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Absence of Sex Difference in Digit Ratio (2D:4D) Among the Elite Sportspersons: Further Evidence Among the Polish
Marek Kociuba1, Slawomir Kozieł2,3, Zofia Ignasiak3
1Department of Physical Education and Sports, General Tadeusz Kosciuszko Military University of Land Forces, Wroclaw, Poland.
Background:
Variation in exposure to prenatal androgens was linked with athletic abilities and varied performance in different sports. The ratio between the second and fourth digit lengths (2D:4D) is a proxy indicator of prenatal testosterone exposure. A higher exposure leads to a lower 2D:4D and vice versa. Negative associations between digit ratio and several sports performances were consistent in earlier research.
Aim:
The aim of the present study was to assess if 2D:4D was lower among the Polish competitive swimmers compared to non-sporting individuals and the heterogeneity in sex difference among different levels of swimmers and the non-sporting group.
Method:
This cross-sectional study assessed 2D:4D among two groups of swimmers from the Polish national team and other higher level swimmers, and a control group (54 males and 34 females). Height, weight, and lengths of 2D and 4D were measured.
Results:
The control group showed a significant sex difference in the right hand 2D:4D; the females showed a higher ratio than the males (t = 2.17, p < 0.05). However, no sex difference was evident in any of the swimmers' groups. The difference in 2D:4D among the three study groups was significant only for the left 2D:4D in males and only for the right 2D:4D in females. The female swimmers (both national and general) showed significantly lower right 2D:4D than the control females, whereas the male swimmers showed significantly lower left 2D:4D than the control males.
Conclusion:
The swimmers had lower 2D:4D than non-sporting individuals; the top level swimmers had the lowest 2D:4D. The female swimmers, particularly the elite group, showed "masculine" 2D:4D similar to their male counterparts. A plausible positive selection for a masculinised digit ratio (higher prenatal testosterone exposure) among the females in highly competitive professional sports was hypothesized.
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