Published data on sporting ability and 2d:4d thus far has mainly focused on male participants. Manning and Taylor10
explored the relationship between this skeletal ratio by direct 2d:4d measurement and sports rank (self recorded on a 1–10 scale, 10 indicating international participation) in 128 men. Some 45% of participants practised running, 14% football, 10% martial arts, 8% rugby, 8% tennis or squash, 7% swimming and 5% hockey. They found a significant negative relationship (b
0.01) between 2d:4d and sports rank even when the effects of age, sports experience and type of sport were removed. As part of the same study, the authors contrasted photocopied 2d:4d in 304 current or historical male participants in professional English soccer and 533 controls. Professional players had a significantly lower 2d:4d (derived from right and left 2d:4d) compared with controls. Internationals had a significantly lower mean 2d:4d than non‐international players. From these data, the authors felt that 2d:4d in men is a correlate for ability in many sports, including football. They hypothesised that this relationship may arise through the influence of prenatal testosterone on development of the right hemisphere and visuospatial ability, and/or through environmental effects of prenatal sex hormone and developmental stability of the cardiovascular system. These effects may be of clear benefit in the development of a sporting individual.
Similar results were obtained when the relationship between directly measured 2d:4d and fastest dry slope skiing time was examined in 72 competitive skiers (52 men, 20 women) and controls matched for age, sex and ethnicity.11
Controls had a higher mean 2d:4d than skiers, and a lower 2d:4d correlated with a quicker course time, this relationship being independent of sex, age and experience. Aside from significant sex differences in mean 2d:4d, specific data relating to the female cohort were not presented.
This is the largest study to date exploring the relationship between female sports ability and 2d:4d across a wide range of sports. It lends support to recent smaller studies that show female sports ability and fitness appear to be negatively associated with 2d:4d.12,13
The strongest association appears to hold for running when analysed in isolation, although trends towards a negative association with 2d:4d were observed for many of the individual sports. This may be because running forms a common integral part of many of the sports examined or their training schedules. Our study was underpowered to examine associations between participation level in all of these sports and 2d:4d because of small numbers in particular sports. No data were available to adjust for sports experience and type of sport, but this is being evaluated as part of an ongoing prospective study.
What is already known on this topic
- The second to fourth finger length ratio is thought to be related to diverse traits including cognitive ability, disease susceptibility, and sexuality.
What this study adds
- A low second to fourth finger length ratio is related to increased female sports ability.
- It can be postulated that this ratio may predict potential sports ability.
If 2d:4d is fixed before birth and remains constant during life, this offers up the tantalising question: can 2d:4d be used to predict future potential in sport? Prediction of future ability is ascertained in many aspects of education, and several researchers have attempted to look at particular characteristics that may predict suitability/future excellence in sport. Testing the theory that future ability and performance in sports may be reliably predicted by 2d:4d would require a large prospective study following children from a young age through to their competitive peak in their chosen event, although the performance of childhood athletes may not correlate well with best adult performance because of variability in developmental rate.4
Detection of sports potential by examining 2d:4d—for example, as part of a talent identification programme—may, however, help to identify talented individuals at a pre‐competitive stage. Potentially of more interest is determining the exact biological correlate of 2d:4d that influences sports ability. Although developmentally important homoeobox mutations have been linked to abnormalities in the development of digits and gonads, no specific gene candidates have been identified for the determination of 2d:4d, and therefore it is likely that this skeletal ratio is under polygenetic influence. In a classical twin study, we have recently shown that 2d:4d shows strong heritability with relatively little influence of common environment,14
and this may explain why sporting parents often have sporting children.
A possible source of conflicting data is the method of measurement. Most work on 2d:4d has involved measuring finger lengths from hand photocopies, which reduces collection time and provides a permanent record; this form of measurement may yield lower ratios than direct finger measurements,15
although correlation is reportedly high for both these methods.16
Manning et al17
confirmed that measurements of 2d:4d from hand photocopies and radiographs are significantly correlated, although mean radiograph‐derived 2d:4d showed less sexual dimorphism, and ratios were lower than those derived from photocopies. The authors suggested that this may be because photocopy measurement includes measuring soft tissue as well as bone lengths.
Recall bias is a possible source of error as there was no independent verification of sports level achieved. However, this is likely to be small, as subjects are unlikely to forget competition at national and sub‐national level. Owing to small numbers, it was difficult to draw firm conclusions for certain groups. Selection bias is unlikely to be a problem in our study, as x
ray examinations were performed for other reasons. Also, the study population has been found to be similar to a population‐based singleton sample for a number of common medical conditions and lifestyle characteristics.18
In conclusion, using a precise radiographic phenotype we have provided evidence that low 2d:4d is related to increased running and sporting ability in women. We postulate that 2d:4d is a predictor of potential sports ability. Understanding the mechanisms underpinning this relationship would give important insights into musculoskeletal fitness, health and disease. Further work may determine whether this ratio can be used at a pre‐competitive stage to predict future ability.