Leg Cramps and Sport

Leg cramps in athletes (even when frequent) are not a disease but a symptom. They indicate that something isn’t right during your training or matches. Let’s go through what can increase the tendency of your calf muscles to cramp.

Causes of leg cramps

Most often there are simple physiological causes which, once identified, are easy to address.

Increased cramp tendency can be caused in part by lack of conditioning, inappropriate training work, lack of refueling during a match, prolonged activity performed in the anaerobic zone, the resulting neuromuscular fatigue, and insufficient regeneration. Each of these, alone or in combination, can contribute to your calf responding to prolonged strain with a cramp.

Cramps that occur during training usually appear when you work much harder and longer than your body is used to: your body then has to adapt to the increased effort, longer training time and higher intensity.

The best current theory explaining muscle cramps that occur during training is related to neuromotor fatigue. The nerves that transmit signals between muscles and the brain tire just like the working muscles do. During neuromotor fatigue the nerves send interfering, uncontrolled signals to the muscles. This can cause muscle twitching, muscle cramps, dysfunctional muscles and the affected person may feel unable to exert force.

However, the pathway leading to neuromuscular fatigue is complex.

Energy – the basis of muscle function

Movement is made possible by alternating contractions of muscles. In response to a signal through the motor nerve, the actin-myosin and titin molecules of the muscle fibers slide past each other using energy, causing the muscle to shorten, then return to the original state.

The cellular processes that enable contraction require a continuous supply of ATP. Since muscles store only a small amount of ATP, it must be produced during activity. There are two main metabolic pathways: oxidative (aerobic) and glycolytic (anaerobic). Which pathway dominates depends primarily on exercise intensity and duration. During intense muscle work glycolysis predominates; at slow or moderate pace the oxidative pathway predominates.

Many factors can influence the energy-producing process.

Muscle composition

Your skeletal muscles are a mix of three types of muscle fibers.

Type I fiber (also called slow or red fiber)

Surrounded by a dense capillary network, which gives it its red color. Suited for long-term, continuous, moderate force output, these fibers produce the energy for their function themselves (oxidative metabolism). Type I fibers fatigue very little, i.e. they are endurance-capable.

Type IIa fast fiber (also called intermediate)

Have properties between Type I and Type IIb fibers. They can produce energy both aerobically and anaerobically (oxidative and glycolytic). With low energy investment they can produce fast and sustained contractions (lasting several minutes), i.e. they are enduring.

Type IIb fast fiber (also called super-fast)

These fibers are white due to high glycogen and glycolytic enzyme content. Because of the near absence of mitochondria they cannot produce energy for long and therefore operate effectively only as long as their glycogen stores last. Their contractions are fast and powerful but last at most about 1 minute, although they can produce extraordinary force.

The proportion of these fibers is genetically determined and, according to current knowledge, cannot be converted from one type to another. You have to get the most out of your innate fiber composition through training and stimulation.

If you have many slow fibers, you are better suited to slower-paced but endurance-demanding sports. If fast fibers dominate, short-duration, high-force activities suit you better.

A high tendency to cramp can be caused by a high proportion of IIb fibers in your calf muscles. Their metabolism relies on breaking down stored glycogen and producing lactic acid. They quickly reach neuromuscular fatigue and even exhaustion, which directly increases cramp tendency.

A solution to this problem can be “refueling” before training and, for example, during a match break. A fast-absorbing energy gel and some isotonic electrolyte can do wonders for the energy supply of fast fibers.

Level of conditioning

A common sight in the second half of football matches is a player lying on the grass whose teammate “pulls back” the foot to relieve a cramp. A few training sessions per week common in lower divisions (short warm-up, shots on goal, a few ball drills, then small-sided games) are usually not enough for a player to sustain 90 minutes of intense running during a match. So it’s not surprising. With 3–4 training sessions a week, it’s actually surprising if cramps start only toward the end of the match.

Football requires endurance. During a match, high-intensity running alternates with rest, walking and low-intensity work. During frequent high-intensity actions (sprints, pressing back with an attack) the muscles work at maximal or near-maximal intensity, in the anaerobic zone or at its border. Lactic acid is produced then and cannot leave under load (only during rest), so with every sprint, every defense, every collision it accumulates.

For each person the point when a muscle “steeped in acid” starts to cramp comes at a different time (depending on conditioning). In an acidic environment neither the muscle fibers nor the motor nerve supplying the muscle function properly. The less trained someone is, the earlier this point arrives.

The goal of regular muscle training is to prepare the muscle for the demands of competition/matches. Therefore training load is planned according to expected performance. Gradual training leads to adaptation. Muscle fiber size, mass, metabolism, capillary supply, tolerance to oxygen deficit and glycogen stores improve.

But not only the muscle fibers: heart function, circulation, breathing and gas exchange (oxygen uptake, CO2 tolerance) and energy production all improve.

Endurance of the muscles — their blood supply, oxygen uptake and even metabolism — can be improved. So with more training fatigue and thus cramp tendency can be reduced.

Warm-up

Warming up is very important before both training and matches – I wrote a separate article about this earlier, read it.

Some sports (for example football) particularly stiffen the muscles, so it is especially important to prepare the muscles for activity: open the blood vessels, warm up and loosen the tendons, and speed up oxygen delivery to muscle cells.

Starting intense activity with un-warmed muscles immediately makes the muscle oxygen-deficient and metabolites begin to accumulate right away. This increases the risk of injury and by the 70–80 minute mark can already make muscles acidic; in such an environment they cannot move normally, become stiff and tired, and movement slows.

Improving the warm-up alone helps push out the threshold for fatigue and cramping.

Refueling – the mysteries of sports nutrition

Sports nutrition is a complex topic I won’t detail now, but I’ll mention that fatigue, decreased muscle performance and muscle cramps can be prevented with proper refueling, which should not be handled only at the end of training, especially during longer activities.

You need: fluids and electrolytes, and energy.

Although plain water is a kind of electrolyte-fluid mix, isotonic mixes developed for sport (with a composition similar to physiological needs) help more effectively! These usually provide some energy replacement as well, which helps maintain effective performance during activity and prevents cramps and fatigue.

For short training sessions, fluid is far more important than the electrolytes in it. The mix obviously offers an advantage in performance: a carbohydrate source (sugar/glucose). Some electrolyte supplements can be low- or zero-calorie, but mixes containing both carbohydrates and electrolytes are much more common.

Maintaining muscle function requires active energy expenditure. The basic source of energy is ATP, which is produced in the mitochondria of cells by “burning” carbohydrates and other nutrients. The most efficient ATP production occurs in the presence of oxygen. If there are not enough nutrients in the blood that can be converted to ATP, the body uses stored materials for energy. This is slower, so during training and competition you should consume things that are quickly absorbed and can be converted into energy without long digestion. Carbohydrate-electrolyte mixes developed for sport effectively replenish energy during long activity.

Fluid and electrolyte content

When you sweat you lose fluid and “electrolytes”, which are ions and minerals essential for bodily functions. Sodium (salt) is one of the most common electrolytes lost in sweat and is needed for electrolyte balance.

With sweating you lose more water than electrolytes. Fluid loss limits your performance, so it is important to replace it during exertion. If your training lasts more than 90 minutes and especially more than 4 hours, you will lose electrolytes as well as fluid, so you must replace both.

Studies have shown performance is significantly impaired when fluid loss approaches about 2% of body weight (for a 75 kg person this means losing 1.5 liters of water, which is very realistic). As blood volume decreases, your heart rate increases, which you may not notice because your pace slows. However, the longer the exercise, the more mercilessly the heart rate rises. If you see this, know that your fluid-electrolyte replacement has failed.

Strive to drink during activity and replace lost fluid; general guidance suggests consuming at least 500–750 ml per hour during longer training. If your sessions are long, consider salt tablets to replace lost minerals every 40–60 minutes.

Can you drink too much?

Yes. Excesses are always a mistake! Too much “plain” water or too many salt tablets can both upset the system.

Don’t think that drinking two liters at once is appropriate! Your kidneys will try to remove the large, currently unnecessary volume, you will have to urinate soon and only part of the water remains “useful.”

The same applies to too much salt – the body wants to get rid of the excess, and the kidney can only do that by producing more urine. Even if you drank the right amount of fluid, if you “overdid” the salts, you will lose a lot of water during their excretion and become dehydrated.

In short: keep balance! Take in what you need. Always test the necessary amount during training and perfect your refueling then, not on race day!

Fortunately, electrolyte imbalance usually appears only during longer activities, mainly in strenuous ultra-endurance events (marathons, Ironman triathlons, etc.). Symptoms rarely appear during a 40–50 minute training session, at most in the form of muscle cramps.

Incorrect fluid and electrolyte replacement can affect performance even in short activities, and underhydration is more likely than overhydration. To experience hyponatremia symptoms you must drink a lot, while dehydration is much easier to reach.

The role of rest in preventing calf muscle cramps

Rest for muscles is extremely important! Removal of accumulated waste products (e.g. lactic acid) happens during rest. Intense training produces a lot of waste products, which is why you feel tired the next day. If you don’t reduce intensity then injury risk increases; if you reduce intensity, training effect falls. Neither is good!

Nowadays several methods are used for muscle regeneration. Cool-down jogging, gymnastics and massage are traditional. Some studies found electrostimulation regeneration programs more effective. The newest methods are devices that combine cooling and compression.

Rested muscles cramp less often, allow you to keep training intensity high for longer, and reduce injury risk.

Regeneration and muscle cramps

I already mentioned that lactic acid produced during exertion cannot leave the muscle while you’re working. It must be worked out of the muscle during rest, and as soon as possible.

If you frequently suffer muscle cramps, you must pay particular attention to regeneration.

What can you do against leg cramps?

There is nothing magical: gradually expose your body to longer and harder training sessions and you’ll see that cramps will appear later and later. Train in the cold and the heat and your body will adapt. You will experience that your body can get used to any condition without reacting with muscle cramps.

Prepare well for an event: be fresh, rested, eat properly and replace fluids, especially before a demanding event. Have a well-thought-out hydration and nutrition plan before, during and after the competition.

In the evening, before bed, relax and stretch your muscles. This alone can solve your complaints. If you are on your feet all day, walk a lot or stand a lot and your calves feel tight in the evening, stretching and relaxing will almost certainly help and relieve your symptoms.

How to relieve a leg cramp?

• If you use a warming cream before activity, that alone can help prevent muscle cramps.
• The simplest method to relieve cramps is passive stretching. Don’t try to get rid of cramps while sitting on a bike — dismount and properly stretch the affected muscle.
• Drink and replace electrolytes during training!
• If possible, cool the muscles heated during activity. An ice pack or a bag of ice cubes will do, and there are garments designed for this purpose.
• If cramps recur, you will have to reduce the pace. This eases the work of the muscles, heart and lungs, and the neuromotor system. The neuromotor system can then switch off and be able to regenerate.
• After training use a muscle stimulator with a regeneration program (Elite SII, Runner Pro and similar) and/or a compression therapy unit (Power Q-2200 or similar) and/or cold massage.