Why muscle cramps suck & what you can do about them

Muscle cramps, responsible for leaving their victims reaching for their toes on the sidelines of a running race, to screaming in silence in bed at 3 am. So why do muscles cramp? Is there more we can do other than letting it pass or getting another massage/rub down? Do salt tablets actually work?

Muscle cramps are one of the most frustrating things a runner can experience.

You are cruising along feeling good… and then suddenly your calf locks up. Or your hamstring grabs. Or you wake up at 2am with your foot in a vice.

They hurt. They derail sessions. They can ruin races. But despite how common they are, we still see a lot of outdated advice floating around

What Are Exercise-Associated Muscle Cramps?

Muscle cramps are described as sudden, spasmodic, painful involuntary muscle contractions that mostly last less than 60 seconds. Muscle cramps can occur as a symptom of a range of medical conditions, genetic causes, or exercise. In this blog, we will focus on exercise-associated muscle cramps (EAMC).

Exercise-associated muscle cramps are painful, involuntary muscle contractions that occur during or immediately after exercise.

In runners, they most commonly affect:

• Calves

• Hamstrings

• Quadriceps

• Intrinsic foot muscles

They typically last seconds to a few minutes, but they can recur if you continue at the same intensity.

They are common in endurance events, especially when intensity creeps above what you are conditioned for.  However, they are also common in AFL players, cyclists, and other sports where a rapid change in intensity is required (such as accelerating from a jog to a sprint). Although EAMC is generally short-lasting, they often recur if activity is continued at a similar intensity, having a direct negative impact on performance.

The Old Theory: It’s Just Dehydration

For years, cramps were blamed almost entirely on dehydration and electrolyte loss.

• Low sodium.

• Low potassium.

• Not enough fluids.

Simple.

Except controlled research has consistently failed to show that dehydration or serum electrolyte concentration independently predicts cramps (Schwellnus 2009; Schwellnus 2011).

Athletes cramp when hydrated.

Athletes do not always cramp when mildly dehydrated.

Electrolyte levels are often normal in those who cramp (Schwellnus 2011).

Recent reviews continue to support that electrolyte depletion alone is insufficient to explain EAMC (Miller 2022).

That does not mean hydration is irrelevant. It means it is not the primary mechanism.

The Current Evidence: It Is a Neuromuscular Fatigue Problem

When a muscle becomes fatigued:

• Excitatory input from muscle spindles increases

• Inhibitory input from Golgi tendon organs decreases

• Alpha motor neuron excitability increases

• Sustained involuntary contraction occurs

  
  

This imbalance between excitation and inhibition appears central to EAMC (Schwellnus 2009; Miller 2022).

More recent mechanistic work continues to reinforce that cramps are most closely associated with fatigue-induced changes in spinal reflex control rather than fluid shifts (Miller 2022).

This explains why cramps:

• Occur late in races

• Occur when pacing exceeds preparation

• Occur in cool conditions as well as hot conditions

• Tend to affect overloaded muscle groups

In short, cramps are usually a fatigue management problem.

Who Is More Likely To Cramp?

Cramps are not evenly distributed across athletes. Certain factors consistently increase risk:

Previous History of Cramping

The single strongest predictor of future cramps is having cramped before (Schwellnus 2011; Miller 2022). If you have cramped in prior races, your risk is higher. That likely reflects neuromuscular susceptibility rather than hydration habits.

Higher Relative Intensity

Athletes racing at a higher percentage of their maximal capacity are more likely to cramp (Schwellnus 2011). This reinforces the fatigue model.

Longer Event Duration

The longer you are exposed to fatigue, the greater the neuromuscular strain. Ultra-distance events show higher cramp prevalence than shorter races.

Older Age

Some endurance studies suggest increasing age is associated with higher cramp risk, possibly due to altered neuromuscular control and reduced fatigue resistance (Miller 2022).

Male Sex

Several large race datasets show males report cramping more frequently than females (Schwellnus 2011). The exact mechanism is unclear. It may relate to pacing strategies, muscle mass differences, or intensity selection rather than biology alone.

Cramps are rarely random. They follow patterns.

Hydration and Electrolytes: Still Relevant, But Indirect

Hydration and sodium intake influence thermoregulation, cardiovascular strain, and perceived exertion.

Those variables influence fatigue.

Fatigue influences neuromuscular control.

So hydration likely plays an indirect role by modifying fatigue risk rather than directly preventing cramping (Maughan 2019; Miller 2022).

That distinction matters.

Hydration supports performance.

It does not “switch cramps off.”

Why Stretching Works

Stretching the cramping muscle is still the fastest way to stop it.

This increases inhibitory feedback via the Golgi tendon organs, which helps calm the overactive contraction.

That is why:

• Calf cramps ease when you dorsiflex

• Hamstring cramps ease when you extend the knee

It is a neurological reset.

Pickle Juice and Strong Flavours

Evidence shows that strong oral stimuli, including vinegar-based solutions (such as pickle juice), can reduce cramp duration more rapidly than water (Miller, 2010).

Importantly, this effect occurs too quickly to be explained by electrolyte absorption.

The proposed mechanism is stimulation of transient receptor potential channels in the oropharynx, triggering a reflex reduction in motor neuron excitability (Miller, 2010).

Again, this supports the neuromuscular model.

It is important to note that while pickle juice or vinegar may help relieve a cramp once it starts, there is currently no evidence that taking them beforehand prevents cramps from occurring.

Recovery Matters Too

Recovery is an often overlooked piece of the cramp puzzle. If fatigue is a primary driver of cramps, then anything that influences cumulative fatigue may influence cramp risk.

Recovery itself has not been thoroughly investigated as a direct predictor of exercise-associated muscle cramps (Miller, 2022).

However, we know that:

• Poor sleep impairs neuromuscular performance

• High stress increases central fatigue

• Inadequate recovery reduces motor control and force output

All of these contribute to the overall fatigue load. If you are consistently under-recovered, your nervous system is already operating closer to its threshold before you even start your session. That reduces your buffer before neuromuscular imbalance occurs.

We cannot yet say that poor sleep directly causes cramps. But it is entirely reasonable to consider sleep quality, stress levels, and overall recovery capacity when managing recurrent cramping.

Fatigue does not just accumulate in the legs. It accumulates in the system.

How To Reduce Your Risk of Cramping

If fatigue-driven neuromuscular imbalance is the key mechanism, prevention strategies should reflect that.

Build Specific Endurance

Cramps commonly occur when exercise intensity exceeds habitual training load.

Progress volume gradually. Respect long-run progression. Avoid large intensity spikes.

Strength and Neuromuscular Training

Improving muscle endurance and fatigue resistance reduces the likelihood of reflex imbalance.

Strength training enhances:

• Motor unit recruitment efficiency

• Fatigue tolerance

• Tendon stiffness

• Neuromuscular coordination

Train at Goal Pace

If race pace is never rehearsed in training, neural demand exceeds conditioning on race day.

Controlled exposure builds tolerance to higher motor neuron drive.

Smart Pacing

Going out too hard accelerates fatigue and increases cramp likelihood.

Relative intensity appears more important than hydration markers (Schwellnus, 2011).

Prioritise Recovery

Fatigue is cumulative. If you consistently train in a state of under-recovery, your nervous system starts sessions closer to its fatigue threshold.

Optimising:

• Sleep quality

• Total sleep duration

• Stress management

• Adequate fueling

• Spacing of hard sessions

May increase your buffer before neuromuscular imbalance occurs.

Recovery has not been thoroughly studied as a direct cause of cramps (Miller, 2022), but from a fatigue management perspective, it makes physiological sense to include it in any prevention strategy.

Hydrate and Fuel Appropriately

Hydration supports thermoregulation and fatigue resistance. It is supportive, not curative.

The Take Home

Muscle cramps suck. But they are not primarily a salt deficiency problem.

They are most consistently explained by fatigue-induced alterations in neuromuscular control (Schwellnus, 2009; Miller, 2022).

The solution is not simply more electrolytes.

It is better preparation.

Better conditioning.

Better pacing.

Better strength.

Better load management.

Better recovery.

Prepared tissues and prepared nervous systems cramp less. And that is trainable.

References:

• Garrison SR, Allan GM, Sekhon RK, Musini VM, Khan KM. Magnesium for skeletal muscle cramps. Cochrane Database Syst Rev. 2012;2012(9):CD009402. Published 2012 Sep 12.

• Maughan, R.J. & Shirreffs, S.M., 2019. Muscle cramping during exercise: causes, solutions and questions remaining. Sports Medicine, 49(S2), pp. 115–124.

• Miller KC, Mack GW, Knight KL, et al. Reflex inhibition of electrically induced muscle cramps in hypohydrated humans. Med Sci Sports Exerc. 2010;42(5):953-961.

• Miller KC, Mack G, Knight KL. Electrolyte and plasma changes after ingestion of pickle juice, water, and a common carbohydrate-electrolyte solution. J Athl Train. 2009;44(5):454-461.

• Miller, K.C., McDermott, B.P., Yeargin, S.W., Fiol, A. & Schwellnus, M.P., 2022. An evidence-based review of the pathophysiology, treatment, and prevention of exercise-associated muscle cramps. Journal of Athletic Training, 57(1), pp. 5–15.

• Minetto MA, Holobar A, Botter A, Ravenni R, Farina D. Mechanisms of cramp contractions: peripheral or central generation?. J Physiol. 2011;589(Pt 23):5759-5773.

• Nelson NL, Churilla JR. A narrative review of exercise-associated muscle cramps: Factors that contribute to neuromuscular fatigue and management implications. Muscle Nerve. 2016;54(2):177-185.

• Schwellnus MP. Cause of exercise-associated muscle cramps (EAMC)--altered neuromuscular control, dehydration or electrolyte depletion?. Br J Sports Med. 2009;43(6):401-408.

• Schwellnus, M.P., Drew, N. & Collins, M., 2011. Muscle cramping in athletes: risk factors, clinical assessment and management. Clinical Journal of Sport Medicine, 21(5), pp. 405–410.

• Shang G, Collins M, Schwellnus MP. Factors associated with a self-reported history of exercise-associated muscle cramps in Ironman triathletes: a case-control study. Clin J Sport Med. 2011;21(3):204-210.