Expert explains

What often triggers calf cramps

There are many different causes of calf cramps.

(Bild: Viacheslav Iakobchuk/stock.adobe.com)

There is hardly anyone who has not suffered from calf cramps. Without warning, the muscles at the back of the lower legs contract and harden extremely painfully. A doctor can explain the various causes behind this.

Depending on age and time of day, there can be different triggers for calf cramps, as Prim. Dr. Thomas Maca, internist and head of the Department of Internal Medicine III at the Evangelical Hospital Vienna, reports. He explains: "While foot deformities or incorrect loading or overloading during sport often lead to sore muscles in adolescence, the causes are different in old age."

If the calves do not cause any discomfort in the morning, but feel increasingly heavy during the day, this can be seen as an overload reaction of the veins that have become congested due to prolonged sitting. "Vein problems typically increase during the day and then peak in the afternoon or evening, depending on working hours," says the cardiovascular disease expert.

Circulatory disorders as the cause
According to Prim. Maca, a reduced blood flow caused by vascular occlusion usually occurs during exercise. Those affected can walk a few hundred meters quite well before their calves suddenly hurt so badly that they have to stop. This circulatory disorder, known as peripheral arterial occlusive disease (PAD), not only occurs predominantly in cigarette-smoking patients with high blood pressure and elevated blood lipid levels, but also in diabetes mellitus.

Circulatory cramps can occur if the reduced blood flow is so extreme that the lower blood pressure at night causes severe oxygen deficiency (ischemia) in the tissue. However, this usually only affects one leg - namely the leg with poorer blood circulation - with a cold white foot, as the specialist explains.

Side effects of some medications
Certain medications are also sometimes the cause of calf cramps. Prim. Maca: "Insulin therapy can lead to lower potassium levels in the blood. Hypokalemia is then characterized by general weakness, muscle tremors, but also muscle cramps. Even more cramps are caused by too little calcium - hypocalcemia, which can be seen in kidney disease, among other things." The simple determination of electrolytes (sodium, potassium, chloride, magnesium, calcium, phosphate) can provide crucial information.

Taking some medications can also result in sore muscles.

(Bild: DenisIsmagilov, stock.adobe.com / KroneMED)

For patients taking various medications, such as those for diabetes or heart and kidney failure, Prim. Maca recommends carrying out a urine and blood gas analysis to clarify whether a precursor to ketoacidosis (metabolic acidosis) is present. "That would be a very rare side effect. But you should still think about it".

If patients take high doses of gastric protection (proton pump inhibitors) for a long time, this can indirectly lead to a reduced absorption of vitamin B12, as the doctor goes on to explain. This vitamin is not only important for our immune system and the formation of red blood cells, but also for nerve function. "Reduced nerve function in the form of neuropathy can lead to or contribute to unsteady gait, weakness and nocturnal calf cramps," says Prim. Maca.

Nerve damage due to diabetes
If diabetic polyneuropathy is behind the agonizing, nocturnal calf cramps, they are usually felt almost equally on both sides. Prim. Maca: "The symptoms usually only occur after many years of diabetes. To confirm this suspected diagnosis, a neurological measurement of the nerve conduction velocity (NLG) of the legs can be carried out. This can be used to determine which parts of the nerve fibers have already been affected and to what extent. Medication can then be administered. In some cases, electrical treatments using high-frequency therapy or physical therapies are also useful."

Orthopaedic problems in the lumbar spine, for example, can lead to calf cramps in several ways. Intense sport, such as cycling or swimming, places incorrect strain on both the cervical and lumbar spine. Prim. Maca: "In addition, all areas close to the calf, such as the knee region or the Achilles tendon, can affect the calf muscles. However, the symptoms tend to occur unilaterally and during exercise. Sometimes it would be advisable to have a (sports) orthopaedic assessment."