Elite female soccer players do not suffer injuries during menstruation

Elite female soccer players do not suffer injuries during menstruation

A study conducted over four seasons shows that while menstrual bleeding does not increase injury rates in elite women's football, it is linked to injuries that result in players being sidelined for much longer periods Study: Menstruation and Injury Frequency; a four-year observational study of elite female soccer players. Photo credit: Drazen Zigic/Shutterstock.com

An article recently published in the magazineLimits in sport and active lifeexamines injury rates in elite female soccer players during bleeding days (the early follicular phase), when ovarian hormone levels are expected to be low.

Hormonal changes raise questions about injury risk

Menstrual bleeding results in the loss of one milligram of iron per day over a period of 4 to 8 days per cycle. This can lead to iron deficiency, which reduces training load, weakens endurance and slows recovery. Muscle health, post-workout recovery, inflammation, and neuromuscular performance are other areas that can be susceptible to hormonal fluctuations during the menstrual cycle.

Much of the research to date has focused on tracking injury risk across the entire menstrual cycle. Conflicting results from previous studies make it difficult to determine whether a particular phase of the menstrual cycle increases the risk of injury. The difficulty lies in the need for invasive testing to accurately identify each phase through hormonal measurements.

This knowledge would develop safe and optimal training and recovery strategies to protect the health of female athletes and prevent injuries when possible.

Four seasons of injury and cycle tracking

33 players from a single Spanish professional team took part in the study. They were followed over four seasons, from 2019-20 to 2022-23, during which they won two UEFA Women's League titles. None of them were taking combined oral contraception and all were menstruating during the study period.

While the first season included 17 players, the second and third seasons included 20 and 18 players respectively, and the final 22. Eleven players were included in all four seasons.

Their cycles were recorded using a digital calendar and had an average length of 31 days. The average number of bleeding days was four, accounting for 13% of the total cycle. For this study, only bleeding days were counted as early follicular phase days; the remainder were documented as bleeding-free days.

This classification was used because no hormonal measurements were available and menstruation is the only period during which ovarian hormone concentrations can be concluded with relative certainty.

Injuries were documented and classified using Orchard Sports Injury Classification System (OSICS-10) codes.

Injury severity was reported based on the number of time-loss injuries, i.e. h. Injuries that resulted in not taking part in the next training session or game. They were classified according to the UEFA model, based on the number of days from the time of injury to the end of sick leave. Mild, moderate, and severe injuries resulted in loss of 1–7, 8–28, and >28 days, respectively.

The frequency of injuries remains unchanged, but the consequences of injuries are increasing

The players suffered a total of 80 injuries in 852 menstrual cycles. Injuries during the game accounted for 22.5%, compared to 77.5% during practice. Most injuries (57.5%) involved muscles, with ligaments and tendons accounting for 30% and 12.5%, respectively.

Eleven injuries occurred on the bleeding days, accounting for 13.7% of all injuries. The incidence of injury in this phase was 5.46 per 1,000 hours compared to 6.6 per 1,000 hours in all other phases. The overall incidence was 6.42 per 1,000 hours. There is therefore no connection between the frequency of injuries and the bleeding days.

Importantly, bleeding days accounted for a very small proportion of the total, limiting the study's power to accurately determine the risk of injury on these days.

A much higher injury burden occurred during the bleeding phase. Soft tissue injuries during bleeding days resulted in approximately three times as many lost days, 684 days per 1,000 hours. In contrast, only 205 lost days were recorded in all other phases.

This may be attributed in part to the fact that two out of four total ACL injuries occurred during the bleeding days, which are known for their very long recovery times.

Ligament injuries caused the most lost days of all injury types, with a mean of 29 days and a total of 187 days, although they occurred significantly less frequently than muscle injuries, at 1.9 and ~3.7, respectively. In contrast, days lost due to muscle injuries amounted to approximately 84, less than half of the days lost due to ligament injuries.

Severe injuries accounted for 31% of all injuries, but moderate injuries resulted in the most lost days. Major injuries accounted for 2.01 per 1,000 hours, versus 3.05 and 1.4 for moderate and minor injuries, respectively.

This suggests that “injuries during menstruation had more serious consequences.” One possible explanation is that estrogen levels are low in the early follicular phase; However, the authors caution that this alone is unlikely to fully explain the results. Low estrogen levels are associated with exercise-induced muscle damage, increased delayed onset muscle soreness (DOMS), and reduced strength recovery after injury.

This could mean that female athletes experience differences in recovery and injury outcomes when estrogen availability is low, rather than a higher risk of injury occurrence. Further large studies are needed to confirm this hypothesis, especially given that the risk of injury is multifactorial and especially since high estrogen levels are also associated with lower tissue stiffness and reduced neuromuscular control.

Another recent study of women who exercised for recreation suggested that symptoms were most severe during menstruation. The women felt that they performed worse during these days and took longer to recover.

Symptom severity, fatigue, training load, diet, and recovery factors could therefore contribute to the observed increase in the burden of serious injury, independent of hormonal effects.

Tracking the menstrual cycle can improve injury management

While there is no significant increase in injury incidence during menstrual bleeding, injury severity is significantly higher, suggesting that elite female athletes are at risk for more severe injuries during the bleeding phase.

These results highlight the importance of individual menstrual tracking for injury prevention and health management of athletes.

However, the authors emphasize that calendar-based tracking has limitations and that future work should validate these results using objective hormone measurements as well as broader physiological and contextual data to better inform training and recovery strategies for female athletes.

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