Muscle Fatigue & Weakness Following Intense Exercise


While many athletes have performed extraordinary feats of strength and speed, not a single one of them is immune to the effects of muscle fatigue. Although they propel an athlete’s dynamic movements, muscles do fatigue and have their limits. Muscle fatigue is especially common after performing intense physical activity. Knowing the physiological factors behind muscle fatigue and how to prevent it allows you treat it and lessen its effects.

Lactic Acid Buildup

  • In order to perform intense physical exercise, your body needs energy quickly. This energy is provided in the form of adenosine triphosphate, or ATP, through different energy pathways. One of the key energy pathways for rapid replenishment of energy for intense exercise is anaerobic glycolysis or the lactic acid system. When this energy pathway is highly active, glycogen within your muscles is broken down into ATP to provide your body with energy for intense exercise. However, this process releases a byproduct known as lactic acid, which causes a burning and cramping sensation in your muscles. As a result, performance drops drastically after lactic acid buildup.

Muscle Soreness

  • Your muscles are made up of complex bundles of intricate fibers. When performing strenuous physical exercise that your body is not adapted to, minute tears occur within the muscle fibers. Shortly after the damage has been incurred, your body initiates an inflammatory response. This causes strength loss, pain, muscle tenderness, swelling and muscle stiffness. The pain or discomfort may last for two to three days after an intense training session. Muscle soreness is most common in exercises that require extensive eccentric muscle contraction. Eccentric contraction is the lengthening of the muscle fibers during tension. As a result, muscle soreness is commonly experienced after performing strenuous strength-training exercises.


  • After a session of intense exercise, your body needs time to recuperate. Not giving your body sufficient time to rest may lead to overtraining, a condition that causes impaired muscle recovery, decreased physical performance and chronic muscle fatigue. Muscle soreness and fatigue typically go away after a few days of rest. However, if a person continues to perform intense activity despite having fatigued muscles, the recovery process is disrupted and delayed. As such, muscle fatigue and soreness become more prolonged and persistent.

Muscle Recovery

  • While fatigue is common after intense exercise, it is possible to effectively treat and alleviate the effects. Rest is the key treatment for muscle fatigue. The amount of rest you need depends on the situation. For example, to ease the effects of lactic acid buildup, you only need to rest for about a few minutes or a few hours. Muscle soreness requires days of rest for full recovery. An article published in “Sports Medicine” indicates that it takes months to recover from overtraining syndrome. To speed up the recovery process, it is important to cultivate healthy eating habits. For example, high-protein meals expedite muscle recovery, because they stimulate muscle growth. A nutritious diet combined with enough rest provides good results. For instance, a study published in 2012 in “Medicine and Science in Sports and Exercise” showed that protein intake before bed speeds up muscle recovery overnight.

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