Cramps during a session? Recovery that seems endless? Fatigue setting in for no apparent reason?
You do everything right: training, sleep, protein. So why do you feel like you're running on empty?
In many cases, the answer comes down to one word: magnesium. Because the more you push your body, the more your needs increase.
In this guide, we explain why magnesium is essential for athletes, how to recognize a deficiency, and how to remedy it.
Why is magnesium essential for athletes?
Magnesium is one of the four major electrolytes involved in physical exertion. For an overview of their role and proper dosage, consult our complete guide to electrolytes for sport.
According to a recent review published in Nutrients, magnesium is involved in several key functions related to exertion and recovery.
The role of magnesium in muscle contraction
Behind each of your movements, there is a fine balance between different minerals (calcium, sodium, potassium, and magnesium).
Calcium triggers muscle contraction.
Magnesium then promotes muscle relaxation by modulating calcium's action.
It also supports the functioning of the sodium-potassium pump, a mechanism that helps the muscle fiber restore its electrical balance after each contraction.
Magnesium and energy production
You've probably heard of ATP, the main energy source for muscle cells. To be usable, this molecule must bind to magnesium to form the Mg-ATP complex.
Furthermore, this mineral is essential for the enzymes involved in producing new ATP molecules from the carbohydrates and lipids you consume.
The role of magnesium in sports recovery
After exertion, your body enters a recovery phase. Magnesium then continues to play several important roles.
- It supports protein synthesis, which is necessary for muscle repair.
- It helps limit oxidative stress and the inflammatory response related to exercise.
- It participates in neuromuscular recovery by helping the nervous system regain its balance.
Why do athletes have increased magnesium needs?
Magnesium loss due to perspiration
You can lose an average of 3 to 10 mg of magnesium per liter of sweat during each session. This value varies between individuals and increases during prolonged efforts or in hot and humid conditions (Baker et al., 2011).
The impact of physical exertion on magnesium reserves
To support energy production, active muscles draw more heavily on your magnesium reserves. After the session, muscle repair and adaptation to oxidative stress continue to mobilize more of this mineral.
Under certain conditions, magnesium loss through urine may slightly increase in the hours following the session.
Increased risk of deficiency in athletes
The accumulation of these losses and the intense demand on muscles, combined with an often insufficient intake in athletes, creates fertile ground for a chronic deficiency.
A study of 855 athletes confirmed that serum magnesium levels in athletes were significantly lower than average, despite a higher dietary intake than sedentary individuals.
What are the benefits of magnesium for sports?
Reduction of cramps and muscle spasms
Scientific data remains mixed on this point, but supplementation can help reduce these episodes in people with a confirmed deficiency.
Improved muscle recovery
According to the findings of a systematic review published in the Journal of Translational Medicine, magnesium supplementation can lead to a reduction in post-exercise muscle soreness, improved recovery, and a potential protective effect on muscle damage.
Reduction of physical and nervous fatigue
Adequate magnesium intake is associated with a reduction in muscle and nervous fatigue induced by the physiological stress of exertion.
Improved sports performance
A course of magnesium can concretely improve your endurance and resistance to fatigue. Recovery between sessions is also facilitated. That said, supplementation only improves performance in athletes with a confirmed deficiency.
What are the signs of magnesium deficiency in athletes?
A magnesium deficiency is not always detected by standard blood analysis (Razzaque, 2018). Intracellular reserves can be depleted long before serum levels drop. Here are the signals not to ignore.
Frequent muscle cramps
Cramps that occur regularly during or after exercise can be a warning sign. Take them seriously, especially if they persist despite good hydration.
Persistent fatigue
Fatigue that is disproportionate to your training load and does not go away with rest should not be ignored. Since magnesium is at the heart of energy metabolism, its deficiency can result in exhaustion that is difficult to overcome.
Muscle weakness
An unexplained drop in your strength or muscles that "give out" faster than usual deserves attention. Reduced endurance for no obvious reason can also signal a magnesium deficiency.
Stress and sleep disorders
A deficiency often manifests as unusual irritability and difficulty "winding down" after exertion. If you often wake up tired after a long sleep, a nutritional assessment including magnesium is essential.
What form of magnesium should you choose for sports?
Magnesium Bisglycinate
Advantages
Its chelated structure allows it to easily cross the intestinal barrier. It has excellent digestive tolerance, with little to no laxative effect at usual doses. The associated glycine has a calming effect on the nervous system, which is beneficial for recovery and sleep.
Disadvantages
Its elemental magnesium content is lower. Its price is generally higher than that of inorganic forms such as oxide or chloride.
Magnesium Citrate
Advantages
It has very good bioavailability due to its high water solubility. Its elemental magnesium content is slightly higher. It can relieve constipation, which is an advantage for concerned athletes. Its price is generally more accessible.
Disadvantages
A laxative effect is possible at high doses, due to osmotic effect. It can also cause digestive discomfort in sensitive intestines.
Other alternatives exist (such as magnesium malate) with interesting bioavailability as well.
Which form is best absorbed?
Available data places bisglycinate and citrate at a comparable level. A slight advantage is sometimes observed for bisglycinate, but this is not universal. The choice depends primarily on your digestive tolerance and your budget.
When and how should athletes take magnesium?
When to take magnesium: before or after exercise?
Taking it after exercise, during a meal, remains the most relevant. It coincides with the body's active recovery phase. If the dose is significant, divide it into several intakes for better absorption (Schuchardt & Hahn, 2017).
What is the magnesium dosage for an athlete?
The European Food Safety Authority (EFSA) recommends 350 mg per day for men and 300 mg for women. If you train regularly, these thresholds may prove insufficient and justify higher intakes.
Cure or daily intake: which to choose?
In case of deficiency, a 4 to 8-week course is generally recommended. For regular training throughout the year, a daily low-dose magnesium intake is often more appropriate. When in doubt, consult your nutritionist or a healthcare professional.
What are the natural sources of magnesium?
Magnesium-rich foods
Your diet remains the primary lever. The most concentrated sources are pumpkin seeds, almonds, Brazil nuts, and 70% dark chocolate.
Legumes, whole grains, cooked spinach, and certain dried fruits like dried apricots also provide good amounts.
To learn more, consult our complete guide to magnesium-rich foods: full list, benefits, intakes, and tips to avoid deficiencies.
Magnesium-rich water
Mineral waters rich in magnesium are a complementary natural source. However, they do not replace plain water for daily hydration and should only be used under certain conditions.
Food supplements for athletes
Products formulated with magnesium extracted from purified seawater or salt marshes are also natural sources.
Should you take a magnesium supplement when exercising?
Cases where supplementation is useful
Supplements can be particularly relevant in the following situations:
- deficiency confirmed by an assessment;
- abundant and persistent perspiration;
- hypocaloric diet or cutting phase;
- regular practice in hot or humid environments;
- intensive training or more than four sessions per week.
Cases where diet is sufficient
Supplementation is not always necessary if you meet these two conditions:
- moderate physical activity, at a rate of two to three sessions maximum per week;
- regular consumption of oilseeds, legumes, whole grains, and green vegetables.
How to choose a suitable supplement
Going beyond price is essential. Here are some tips for making a good choice:
- Check the elemental magnesium content.
- Opt for forms with good bioavailability: citrate, bisglycinate, or malate.
- In case of digestive sensitivity, bisglycinate is often better tolerated.
- Prefer products containing few unnecessary additives.
- Choose a format that is convenient for you: capsules, tablets, powder, or oral solution.
FAQ: Athlete's Magnesium
Why is magnesium important for athletes?
Your needs increase with effort. Even a slight deficit can lead to a drop in energy, less effective recovery, and neuromuscular problems.
Which magnesium to choose for sports?
Opt for bisglycinate or citrate. Always check the elemental content on the label: that's the number that really matters.
When to take magnesium for sports?
Take it after your session, during your post-exercise meal. If taking a large dose, split it into two intakes for better assimilation.
Does magnesium improve athletic performance?
Magnesium can impact performance, but mainly if you start from a deficiency. When levels are already optimal, the effect on performance remains limited.
Can you take magnesium every day?
Yes, it's possible and often beneficial to compensate for deficiencies. However, seek advice from a sports nutritionist beforehand.
How much magnesium to take when exercising?
Whether for endurance or strength training, the ideal dose should be adjusted to your needs. Diet and supplementation should be evaluated together, ideally with a sports nutrition professional.
Bibliography
Dominguez, L. J., Veronese, N., Ragusa, F. S., Baio, S. M., Sgrò, F., Russo, A., Battaglia, G., Bianco, A., & Barbagallo, M. (2025). The Importance of Vitamin D and Magnesium in Athletes. Nutrients, 17(10), 1655. https://doi.org/10.3390/nu17101655
Zhang, H., Wang, R., Guo, S., Tian, Q., Zhang, S., Guo, L., Liu, T., & Wang, R. (2023). Lower serum magnesium concentration and higher 24-h urinary magnesium excretion despite higher dietary magnesium intake in athletes: A systematic review and meta-analysis. Food Science and Human Wellness, 12(5), 1471–1480. https://doi.org/10.1016/j.fshw.2023.02.015
Nielsen, F. H., & Lukaski, H. C. (2006). Update on the relationship between magnesium and exercise. Magnesium Research, 19(3), 180–189. https://pubmed.ncbi.nlm.nih.gov/17172008/
Baker, L. B., Stofan, J. R., Lukaski, H. C., & Horswill, C. A. (2011). Exercise-induced trace mineral element concentration in regional versus whole-body wash-down sweat. International journal of sport nutrition and exercise metabolism, 21(3), 233–239. https://doi.org/10.1123/ijsnem.21.3.233
Razzaque M. S. (2018). Magnesium: Are We Consuming Enough?. Nutrients, 10(12), 1863. https://doi.org/10.3390/nu10121863
Schuchardt, J. P., & Hahn, A. (2017). Intestinal Absorption and Factors Influencing Bioavailability of Magnesium-An Update. Current nutrition and food science, 13(4), 260–278. https://doi.org/10.2174/1573401313666170427162740
EFSA Panel on Dietetic Products, Nutrition and Allergies (NDA). (2015). Scientific Opinion on Dietary Reference Values for magnesium. EFSA Journal, 13(7), 4186. https://doi.org/10.2903/j.efsa.2015.4186
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