Three-Factor Model of Fatigue (3F)
by Mladen Jovanovic
Before I even start, check this article!
Discussing on CNS Fatigue thread, I got the idea to create Three-Factor Model of Adaptation — 3F. Here is the basic premise:
Preparedness = Fitness + Fatigue + Facilitation
Fitness, fatigue and facilitation are “immediate” and specific effects of a training stimuli.
Fitness is level of particualar trait/ability. It is the most “inertial” factor… slowly raise, slowly falls (compared to other two)… Fitness increase spents C.A.R. (Current adaptation Reserve) — or some form of "adaptation energy "— which should be “reffiled” from bigger “buffers” during unloading phases. This is one of mine premise for wave-like loading and unloading principles. Others are: fatigue accumulation, synchronizations of the traits, rest, general/specific ratios etc… Fitness increase is limited by Upper Genetic Limit and Genetic Adaptation Reserve (which can be spend prematurelly by non-continuous training, stress etc, before even reaching Upper Genetic Limit)
Fatigue is (according to my undestanding) an „expression“ (and sensation as RPE, tiredness etc) of control mechanism which limit performance to protect the body from damage or death. It can have various forms and various properties like delayed phenomena in HI CNS fatigue. Fatigue is also specific as fitness is. Fatigue have allways negative sign (contrary to Fitness)… Fatigue is related to Fitness — as athlete advances he need more stress to produce only small increase in Fitness, but it increase great amount of Fatigue.
Facilitation is the the shortest effect of training load. It is also called PTP — Post Tetanic Potentiation, but it may be also due arousal, stimulants, etc. Higher Facilitation can cause higher levels of fatigue afterwards due higher system taxing. It can also have positive effects on performance as negatives — depends on the level of it.
All three of mentioned factors are conceptuall and interconnected!
Speed of adaptation/improvement depends on the “dose-response”, or the ammount of work/load needed to increase fitness (and the level of that increase), but also of the fatigue created by the same ammount of load and the time of recovery (recoverability)! Thus, for best resutls (at the current point in athlete’s career) the one should find the optimal workload to produce optimal adaptation but to also allow the recovery from the same!!! Thus you should use the minimal load to provide adaptation and fast recovery. If you use larger loads, the fitness will increase more, but it will take more time for Fatigue to decline, and thus effects will be less. One should search for optimal loading protocols for a given athlete at a given point in athlete’s career. Note that relations are non-linear!
3F Model can explain all the “modern phenomena” in training better than 2F and 1F models, like: delayed fatigue, fatigue accumulation, facilitation, need for unloading, etc. Due interactions of Fitness, Fatigue, Facilitation and presented „energy adapation drain“, it can be pretty simple to understand the superiority of Conjugate Sequence System and the fight of various traits (e.g. strenght and speed) for same adaptation energy!