Central Governor - Criticisms

Criticisms

The existence of a central governor over physiology has been questioned since ‘physiological catastrophes’ can and do occur in athletes (important examples in marathons have been Dorando Pietri, Jim Peters and Gabriela Andersen-Schiess). This suggests that humans can over-ride ‘the central governor’. Moreover, a variety of peripheral factors in addition to those such as lactic acid build up can impair muscle power and might act to protect against "catastrophe". Another objection is that models incorporating conscious control also provide an alternative explanation, but also see Noakes’ reply.

Exercise fatigue has also been attributed to the direct effects of exercise upon the brain such as increased cerebral levels of serotonin, reduced level of glutamate secondary to uptake of ammonia in the brain, brain hyperthermia, and glycogen depletion in brain cells.

The idea of exercise causing hypoxia at the heart, in the absence of arterial disease, moreover can be questioned due to the heart with every beat is delivering through coronary arteries that arise from first branches from the aorta freshly oxygenated blood to its own cells. Other factors exist that could in a self limiting way limit oxygen uptake. For example, as more accessory muscles of respiration are recruited, (as occurs at near maximal values of VO2), the energy cost of increasing rib cage expansion is nearly equal to that gained by the oxygen obtained from doing so. Indeed, the Fick equation (see VO2 max) itself includes terms of limitation: Q (cardiac output) is determined by stroke volume and heart rate. Stroke volume has a natural, physically limited upper bound (the heart obviously has a maximal volume, and is restricted by surrounding structures such as the pericardium), while heart rate is limited by the ability rate at which cardiac cells can maintain rhythmicity. There are also natural limits to the rate at which oxygen can diffuse from the blood to the tissues, i.e. gas exchange is itself a limiting factor.

These criticisms suggest the potential exists for known physiological processes to adequately carry out what Noakes and others attribute to a complex, pre-calculated central mechanism of homeostasis. (Though they may be relevant for accounting for some types of observations such as the effects of altitude on cardiac and other muscular capabilities.)

Another criticism is that Hill's original suggestion of a central governor uses a study in which a VO2 max test was conducted in which some of the subjects did not achieve a plateau in oxygen uptake. This failure led to his suggestion that VO2 max itself is a failure to account for their fatigue requiring the existence of another mechanism that could limit aerobic performance. However, this plateau requires that subjects are highly motivated, as the protocol of the test requires work at near maximal levels for protracted periods, and this might not have been the case.