Late menarche in athletes and archers: Fujii 2011

The study builds a criterion for judging whether a girl's first period, menarche, comes late relative to her physical maturity, and applies it to Korean athletes. The reference point is the age at peak height velocity, which the authors take to be unaffected by training. In 345 non-athlete students at a high school in Pusan, menarche came at 12.4 years on average, 0.8 years after peak height velocity (11.6 years). In 120 athletes from a sports high school in the same area, leaving out 4 with amenorrhoea, the growth peak came at almost the same age (11.7 years) but menarche later, at 13.6 years, an interval of 1.9 years; the differences in menarche and in the interval were significant (p<0.01).

On the regression criterion built from the non-athletes, 84 of the 120 athletes had delayed or somewhat delayed menarche. The 8 archers were the exception: 3 somewhat early, 3 normal, 2 somewhat delayed and none clearly delayed, whereas in track and field (18 of 24) and taekwondo (11 of 14) delay was the rule. About 80% of the athletes reported moderate or severe menstrual pain, and among those with delayed menarche the distribution was similar to that of the whole group.

The athletes were second-year students at a specialist sports high school near Pusan, all prize-winners at regional level and selected for national competitions, across thirteen sports; since the start of junior high school they had trained for three or four hours a day, six days out of seven. The non-athletes attended an ordinary high school in the same area and did not belong to school sports teams. For all of them the authors reconstructed height growth from school health records, measured every May from age 7 to 17, and asked in an interview for the age at menarche to the month; anyone who could not recall it that precisely was excluded.

From each girl's growth curve, interpolated with a wavelet-based method, they derived the age at peak height velocity. They then built two criteria on the non-athletes: one based on the mean and standard deviation of the interval between peak and menarche, the other on a regression of age at menarche on age at peak. Of the polynomials from first to fourth order, the third-order one fitted best, and the five judgement bands are set at half and one and a half standard deviations from the curve. Menstrual pain was measured on a 0 to 10 visual scale.

There were only 8 archers, too few to say that menarche is not delayed in archery: one or two more girls in the delayed bands would change the picture, and the study makes no statistical comparison between sports. The authors' explanation, that archery involves little whole-body strength work and does not change body composition, was not measured: fat and lean mass are not reported, nor are training hours by sport. It is also worth noting that in shooting, another precision sport, 9 of the 10 athletes had delayed or somewhat delayed menarche, so the idea that the type of movement is what matters remains unproven.

Students at a sports high school are a selected group: girls who mature later may be better suited to certain sports, and the difference does not tell us how much comes from training. Age at menarche was recalled years later. Menstrual pain was measured once and only in the athletes, with no comparison with the non-athletes, so the link with delayed menarche is the authors' interpretation. The English of the paper is unclear in several places.

For a female archer, or anyone coaching girls, the study offers one isolated finding: among the 8 archers at a Korean sports high school, the first period did not come late relative to growth, unlike in track and field, taekwondo or gymnastics. With numbers this small we cannot say that archery protects against delayed menarche, or that it differs from other sports; we can only say that no delay showed up in this sample.

The wider issue concerns anyone coaching girls through their growth years: heavy training during puberty can go with later menarche and painful periods. A late first period or severe menstrual pain is a matter for a doctor, and the study offers no guidance on how to structure training.