Muscles and Fatigue

Why do we fatigue during endurance training and competition? As we all have experienced, muscles ultimately tire in the course of endurance activity. In some cases, fatigue slows us down, but in other situations it can lead to complete exhaustion. Whether it just slows us down or causes us to drop out of competition, it’s a situation that we have control over.

Fatigue itself may be a symptom of other metabolic, neuromuscular, and training problems. And, when we attempt to push ourselves past our limits of fitness, exhaustion may actually be protecting us from more serious damage. Ultimately, as noted above, it’s the brain that slows us, not our muscles. But there are various muscle factors that tell the brain to slow us down.

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The first reason fatigue impairs our brain and body is the lack of optimal development of the aerobic system. Properly trained, our body is equipped to endure for very long periods because the aerobic system is very resistant to fatigue, as previously discussed. In fact, the aerobic muscles improve function when activated, rather than fatigue. That’s why power output of aerobic muscles can be greatest at the very end of competition during the final kick. This requires a properly trained aerobic system, which when highly developed enables us to continue running a marathon at a relatively fast pace with less fatigue.