Theory 09/Sports & Exercise Physiology /Fatigue theory/3 min
Fatigue Is a Prediction, Not a Governor
The brain is said to hold a governor. It may be running a forecast.
Fatigue is the output of a predictive model of remaining capacity rather than a central governor that protects the body, so it should be updated by unexpected evidence and should be manipulable by information at fixed physiology.
01The evidence
- The central governor model has been critically reviewed, with the review noting that the model explains the phenomenology but lacks a specified mechanism and makes predictions that are hard to falsify.British Journal of Sports Medicine
- The critique identifies the gap that a predictive account would fill: a mechanism that generates the pacing decision from available information rather than a homunculus that limits output.CGM critique
02The tension
Fatigue is explained either peripherally, by metabolite accumulation, or centrally, by a governor. The peripheral account fails because fatigue can be reversed by motivation, and the governor account fails because it names an agent without describing what it computes.
03The theory
The brain continuously forecasts how long the current effort can be sustained, using prior experience, afferent feedback and the expected task duration. The forecast, not the metabolite concentration, sets the chosen output.
A forecast can be wrong, and it can be updated by information. That predicts that misleading information about the remaining distance should change output at fixed physiology, and that unexpected progress should increase it.
The prediction is that pacing should be predicted by the forecast error rather than by any physiological variable, and that interventions which change the forecast should change performance without changing the body.
The practical consequence is that pacing strategy becomes an information problem, and that fatigue in clinical populations could be assessed as a forecasting deficit rather than as a metabolic one.
04What this is not
The governor names a limiter without specifying its computation. This specifies a forecast, which makes falsifiable predictions about information effects at fixed physiology.
05Predictions
- P1Misleading distance information should change output at fixed physiology.
- P2Pacing should be predicted by forecast error rather than by metabolites.
- P3Unexpected progress should increase output.
06What would refute it
Output invariant to information at fixed physiology would leave the governor's implicit determinism intact.
07What it would change
It would make pacing an information problem and change how fatigue is assessed clinically.
08Evidence base
- Is fatigue all in your head? A critical review of the central governor model — BJSMhttps://bjsm.bmj.com/content/40/7/573.short
- Central governor model — critical review recordhttps://scholar.google.si/citations?view_op=view_citation&hl=en&user=GZCp8PoAAAAJ&citation_for_view=GZCp8PoAAAAJ:O3NaXMp0MMsC