Hamstring cramps are very common. They can come on suddenly, causing localized tightness and pain on the back of the thigh.

What’s happening? The hamstring muscle is contracting (tightening) involuntarily. You may even see a hard lump beneath the skin. That’s the contracted muscle.

While the cause of hamstring cramps isn’t always known, there are several things — like dehydration and muscle strain — that may contribute to them.

Here’s what you need to know about why you might experience hamstring cramps, as well as how you can relieve the pain and prevent them from coming back.

Some 3 out of 4 cases of muscle cramps happen at night during sleep. Interestingly, many cases of hamstring cramps are considered idiopathic. This means that doctors can’t always point to a specific cause.

That said, there are several situations that may lead to muscle cramps. Read on to learn what these may be.

Muscle strain

Hamstring cramps may result from improperly warming up for an activity or doing too much activity. Muscle strain is the most common cause of cramps.

When you don’t warm up or stretch before exercise, the muscles may feel stressed, making them vulnerable to cramping and other injury. When people overuse their muscles, lactic acid may build up and cause tight cramps.

Dehydration

Exercising and not drinking enough water may also cause hamstring cramps. The idea here is that when water and electrolytes are lost through sweat and not replaced, the nerves become sensitized and make muscles contract.

In particular, working out in hot or humid weather may speed up the process of dehydration and muscle cramping.

Mineral deficiency

Too little magnesium, potassium, and calcium in the body may produce hamstring cramps. These minerals are also called electrolytes.

While drinking plenty of water is crucial during exercise and everyday activity, including these electrolytes is equally important to replenish mineral stores.

Other risk factors

There are also certain risks factors that may make a person more likely to experience hamstring cramps:

  • People who are older generally don’t have as much muscle mass and may stress muscles more easily, leading to cramping.
  • Athletes who frequently exercise in warm weather or who otherwise deal with dehydration may have more cramps.
  • People living with diabetes, liver disorders, nerve compression, and thyroid disorders may experience muscle cramps.
  • Women who are pregnant tend to experience hamstring and other muscle cramps. If these cramps are new, they may go away after delivery of the baby.

Hamstring cramps and other muscle cramps can come on without warning. You may feel a slight tightness at first followed by sharp pain and increasing tightness.

If you look at your muscle, you might even see a lump of tissue under the skin. This is your contracted muscle. The cramp can last from just a couple seconds to 10 minutes.

After the initial cramping has passed, you may experience a feeling of tightness or tenderness for a few hours.

Act fast when you feel a hamstring cramp coming on. While you may not be able to stop it entirely, you may be able to lessen the severity.

Floor stretch

As the cramp takes hold, try gently stretching the muscle in the opposite direction of the tightening. Sit on the floor with the affected leg extended in front of you and your foot flexed. Lean forward gently until you feel a stretch in the hamstring.

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You can also stretch the hamstring from a standing position. Place the heel of the foot on the affected leg on a curb or other slightly raised surface. It helps to steady yourself by holding on to a tree or other stable surface, like a wall. Slowly bend the knee of the standing leg until you feel a slight stretch in the hamstring.

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Massage

As you stretch, you may also consider applying firm pressure and rubbing the muscle to help it release the cramp.

If you have a foam roller, you might try sitting on the floor with the roller under the affected thigh. Slowly use your arms to raise your hips off the floor, keeping your opposite leg slightly bent. Then slowly roll it between your knee and buttocks.

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Hot and cold therapy

The general rule is to apply heat to muscles when they’re tight. So, at the most acute phase of the cramp, heat can help.

You can make a hot compress at home by placing a towel in a bowl of hot (not scalding) water. Wring out the towel, then fold it into a square before applying to the area for 20 minutes.

Alternatively, you can fill a sock with rice, tie it off, and microwave it for 15-second increments until warm. Apply it on the cramp for 20 minutes.

After the contracting has passed, try applying ice packs to ease sore muscles.

You may be able to tweak some things in your everyday routine and kick those hamstring cramps to the curb.

Hydrate

Experts say men should drink 15.5 cups of fluids per day and women should drink 11.5 cups.

These are general guidelines. You may need to consume more fluids depending on your activity level, your age, the weather, or different medications you’re taking.

Women who are pregnant or breastfeeding may need to drink 13 cups of fluids to stay hydrated.

Good fluid choices include plain water, milk, fruit juices, and herbal teas. Sports drinks can help if you’ve been exercising hard for longer than an hour, as they replenish minerals and sugars.

Address deficiencies

Try eating more beans, dried fruits, nuts, and seeds to boost your magnesium stores. Potassium can be found in bananas, prunes, carrots, and potatoes.

If you still think you may be lacking these essential minerals, consider asking your doctor about taking supplements. Pregnant women, for example, often take magnesium supplements to address muscle cramps.

Warm up

Getting your muscles primed and ready for activity can help prevent the strain that leads to cramping. It’s especially important to warm up your hamstrings before exercise if you notice they’re tight.

Instead of starting off with a full run, try walking for several minutes, then:

  1. Stand with your feet hip-distance apart. Bring one foot a few inches in front of the other with the heel touching the ground.
  2. Hinge your upper body forward by bending the standing leg and bringing your buttocks back.
  3. Return to starting position.
  4. Repeat this rocking motion several times for both legs.

Stretch

Along with properly warming up for exercise, try gently stretching the hamstring muscles. Perform the stretches while sitting or standing, whatever feels best to you.

Regularly engaging in yoga may also help. There are different poses that specifically target the hamstrings, including Downward-Facing Dog, Extended Triangle Pose, and Staff Pose.

If you often get cramps at night, do these stretches before going to bed.

While muscle cramps aren’t usually the sign of a more serious condition, they may sometimes be related to underlying health issues, such as:

  • Blood supply issues due to hardened arteries in your legs. This means the arteries to the legs may be too narrow to supply enough blood, especially during exercise.
  • Nerve compression, specifically in the spine due to lumbar stenosis. Pain and cramping with this condition may be worse after long periods of walking.
  • Depletion of potassium, magnesium, or calcium. You may develop insufficiencies through poor diet or by using medications that act as diuretics.

Consider seeing your doctor if your muscle cramps happen frequently and cause severe pain. Also see your doctor if you have:

  • swelling or redness in the legs
  • muscle weakness
  • cramping that doesn’t respond to home care measures

What to expect at your appointment

Before performing a physical exam, your doctor will likely ask you to explain your symptoms. They’ll ask you when the cramps occur, how often, and their severity.

Your doctor may also ask you to provide information about your medical history, including any conditions you have or medications you’re taking.

It’s also important to note what activities you participate in or anything else that may be contributing to cramps.

There are a number of reasons why you may be experiencing hamstring cramps. While unpleasant, cramps are common and may respond favorably to a few simple lifestyle changes, like drinking more water.

If not, make an appointment with your doctor to make sure there aren’t other health issues causing them that need to be addressed.