Correlation of Digit Ratio (Second to Fourth) and Fitness

Abstract

Digit ratio (second to fourth or 2D:4D) is related to the concentration of prenatal androgens. Testosterone affected fetal brain and body development; digit ratio varied due to sexual dimorphism, and exhibited correlations to athletic prowess and behavior. We investigated the sexual dimorphism of college students' digit ratio in Taiwan, and understood the correlation between digit ratio and other different fitness indicators, as well as sports participation behaviors. Additionally, we compared the digit ratio in different levels of sports participators. Total 813 college students (338 males, 475 females, aged 18-19 years) were participated in this study. Subjects were measured based on fitness and asked to complete surveys on sports participation behavior. Digit ratio was analyzed using a scanning method. Digit ratio of male subjects ( .955 ± .028) was significantly (p＜.01) lower than female subjects ( .971 ± .031). As for athletic prowess of all subjects, muscle strength (handgrip strength and leg pressing), muscular endurance (sit-ups per minute) and cardiopulmonary fitness (Harvard step test) displayed a negative correlation with digit ratio of both hands (p ＜ .05). As for sports participation of all subjects, left hand digit ratio displayed a negative correlation with exercise habits (r=-.13, p ＜ .01) and accumulated exercise time per week (r=-.13, p ＜ .05). We distinguished two groups by gender, which only male group cardiopulmonary fitness and accumulated exercise time per week showed a negative correlation with left hand digit ratio, while female digit ratio didn’t showed correlation with any fitness and sports participation indicators. Left hand digit ratio of male and female members of school sports teams, which had higher athletic training frequency was significantly lower than members of non-school sports teams. Our results indicated that digit ratio might affect subsequent levels of sports participation. Male groups with lower digit ratio exhibited higher levels of sports participation behavior, therefore, resulted in better cardiopulmonary fitness.