Don’t cramp your style

The conventional wisdom on muscle cramps – that they’re punishment for sweating out too much f luid and electrolytes without replacing them – has been under attack for more than a decade. Research keeps failing to support that explanation, and an alternative theory based on disrupted neuromuscular ref lexes has gained support. There’s even a product called HotShots, with a barely palatable spiciness that promises to jolt the affected nerve receptors and disrupt the cramp. But although there’s some evidence that this approach can be helpful, it’s far from a reliable cure. So what’s a cramp-prone runner to do?

A new study by Spanish researchers in the Journal of Strength and Conditioning Research suggests some ideas. The researchers performed a series of tests on 84 runners before and after the Valencia Marathon. Twenty of the runners ended up cramping during or immediately after the race. As with previous studies, blood and urine tests found no difference in the hydration or electrolyte levels of the crampers compared to the non-crampers. They also didn’t find any obvious differences in training or pacing: the crampers hadn’t started the race unusually fast relative to their fitness.

But there were two key differences. The crampers had much higher levels of markers of muscle damage in their blood, and only 25 per cent of the crampers reported regular lower-body resistance training, compared to 48 per cent of the non-crampers. This led the researchers to speculate that lifting leg weights helps your muscle fibres resist the micro-damage that accumulates during a marathon, lowering the chances that you’ll end up cramping. At this point it’s just a theory, but if you’re a habitual cramper, it could be one more reason to step up your strength training.

Alex Hutchinson is a Toronto journalist specializing in the science of running and other endurance sports.