The Central Governor Model Cannot be Adequately Tested by Observing its Components in Isolation

Excerpt

In a recent issue of Sports Medicine, a current opinion article was published entitled “Is it Time to Retire the ‘Central Governor’?” in which the author Roy Shephard concluded that, based on a lack of experimental evidence, the Central Governor Model (CGM) should be treated with scepticism.[1] In the opening few pages of the article Shephard provides a concise overview of CGM before claiming that the CGM is “… hampered by the absence of a systematic and clearly enunciated listing of its inherent correlates.” Although this statement is to some extent true, it should be pointed out that the apparent lack of detailed evidence to which Shephard refers is perhaps a reflection of CGM ‘complexity’, which, in fairness to Noakes and his colleagues, is something that they have repeatedly acknowledged.[2‐5] The complexity of CGM, involving feed forward muscular control derived from the integration of numerous afferent peripheral signals, presents considerable methodological challenges that, for the time being at least, leaves Noakes in the rather difficult scientific position of having to defend his model with only partial and inconclusive evidence. Attempts to discredit the CGM, which are summarized in Shephard’s article, have largely been deduced from empirical observations of component physiological systems that, despite being isolated from the CNS, exhibit self-limiting functions. However, we should be cautious about rejecting the CGM based upon such deductions because this approach essentially disregards the complex physiological, neurological and psychological interactions that model proposes and therefore does not constitute a sufficiently rigorous test. For instance, one of the claims made by Shephard is that a central governor is not needed because of a study[6] that showed gradual rather than catastrophic reduction in the force production of locally stimulated soleus muscles. In fact, all that can really be interpreted from this study is that locally stimulated muscles gradually fatigue. The study does not provide any definitive evidence to rule out the existence of a central governor further up the neurological chain since the lack of attenuation of efferent command when a locally stimulated muscle becomes fatigued could be explained by the absence of other afferent signals that are usually present during ‘whole body’ exercise to represent changes in temperature, oxygen uptake, substrate availability and pH to name a few. Under such circumstances it is of no surprise that the efferent signal was not attenuated since the failure of single locally stimulated muscle does not really threaten overall homeostasis of the body and therefore does not test what Noakes et al. have proposed is the main purpose of the central governor.[2‐5] In other words, the apparent normality of isolated CGM components should not be used as evidence against the model because it does not reflect the inherent complexity of Noakes’ model that, with time and methodological advances, might yet be proved correct. …