Digit Ratio (2D:4D) and lactate response during a football-specific intermittent field fitness test in women

Abstract

Background
Lactate, an important respiratory substrate, is generated during exercise. Digit ratio (2D:4D) is strongly associated with lactate in men over a range of exercise intensities, but in women the association has been reported as weaker and restricted to high running speeds. Here we report a replication of this finding in women employing the 30–15 Intermittent Fitness Test (30–15 IFT).

Method
The participants were amateur female football players. Digit lengths, height, body composition and VO2max were measured. The 30–15 IFT involves 30-s shuttle runs between lines positioned 40 m apart. Audio signals determine the pace, starting at 10 km/h and increasing by 0.5 km/h to a maximum of 18 km/h.

Results
Mean lactate levels (mmol/L) rose with running speed, ranging from 2.13 (±0.78) to 13.63 (±2.83). At running speeds 12 km/h to 16 km/h (n = 28 and 26 respectively) there were positive correlations between lactate and weight and BMI and negative associations with VO2max. At 18 km/h (n = 16) right 2D:4D was positively related and height negatively related to lactate. The former remained significant after the effect of height was removed.

Conclusion
Our findings from the 30–15 IFT in the field are similar to those reported from a laboratory treadmill test. The digit ratio, especially right 2D:4D, is positively associated with lactate levels during running in women, independent of height. In contrast previous findings in men the association applies to high running speeds only.