The notion of tailoring lifestyle habits according to the phases of the menstrual cycle is gaining momentum both in scientific fields and on social media. Recent studies indicate that when athletes incur sports injuries during their menstrual periods, recovery times are notably extended compared to other cycle stages.

#cyclesyncing has been widely featured across social media, advocating for adjustments in both dietary choices and physical activity based on the fluctuations in hormones throughout the menstrual cycle. However, the scientific backing for these dietary modifications remains limited, while research regarding exercise provides mixed results. Still, teams such as the American and British rugby squads have already adapted their training to align with players’ menstrual cycles.

To investigate this further, Eva Ferrer and her team at Sant Joan de Deu Hospital in Barcelona monitored 33 professional athletes from FC Barcelona’s women’s team over a four-season span from 2019 to 2023.

During their standard training routines, the athletes documented their menstrual cycle days. All injuries sustained during the season were classified by severity by medical professionals applying a standardized assessment scale.

The findings revealed that while the athletes did not experience injuries specifically during their menstrual days, those incurred during this period appeared to be more severe. For instance, soft tissue injuries sustained while menstruating led to over three times the duration of training lost compared to injuries incurred at other times.

These outcomes may be influenced by decreased estrogen levels during menstruation. This hormone is vital for muscle recovery and rehabilitation. “The combination of reduced estrogen, potential iron depletion, increased symptom severity [like cramps], and heightened fatigue during this phase can negatively affect injury recovery,” notes Ferrer.

However, Stuart Phillips from McMaster University in Canada emphasizes that the intricacies of estrogen’s role in muscle repair remain unclear. “Estrogen is believed to offer protective and reparative qualities [for muscles],” he states, “but much of this evidence derives from animal studies rather than human experiments.” Furthermore, their study did not account for possible confounding variables like women’s iron levels or fatigue.

Ferrer acknowledged that while they recorded a total of 69 injuries on non-bleeding days, only 11 occurred during menstruation. “When you overlook sample sizes and confidence intervals, a small number of critical injuries can distort the overall results,” she explains. Additionally, it remains uncertain if these findings are applicable to less competitive athletes or casual sports participants, according to Ferrer.

She hopes that future research will elucidate these issues and possibly lead to exercise recommendations tailored to various menstrual cycle stages. “The most prudent approach is to make individualized decisions regarding training loads and types of exercise during menstruation. Ongoing research will consider each athlete’s symptoms alongside objective data (internal and external workload, injury histories, health metrics, etc.), while also integrating hormone measurements, iron levels, sleep patterns, nutrition, and other factors that may enhance these recommendations,” Ferrer asserts.