Replenishing sodium during exercise is something many people already know, but what few people know is that, in the case of women, this replenishment can (and should!) also take into account the phases of the menstrual cycle. Furthermore, consuming sodium before starting to train, especially on hot days, can be a strategy to improve performance and help the body endure longer periods of activity.
That's exactly what a study published in 2025 in the International Journal of Sport Nutrition and Exercise Metabolism investigated. Researchers followed a group of women who were not used to training in the heat and tested the effects of so-called hyperhydration. One strategy involves consuming 1.2g of sodium before exercise, with the goal of optimizing fluid retention and regulating body temperature. Most interestingly, the study controlled for the phase of each participant's menstrual cycle (follicular and luteal), recognizing that these hormonal variations directly impact how the body responds to exertion and heat.
The participants performed an intense exercise session in a hot environment (35 °C) and were divided into a group that consumed the sodium-enriched drink before the activity and another that did not. The objective was to understand how sodium would act in different phases of the cycle, comparing the physiological responses between those who consumed and those who did not consume the extra electrolyte.
The results were noteworthy: during exercise, women who hyperhydrated showed a number of benefits: their body temperature increased less, their hearts had to work less intensely, and they were able to exercise for longer before reaching exhaustion. In other words, sodium helped the body better preserve hydration and maintain thermal balance, reducing the physiological stress caused by the heat.
Another important point was that positive effects were observed in both phases of the menstrual cycle , despite the natural differences that each brings in thermoregulation and response to exertion. The group that did not ingest the extra sodium had more difficulty controlling body temperature, a higher heart rate, and a shorter time to the onset of fatigue.
This study reinforces the importance of considering not only the environmental context (such as heat), but also the particularities of female hormones when devising a good hydration strategy. Hyperhydration can be a promising tool for female athletes or even recreational athletes who train in high temperatures and want to maintain performance without putting their health at risk.
Reference: Lemire, RD, Stapleton, LM, Campbell, IG, & Beaven, CM (2025). Sodium hyperhydration improves endurance performance in the heat in women regardless of menstrual cycle phase. International Journal of Sport Nutrition and Exercise Metabolism , 35(2), 99–109.
Available at: https://journals.humankinetics.com/view/journals/ijsnem/35/2/article-p99.xml
