Why do I get cramp and how do I stop it?


30.03.16 at 4:17 pm

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When I first started competing in longer distance races, marathons and Ironman events, I initially had difficult races. I was fully trained and not overreaching but typically towards the end of a race, I would suffer badly from cramping and loss of performance. This was despite following widely accepted hydration advice available at the time.

I’m definitely one of those guys that sweats a little more than average and I’m always  coated head to toe in a white residue post-race. I started to put two and two together and the topic of sweat and the effect it has on performance started to become a hot topic of interest for me. Initially I thought it was down to the amount of fluid I was losing, what I didn’t realise, is sweating profusely results in a dramatic loss of minerals – in particular sodium and potassium – and this has a massive effect on performance.

It was this realisation and the subsequent sweat test (offered by Precision Hydration) that helped me overcome my issues and squeeze as much benefit out of my training as possible. The first time I used and understood the importance of replacing the salt (as well as hydrating) in a race I managed to break 3.30 for a marathon. I then went on to comfortably break 12 hours for Austria Ironman, two events which would have been previously out of my reach.


So why is sodium important? You might associate sodium with heart disease and high blood pressure, but serves a very important function in keeping our bodies healthy. Firstly, it helps maintain fluid balance in our cells. It assists with the transmission of nerve impulses throughout the body, and also helps muscles contract and relax.

If you’re sweating a lot, the logic is you’re probably also losing a lot of sodium. Sodium deficiency causes muscle cramps and fatigue and therefore has a knock on to performance. Often athletes (me being one) consume a great deal of plain water to combat fluid loss, but a danger of this is something called hyponatremia. Hyponatremia is a very serious condition in which – if there is not enough sodium in your body fluids and this deficiency becomes extreme – the body can go into shock and the circulatory system can collapse.

We should also be concerned with potassium intake as it plays a role in the storage of carbohydrates, and fuelling the muscles. The frequency and degree to which muscles contract depends heavily on having the right amount of potassium in the body. When you don’t get enough potassium in your diet, or when the movement of potassium through the body is blocked, your nervous and muscular systems can become compromised.

I’ve spent more than a little time trawling blogs and chasing easy victories, from bitter cherries to ketosis, so it’s fair to say any input that might give me even a tiny edge in training or on race day was more than welcome. When the guys at Precision Hydration mentioned their instant sweat test I was keen to give it a try and before you ask, I did pay for my own test.

After applying a mysterious chemical called ‘Pilocarpine’ to my arm, Jonny from Precision Hydration, hooked me up to a machine originally developed to help people who suffer from cystic fibrosis. The chemical works in tandem with a series of little electric shocks from a strap on my arm to stimulate my skin, and cause it to begin sweating.

The Precision Hydration sales pitch claims that the key to success is proper hydration, and when chasing the right balance of fluids and minerals, it’s not how much you sweat that matters, but its composition.

As I’ve mentioned already, I’m among the sweatier people I know, much to the delight of my colleagues when I return from a lunchtime run. My sweat was analysed by Precision Hydration in just a few minutes and the results were also delivered a few minutes after that. Depending on how you fare, Precision Hydration recommend one of their range of proprietary drink tablets to provide optimum hydration before, during, and after exercise.

The tests run at £95 a go, so by no means cheap, but Precision Hydration insist the figure you get won’t change with time or even a change in training intensity, so the test only needs to be carried out once. They also provide a simpler online test which will gauge your sweat composition based on a series of multiple choice questions.

There have been times I’ve climbed off the Watt Bike to find myself partially blinded by the salt in my eyes, so it was no surprise to me that I came out rated ‘very high’, losing 1412mg of sodium for every litre of sweat.

Results graph

There’s no doubting that replacing electrolytes during exercise is important, it’s the reason we have been drinking hypotonic sports drinks for years. Your concentration of electrolytes affects the rate at which fluids enter and leave your blood stream. As mentioned it affects the efficiency with which your muscles contract, and low levels of electrolytes have been linked to cramping and increased fatigue during exercise.

If you are losing 1400mg of sodium per litre of sweat, and your preference of sports drink is only replacing 500mg per litre, you’re fighting a losing battle from the start.

Precision Hydration sell their own brand of hydration tablets called H2Prohydrate alongside their testing service.  There’s nothing to stop you from taking the numbers off your report and finding something you prefer with similar electrolyte content from a competitor like SiS or High5, but it appears that for someone who loses as much salt as I do, no other brand contains the high level of sodium in a single tablet.

Whether using Precision Hydration scientifically derived ‘optimum’ electrolyte concentration over something more generic has any ‘real-world-benefit’ remains to be seen. The science behind the idea sounds convincing if nothing else, and sometimes that’s all it takes to give you the confidence to push a little harder.


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