HANDELSMAN STUDY ON PRE-PUBERTAL DIFFERENCES
A study pointing out that it could be effects from the mini puberty as an infant and/or muscle memory differences between male and female children.
The ontogeny of sex differences in exercise performance
https://academic.oup.com/jes/article/10/4/bvag042/8500320?login=false#google_vignette
David Handelsman and Grant Tomkinson
April 2026
Abstract
Sex differences in adult athletic performance are driven by the 20-to 30-fold increase in testosterone production of male puberty creating larger and stronger muscle, bone and cardiorespiratory functions, and higher hemoglobin creating male physical advantages in power sports, where strength, speed, or endurance determine success. Before puberty, boys also surpass girls in age-group records despite no difference in circulating testosterone over the decade from minipuberty to puberty. However, the relative magnitude of the prepubertal, relative to pubertal, sex differences in exercise performance remain uncertain. To investigate the magnitude of these differences in a unitary dataset, this was a secondary analysis of a exercise performance of 85 347 healthy 9- to 17-year-old Australian schoolchildren between 1985 to 2009. Boys surpassed girls in 8 of 9 exercises excepting 1, a stretching exercise, in which girls surpassed boys. For each exercise the magnitude of the pubertal changes were much larger than those of prepubertal differences. These findings in normative tests extend previous studies of competitive age records of prepubertal children and compare the same tests over the pubertal transition. These findings confirm that the quantitatively dominant sex differences in exercise performance are those of puberty. That at least 1 prepubertal exercise test is dominated by girls indicates that the prepubertal differences are more likely to be biological rather than sociological, related to boy's greater habitual play or exercise. It is postulated that these prepubertal sex differences may arise from the combination of androgen imprinting during minipuberty propagated by muscle memory.
Discussion
The present findings are consistent with the evidence of sex-related differences in prepubertal children as assessed from age group records in athletics and swimming competitions [6, 7, 16-22]. These sex differences are likely due to the combination of androgen imprinting during male minipuberty plus the effects of muscle memory.
Male minipuberty involves sustained exposure to elevated circulating testosterone concentrations for the first 6 months of neonatal life in boys, but not girls [12]. These reach transiently for a few months adult male concentrations [29-31] sufficient to invoke androgenic effects. This is manifest in androgen-dependent sex differences in testis [32-35], penile [36] and somatic [37] growth as well as muscle mass and strength [38, 39]. Furthermore, neonatal testosterone exposure dictates the sexual dimorphism in patterns of pulsatile GH secretion, which in turn determines highly specific sex-specific expression of hepatic cytochrome P450 metabolizing enzymes and other enzymes including steroid 5α reductase type 2 [40-45]. In addition to the androgen imprinting of male minipuberty, the present findings may also be due to muscle memory. That is a mechanism proven experimentally in rodents whereby initial muscle stimuli (exercise, androgens) primes the muscle cells so that subsequent stimuli trigger a greater muscular force response starting from a higher baseline [46]. This mechanism reflects stimulus-induced fusion of muscle stem (satellite) cells with multinucleate myofibers, thereby increasing the numbers of myonuclei which then remain after the initial stimulus ceases. This creates a higher latent starting point for response to a renewed stimulus [25]. Although this mechanism remains difficult to prove in humans and further research is needed, if it prevails in humans then the androgen imprinting in male minipuberty may prime muscles to a stronger response to the future stimuli such as the dramatic rise in circulating testosterone of male puberty [47]. In concert, these 2 features may explain the finding that boys exercise performance generally surpasses that of age-matched prepubertal girls [16-22, 48].
Although late gestational effects of high testosterone exposure in girls with congenital adrenal hyperplasia have lasting neurobehavioral effects into postnatal life such as increased male-typical preferences for play and sexuality [49], it is not known if those late gestational effects influence the same androgen-sensitive features of male minipuberty.
The Y chromosome has the evolutionarily specialized role for male sex determination, achieved by its expressing the SRY gene, the single master gene necessary and sufficient to induce testis development [50]. SRY gene expression dictates male genetic and phenotypic sex signifying that a testis is, or likely will be, present, which is then capable of synthesizing and secreting testosterone to achieve adult male testosterone concentrations and, subject to normal androgen sensitivity, will achieve the physical advantages of male puberty for exercise. The other Y chromosome genes, fewer than 40, are involved in cellular housekeeping and not reproductive roles [51], and none has any role in exercise performance [1, 4].
The differences observed in this study are based on calendar age group data as objectively determined from the date of birth recorded in birth certificates. However, the substantial variability among individuals and ethnicities in the age and tempo of puberty may create anomalies when findings are based on the extremes of individual record performance. The performances of those with earlier onset and faster progression of puberty and growth toward adult body dimensions may have a physical performance advantage during childhood and adolescence. To partially overcome this potential extremity bias of the individual record holders, sex- and age-specific records of the top 10 and top 100 performances have been examined with concordant findings [6, 18-22]. Such findings are consistent with the findings of the present study, which bring more of a community focus and show that for most, but not all exercises, prepubertal boys typically outperform age-matched girls in study cohorts that are broadly population-representative.
The present findings are also consistent with other reports of prepubertal sex differences in exercise performance with boys outperforming girls on most, but not all, exercises [6, 7, 16-22]. A notable finding in the present study is that at least for 1 exercise test—the sit-and-reach test of flexibility—girls outperformed boys at every age with the gap larger after puberty. Similar findings of girls' superiority in flexibility have been reported elsewhere [52, 53]. These findings cast doubt on the hypothesis that the sex-related differences before puberty are due to boys having greater habitual physical activity levels (eg, recreational sports participation) [54, 55]. Instead, these collective findings argue for a biological basis for the sex-related differences in exercise performance during childhood and adolescence rather than behavioral or psychosocial causes.
There is a well-established basis for the binary sex classification for fairness and safety in adult elite sports based on physical advantages arising from male puberty [1, 4]. Nevertheless, the need for a binary sex classification is not evident or necessary in sports or events where physicality is not crucial to success (eg, board sports, target shooting). Nor is sex classification required in recreational, community, and junior (<12 years old) sports like in soccer, where mixed sex competitions already exist. However, future elite athletes often start competing at an early age so that competitive underage events, where times or distances are recorded, or where girls are at greater risk of injury competing against boys may require adult sex categories for fairness and/or safety.
The present findings reinforce other recent findings [6, 7, 16-22], indicating that there is a physical performance advantage for boys in most, but not all, exercise disciplines before puberty. Hence, whether this requires sex-selective sporting events in childhood depends on the importance of the outcome to the competitors. If children are seriously competing for medals, podium places, or team inclusion, then sex-specific events are required depending on the sports discipline involved. Where the outcomes are not critical, such as in recreational or communal sports events or where the noncompetitive social and physical activity rationales predominate, then sex-specific events may not be useful or warranted.
This study has strengths in that it used large, general, and broadly representative samples of apparently healthy children of known age and sex who were tested using widely known, feasible, scalable, standardized exercise performance tests. It is limited in that performance testing was not overtly competitive between individuals so that it may not be directly comparable with formal competitive athletic performances in childhood analyses of world or national age-group records are probably biased toward the early maturing children when based on world or national age-group records. Additionally, the physical impact of male puberty is not finalized by the age of 17 years so the magnitude of the pubertal effect on exercises may be underestimated.