Voluntary muscle contraction is the result of an intricate step-by-step process leading to relaxation. Muscle cramps occur when a muscle is contracted involuntarily and does not relax. Cramps in the leg are fairly common in the calf muscle--a cramp often called a "charley horse"--and in the quadriceps, at the front of the thigh, and the hamstring, at the back of the thigh. The exact cause of muscle cramps is relatively unknown; however, an array of factors are believed to predispose individuals to leg cramps.
Dehydration and Electrolye Depletion
Short-term, high-intensity exercise or prolonged, sub-maximal exercise often leads to significant fluid loss and subsequent electrolyte depletion,muscle fatigue and a reduced ability to perform work. Low levels of electrolytes, or electrically charged ions, are a common cause of leg cramps. Adequate levels of potassium, sodium, calcium and magnesium are required for muscle contraction and relaxation.
According to Buzzle.com, the most common cause for leg cramps is insufficient intake of water. Exposure to excessive heat increases the risk of cramping. Aside from athletes and those participating in rigorous activity, infants, young children and the elderly are also very susceptible to cramping in these conditions.
Poor Conditioning and Fatigue
Lack of flexibility, lack of stretching and lack of physical activity produces shortening of the muscles and connective tissues, thereby restricting joint mobility. Moving the joints and muscles of the leg in a repetitive pattern restricts range of motion due to the tightening and shortening of the muscle tissue. Failure to properly stretch in order to elongate muscle fibers in the leg can lead to cramping. Poorly conditioned individuals are at a heightened risk for oxygen depletion within the muscles and subsequent buildup of waste in the muscles, ultimately leading to cramping.
Other Conditions and Diseases
According to Dr. Nathan Wei, conditions that interfere with blood circulation--such as diabetes, rheumatoid arthritis and thyroid disease--can cause repeated cramps. According to the Mayo Clinic, compression of the spinal nerves that run from the back to the back of the thigh can result in leg muscle cramps. This is commonly seen with conditions such as tumors of the spine, osteoarthritis and herniated disk. Conditions including Lou Gehrig's disease, hardening of the arteries, narrowing of the spinal canal and thyroid disease can also cause muscle cramping.
