How to avoid muscle cramping in rugby games

This weekend, many of the country’s best amateur rugby players will be participating in the round of 32 and sweet 16 playoffs. It’s a big weekend, one of the most challenging on the American rugby calendar.

What makes it so tough? Mostly it’s the fact that players will be asked to perform at their highest level to date on back to back days. That’s right, these first two rounds of playoffs will be played on Saturday AND Sunday, a brutal test of endurance for amateur rugby players.

In Central Texas, we’re expecting temperatures to be 85+. No doubt other hosts will have similar or even more severe conditions.

This weekend, you’re going to see a lot of muscle cramping. You’re going to see a lot of players going down with severe calf cramps specifically. And your initial thought is going to be that those players are under-hydrated. Or if you’ve read slightly more on the topic, you’ll think they’re suffering from a lack of electrolytes.

Contrary to popular belief, neither of these things causes muscle cramping during athletic competition. Is it good to stay hydrated? Absolutely. Is it good for you to have enough salt? Definitely. But the science suggests muscle cramping is caused by something else that will also be on display this weekend… more intense competition.


A muscle cramp is identified as a sudden, painful contraction of a muscle (or part thereof). They usually persist for between a few seconds and a few minutes. In rugby players, they will typically occur in the calf or foot muscles first followed by the hamstrings and quadriceps. Cramping in the lower legs often happens on the rugby field during a game. Whereas cramping of the upper legs is more common after a match, when you’ve had the chance to sit down.

Muscle cramping in athletes has been studied and misunderstood for the better part of a Century. For most of that period, it’s been thought that cramping was the direct result of dehydration and electrolyte deficiency. In recent years, a slew of products have hit the market that purport to prevent and treat cramp through nutritional supplementation.

But a European study in 2013 titled ‘Origin and Development of Muscle Cramps‘ determined that “the main risk factors for exercise-associated muscle cramps (EAMC) include; family history of cramping, previous occurrence of cramps during or after exercise, increased exercise intensity and duration, and inadequate conditioning for the activity.”

Why aren’t cramps due to dehydration?

study published in Medicine & Science by researchers at North Dakota State University showed that when fatigue is removed from the equation, muscle cramping can be induced by electrical stimulation at various levels of hydration. If dehydration were the cause of skeletal muscle cramps, the less hydrated subjects would have suffered cramping faster than their more hydrated counterparts. So when there is no physical exertion involved, cramping happens at the same stimulation level whether independent of hydration.

Another mark against the dehydration argument involves recovery. If dehydration caused skeletal muscle cramping, it would follow that rehydration would stop the cramping in close to 100% of cases. Cramps will often subside while an athlete is rehydrating. But this does not happen universally. While it’s convenient to attribute a cramp subsiding to an athlete ingesting fluids, this is very often coincidental rather than causal.

Why aren’t cramps due to electrolyte depletion?

If deterioration of electrolytes causes skeletal muscle cramps, we would expect to see a particular pattern of muscle groups being affected. Electrolyte deficiency, in particular, would cause cramping to begin in smaller muscles and spread to become a generalized phenomenon. But that’s not the pattern we see in rugby players. Cramping almost always occurs in the lower legs first which would indicate a different metabolic process is causing the sustained contraction. In short, we know that a shortage of electrolytes is not the cause of muscle cramping because the phenomenon is not generalized across the body’s smaller muscles.

It’s generally understood that electrolytes are lost through sweat. While that’s true, it’s also deeply misleading because sweating is hypotonic. That means you lose more water when you sweat than electrolytes in the form of salt. This higher ratio of water depletion is the case even if you think you’re a salty sweater. Because you’re losing more water than salt, your body’s electrolyte concentration is INCREASED not decreased by sweating.

So what causes muscle cramping in athletes?

Finding quality information on the interwebs can be hard. Most of the stuff you’ll see in a Google Search for ‘what causes muscle cramps’ will repeat all the same old nonsense about hydration and stretching. Here are just a couple of examples of articles that profess to understand and diagnose what causes cramping in athletes:

But if dehydration or electrolyte depletion aren’t causing cramping in athletes, what is? A brief explanation was given earlier, ‘increased exercise intensity and duration, and inadequate conditioning for the activity’. Now known as ‘neuromuscular fatigue.’




Neuromuscular fatigue is the inevitable result of any sustained physical exertion. When you’re training for or playing rugby, dozens of processes in your central nervous system work together to send activation signals to your muscles. What happens in the muscles themselves is pretty complex. But suffice to say that neuromuscular fatigue is the result of these mechanisms being stressed and breaking down. 

Because playing rugby necessitates a high level of output, when neuromuscular fatigue starts, your body is unable to sustain its efficiency. As a result, your system must work harder to continue performing at the same level. This can’t be maintained for long though. As neuromuscular fatigue sets in, performance declines since your system is stressed beyond its capability. The result is that you can’t run as fast, jump as high or scrum for as long. 

There is a field of research devoted to the study of peripheral Vs central neuromuscular fatigue. That is, the difference between the level of fatigue in the muscles performing the task and the level of fatigue in the system as a whole. It’s thought that the level of central fatigue could play a role in how severe the peripheral effects might be. But for our purposes in addressing what causes muscle cramps in rugby players, its enough for us to work with peripheral fatigue, particularly in the lower legs. 


Since we now know that neuromuscular fatigue is causing cramping in rugby players, its useful for us to understand (and be able to predict) what level of physical exertion will cause a player to suffer cramping. This is known as the cramp threshold frequency (CTF). 

Steven Wilding and Dr. Kenneth Knight, Professor of Exercise Sciences at BYU explain that:

“The minimum frequency of electrical stimulation at which a person develops a cramp, termed “threshold frequency”, is an indicator of a person’s risk of developing muscle cramps. Lower threshold frequencies indicate an increased predisposition to cramp, while higher threshold frequencies indicate a decreased predisposition to cramp.

In short, the lower your CTF, the more likely you are to get muscle cramps when you’re asked to increase your level of exertion. This is particularly important for amateur rugby players, since we almost always train at a lower level of exertion than we play.  

20-1-20 PROGRAM



“Prolonged exercise at a relatively higher intensity, compared with training, is therefore associated with a higher risk to develop exercise-associated muscle cramping in… athletes.” – Susann Kraeftner

Rugby players who don’t train as hard as they play are more likely to suffer cramping. Also, when the level of competition is increased significantly, around finals time for example, rugby players will be more prone to cramp. The science tells us that hydration and electrolytes aren’t going to have a significant effect on preventing or reducing cramping, so what else can be done?

Luckily for us, there was an important study into threshold frequency published in 2010. From it, we’ve drawn out some lessons that rugby players can use to help avoid muscle cramping in rugby games. 

Train Harder

As much as we’d love to tell you ‘just have a sports drink before your game’. That’s not going to stop you cramping during a rugby game. Unfortunately, there is no short-cut to avoiding cramping. The only tried and true method is to train harder. At a level of exertion that replicates a game of rugby. We’ve outlined before why we think its crucial to start rugby training with cardio, now we have another reason – the conditioning can help prevent cramping during rugby games. 

Localized Fatiguing Exercises

A 2010 paper in the Journal of Sport Science found that the threshold frequency of an electrically induced cramp could be increased by using a regime of localized fatiguing exercises. The study showed that when subjects stressed a muscle, rested for 30 minutes and then induced a cramp using electricity, it took more electricity to cause the cramp. This has ramifications for rugby players who want to train to avoid cramping. 

Since we know that most players cramp in their lower legs first, we need to design a localized fatiguing exercise that focuses on the calves. The best one we know of is skipping. So grab a rope and start jumping. A simple program to follow is our 20×30 session. It works like this: 

  • Start skipping at the top of the minute
  • Skip 60 times (this will naturally work out at about 30 seconds)
  • Rest until the top of the next minute
  • Repeat
  • After 20 minutes, you’ll have completed 20 sets of 30 seconds skipping sprints

More Plyometrics

There is a good deal of discussion in the strength and conditioning community that suggests training using plyometrics might be an effective way to avoid muscle cramps during rugby games. It seems from the research that plyometrics might also fall into the category of localized fatiguing exercises. Typically most strength and conditioning coaches won’t program plyometrics as a conditioning drill. More research on this topic specifically might be warranted. But for now, performing box jumps, single leg box jumps and burpees might help to increase a rugby player’s CTF. 

Increase Serum Magnesium

It has long been believed that electrolyte depletion was the cause of muscle cramps in athletes. However, multiple studies have shown that increasing sodium, calcium or potassium levels is an ineffective method for preventing muscle cramps. Because serum magnesium is more difficult to detect in blood tests, less is known about its impact on EAMC. There is some speculation that since magnesium is crucially important for cell function, having enough magnesium could help calm cells and prevent muscle cramps. It’s not known whether increased levels of magnesium could raise a person’s CTF, but it is believed that lower levels of magnesium could cause a drop in CTF which would make you more prone to cramping. In short, eat dark green vegetables as we explained in our rugby game day nutrition guide

Electrically induced muscle cramps

study released at the end of 2015 suggested that it might be possible for athletes to reduce their risk of cramping in competition by electrically inducing muscle cramps once a week. We should stress, this is a very new concept and it is not widely used in any strength and conditioning programs that we’re aware of.

But for the extremely adventurous, this could be an option. Since cramp threshold frequency is known to be positively correlated with individual cramp susceptibility, increasing CTF through periodized electrical stimulation might have benefits for the rugby field. In the study, participants reported less perceived discomfort following multiple bouts of electrically induced cramping. But again, this isn’t a battle-tested technique. Use with extreme caution.


Still think nutrition matters? It definitely does, just not as much for cramping as we’ve been told. Try our stacks, they’re designed for different seasonal training periods or our post-rugby formula, which provides electrolytes. Then follow one of your halftime protocols for more ways to avoid muscle cramping during rugby games. 


Tim Howard

Tim Howard

Tim is one of the founders at Ruck Science who settled in Austin, TX after playing rugby all over the world for the past two decades. He's constantly used as a guinea pig for our most advanced or controversial diet and training experiments.