Muscle cramps can be a debilitating and extremely unpleasant part of exercise.
In this post we’ll take a deeper look at what causes muscle cramp and how to prevent it.
First up, have you seen the film Pineapple Express?
Stay with me, this is relevant.
Do you remember the scene when Saul tries to kick out the windscreen of the car whilst driving and gets his leg stuck?
As a former road racing cyclist, that clip perfectly illustrates my drive home from early season bike races.
At some point, usually on an anonymous piece of motorway, I’d suffer with leg cramps that would require me to get the afflicted leg as straight as possible.
Easier as a passenger, more challenging as the driver.
The strange thing was, after a month or so I would have no further issues and the motorways of Britain would be a safer place.
Let’s take a look at what the research says about the causes of cramp.
Fluid and electrolyte imbalance.
Ask most health care professionals how to prevent cramp and they’ll tell you to take on more fluids and make sure you replace lost salt and electrolytes.
The evidence for this approach can be traced back some 100 years or so to the industrial revolution.
Miners working in the hot and humid conditions of the pit reportedly suffered from muscle cramps.
These were thought to be due to a loss of salt through excessive sweating and ‘water poisoning’; in effect dilution of the miner’s sodium concentrations through drinking water.
The condition of the miners was improved in most cases by adding salt to their drinks.
Likewise stokers who worked on ocean liners suffered similar issues. They reportedly found adding sea water to their drinks reduced incidence of cramp.
More recently it’s been shown that American football players who historically suffered from cramp, demonstrated higher salt concentrations in their sweat versus those who had no history of cramping.
Additionally, increasing dietary salt intake has been shown to reduce cramps in tennis players who were experiencing issues in hot and humid conditions.
But wait a minute I hear you say, sometimes I cramp when it’s not hot and humid.
Yes that was certainly my experience too. Early season bike races in the U.K are more bone chilling cold than tropical heat.
Just a cursory viewing of this year’s London marathon, which took place in relatively chilly conditions, will show you people were still cramping.
It would appear that whilst fluid and electrolyte balance are one potential cause of this issue, they are not the only one.
Exercise induced muscle cramps.
Exercise induced muscle cramps occur irrespective of weather conditions and fluid loss. Several studies have confirmed this.
In a trial looking at male runners before and after a marathon, no difference was found in fluid and electrolyte balance between the runners who suffered cramps and those who didn’t.
This South African study on Ironman triathletes, found those who suffered from cramp had no significant difference in either percentage body mass loss or serum electrolyte concentrations. Post race serum sodium concentrations were lower in the cramping group, but deemed to be within normal clinical ranges.
Interestingly this group also measured electrical activity in muscles that had cramped and compared it to those that hadn’t. They noted increased electrical activity in the cramping muscles which they thought was due to the neuromuscular system.
More on the significance of this in a moment.
In a further study using Ironman triathletes, subjects were surveyed before an event and asked questions about personal best performances, current training loads and cramp history.
The researchers found that athletes who experienced cramp during the event had exercised at a higher intensity during the race and had a faster overall time. This despite having similar preparation and performance histories to those who didn’t cramp.
The researchers concluded that fatigue is a greater predictor of cramp than dehydration or serum sodium changes.
More recent theories about exercise induced cramp have investigated fatigue related disturbances in the neuromuscular system.
You have probably found that the most reliable treatment for a cramping muscle is to stretch it immediately. It’s certainly our instinctive response.
If the most reliable treatment for cramp involves adding tension to the afflicted muscle, then perhaps one of the underlying causes is a lack of tension. Or more precisely, a lack of tension on specific structures.
Embedded within the tendons of muscles are receptors called Golgi tendon organs (GTOs). The role of the GTO is to measure, feedback and reduce tension within the muscle when necessary.
It’s thought that in the fatigued state there is a reduced inhibitory effect from the GTOs. The regulation of tension becomes unbalanced as the muscle is subjected to greater excitatory signals from the alpha motor neuron. Cramp eventually ensues.
This theory is supported by the increase in electrical activity that has been demonstrated in cramping muscles.
It’s also been shown that muscles are more prone to cramp when in their shortened ranges.
This is particularly true of two joint muscles such as the hamstrings. It’s thought that the unloading of the GTO also plays a role in this effect.
So what steps can you take to reduce your risk of cramp?
1) Fluid and electrolyte imbalance.
It goes without saying that preventing dehydration is important. It’s also probably worth making sure you are replacing lost salt. Or at least not diluting your existing levels by solely drinking water.
This is particularly relevant if you are exercising in hot conditions, or know you are a salty sweater. Look for salt deposits on your skin or clothes as evidence of this.
Specific recommendations are difficult to make as we all lose salt at different rates. Carrying some salty snacks with you when you exercise, or adding a little more salt to your dietary intake could be worth trying.
2) Muscle fatigue.
It’s no coincidence that most of us cramp more during early season events, or when we’re attempting a particularly difficult challenge. In this context cramping can be seen as a message that we need to improve our conditioning.
Studies looking at individuals who always cramp in the same muscles, usually in the later part of endurance events, have shown strength work can be effective in eliminating these type of occurrences.
A strength training programme which begins by isolating the muscles involved in your particular activity is a good place to start.
3) Neuromuscular fatigue.
Theories on neuromuscular fatigue as a cause of cramp not only give us an effective intervention (stretching), they also gives us potential areas to focus on to avoid it in the first place.
Resistance train into positions of weakness.
We know that muscles are more likely to cramp when taken into their short position. We can however train muscles to tolerate these positions better.
For example, two joint muscles like your hamstrings may be prone to cramp when your hip is extended and your knee is flexed. If you find this to be the case then it’s likely you’re also weak in this position.
Applying resistance to these positions will not only reduce your risk of cramping, but may have the additional effect of improving your performance in your chosen activity.
If cramp strikes, stretch!
If all else fails and cramp does strike, the best thing to do is keep moving if possible.
Should this proves fruitless you have no other option but to stop and stretch the cramping muscle.
Hold the stretch for 10 seconds or so and the cramp should pass. Repeat again if necessary.