (s), heart rate (HR, bpm), ratings of perceived exertion (RPE, units), and electromyography of five bilateral muscles (EMG) were recorded for each set of both trials. The CP group ran slower than the AB group, and pacing differences were seen in the CP DEC trial, presenting as a flat pacing profile over the trial (P < 0.05). HR was higher and RPE was lower in the CP group in both trials (P < 0.05). EMG showed small differences between groups, sides, and trials. The present study provides evidence for a possible pacing strategy underlying exercise performance and fatigue in CP. The results of this study show (1) underperformance of the CP group, and (2) altered pacing strategy utilization in the CP group. We proposed that even at high levels of performance, the residual effects of CP may negatively affect performance through selection of conservative pacing strategies during exercise.
    No preview · Article · Oct 2015 · Scandinavian Journal of Medicine and Science in Sports
    • "According to the corollary discharge model (Marcora 2009), the perception of effort is determined by a feedforward mechanism, where increases in RPE over time are the result of a " … conscious awareness of the central motor commands to the locomotor and respiratory muscles " (Marcora 2009, p 2061). In contrast, the central governor model proposes that exercise responses are predetermined by an unconscious " governor " and that these responses are independent of any efferent or afferent inputs (Noakes et al. 2005). The exercise pressor reflex model suggests that group III and IV afferent fibers in the working muscle (leg, thigh, or respiratory muscles) respond to mechanical (group III) and metabolic (group IV) stimuli and provide feedback that contributes to ventilatory, cardiovascular, and perceptual responses (Amann et al. 2010; Kaufman et al. 1983; St. Croix et al. 2000). "
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    ABSTRACT: This study examined: (1) the sustainability of the critical heart rate (CHR) minus 5 b min(-1) (CHR - 5) and CHR plus 5 b min(-1) (CHR + 5); (2) the ratings of perceived exertion (RPE), velocity, [Formula: see text], minute ventilation ([Formula: see text]), breathing frequency (f b ), and electromyographic amplitude (EMG AMP) and EMG mean power frequency (MPF) responses during treadmill running at CHR - 5 and CHR + 5 to determine what factors underlie the perception of effort when heart rate (HR) is held constant; and (3) the relationships among RPE, [Formula: see text], and HR, to determine which variable(s) reflect exhaustion during exercise performed at a constant HR. The CHR was determined in eight runners (mean ± SD; age = 24 ± 3 years) from a series of four exhaustive, constant velocity runs. The RPE, velocity, [Formula: see text], [Formula: see text], f b , EMG AMP, and EMG MPF responses were recorded during runs at the CHR - 5 and CHR + 5. At CHR - 5, RPE, f b, and EMG MPF increased, while velocity, [Formula: see text], [Formula: see text], and EMG AMP decreased. At CHR + 5, RPE and f b increased, velocity, [Formula: see text], [Formula: see text], and EMG AMP decreased, and EMG MPF remained constant. The close association between f b and RPE throughout the run at CHR - 5 and during the last 50 % of the run at CHR + 5 indicated that muscle afferents may have provided feedback from metabolic and mechanical stimuli that contributed to the perceptual responses. In addition, only RPE consistently indicated exhaustion and the current findings supported its use to monitor exercise performed at a constant HR.
    No preview · Article · Jun 2015 · Arbeitsphysiologie
    • "From this research, the regulation of intensity during exercise appears largely regulated by complex relationships between the brain and other physiological systems, with several models proposed to explain this phenomena, including the central governor model[1], teloanticipatory theory[2], pacing awareness model[3], psychobiological model[4,5], the flush model[6], perceptions-based model[7]and complex systems model[8,9]. Many of these models indicate that afferent sensory feedback from various physiological systems is received by the thalamus and regulated within the brain[1,2,5,9]. This information, in addition to several other factors such as knowledge of the task duration/distance remaining, memory of past similar experiences, motivation and mood[5,10], is believed to be important in the regulation of pace. "
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    ABSTRACT: Ratings of perceived exertion (RPE) and effort are considered extremely important in the regulation of intensity during self-paced physical activity. While effort and exertion are slightly different constructs, these terms are often used interchangeably within the literature. The development of perceptions of both effort and exertion is a complicated process involving numerous neural processes occurring in various regions within the brain. It is widely accepted that perceptions of effort are highly dependent on efferent copies of central drive which are sent from motor to sensory regions of the brain. Additionally, it has been suggested that perceptions of effort and exertion are integrated based on the balance between corollary discharge and actual afferent feedback; however, the involvement of peripheral afferent sensory feedback in the development of such perceptions has been debated. As such, this review examines the possible difference between effort and exertion, and the implications of such differences in understanding the role of such perceptions in the regulation of pace during exercise.
    No preview · Article · Jun 2015 · Sports Medicine
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