Muscle Meltdown – Rhabdomyolisis
Another marathon runner breaks down at the finishing line and is rushed to the hospital for treatment. Chances are that the athlete has overheated some muscles and suffers from a potentially life-threatening muscle meltdown. ‘I’m not a marathon runner, so why should I care?’ you say. Unfortunately, the illness is quite common. Rhabdomyolisis, as it is known to doctors, may strike by itself or can coexist with other heat-related illnesses, such as heat intolerance or heatstroke. Estimates put its occurrence at 1 in 10,000 people, regardless of age or gender. Untrained or non-acclimatized people exerting themselves in hot and humid weather are potential victims.
When the muscles overheat, they accumulate large amounts of calcium in their cells. This activates enzymes, which in turn kills the cells. The residue of the cells is then released into the bloodstream and filtered out by the kidneys. One compound of the dead cells is myoglobin. Just as cholesterol can congest your blood vessels, myoglobin clogs up the fine canals in the kidneys. Once the myoglobin breaks down, it becomes toxic. Both effects, the clogging and the toxicity, may lead to kidney damage or failure.
This condition is a temporary loss of consciousness, or fainting, triggered by prolonged standing in the heat. The dilated blood vessels allow the blood to pool in the otherwise stationary lower parts of the body. If someone is unable or unwilling to move their legs, the brain suffers temporarily a shortage of blood – and fainting occurs. A horizontal body position aids the blood flow to the brain and the situation corrects itself within minutes.
Heat syncope occurrences during parades of soldiers or the police are a typical example. As fit as most of them are, standing still in hot conditions and enduring boring speeches or presentations fells even the toughest. And a felling it is. Without much warning, the person faints and hits the ground. He or she will wake up in the arms of a caring ambulance officer. Unfortunately, not only the ego may be bruised.
‘I hate the heat.’ No, this is not heat intolerance. Heat intolerance is an illness that impairs the normal functions of the body’s temperature regulation system. Even the slightest rise in temperature triggers hot flushes and profuse sweating in some patients. Normally, your body adapts to hot conditions (see ‘Acclimatization’), but someone with heat intolerance doesn’t adapt, or does so very slowly.
One common cause is the excess hormone production of the thyroid gland – a condition known as hyperthyroidism. Too much of the hormone increases the metabolic rate, which creates more heat. Exercise and medication can aggravate hyperthyroidism, so if you have the condition you should maintain a comfortable room temperature and replenish lost fluid.