How footballers' fingers and height can predict their exercise performance

Regarded as the preferred fuel for nerve and muscle cells, vigorous exercise results in the release of lactate into the blood stream but high levels may indicate that the body is in a state of stress.

Scientists are trying to find out if it is possible to predict just how much lactate a person will produce based on the physical attributes of finger length and height.

The relationship between the length of a person's index and ring fingers, known as the 2D:4D ratio, has already been correlated with their performance in distance running, age at heart attack and severity of Covid-19.

Now Professor John Manning, of Swansea's Applied Sports, Technology, Exercise and Medicine (A-STEM) research team, has been working with colleagues in Cyprus, Poland and Spain to monitor the performance of male and female professional footballers.

Two recent studies have shown a rapid accumulation of lactate in both male and female players during treadmill tests with running speeds up to 16 Km/h.

The team's latest findings highlighting the females' results have just been published by journal Early Human Development and follow on from last year's paper examining male players.

Some footballers showed very small increases in lactate while others registered a rapid increase. In males, digit ratio or 2D:4D -- the relative length of the index (or second finger) and ring finger (4^th) -- was the strongest predictor of lactate.

Professor Manning said: "Men with a long ring finger relative to their index finger produced little in the way of lactate. For women, there were two predictors, height and 2D:4D. Lactate levels were low for tall women and women with a long ring finger relative to their index finger. The link here is thought to be testosterone-oestrogen balance in the womb and at puberty."

A long ring finger is a marker of higher levels of prenatal testosterone, and a long index finger is a marker of higher levels of prenatal oestrogen. Generally, in comparison to women, men have longer ring fingers, whereas in comparison to men, women have longer index fingers.

He said: "Men who have experienced high testosterone and low oestrogen (long ring fingers) before birth and women who have experienced high testosterone and low oestrogen before birth (long ring fingers) and at puberty (tall women) produced low levels of lactate in an incremental treadmill test.

"These results have implications beyond football -- in sports including distance running as well as in clinical settings in which high lactate is found in serious medical conditions such as following heart attack."

Professor Manning has pioneered work investigating relationships of 2D:4D with various measures of fertility, health, and behaviour. His most recent research has examined the connection between digit ratio and footballers' oxygen consumption and also looked at the link between finger length and a person's drinking habits.