Potassium is an electrolyte essential in the function of muscles and nerves. Along with sodium, it maintains the body's water and pH balances, sustaining blood pressure and other physiologic processes. Hypokalemia is the clinical name for low potassium levels and refers to blood levels lower than 3.6 to 5.2 mmol/L. Potassium levels below 2.4 mmol/L can be life-threatening. Exercise can lead to hypokalemia because of the loss of electrolytes during perspiration and urination. Diarrhea and vomiting can worsen dehydration and potassium loss.
Muscle Cramps and Weakness
The role potassium plays in muscle and nerve function can lead to muscle cramps, muscle pain, muscle weakness and fatigue. Low potassium can be a cause of leg cramps in athletes and dancers. Reduced blood flow and the impaired ability of muscles to contract that occurs in severe cases of potassium deficiency can lead to paralysis.
Low potassium levels affect the heart's ability to respond to signals and contract. Potassium deficiency and its effect on blood pressure can further complicate cardiac processes, causing disrupted heart rhythms or arrhythmias and, in severe cases, cardiac arrest.
Another symptom of potassium deficiency caused by exercise is nausea. Falling blood volume and the loss of sodium prohibit absorption of either food or water. Any water taken at this point will simply pass through and out of the body; an athlete with severe potassium deficiency will turn away from food.
Sodium loss can cause swelling in the hands and feet, and low potassium levels can result in irrational behavior. In cases of severe hypokalemia, intestinal paralysis may cause abdominal pain, bloating and constipation. Symptoms of low potassium levels aren't always evident.