Muscle exhaustion is an unavoidable problem. It is also a phenomenon not completely understood. Muscles may grow tired from a lack of energy, but they tend to remain tired long after the rest of the body has returned to its resting state--so a deeper physiological problem is also occurring.
Definition
According to a 2008 paper called "Muscle Fatigue: What, Why and How It Influences Muscle Function" published in The Journal of Physiology, muscle fatigue is defined as the transient decrease in muscle performance capacity, which is characterized by the inability to generate a reasonable level of force or power. The duration and intensity of the fatigue depends upon the person and the conditions which caused the exhaustion.
Physiological Causes
Exhaustion can occur in the muscles due to repeated and sustained contractions, especially if a great enough force is exerted upon them. This causes impairment to the contractile muscle filaments and the neurological transmission mechanisms within the muscles. Any type of exertion over a long enough period of time can cause exhaustion, from weight lifting to calisthenics to running or walking.
Calcium
According to a 2008 report by researchers at Columbia University, calcium flow inside of the muscle cells could be responsible for muscle fatigue. Calcium typically controls muscle contractions; but when muscles grow tired, tiny channels begin to leak calcium, weakening contractions and stimulating enzymes that eat into muscle fibers. Another culprit might include interference in the process of cellular metabolism.
Aggravations
There are a number of factors that can exacerbate muscle exhaustion such as daily stress, lack of sleep, poor technique during exercise and bad habits. These bad habits can include smoking, drinking and an unhealthy diet, which all tend to inspire lethargy. Continuous practice can increase resistance to muscle fatigue.
Symptoms
One physical symptom associated with muscle exhaustion is a temporary loss of strength, which may take several days to fully convalesce. However, attenuated strength can also expose the muscles to tears and sprains which are much longer and more severe in nature. This is because exhausted muscles fail to protect the connective tissue, increasing the risk of damage to the bone, cartilage, tendons and ligaments. Loss of technique and poor mental acuity associated with fatigue simply serve to exacerbate the problem. Running more than 40 miles a week may increase the risk of injury greatly.
References
- San Diego State University: Muscle Fatigue
- Weight Loss for All: Fatigue During Exercise
- New York Times; Finding May Solve Riddle of Fatigue in Muscles; Gina Kolata; February 12, 2008
- The Journal of Physiology: Muscle fatigue: what, why and how it influences muscle function
- Brian Mac Sports Coach: Injury Prevention
