Causes of Hamstring Cramps

Hamstring sprain or cramps
A runner feeling a hamstring cramp (Image: Maridav/iStock/Getty Images)

Your hamstrings are muscle group located on the rear of each upper thigh. It's common to experience tight, strained or cramped hamstrings, which can occur for several reasons. Upon dealing with hamstring cramps, take steps to prevent them from occurring again. Before trying any new exercise or treatment, talk to your doctor and have your condition properly diagnosed.

Muscle Fatigue

Hamstring cramps are common among people who are unconditioned and those who participate in seasonal intense sports, reports the American Academy of Orthopaedic Surgeons. During strenuous bouts of exercise, your hamstring muscles can fatigue and cramp due to the muscles not getting enough oxygen. When they lack oxygen, your hamstring muscles will contract and spasm involuntarily. Thorough stretching, and then starting out slowly and gradually working up to a more intense level of exercise, can help avoid these types of cramps.

Muscle Tightness

When hamstring muscles are overly tight, they can start to contract and spasm. People who are sedentary can find their hamstring muscles feel tight or hard. Hamstring cramps due to tight muscles can happen when you are active, sitting or lying down. A daily program of general stretching or a program geared to your sport can often help you prevent hamstring cramps. It is equally important to properly warm up before and cool down after any activity.

Heat and Humidity

Exercising in hot, humid conditions can lead to hamstring cramps. When your body loses too much fluid through excessive sweating, you can also develop an electrolyte imbalance. Substances such as calcium, potassium and others are necessary to help your muscles contract properly. If your body is low in any of these substances -- either through a poor diet or dehydration -- your muscles can involuntarily contract and spasm. Drinking enough water and eating healthily before and after exercise can help resolve these kinds of cramps.

Medical Conditions

People with medical conditions that interfere with their body's muscular or nervous system can often hamstring cramps. A disc injury in your back that compresses nerves, for example, can cause your leg muscles to tighten and spasm. Certain medical conditions, such as Parkinson's disease, multiple sclerosis and cerebral palsy, can make your leg muscles rigid and prone to cramping. In addition, MedlinePlus states diseases that affect your levels of potassium or calcium can also contribute to this symptom. These include thyroid diseases, kidney problems and alcoholism. Being pregnant can also stress your body and cause hamstring cramps. Discuss any unexplained cramps that you cannot resolve with stretching or diet improvements with your doctor.

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