Menstrual cycle in female archers: Serin 2019 study

Ten licensed female archers from a club in Muğla, Turkey, aged 18 to 30, were measured twice: on the third day of menstruation and on a day outside the menstrual period, both times shooting at 50 metres with a compound bow. Alongside the score, the authors collected a long list of physical, physiological, psychological and environmental measures.

The mean score did not change significantly: 8.79 during menstruation and 9.04 outside it (p = 0.285). Several physical measures did change. Strength was slightly lower during menstruation: right handgrip (28.27 against 30.34 kg) and left handgrip (30.08 against 32.36), back strength (100.03 against 103.31) and leg strength (95.42 against 98.00). The beam balance test (3.50 against 1.30, with no unit given) and body temperature (37.7 against 37.12 degrees) also differed. Total testosterone was lower during menstruation (0.43 against 0.49), while blood count, thyroid hormones and oestradiol did not differ. Heart rate while shooting (116.54 against 101.45 beats) and the time from draw to release (6.60 against 5.93 seconds) were higher during menstruation, but not significantly.

In the correlations with score, no measure was linked to the result during menstruation. Outside the menstrual period a longer time between draw and release went with lower scores (r = -0.69), and a higher TSH value with higher scores (r = 0.74).

Measurements were collected over three months at the Atatürk stadium in Muğla, between 3 and 5 pm, on the third day of menstruation and, outside the menstrual period, during a normal training session. Shooting was at 50 metres, the compound competition distance, with a Contender Elite bow of 40 to 50 pounds described as the federation's standard bow. The text does not say how many arrows were shot, on what target face, or how the score was calculated.

Heart rate was recorded with a Polar RS400 chest strap during shooting and the time from draw to release with a stopwatch. Grip, back and leg strength were measured with Takei dynamometers, temperature with an infrared thermometer, balance with the flamingo test on a beam and state anxiety with a 20-item questionnaire. Blood and hormone tests were done at the laboratory of the Muğla teaching hospital, while air temperature and humidity come from official weather records. The two phases were compared with the Wilcoxon test and the links with score with Pearson correlation.

Ten archers, measured once per phase as far as the text makes clear, are too few to detect a small difference in score: 8.79 against 9.04 shows that no difference emerged, not that there is none. The non-menstrual phase is not defined: it is not known where in the cycle it fell, and the almost identical oestradiol values in the two measurements (72.49 and 70.00) do not help to tell. Nor is it clear whether measurements were repeated over several cycles during the three months or taken only once.

The two sessions were not held under the same conditions: air temperature and humidity differed significantly, and the non-menstrual measurement coincided with a normal training session, so some of the differences may come from the day rather than the cycle. There are dozens of correlations, calculated on 10 people with no correction for multiple comparisons: the two significant ones with score, draw time and TSH, could be due to chance, and the text offers no explanation for the link with TSH.

The score is not described, it is unclear whether the archers used their own bows or the standard bow mentioned, and the text contains inconsistencies (the summary reports the testosterone difference as significant with p > 0.05). The journal has questionable editorial standards.

For a female archer, the study shows no drop in score on the third day of menstruation, but it is too small and too imprecise to rule one out. What it does show is slightly lower strength on that day, in the order of 2 or 3 kg on grip and back, which with a compound bow at that draw weight does not seem enough to change the result.

The finding on draw time, with lower scores when the shot took longer, applies only to the non-menstrual phase and is a correlation across ten people. Every archer experiences her cycle differently: for anyone who notices recurring drops or symptoms, a diary of her own scores and her doctor's view say more than these numbers.