Relationships between the Digit Ratio(2D:4D) and Exercise-Related Physical Fitness Components in Males and Females

The relative length of the second and fourth fingers(2D:4D ratio) is a putative biomarker for prenatal testos-terone. Low 2D:4D has been known to correlate with morphological, physiological, psychological, and high levels of athletic performance and physical fitness. In this study, it was examined the relationship between the 2D:4D ratio and two important exercise-related fitness components(speed and power) in nonathlete young adults. A total of 108 healthy recreationally active university students(73 male and 35 female, aged 18-20 years) were participated in this study. Body weight and height were measured, and body mass index(BMI) was calculated. The lengths of the second and fourth fingers of the right and left hands were measured, and the 2D:4D ratios were calculated. The difference of the digit ratio between the right and left hands(Dr-l) was also calculated. Speed and power performance were assessed by measuring 100-meter sprint record and handball throwing distance, respectively. Independent t-test was performed to analyze differences between males and females about all var-iables of physical(height, weight, BMI) and anthropometric(lengths of 2D, 4D, and 2D:4D ratio of both hands, and Dr-l) characteristics. The association between physical and anthropometric characteristics and the speed and power-related performance in each sex(male: speed, power, female: speed only) was determined by the Pearson correlation coefficient. Statistical significance was set at P < 0.05. As the main findings of this study, the lengths of the 2D and 4D of males were significantly longer than those of females(P < .001), while male digit ratios in both hands were significantly lower than females(P < .01). There was no significant sex difference in Dr-l. In males, significant positive correlations were observed between the handball throwing distances and the body weight(P < .05) and BMI(P < .01). In females, there was a significant negative correlation between the length of the fourth digit and 100-meter sprint record(P < .05). However, the 2D:4D ratio was not correlated with the speed and power performance in males and females. These results suggest that the 2D:4D ratio is not a major parameter in predicting exercise potential in the nonathlete young adult, and more research is needed that focuses on other factors that can affect exercise potential in the population that is similarly affected by prenatal sex hormones.