CNS and PNS fatigue as related to hypertophy

While CNS and PNS fatigue can be distinguished, they are still related because they both affect force production during the course of a training session.

Importantly, when the goal is muscular hypertrophy, we usually want to minimize CNS Fatigue, which is the reduction in force production caused by the brain and spinal cord, which results in decreased motor unit recruitment.

The reason why CNS Fatigue should be minimized, it’s because it affects the highest-motor units, which actually govern the largest muscle fibers (which are also the ones that grow the most through strength training).

At the same time though, it’s important to keep in mind that CNS fatigue is unavoidable, to an extent, as it naturally occurs through the length of a workout.

This implies that monitoring training volumes & intensity, as well as implementing the right recovering strategies will be important to minimize CNS Fatigue & optimize hypertrophy.

On the other hand, PNS Fatigue affects the working muscle fibers, and causes a reduction in force production as well, which is what contributes to causing us to reach failure within a training set. However, this fatigue can also *increase motor unit tecruitment* (which is important for hypertrophy) by forcing additional fibers to work and compensate for ‘tired muscle fibers’, via metabolite accumulation–following Henneman’s Size Principle–during prolongued exercise.

While CNS Fatigue should generally he avoided to optimize training stimulus, some amount of PNS Fatigue can be beneficial, if adequately programmed.