Know Your Fatigue Facts


Fatigue has many faces.  Barbell fatigue is different than marathon fatigue.  Let’s talk  tech on some physiology regarding fatigue.  Muscle fatigue is defined as a reduction in muscle power output that can result from a decrease in both muscle force generation and shortening velocity (S.K. Powers, Exercise Physiology Theory & Application).  Basically speaking, HIIT will cause a quick decline in your ability to maintain or generate power.  

Keep in mind that athletes can develop what's called tolerance to fatigue.  This is the training effect of adapting to a properly balanced training program (remember our Training Matrix?).  This is a big reason why World Gym Athletics will help build strong, fast and efficient systems (athletes).  Tolerance can be trained.  But you have to train and disturb your body to adapt.

Keep in mind that exact causes of muscular fatigue remain uncharted in science. Several factors, not just fitness level, affect fatigue.  Time of day, ambient temperature, nutritional/chemical status, muscle fiber type composition, type of activity, duration of activity, central nervous system readiness and pure drive all affect fatigue.  A short, HIIT style activity (let’s say 60-90 seconds or sprinting 400m) may lead to fatigue variables such as accumulation of lactate, hydrogen ions, inorganic phosphate, and free radicals within the active muscle fibers.  Conversely, fatigue that occurs in an endurance event lasting more than 90 minutes may also involve an accumulation of free radicals in the muscle tissue but other factors such as chemical interruptions in muscle/extracellular electrolyte homeostasis and depletion of muscle glycogen may also contribute.  What’s this mean?  Well, AMRAPs of four minutes will affect our physiology much differently than longer sessions.  As a coach, know these differences physiologically!

Does this mean that our 4-14-24 approach should be extended out to an hour or more? What do you think?  Ask your fellow coaches whether or not we should all be doing sessions that last longer than 24 minutes.  

Research & Science