Don’t cramp your style!

A muscle cramp occurs when a muscle, or even a few fibres of a muscle contract involuntarily (ie without you consciously willing it). Muscle cramps can affect any skeletal muscles in the body, but are most common in muscles or muscle groups that span two joints. The most common sites in the body for muscle cramps include:

• The calf muscles of the lower leg (gastrocnemius);
• The hamstring muscles of the rear thigh (see figure 1);
• The quadriceps muscles of the frontal thigh.

However, in addition to these areas, cramps can also affect the hands, tummy muscles (abdominals), the muscles
around the rib cage, and the feet and toes. Muscle cramps can last anywhere from a few seconds to (in severe cases) 15 minutes or longer. A muscle cramp in a particular location may also recur multiple times before it finally goes away.

What causes muscle cramps?

Despite being a very common condition, the exact causes of cramps have remained something of a mystery. What we do know is that cramping occurs when the mechanisms controlling the electrical stimulation of muscle fibres (contraction - motor unit firing) and subsequent deactivation (relaxation) become impaired in any way. Physiological factors that have been investigated as possible contributors to this impairment of electrical control are shown in box 1.

However, most authorities agree that ‘true cramps’ – those we normally associate with vigorous exercise, fatigue and dehydration/electrolyte imbalances etc - are caused by hyperexcitability of the nerves that stimulate the muscles, which also explains why much attention on preventing cramps has been focussed at minimising this excitability through optimum nutrition and conditioning protocols.

Anyone can experience muscle cramps, regardless of age, gender or fitness level. But in otherwise healthy people, muscle cramps are most common in endurance athletes such as marathon runners and triathletes, and those who perform strenuous physical activities without previous experience or lacking base conditioning. In short, the fitter and better trained you are for your event, the lower the risk of muscle cramps. The obvious implication is that with improved fitness and conditioning, the risk of cramps can be significantly reduced. However, an important question to ask is what other strategies can reduce cramping risk and in particular, whether improved nutrition and hydration can help?

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Figure 1: Hamstring muscles of the rear thigh

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Reducing muscle cramping risk

Strategies involving stretching and relaxing muscles are proven ways to reduce cramping risk and help treat cramping when it occurs. When it comes to improved nutritional strategies however, the scientific evidence about what actually reduces the risk of cramping has been far from clear-cut, mainly because there’s actually very little data from published studies.

To add to the confusion, the studies that have been conducted have often produced mixed results. For example, South African scientists studied 72 runners competing in an ultra-distance marathon and compared data from those who suffered exercise-induce cramps and those who didn’t^{Br J Sports Med. 2004 Aug;38(4):488-92}. Although they found small variations in blood levels of post-exercise sodium and magnesium, they concluded that there were no clinically significant alterations in blood electrolyte concentrations and no alteration in hydration status in runners with ‘exercise associated muscle cramping’ (EAMC).

Despite the lack of unequivocal evidence however, most scientific authorities agree that any nutritional cramp-prevention strategy should aim to address three important areas:

1. Maintaining adequate hydration^{Int J Sport Nutr Exerc Metab. 2005 Dec;15(6):641-52} – because all electrical signalling activity in the muscles takes place in an aqueous (water) environment and even small shortfalls in hydration levels could lead to impaired electrical signalling and an increased risk of cramping;
2. Ensuring adequate dietary intake of the electrolyte minerals^{Med Sci Sports Exerc. 2005 Jul;37(7):1081-5}; sodium and potassium because they’re involved in conducting electrical signals to/from muscles, and calcium and magnesium, which are essential for the contraction and relaxation of muscle fibres;
3. Replenishing energy in the form of carbohydrate – because even small drops in the level of stored muscle carbohydrate (glycogen – your body’s premium fuel for exercise) can lead to increased fatigue, which may in turn increase the risk of muscle cramps.

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Box 1: Factors linked to increased cramping risk

• Inadequate hydration and insufficient levels of the electrolyte minerals in muscles.
• Poorly-trained muscles that are inflexible and/or insufficiently conditioned for the exercise being undertaken (muscle cramps are much more likely to occur in muscles that are unused to vigorous training).
• Inadequate rest and recovery - we know that muscles are much more likely to cramp when fatigued.
• Genetics – all other things being equal, some people are simply more prone to muscle cramping than others, which is thought to be down to genetic makeup.
• Age - muscles in the elderly are more prone to cramping than in younger people.
• Injury - the risk of cramps can also be increased by injury, where certain muscles may go into spasm in order to ‘brace’ and protect the injured area.

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BOX 2: STRETCHING AND CRAMPS

One thing that nearly everybody agrees upon is that a regular stretching program targeted at muscles prone to cramping can greatly reduce the incidence of exercise associated muscle cramps as well as stopping cramp once it’s started^{J Sports Sci 1997 Jun;15(3):277-85 Clin Sports Med 2008 Jan;27(1):183-94, ix-x}. Passive stretches held for 15-30 seconds at a time seem to be effective. The mechanism is unclear but a regular program of stretching is known to lengthen muscle fibres, favourably altering spinal neural reflex activity. Regular massage may also be beneficial as it promotes general muscle relaxation and helps accelerate the disposal of exercise metabolites from muscles cells.

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A revolutionary approach

Although there’s been agreement among scientists about the factors that are known to increase the risk of muscle cramps, the precise physiological and biochemical mechanisms responsible for causing cramps have remained poorly understood. This has meant that a truly effective means of preventing cramps has proved elusive. However, very recent research has managed to unlock much of the mystery surrounding muscle cramps, leading to an effective prevention strategy.

The story started when two avid sea kayakers sustained serious episodes of muscle cramps while winter paddling. However, these were no ordinary kayakers; one was Professor Rod MacKinnon, a Nobel Laureate in chemistry for researching ion channel activation in the nervous system, while the other was Bruce Bean, a professor of neurophysiology at Harvard Medical School.

Eager to try and find ways to prevent or treat such cramps, they found no supportive data on common remedies used to ease the cramps, including electrolyte drinks and bananas. What they did learn however was that a muscle needs to be ‘innervated’ to cramp effectively. That implicated the nervous system (not muscles) as a key element of muscle cramps - and also the intriguing possibility that a nerve block might be able to prevent cramps.

The nerve block they had in mind however was to ‘shock’ the nervous system by providing a strong sensory stimulus input into the brainstem and spinal cord. Without delving too much into detail, it so happens that providing a shock to the input side of the nervous system (by activating proteins called ‘TRP ion channels’) helps to tone down over-excitability in the motor neurons that supply the muscles (known as alpha motor neuron activity), and which can lead to cramps.

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Professors Rod Mackinnon and Bruce Bean - keen kayakers and pioneers in cramp research

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Spicy options

The trick was to find an effective way of delivering this shock to the input side of the system. The researchers hypothised that a combination of spices taken before exercise might do just that. This combination included a mix of ginger, cinnamon and capsicum from spicy pepper plants (see figure 2). By applying a strong sensory input and stimulating receptors in the mouth and oesophagus, the theory was that the pungent taste would overload nerve receptors, producing a kind of numbing effect – a bit like a curry hit!

To test the hypothesis, Mackinnon and Bean carried out experiments on themselves and then on cooperative family members. Although tested on only a few willing people, it appeared to work well, both on exerciseinduced cramps in athletes and in people who experienced night cramps.

Following this initial research, they replicated their findings in very carefully controlled scientific studies^{Neurology April 6, 2015 vol. 84 no. 14 Supplement S17.003}. Firstly, they showed that the spice combination was very effective at activating the TRP ion channels. Secondly, they tested the combination in 37 healthy volunteers across three studies. These volunteers took the spice-flavoured formulation in the morning and shortly afterwards underwent electric stimulation to induce muscle cramping.

Compared with findings in untreated participants, muscle cramp intensity and frequency was reduced 3-fold. Even better, this preventative effect was evident within minutes and lasted up to 8 hours. At last, a proper explanation of muscle cramping, and a scientifically validated way of preventing muscle cramps had been found!

But is this approach dangerous I hear you ask? Does the pain from a muscle cramp have a purpose, like the pain that makes us pull our hand away from a hot stove? MacKinnon and Bruce did consider this possibility but concluded there is no benefit to a muscle cramp. As Professor Mackinnon explained “The debilitating pain we experience from cramps doesn’t prevent injury. We experience it not to help us survive but because the human body isn’t a perfectly evolved machine.”

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Figure 2: Nerve-numbing triple whammy

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CASE STUDY: Paula Radcliffe

One of the most high-profile cases of cramping is that of Paula Radcliffe in the 2004 Athens Olympic marathon event. Radcliffe went into the Athens Games at the peak of her powers as favourite for marathon gold, having broken the world record in 2002 and 2003. However, severe stomach muscle cramping that got steadily worse during the race meant that she had to pull out of the race after around 22 miles, and she was left sitting and weeping inconsolably on the side of the road. As Paula describes in her biography:

After 10km, my stomach began to give me trouble; my stomach began to cramp violently and the more I fought it, the worse it got. For a while it did feel better. But after a bit the cramp returned and got worse. After about 18km, we got to the tougher part of the course and, once on the hills, the Japanese runners began surging. At the very moment Mizuki Noguchi made her break, I was having really bad stomach cramps. When they eased, I started to work my way back. My mind was still strong – I knew I could run the closing 10km of a marathon faster than most people. But around the 36km point I knew I was in big trouble. I could hardly pick my legs up at all; they were like sore lead weights. I felt so empty, yet I was only 1km past the previous feeding station. I knew that I wasn’t going to be able to get anywhere near the next drinks station, let alone to the finish. I knew I couldn’t do it – I had nothing left.

Other runners went past and seeing them go by was awful. They were still in the Olympics, and I wasn’t. I then went to the other side of the road, where there were fewer people, and although I was in shock, I just wanted to get away from there. All the time I was crying - I didn’t understand what had happened. Then the medical van came along. They checked my pulse and blood pressure because they imagined that it was probably heatstroke. But my pulse and blood pressure were normal. They put me in the van, wrapped a blanket around me and took me back to the stadium. Sitting in the van, I couldn’t cry anymore because I had cried myself dry.

However, just 3 months later, Radcliffe stormed to victory in the New York Marathon, showing that her marathon talent hadn’t deserted her – she had just fallen victim to a severe bout of muscle cramping just when she needed it least!

Applying the findings

Back in 2016, a product called ‘HOTSHOT’ appeared on the market, which contains the same spice blend as used in the research by Prof MacKinnon. Taken 15-30 minutes before exercise, or at the first signs of cramping during exercise (or during recovery), this product is the first of its kind for effective cramp prevention.

Unfortunately for UK readers, this is not yet widely available this side of the Atlantic. In the meantime however, there’s no reason to assume that a homemade blend of hot spices taken before exercise wouldn’t provide at least some benefits. Remember that these spices don’t work by changing muscle chemistry in any way. They simply provide a ‘shock’ to the input side of the nervous system, which helps tone down the motor neurons supplying the muscles. Curry for breakfast anyone?!

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GENERAL STRATEGIES FOR AVOIDING MUSCLE CRAMPS

Until very recently, there’s been no guaranteed method of avoiding cramps entirely. The new research on hot spice administration before exercise is extremely promising but cramp-prevention products based on this research are not yet widely available. With that in mind, here are some recommendations that may help to reduce your risk of muscle cramps during or after exercise:

1. Consuming spicy, peppery foods before exercise (even several hours before) may help reduce your risk of muscle cramps. Try experimenting with homemade recipes but remember that any foods you consume in the hour or two before exercise should be light (low fat) to allow them to empty from the tummy before exercise begins. Never experiment before a competition – only before a training session!
2. Build your training intensity gradually. We know that the central nervous system plays a significant role in the aetiology of muscle fatigue during exercise, and this almost certainly explains why unaccustomed fatigue greatly increases the risk of muscle cramps.
3. Related to point 2, ensure you ease up on your pre-race training. Make sure you arrive at the start line fully recovered.
4. If you suffer from recurrent cramps in one particular muscle group, it might be worth carrying out some strength training for the relevant muscles. Higher levels of strength can delay the onset of local muscle fatigue by lifting the ‘threshold’ at which fatigue is experienced
5. Stretch regularly, particularly the key muscle groups recruited in your sport. Runners in particular should perform regular static stretches for the hamstring and calf muscles (see figure 3). To maximise performance for an event however, these stretches should NOT be performed immediately beforehand.
6. Consume a carbohydrate-rich diet, drink plenty of fluid and ensure that you eat plenty of magnesium-rich foods in your dayto-day diet such as green leafy vegetables, whole grains, nuts and seeds, and pulses (beans, peas and lentils).Magnesium has been shown to reduce the risk of night-time cramps.
7. Use massage-therapy as an additional method of relaxing muscles, particularly after tough workouts.

Figure 3: Hamstring and calf stretches

Hold each stretch for 30 seconds, repeating 3 times. Stretch at least twice per week but not before training or competition.