Words: Anna Beck                                                                                      Photos: Phil Gale
Dr Tim Noakes MD was the first to introduce the concept of the central governor theory: which posits that fatigue and reduced performance is wholly managed by the brain (the centre) as a protective mechanism against physical damage, prior to damage occuring. Noakes put forward a model of fatigue that had all athletes never quite reaching their potential due to the brain’s ongoing need to maintain equilibrium or homeostasis. How else could exhausted marathon runners surge towards the end of a maximal effort event?
The earlier focus of  fatigue was the peripheral model, understood as events related to an inefficient tissue oxygen delivery, metabolic accumulation, muscular acidosis and muscle substrate depletion[1]. This theory began in the 1920s, and was ‘validated’ by experimental trials to exhaustion in which oxygen was administered, increasing time to exhaustion. This theory stated that lack of oxygenation to muscles was the main cause of fatigue and pain in exercise: pain equals damage at the onset of pain.
In all likelihood, there are many sources of fatigue that likely involve both central and peripheral effects. Reduced glycogen and increased temperatures being just two measurable physiological markers that can suffer result in feeling the effects of fatigue or pain in sport.

[1] Lima, F. D. R. D., Brietzke, C., Franco-Alvarenga, P. E., Asano, R. Y., Viana, B. F., Santos, T. M., & Pires, F. O. (2018). Traditional Models Of Fatigue And Physical Performance. Journal of Physical Education, 29(1). doi: 10.4025/jphyseduc.v29i1.2915

[2] Tesarz, J., Schuster, A. K., Hartmann, M., Gerhardt, A., & Eich, W. (2012). Pain perception in athletes compared to normally active controls: A systematic review with meta-analysis. Pain, 153(6), 1253–1262. doi: 10.1016/j.pain.2012.03.005

[3] Jones, M. D., Booth, J., Taylor, J. L., & Barry, B. K. (2014). Aerobic Training Increases Pain Tolerance in Healthy Individuals. Medicine & Science in Sports & Exercise, 46(8), 1640–1647. doi: 10.1249/mss.0000000000000273.