Conceptualising, measuring, and researching fatigue in sport and exercise

The study of fatigue in humans has been a source of interest for over a century, since the early work of Mosso ¹ and Hill. ² Despite huge forward strides in technology that provide us with a much clearer and in-depth perspective of the function of the body, many of the observations made by these early pioneers still provide the foundation on which we study fatigue today:

The first (phenomena characterising fatigue) is the diminution of the muscle force. The second is fatigue as a sensation. That is to say, we have a physical fact which can be measured and compared and a psychic fact that eludes measurement. ¹

With young athletic people one may be sure that they really have gone ‘all-out’, moderately certain of not killing them, and practically certain that their stoppage is due to oxygen want and to lactic acid in their muscles. Quantitatively the phenomena of exhaustion may be widely different; qualitatively they are the same, in our athlete, in your normal man, in your dyspnoeic patient. ²

(The limit of exercise) has often been associated with the heart alone, but the facts as a whole indicate that the sum of the changes taking place throughout the body brings about the final cessation of effort. ³

Fatigue of brain reduces the strength of the muscles. ¹

Strength is kept in bounds by the inability of the higher centres to activate the muscles to the full. ⁴

It is not will, not the nerves, but it is the muscle that finds itself worn out after the intense work of the brain. ¹