Hydration during exercise is not limited to quenching thirst. Every endurance session results in mineral losses—sodium, magnesium, zinc, potassium—which accumulate and directly influence the quality of recovery. Ignoring these losses between training sessions means starting the next session with an existing deficit. Understanding which minerals are critical, how quickly they are depleted, and how to effectively replenish them changes daily nutritional strategy—far beyond race day alone.
Sodium: The primary hydration lever, but an individual equation
Sodium is the most well-documented mineral in a sports context, and for good reason: it regulates plasma volume, triggers thirst, and is the main ion lost in sweat. But what generic protocols ignore is the magnitude of inter-individual variability. According to data compiled by Baker (2017, Sports Medicine), sodium concentration in sweat varies from 20 to 80 mmol/L depending on the athlete—a 4x factor. A fixed protocol of 500 mg/hour will be insufficient for an athlete with high sodium sweat rates and unnecessarily high for another.
This variability has concrete consequences. The prospective study by Almond et al. (2005, New England Journal of Medicine) on 488 Boston Marathon participants found that 13% exhibited post-race biochemical hyponatremia—not due to sodium deficiency but due to hypotonic overhydration. Conversely, an athlete who sweats a lot and consumes little sodium can accumulate a progressive sodium deficit over a week of competition or training camp. Both situations exist, and identical protocols for all serve neither.
White marks on clothing, a very salty taste in sweat, or recurrent cramps during long efforts are field indicators of high sodium sweating. These signs justify adapting the protocol upwards, especially in hot conditions.
Magnesium and zinc: Minerals depleted during an intensive block
Sodium is visible; it leaves traces. Magnesium and zinc deplete without immediate signs. Nielsen & Lukaski (2006, Magnesium Research) documented that exercise increases urinary and sweat losses of magnesium, with a redistribution to active muscles during exertion. An effort of 2 hours or more measurably lowers serum magnesium. In athletes whose diet does not compensate for these losses—which is common during periods of high load—depletion gradually sets in.
Zinc follows a comparable mechanism. Studies by Lukaski (1983, American Journal of Clinical Nutrition) on zinc concentration in sweat (~0.5 to 1 mg per liter) estimate that a week of high-volume training (12 to 15 hours) generates cumulative losses approaching 7 to 10 mg—almost a recommended daily intake—without specific dietary compensation. Zinc is involved in protein synthesis, immune function, and hormonal regulation: three areas directly involved in recovery. The first signs of depletion—repeated ENT infections, slowed recovery, lingering tendon injuries—appear before any detectable biological deficit.
| Mineral | Losses during exercise | Signs of depletion | Strength of evidence |
|---|---|---|---|
| Sodium | 20–80 mmol/L of sweat (4× variability) | Cramps, white marks, muscle fatigue | High |
| Magnesium | Increased urinary + sweat losses from 2h of effort | Night cramps, disturbed sleep, irritability | Moderate |
| Zinc | ~0.5–1 mg/L of sweat, significant accumulation on intensive block | Frequent infections, slow recovery | Low-moderate |
| Potassium | 4–8 mmol/L of sweat, moderate renal losses | Muscle cramps, early fatigue | High (but rapid self-correction via diet) |
Bioavailability of mineral forms: why read the label down to the chemical form.
The mention "300 mg of magnesium" on a label does not indicate what proportion of these 300 mg actually reaches the muscle cell. The chemical form of the mineral is the determining factor. The review by Schuchardt & Hahn (2017, Current Nutrition & Food Science) compares the intestinal absorption of different forms of magnesium available in supplements: organic forms (citrate, glycinate, malate) show significantly higher fractional absorption than magnesium oxide, the most common form in entry-level products because it is the least expensive to formulate.
This absorption differential makes no difference for an athlete in nutritional balance and outside any period of high load. However, for an athlete with a slight deficit—heavy training weeks, insufficient diet, hot conditions—choosing the right form can make the difference between functional recovery and a deficit that accumulates over time. The practical rule: do not compare two products based on milligrams; compare the chemical forms.
This logic applies to zinc with the same reasoning: zinc picolinate and zinc bisglycinate show superior bioavailability to zinc sulfate or oxide. Rich food sources (meats, legumes, nuts) remain the most effective vector for most athletes—supplementation becomes relevant only when clinical signs indicate a real deficit.
The Pyrene Protocol: Hydration during and between sessions
Pyrène Hydration is formulated as a pure electrolyte solution (without carbohydrates or effervescent agents): 629 mg of sodium, 300 mg of potassium, 150 mg of magnesium, 150 mg of calcium, and 1.5 mg of zinc per 9g dose to be diluted in 500 to 750 ml. The sodium comes from Pyrenean sea salt flower, the same source as in the Gels. The mineral spectrum covers the four axes of loss identified during exercise.
During exercise, Hydration can be used alone for short outings (<1h30 in hot weather) that do not require carbohydrate intake, or in addition to Gel or DrinkMix for athletes with high sweat rates or in hot conditions. Pyrène Ultra Endurance Gel uses Magnesium Citrate as its magnesium form—a bioavailable organic form, consistent with the product line's formulation logic.
| Situation | Protocol |
|---|---|
| Outing <1h30, hot weather, no carbohydrate need | 1 dose Hydration in 500–750 ml |
| Long effort with heavy sweating or heat | Gel or DrinkMix (carbohydrate base) + 1 dose Hydration as supplement |
| Recovery between sessions (heavy weeks) | 1 dose Hydration in 500 ml, within 60–90 min post-effort |
| Athlete switching from Neutral Gel to Blueberry Gel | Add Hydration: Blueberry contains 2× less sodium than Neutral |
The post-exercise window deserves particular attention. Muscle cells depleted of minerals during exercise are in an active recruitment state within 60 to 90 minutes following the session. Administering electrolytes within this window—rather than several hours later—is consistent with cellular replenishment mechanisms. The Pyrène dose calculator allows adjustment of quantities to effort duration and conditions.
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Key takeaways on hydration and mineral recovery Sodium is the only mineral with robust evidence for supplementation during exercise—and its inter-individual variability (4× factor) invalidates generic protocols. Magnesium and zinc deplete progressively during intense training blocks; choosing bioavailable organic forms (citrate, glycinate, malate) is relevant in situations of marginal deficit. Pyrène Hydration covers the full spectrum of sodium/potassium/magnesium/calcium/zinc in a single dose, before, during, or after the session as needed. |
Frequently Asked Questions
What minerals are lost in sweat during exercise?
Sodium is the most concentrated mineral in sweat (20 to 80 mmol/L depending on the individual), followed by potassium (4 to 8 mmol/L), magnesium, and zinc in lower concentrations, but whose cumulative losses over an intensive block can be significant. Calcium is also present in small quantities. Inter-individual variability is very high for sodium—a high sodium sweat profile justifies a personalized hydration strategy.
Should electrolytes be taken between sessions, not just during exercise?
During heavy training weeks (>10 h/week), daily mineral losses often exceed what diet naturally compensates, particularly for magnesium and zinc. Using Pyrène Hydration within 60 to 90 minutes after the session—even on a day without intense effort—supports mineral replenishment in the post-exercise window, when muscles are still in an active recovery phase. Carbohydrate-free Hydration is particularly suited for this use: no unnecessary energy intake, complete electrolyte spectrum.
Why does the chemical form of magnesium change its effectiveness?
The intestinal absorption of magnesium directly depends on the chemical form of the salt. Magnesium oxide—the most common form in generic supplements—has low fractional absorption. Organic forms like citrate, glycinate, or malate show significantly higher absorption in available studies (Schuchardt & Hahn, 2017). Concretely: a product displaying 300 mg of magnesium as oxide delivers much less to the cell than a product displaying 150 mg as citrate. Read the chemical form, not the milligram figure.
References
Baker, L.B. (2017). Sweating rate and sweat sodium concentration in athletes: a review of methodology and intra/interindividual variability. Sports Medicine, 47(Suppl 1), 111–128. https://doi.org/10.1007/s40279-017-0691-5
Almond, C.S.D., Shin, A.Y., Fortescue, E.B., et al. (2005). Hyponatremia among runners in the Boston Marathon. New England Journal of Medicine, 352(15), 1550–1556. https://doi.org/10.1056/NEJMoa043901
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/
Schuchardt, J.P., & Hahn, A. (2017). Intestinal absorption and factors influencing bioavailability of magnesium — an update. Current Nutrition & Food Science, 13(4), 260–278. https://doi.org/10.2174/1573401313666170427162740
Lukaski, H.C., Bolonchuk, W.W., Klevay, L.M., Milne, D.B., & Sandstead, H.H. (1983). Maximal oxygen consumption as related to magnesium, copper, and zinc nutriture. American Journal of Clinical Nutrition, 37(3), 407–415. https://doi.org/10.1093/ajcn/37.3.407
Micheletti, A., Rossi, R., & Rufini, S. (2001). Zinc status in athletes: relation to diet and exercise. Sports Medicine, 31(9), 577–582. https://doi.org/10.2165/00007256-200131090-00001
