Training load and the achievement of functional overreaching is part of a required cycle of the ‘stimulus-recovery-adaptation model’. However the type of fatigue achieved may well command the type of recovery strategies put in place. The challenge for the trainer is to identify which specific psycho-physiological capacities require recovery strategy and then select recovery modality appropriately in order to restore and provide positive adaptation.
There are four main types of fatigue:
- Metabolic- energy/substrate stores
- Neural– CNS neural drive and PNS localised force production
- Psychological– emotional and social stress
- Environmental– travel, climate
Here is a breakdown of each type of fatigue:
Metabolic fatigue typically occurs as a result of excessive, demanding training loads and culminates as an offset between training and recovery/inadequate nutritional strategy. Whilst it is part of the normal adaptation cycle, if recovery is not provided then potential to move from overreaching into overtraining may occur. There are a number of markers that may highlight metabolic fatigue including measurements of immunoglobins, blood inflammation markers, HPA axis hormones and neurotransmitters.
Neural fatigue can occur in either the central nervous system (CNS) or peripheral nervous system (PNS). Fatigue of the CNS is expressed by a lack of drive or motivation or conversely a lack of power production regardless of mood state. PNS fatigue can be more localized to specific muscles and typical symptoms where reduced force can be seen. For both types of neural fatigue, metabolic fatigue may not be present at the same time. Simple tests such as vertical jumps and dynamometry can provide quick results related to CNS fatigue and should be conducted regularly during high load training. Neural fatigue is likely to occur with higher intensity exercise such as Olympic lifting, heavy weight training and also plyometrics.
Psychological fatigue relates to the stress of sport-related competition (nerves, anxiety, lack of confidence) or non-training stressors of daily life- these may include emotional or social factors but can still culminate and have negative consequences on training ability (stress at work, at home, family, money etc.) It is important to try and manage these stressors as much as possible or risk negative hormone effects such as increased cortisol which can itself negatively affect androgenic hormone balance. Simple tests to assess psychological wellness include the POMS and RESTQ-76 questionnaires which are used commonly in athletic populations.
Environmental fatigue may occur as a result of staleness (lack of change of programming, equipment and/or literal environment). It is important to regularly change exercise focus and modality to reduce this as much as possible. Environmental fatigue may also occur as a result of travelling or changing climate conditions. Whilst the latter may be an issue for competitive sports-people that travel on a regular basis, it is much less likely to be an effector with general population clients. Potential changes in circadian rhythm (as also seen with night shift workers) may occur due to inconsistent sleep-wake cycles, time zones and sleep patterns. Changes in humidity, temperature may even contribute to metabolic fatigue.