You’re deep in a race, feeling strong, smooth, in control — and then it hits.
A muscle locks up like a vice, hard and unforgiving. You try to push through, but it just won’t let go.

Cramps are one of the most frustrating experiences in endurance sports. Almost every athlete has felt them, yet nobody fully agrees on why they happen. Some studies suggest that up to 95% of athletes experience cramps at some point in their career.

The good news? You can do something about it.
With a bit of understanding and awareness, you can learn what your body is telling you — and take steps to prevent cramps before they happen.

What’s behind cramping?

two main Theories explain why muscles cramp during exercise:

1. Fluids and electrolytes

When you sweat, you don’t just lose water — you also lose sodium.

That loss changes the electrical environment around your muscles and nerves.
The result: your nerve cells become overactive, and a muscle suddenly contracts without your control.

This kind of cramp is especially common in the heat or during long, sweaty sessions where sodium losses are high.

2. Fatigue and neuromuscular load

The second theory comes from exercise science. When a muscle is fatigued or pushed past its limits, it loses the delicate balance between contraction and relaxation. The nervous system begins sending mixed signals — and the muscle locks up.

This explains why cramps often show up late in races, when fatigue sets in and your body is pushed to its limit.

It’s rarely just one thing

In reality, it’s usually a mix of both.

It’s race day, the sun’s beating down, and you’re digging deep. Sweat carries salt away, your body heats up, and the effort keeps rising. Lose that balance, and you just set up the perfect recipe for a cramp.

Cramping is multifactorial — hydration status, electrolyte balance, and neuromuscular fatigue all contribute. Environmental conditions, intensity, and individual physiology determine which factor dominates.

Cramping also tends to occur when the body is already under stress — during times of low energy availability, intense training, or hormonal imbalance, especially in female athletes. Prolonged low sodium levels can interfere with how the body controls fluids and blood pressure, and may even impact sleep, recovery, and nervous system stability.

Level up your Hydration - Get your personalized Hydration Plan and race confidently knowing your body is fully prepared.
Start your plan today

Gut-Training and Fuel Compatibility

Cramping can sometimes go hand in hand with stomach issues, especially when fueling with lots of carbohydrates or very concentrated sports drinks. By training your gut during long workouts to handle higher amounts of sodium and carbs, you teach your body what to expect and reduce the chance of any race-day surprises.

Rethinking Sodium in Today’s Endurance Sports

Many endurance athletes still underestimate their sodium needs, largely due to outdated hydration advice (“just drink water”).

Sweat Testing Data from Precision Hydration shows:

• Average sweat sodium: ~900 mg/L
• High-loss athletes: >1500 mg/L
• Standard sports drink: 300–500 mg/L

Many standard drinks are formulated for average use and small sweat rates — but for long efforts in heat, these may fall short for many athletes.

Hydration isn’t only about how much you drink, but what’s in it. Plain water can actually lower your sodium levels, which increases the risk of cramping and low blood sodium during long sessions or races.

How to keep cramps away

Here’s what really works in practice. It’s not about quick fixes, but about understanding what your body needs and preparing it for the stress you’re asking it to handle.

1. Optimize your sodium intake

Most athletes perform better with drinks that contain at least 1000 mg of sodium per liter. If you sweat heavily or race in the heat, you may need up to 1500 mg. Many commercial sports drinks are too low, often around 300 to 500 mg per liter. Using sodium capsules or a stronger mix allows you to adjust your intake to what your body actually needs. HOWEVER, running 3 km around the blocks doesn’t require a sports drink or extra sodium.

2. Train for the stress you’ll face

Cramps often occur when the body encounters an intensity or duration it isn’t prepared for. Include race-pace work and longer sessions to build fatigue tolerance. Strength training, especially eccentric exercises, helps your muscles handle stress and stay in control under pressure.

3. Manage fatigue

Cramps target tired bodies. Allow enough recovery time before races, and avoid stacking heavy sessions right before competition. Keep your glycogen stores full – low energy levels and depleted carbohydrates can increase your cramp risk.

4. Adjust for environment and pacing

Heat and humidity make everything more challenging. Respect these conditions and adjust your pace accordingly. If you’re training for a hot race, do short heat-acclimation sessions a week or two before. Start your race well-hydrated and use cooling techniques early to help keep your body stable. If you’re preparing for a hot race, do short heat-acclimation blocks beforehand. Start your race hydrated and use cooling strategies early to keep your system stable.

5. Support recovery and the nervous system

Recovery isn’t just physical. Stretching, mobility, and massage keep your muscles in balance, but your nervous system also needs attention. Breathing exercises, yoga, or quick mindfulness sessions help your body enter recovery mode. If you experience recurring cramps, targeted release techniques or acupuncture might also be beneficial.

---

Example Sodium Plan — Elite vs. Beginner Athletes

Every athlete’s sweat composition is unique, but understanding your average sodium loss helps you plan smarter.

Research from Precision Hydration reveals that:

• Average sweat sodium = ~900 mg/L
• High-loss athletes = >1500 mg/L
• Standard sports drinks = 300–500 mg/L sodium

This indicates that many athletes significantly underfuel on sodium during long or hot races. An Ironman athlete losing 1 liter per hour for 5 hours could shed 5–7.5 grams of sodium. That’s equivalent to 12–18 grams of table salt. Without replacement, the risk of cramps and performance decline increases dramatically.

Here’s how sodium needs might vary across different durations for Elite and Beginner Athletes:

Race Duration	Beginner (avg. 900 mg/L sweat sodium)	Elite / High-Loss (>1500 mg/L)	Notes
1 hour	500–800 mg sodium total (1 bottle of stronger drink)	1000–1500 mg sodium total	Focus on starting well-hydrated; may not need to drink much during.
2 hours	1000–1500 mg sodium total (1–1.5 L of 1000 mg/L drink)	2000–2500 mg sodium total (1–1.5 L of 1500 mg/L drink)	Replace roughly what’s lost; include small sips regularly.
5 hours (Ironman, long ride, marathon)	2500–4000 mg sodium total (3–4 L of 1000 mg/L drink)	5000–7000 mg sodium total (3–4 L of 1500 mg/L drink)	Combine fluids, gels, and salt capsules. Individualize to tolerance.

---

Quick takeaway

The longer, hotter, and saltier the race, the more important it is to match sodium to your sweat rate—not just to drink more water.

Level up your Hydration and get your personalized hydration plan, so you can race confidently knowing your body is fully prepared.
Start your plan today

Common questions about cramping and hydration

Is too much sodium harmful?

For most athletes, occasional high sodium intake during long races or heavy sweat sessions is not a concern. The key is balance. You’re replacing what you lose through sweat, not adding extra on top. If you have high blood pressure or kidney issues, it’s worth discussing your plan with a doctor. For everyone else, sodium is an essential performance mineral — not something to fear.

What if I get stomach issues when I increase sodium or carbs?

Stomach stress often occurs when you change your hydration too quickly, or when drinks are too concentrated. Train your gut like you train your muscles — start small and gradually build tolerance. Practice your race nutrition during key sessions so your body knows what to expect.

Can cramps still happen even if I hydrate well?

Yes, sometimes they can. Cramping isn’t just about hydration — fatigue, muscle conditioning, pacing, and even the nervous system all play a part. Staying hydrated helps, but it’s only one part of the bigger picture.

How soon will I notice improvement?

Many athletes notice a difference within a few weeks of adjusting their hydration and fueling — especially when they stay consistent in both training and daily nutrition. The goal isn’t just fewer cramps, but improved energy, focus, and recovery overall.