A newly published peer-reviewed study has revealed that significant sex-based differences in running performance emerge in children as young as 6 years old, well before the onset of puberty, challenging current assumptions about when male athletic advantages begin to appear.
The research, published in the journal Exercise, Sport, and Movement, examined 1600-meter running performances of children aged 6-12 years old and found consistent sex-based differences across all age groups.
Titled “Sex Differences in 1600-m Running Performance and Participation for Children Aged 6–12 yr,” the study was conducted by researchers Mandy W. Christensen and Christine M. Griffiths, who sought to determine whether pre-pubertal children exhibit sex-based differences in running performance, and whether such differences stem from biological factors or participation disparities.
The findings directly challenge policies adopted by some sports governing bodies, including World Athletics, which in 2022 updated its eligibility criteria to allow transgender females to compete in women’s categories if they “have not experienced any part of male puberty beyond Tanner Stage 2 or before age 12, whichever is later.”
Such policies have been based on the assumption that male athletic advantages only emerge during puberty, but this new research suggests biological differences affecting athletic performance may be present much earlier.
Dr. Colin Wright, an evolutionary biology PhD and Manhattan Institute Fellow, has previously written about sex-based performance differences in sports. While not involved in this particular study, Wright’s work has highlighted that males who undergo typical male puberty retain lasting athletic advantages over females, even after testosterone suppression.
The debate over transgender inclusion in female sports has largely centered on fairness concerns, with scientific reviews consistently showing that post-pubertal physiological advantages—including increased bone size, muscle mass, and aerobic capacity—persist despite hormone therapy.
This new research adds an important dimension to the conversation by suggesting that some performance differences may be innate rather than solely the result of puberty-driven development. If confirmed by further studies, these findings could have significant implications for how sports organizations approach transgender athlete policies, particularly for youth sports.
The study also investigated participation rates between boys and girls to determine whether performance gaps might be explained by cultural factors or differing levels of engagement in athletics. This addresses a common counterargument that observed performance differences might be more social than biological in origin.
For parents, coaches, and policymakers involved in youth sports, these findings provide new insights into the complex interplay of biology, development, and athletic performance from an early age.
