The central

governor A governor is an administrative leader and head of a polity or political region, ranking under the head of state and in some cases, such as governors-general, as the head of state's official representative. Depending on the type of political ...

is a proposed process in the brain that regulates exercise in regard to a neurally calculated safe exertion by the body. In particular, physical activity is controlled so that its intensity cannot threaten the body’s

homeostasis In biology, homeostasis (British English, British also homoeostasis) Help:IPA/English, (/hɒmɪə(ʊ)ˈsteɪsɪs/) is the state of steady internal, physics, physical, and chemistry, chemical conditions maintained by organism, living systems. Thi ...

by causing

anoxic The term anoxia means a total depletion in the level of oxygen, an extreme form of hypoxia or "low oxygen". The terms anoxia and hypoxia are used in various contexts: * Anoxic waters, sea water, fresh water or groundwater that are depleted of diss ...

damage to the

heart muscle Cardiac muscle (also called heart muscle, myocardium, cardiomyocytes and cardiac myocytes) is one of three types of vertebrate muscle tissues, with the other two being skeletal muscle and smooth muscle. It is an involuntary, striated muscle tha ...

. The central governor limits exercise by reducing the neural recruitment of muscle fibers. This reduced recruitment causes the sensation of

fatigue Fatigue describes a state of tiredness that does not resolve with rest or sleep. In general usage, fatigue is synonymous with extreme tiredness or exhaustion that normally follows prolonged physical or mental activity. When it does not resolve ...

. The existence of a central governor was suggested to explain fatigue after prolonged strenuous exercise in long-distance running and other endurance sports, but its ideas could also apply to other causes of exertion-induced fatigue. The existence of a central governor was proposed by Tim Noakes in 1997, but a similar idea was suggested in 1924 by

Archibald Hill Archibald Vivian Hill (26 September 1886 – 3 June 1977), known as A. V. Hill, was a British physiologist, one of the founders of the diverse disciplines of biophysics and operations research. He shared the 1922 Nobel Prize in Physiology or M ...

. In contrast to this idea is the one that fatigue is due to peripheral "limitation" or "catastrophe." In this view, regulation by fatigue occurs as a consequence of a failure of homeostasis directly in muscles.

History

Archibald Hill

The 1922

Nobel Prize in Physiology or Medicine The Nobel Prize in Physiology or Medicine is awarded yearly by the Nobel Assembly at the Karolinska Institute for outstanding discoveries in physiology or medicine. The Nobel Prize is not a single prize, but five separate prizes that, accord ...

winner

proposed in 1924 that the heart was protected from anoxia in strenuous exercise by the existence of a governor. This hypothesis was disregarded and further research upon exercise fatigue was modeled in terms of it being due to a mechanical failure of the exercising muscles ("peripheral muscle fatigue"). This failure was caused either by an inadequate oxygen supply to the exercising muscles, lactic acid buildup, or total energy depletion in the exhausted muscles.

Tim Noakes

Tim Noakes, a professor of exercise and sports science at the

University of Cape Town The University of Cape Town (UCT) ( af, Universiteit van Kaapstad, xh, Yunibesithi ya yaseKapa) is a public research university in Cape Town, South Africa. Established in 1829 as the South African College, it was granted full university statu ...

, in 1997 has renewed Hill’s argument on the basis of modern research. In his approach, the power output by muscles during exercise is continuously adjusted in regard to calculations made by the brain in regard to a safe level of exertion. These neural calculations factor in earlier experience with strenuous exercise, the planning duration of the exercise, and the present metabolic state of the body. These brain models ensure that body homeostasis is protected, and an emergency reserve margin is maintained. This neural control adjusts the number of activated skeletal muscle motor units, a control which is subjectively experienced as

. This process, though occurring in the brain, is outside conscious control.

Other uses

Noakes created the idea of the central governor in the context of prolonged endurance running. However, he has noted that the central processes involved might also underlie the existence of other kinds of fatigue: In support of this, placebos (which must be mediated by a central process) have a powerful effect upon not only fatigue in prolonged exercise, but also upon short term endurance exercise such as sprint speed, the maximum weight that could be lifted with leg extension, and the tolerance of

ischemic Ischemia or ischaemia is a restriction in blood supply to any tissue, muscle group, or organ of the body, causing a shortage of oxygen that is needed for cellular metabolism (to keep tissue alive). Ischemia is generally caused by problems wi ...

pain and power when a tourniqueted hand squeezes a spring exerciser 12 times.

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 The marathon is a long-distance foot race with a distance of , usually run as a road race, but the distance can be covered on trail routes. The marathon can be completed by running or with a run/walk strategy. There are also wheelchair div ...

have been

Dorando Pietri Dorando Pietri (; often wrongly spelt Petri; 16 October 1885 – 7 February 1942) was an Italian long-distance runner. He finished first in the marathon at the 1908 Summer Olympics in London but was subsequently disqualified. Biography Earl ...

, Jim Peters and

Gabriela Andersen-Schiess Gabriela "Gaby" Andersen-Schiess (born 20 May 1945 in Zürich) is a former Swiss long-distance runner who participated in the first women's Olympic marathon at the 1984 Summer Olympics. Though living in Sun Valley, Idaho, and working as a ski in ...

). 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 (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 Serotonin () or 5-hydroxytryptamine (5-HT) is a monoamine neurotransmitter. Its biological function is complex and multifaceted, modulating mood, cognition, reward, learning, memory, and numerous physiological processes such as vomiting and vas ...

, reduced level of

glutamate Glutamic acid (symbol Glu or E; the ionic form is known as glutamate) is an α-amino acid that is used by almost all living beings in the biosynthesis of proteins. It is a non-essential nutrient for humans, meaning that the human body can syn ...

secondary to uptake of ammonia in the brain, brain hyperthermia, and

glycogen Glycogen is a multibranched polysaccharide of glucose that serves as a form of energy storage in animals, fungi, and bacteria. The polysaccharide structure represents the main storage form of glucose in the body. Glycogen functions as one o ...

depletion in brain cells.

Notes