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What causes cramp? Maybe not water or electrolytes…

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what causes crampMuscle cramping is something everyone has had at some point, and something athletes often battle with, even with adequate liquid and electrolyte consumption – So why does it still happen? To answer this we need to look at new research on what causes cramp and you might be surprised by the results.(2)

Sports drink companies probably aren’t going to like the direction that new research is taking as researchers delve deeper into what causes cramp – specifically exercise-associated muscle cramp.

The theory that dehydration and/or electrolyte loss causes muscle cramp is supported by case studies and observational studies but no high strength studies so they really do need to be taken with a grain of salt…

New research over the last 15 years is suggesting that cramps are actually due to changes in the central nervous system – If this is proven to be definitely the case and hydration is shown not to be a major cause of cramp, it could change a lot as many DNFs and even a few athlete deaths have been put down to over-hydration(1)…

Now neither theories have been definitely proven, so here is a brief summary of the two so that you can make your own mind up on what causes cramp:

1. What causes cramp: The dehydration/electrolyte loss theory?

This theory suggests that sweating from exertion causes the interstitium (also called the “tissue space” or the fluid around your tissue cells) to contract – then causing pressure on nerve endings. This, as well as increased concentration of excitatory chemicals in the interstitium due to decreased volume, is thought to be what causes cramp.

There is reasonably low evidence for this theory and no evidence has shown an increase in this pressure or excitatory chemicals in athletes with cramp. Also on a side note, this theory does not at all explain how static stretching can help cramp as stretching does not change the interstitial pressure or chemical make-up.

2. What causes cramp: The altered neuromuscular control theory?

Alpha motor neuron what causes crampNew studies theorize that when a number of factors combine to increase alpha motor neuron excitability (motor neurons of the spinal cord and brain stem send signals for muscles to contract). Some of these factors (among others) are:

  • Fatigue
  • Poor conditioning
  • Muscle damage

It is not yet fully understood how things like fatigue increases spinal excitability and hence influences muscle cramp onset but none-the-less it is a valid theory and needs to be further explored.

Here is some food for thought on what causes cramp: In a couple of studies, when cramps were induced with low-frequency electrical stimulation – the susceptibility to cramp remained unchanged whether patients were hydrated, dehydrated, pumped full of sodium or with loss of body mass.(2,3,4) So what really contributes to cramping?

Fist aid, Health, Healthy Eating, training

Hydration guide: How much water should you drink?

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advoid dehydration by keeping hydratedIf adequate fluid isn’t taken in, dehydration can happen and will happen. These are the dehydration symptoms to look out for:


  • Thirst
  • General discomfort and complaints


  • Flushed skin
  • Weariness
  • Cramps
  • Apathy


  • Dizziness
  • Headache
  • Vomiting
  • Nausea
  • Chills
  • Decreased performance
  • Dyspnea

Why stopping dehydration is so important:

Water is the essential solvent for your bodies biochemical reactions, and with less of this, your body simply will not function as well. It makes up a huge 63% of our whole body mass (we are basically a big mess of water balloons!) and more importantly at least 80% of our muscles , kidneys and lungs are made up of water – So water is a big part of us. And we don’t just lose water through sweating either; our body is always losing water through our skin, lungs and kidneys, through sweating, urinating and respiration mainly – so this shows that it isn’t only when we are exercising that we need to optimize hydrationSo not only do we lose water throughout the day but when we are exercising, doing physical work or it is a really hot day, we need to be drinking 2-6 times more water to maintain good hydration and keep our cells happy.(5)

It’s not just how much we are drinking – it’s how we are drinking.

Staying hydrated doesn’t mean drinking a couple of liters at the end of the day or after exercise all in one go. The water ideally needs to be consumed in parts – like breaking two liters into four 500ml drinks half and hour apart.

How to monitor dehydration

Even a loss of 2% of body mass can decrease exercise performance, brain function and alertness (1,2), so it is in your best interest to monitor your bodies hydration levels and learn to know how much water intake is right for you.

There are quite a few ways to monitor your hydration but it is important that we can do ones that are easy and inexpensive (unless you are a professional athlete – then you can put some more time and money into it). The two most practical ways to monitor hydration are as follows:

1. Measure your weight loss over an exercise session

Whether this be a sport, running or a busy period of work. Measuring body mass change is a commonly used and safe way to keep an eye on your hydration but is only really useful over a period of 1-4 hours with or without exercise. Weigh yourself before and after your session and calculate the difference – you should aim to keep the change less than 1% loss of body weight.

urine analysis dehydration2. Check your urine color

This is a very easy way to determine how well hydrated you are. All you need to do is check the color of your urine when you go to the bathroom and aim to keep it a very pale yellow (#1 in the chart). If you keep your urine at number 1, then you will generally be within 1% of your baseline body-mass (well hydrated).

This is something that is great to be checked first thing in the morning to know where your hydration is at and start getting it on track.

Combining these two measures is a great one to become more in tune with your bodies hydration needs, which will ultimately mean you perform better and feel better.

So how much should you drink:

Over a normal day, where you aren’t exerting yourself physically (sweating a lot) then this is roughly how much you should aim for:

Women: 2.3 Liters per day

Men: 3 Liters per day

Note: This is not all at once!

If you are exercising then you need to drink quite a lot more:

Before exercise: To make sure you are well hydrated when it comes to exercise, you need to prepare by drinking 500-600ml 2-3 hours before exercise and then 200-300ml 10-20 minutes before exercise.

During exercise: Regularly drinking water or sports drink is key. Ideally, you need to be drinking 200ml every 15-20 minutes (this doesn’t need to be all at once!).

Following exercise: After activity you should aim to re-hydrate within two hours of finishing. Re-hydration should include water for hydration, carbohydrates for your glycogen stores and electrolytes for salt loss when sweating (this also speeds up re-hydration). The amount you need to replenish following exercise varies but you should aim to take in 150% of body weight that you have lost. For example if you have lost 1 kg then you should drink 1.5L of fluid – ideally this should be spaced over two hours.6

Note: Specific individual recommendations are calculated based on sweat rates, sport dynamics, and personal tolerance. It is important to listen to your body as everyone is different and has slightly different needs. Try keeping an eye on the measures talked about here (urine color and body weight loss) and learn what your body needs. It is also very important to not drink too much, too fast.

Lastly, the National Athletics Trainers’ Association has this to say notes that dehydration can compromise athletic performance and increase the risk of exertional heat injury and that in general athletes do not voluntarily drink enough water to prevent dehydration during physical activity.

You need to take it upon yourself to get this right – it makes a big difference to your body.

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