Is digit ratio (2D:4D) a biomarker for lactate in women? Evidence from a cardiopulmonary test on professional female footballers

Abstract

Background
Lactate and digit ratio (2D:4D) have been linked to sports performance, cardiovascular disease, and some cancers. 2D:4D is strongly and positively associated with lactate during exercise across a range of running speeds in men. This study aimed to consider the relationship between 2D:4D and lactate in women during an incremental cardiopulmonary exercise test.

Method
The participants were professional female football players. The treadmill test began at a speed of 6 km/h and was increased by 2 km/h every 3.15 min, with measurements at 6, 8, 10, 12, and 14 km/h.

Results
There were 25 Caucasian and 3 Black participants; 2D:4D and lactate levels were lower in the latter, but the sample size was too small for meaningful comparisons. Lactate levels increased with running speed. The 2D:4D was not associated with lactate at 6 to 12 km/h. At 14 km/h, lactate was positively associated with right and left 2D:4D (stronger for the former) and negatively with height and digit lengths. These correlations were significant for the total sample and Caucasians only. Multiple regressions for the Caucasian sample showed that right 2D:4D was positively related to lactate at 14 km/h, and height was negatively associated with lactate at all speeds.

Conclusion
During exercise, the effect sizes for relationships between 2D:4D and lactate in women are positive but smaller than those reported for men and restricted to higher running speeds. Unlike men, women show a negative relationship between height and lactate. It is suggested that prenatal and pubertal sex steroid effects may explain these sex differences.