Prenatal androgenization (2D:4D) predictions of tennis match-play success in junior players: A search for physiological explanations

AIM

This study aims to investigate the possible association between digit ratio (2D:4D) and match-play success (MPS) in junior tennis players. In addition, we consider the possible explanatory pathways of these associations in relation to psychological, strength, power, and hormonal parameters.

METHODS

We performed a cross-sectional study, with a sample comprised of 64 male junior tennis players (11-18 years old). Digit ratio was calculated from direct finger measurements. In addition, we measured the ratio of wins by number of matches played in 5 years of official competition (MPS), handgrip strength (HGS), standing long jump (SLJ), training (in weekly hours), and expertise (number of years in official competition). Salivary testosterone and cortisol levels were measured before and after physical "challenge" tests.

RESULTS

The 2D:4D correlated negatively with HGS and SLJ. MPS was also negatively associated with 2D:4D, but was positively correlated to HGS, expertise, training, and self-confidence (SC). Multiple linear regression showed 2D:4D and expertise were associated with MPS (43%-54%). None of the physical, or hormonal variables tested explained the links between 2D:4D and MPS.

CONCLUSION

Therefore, the specific fitness components influenced by prenatal androgenization that moderate sports success remain unknown. Future studies should explore the interaction of 2D:4D, with tennis exercises as a challenge to induce hormonal change, the effect of pubertal stage, and the influence of aerobic endurance in determining MPS.

Use of crowdsourced images for determining 2D:4D and relationship to pro-environmental variables

The primary purpose of this study was to examine whether 2D:4D ratios (a putative measure of prenatal androgen exposure) could be determined using participant-submitted hand images. The secondary purpose was to examine whether 2D:4D ratio was associated with pro-environmental behaviors, attitudes, and empathy, given the recent literature linking sex to environmental attitudes and actions. Participants (N = 1065) were asked via an online survey to submit a clear photograph of their right hand, palm side up. Participants also completed a questionnaire to assess (a) demographics, (b) dispositional empathy, and (c) environmental attitudes and behavior. A 2D:4D ratio was calculated for each participant, and the quality of each image was classified as poor, moderate, or good. We then examined the reliability of the 2D:4D image measurements, and the relationship between 2D:4D and our environmental measures. 2D:4D ratios fell somewhat outside of previously reported ranges, but the measurements did show acceptable intra-rater consistency. Although we did not find a sex difference in 2D:4D, we did find a sex by ratio interaction for both empathy and the number of pro-environmental behaviors in which individuals had engaged. Specifically, as 2D:4D ratio increased, males reported lower empathy and less engagement in pro-environmental behaviors, whereas females reported more engagement in pro-environmental behaviors (but no differences in empathy). These findings were contrary to expectations, as we anticipated that greater digit ratios (i.e., feminized) would be associated with greater empathy and pro-environmental behaviors. Overall, the findings of this study present a preliminary examination of the utility of measuring digit ratio with online samples. Furthermore, our results provide information regarding the complex relationship between sex and pro-environmental behaviors.

Digit Ratio (2D:4D) and Physical Performance in Female Olympic Athletes

Background: The second to fourth digit ratio (2D:4D ratio) is suggested to be a negative correlate of prenatal testosterone. Little is known about the role of the 2D:4D ratio in relation to serum and urinary androgens for physical performance in female athletes. We aimed to compare the 2D:4D ratio in female Olympic athletes with sedentary controls, and to investigate the 2D:4D ratio in relation to serum and urinary androgens and physical performance in the athletes. Methods: This cross-sectional study included 104 Swedish female Olympic athletes participating in power, endurance and technical sports and 117 sedentary controls. The 2D:4D ratio was calculated using direct digit measurements. Serum androgens and urinary androgen metabolites were analyzed by liquid chromatography-tandem mass spectrometry. The athletes performed standardized physical performance tests and body composition was established by dual-energy X-ray absorptiometry. Results: The 2D:4D ratio was significantly lower in the athletes compared with controls although serum testosterone levels were comparable between groups and within normal reference values. The 2D:4D ratio correlated negatively with urinary levels of testosterone glucuronide and 5α- and 5βAdiol-17G, whereas there were no correlations to serum androgen levels. Furthermore, the 2D:4D ratio correlated negatively with strength tests and positively with 3,000-meter running in the athletes. Conclusion: Female Olympic athletes had a lower 2D:4D ratio, possibly reflecting a higher prenatal androgen exposure, than sedentary controls. Furthermore, the 2D:4D ratio was related to urinary levels of androgen metabolites and physical performance in the athletes but not to serum androgen levels. It is suggested that the 2D:4D ratio could reflect androgen metabolism and may be of importance for sporting success in female athletes.

Relationships between the digit ratio (2D:4D) and game-related statistics in professional and semi-professional male basketball players

OBJECTIVES

The primary aim of this study was to examine relationships between digit ratio (2D:4D) and game-related statistics in professional and semi-professional male basketball players. The secondary aim was to quantify differences in mean 2D:4Ds between starting and reserve players.

METHODS

Using a cross-sectional design, 93 male basketball players from the professional Australian National Basketball League and the semi-professional South Australian Premier League were measured in-season for height, mass, and 2D:4D, with game-related statistics collected end-season. Linear relationships between right and left 2D:4Ds and game-related statistics were quantified using nonparametric partial correlations, and differences in mean 2D:4Ds between starting and reserve players were quantified using analysis of covariance (ANCOVA). All partial correlations and ANCOVAs were adjusted for playing experience, body size, and competitive standard.

RESULTS

2D:4D was a weak to moderate negative correlate of points scored and assists-to-turnovers ratio, indicating that males with lower 2D:4Ds were generally better offensively as they recorded more points and assists relative to turnovers. The difference in mean 2D:4D between starting and reserve players was negligible.

CONCLUSIONS

2D:4D was favorably correlated with open-skill sports performance, as evidenced by the better offensive statistics of male basketball players with lower 2D:4Ds. These results probably reflect the organizational benefits of prenatal testosterone and indicate that 2D:4D may be a useful complement to traditional physical, physiological, skill, and behavioral predictors of basketball success.

College-aged women in the United States that play overhand throwing sports have masculine digit ratios

Athletic prowess in both males and females is negatively correlated with the ratio between the lengths of the second and fourth fingers (2D:4D), a correlate of prenatal testosterone exposure. Because multiple lines of evidence suggest that prenatal testosterone exposure is associated with sports interest, motivation, and athletic performance we measured the digit ratios of 77 non-athletes, 103 varsity athletes, and 78 club sport athletes to test 8 hypotheses about the relationship between digit ratio and the athletic behavior of college-age women in the USA. Using independent samples t-tests, we found no significant differences between the digit ratios of women that (1) were athletes and non-athletes, (2) were varsity or club sport athletes, (3) had played or were currently playing individual or team sports, (4) played contact and non-contact sports, (5) played sports involving a ball and those that do not, (6) played sports where the outcome was determined by a score or the outcome of direct physical competition or subjectively by judges, or (7) were starters or reserves on their teams. However, women that played overhand throwing sports softball and water polo had significantly smaller digit ratios than did women that played other sports. These differences were not due to scaling effects. The independent samples t-test results were supported by subsequent Monte Carlo bootstrap, Bayesian, Random Forest, and multiple linear regression analyses. We suggest that the organizational consequences of prenatal testosterone exposure may influence the anatomy and physiology of women that leads to success playing overhand throwing sports.