The Study of the Relation between Second-To-Fourth Digit Ratio, Physical Fitness, and Postexercise Metabolic Fingerprint: an Analysis by Anthropological, Exercise Physiological, and Metabolomic Correlates

The ratio of the length of the second digit to that of the fourth digit (2D:4D), a widely studied putative marker for prenatal androgen action; lower 2D:4D indicates higher prenatal testosterone exposure. In recent years, there has been a dramatic proliferation of research concerned with 2D:4D. In late 2016, this literature totalled more than 600 publications. The 2D:4D ratios were demonstrated to be correlated with morphological, physiological, psychological, and behavioral traits, as well as certain disease conditions. Increasing amount of research indicates the 2D:4D is also negatively associated with sports ability (lower 2D:4D has better sports ability), include fencing, long-distance running, rowing, rugby, skiing, soccer, sumo wrestling, and surfing. Our recent study also demonstrated that elite collegiate tennis athletes have lower 2D:4D values than those of non-athletes. Physical fitness plays a major role in the capacity of athlete to meet the physical demands of their sporting disciplines without suffering fatigue. In the previous paragraph, we have mentioned that increasing amount of research addressed the 2D:4D ratio is negatively associated with sports ability (lower 2D:4D has better sports ability). However, comparatively little research has focus on the relationship between the 2D:4D ratio and performance on each component of fitness. Metabonomics is a measurement of the dynamic metabolic response of living systems to stimuli or modification. Empirical studies suggest that physical exercise modifies human metabolism profoundly, and the changes could be found in urine. In addition, a rigorous study pointed out that the better physical fitness has lesser changes in urine metabolite levels after exercise. Based on the above-mentioned points, we hypothesize that lower 2D:4D indicates higher prenatal testosterone exposure, has better physical fitness and lesser changes in urine metabolites after exercise. The specific aims of this 3-year project are as follows: (1) to determine if lower 2D:4D has lesser body mass index and greater capacity for cardiopulmonary endurance, muscular endurance, power, and flexibility in child, (2) to investigate if lower 2D:4D has lesser body mass index as well as greater capacity for 4 health-related physical fitness components (cardiovascular endurance, muscular endurance, muscular strength, and flexibility), and 6 skill-related physical fitness components (agility, coordination, balance, power, reaction time, and speed in adults, (3) to clarify the correlation between 2D:4D, physical fitness, and changes in urine metabolites after exercise.