In this post we discuss what causes muscle cramp and what you can do to prevent it.
Before we start, have you seen the film Pineapple Express?
Stay with me here. There’s a scene in which one of the main characters, Saul, tries to kick out the windscreen of the police car he’s driving and gets his leg stuck.
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 cramp and why we get it.
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 100 years or so to the Industrial Revolution.
Miners working in the hot and humid conditions of the pit reportedly suffered from muscle cramps. This was thought to be due to a loss of salt through excessive sweating and ‘water poisoning.’
They found adding salt to their drinks helped.
Likewise stokers who worked on ocean liners suffered similar issues and added sea water to their drinks to reduce muscle cramps.
More recent research has shown that American football players, who suffered cramps at hot pre-season training camps, 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 practising 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’s certainly my experience too. Early season bike races in the UK tend to be held in bone-chilling cold rather than tropical heat.
It appears 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 seem to 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.
In a South African study on Ironman triathletes, those who suffered from cramp had no significant difference in either percentage body mass loss or serum electrolyte concentrations.
Interestingly, the SA research group also measured electrical activity in muscles that had cramped and compared it to those that hadn’t. They noted increased activity in the cramping muscles, which they thought may be due to increased neuromuscular activity. More on this in a moment.
In a further study using more 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. This was 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’ll have likely found the most reliable treatment for a cramped muscle is to stretch it immediately. It’s certainly our instinctive response. If one of the most reliable treatments 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 found 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?
Fluid and electrolyte imbalance
It goes without saying that preventing dehydration is important. It’s also worth replacing lost salt, or ensuring you’re 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, or adding a little more salt to your diet could prove useful however.
It’s no coincidence that most of us cramp more during early season races or when we’re attempting something particularly challenging. 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, have shown strength work can be effective in eliminating these occurrences.
Theories on fatigue of the neuromuscular system as a cause of cramp give us both an effective intervention and the areas to focus on to avoid it.
We know that muscles are more likely to cramp when taken into their short position. We can however train muscles to better tolerate these positions.
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 are 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.
It also seems that muscles don’t appreciate performing at the exact same lengths for long periods of time. This is an indication to switch up your positions intermittently.
If you’re cycling for example, get out of the saddle now and again and try dropping your heels on the pedals to stretch your calves.
What to do if cramp strikes
If all else fails and cramp does strike, the best thing to do is to try to keep moving slowly.
Should this proves fruitless then you have no other option but to stop what you’re doing and stretch the cramping muscle.
Hold the stretch for 10 seconds or so and the cramp should pass. Repeat again if necessary.