Pulled up short

Heavy exercise can cause painful muscle cramps but there are some solutions worth considering.

Question:
I periodically get signs of cramp while, or after, clearing trap lines, which takes at least four hours of bushwalking in hilly terrain. Experimenting with salt-water drinks has shown benefits in ending them. Of course, it's not science, but I shall continue the trial.

Answer:
Exercise-associated muscle cramps are relatively common, with a study reporting they occurred in about 39% of marathon runners, 52% of rugby players, 60% of cyclists, and a sizeable 68% of triathletes.

Cramps also afflict more than a few Listener readers, judging by the emails following our column on night cramps (A complex problem, April 15). The column suggested trialling a vitamin B complex supplement for night-time leg cramps in older adults (see reader question, opposite).

However, cramps that occur alongside heavy or prolonged exercise, along with potential dehydration, require a different solution.

Although water is essential for hydration, drinking too much plain water during exercise can negatively affect performance. So-called overhydration during ultra-marathons, for example, is the primary characteristic of hyponatremia, which causes painful muscle cramps. Individuals with the condition have abnormally low sodium levels in their blood, which is problematic as sodium regulates the amount of water in and around body cells.

Drinking too much water during exercise may dilute the sodium and other electrolytes in the body, increasing the risk of muscle cramps. Indeed, researchers have found that marathon runners who experience them during an event have significantly lower blood sodium levels than other runners.

Oral rehydration solutions (ORS) treat or prevent dehydration and contain much higher sodium and potassium levels than a regular sports drink.