Why men can run faster than women

 

Under the Microscope / Dr William Reville: I regularly run for exercise. Most of the women in the group I run with would beat me in a 5 km race. There is quite an overlap in performance generally between male and female athletic performance but, all other things being equal, the fastest men run on average about 10 per cent faster than the fastest women.

In 1954, Roger Bannister ran the first sub-four minute mile. In 2002, the men's world record for the mile was 3.43.13 minutes and the women's record was 4.12.56 minutes. So then, men run faster on average than women and there are physiological reasons to think that this may always be the case.

Consider the following athletics outdoor world records, taken from Guinness World Records 2004 (male time first, female time second): 100m (9.78; 10.49); 200m (19.32; 21.35); 400m (43.18; 47.60); 800m (1:41.11; 1:53.28); 1,000m (2:11.96; 2:28.98); 1,500m (3:26.00; 3:50.43); 5,000m (12:39.36; 14:28.09); 10,000m (26:26.75; 29:31.78); 25,000m (1:13:55.80; 1:27:05.90); 100km (6:10:20; 7:23:28).

In a well-known paper published in Nature in 1992, two Los Angeles researchers, Brian Whipp and Susan Ward, claimed the speed gap between male and female athletes was rapidly closing, that female marathoners would run as fast as males in 1998 and would catch men at other distances between 2015 and 2050. However, later re-analysis showed that, while the male/female gap was narrowing throughout most of the 20th century, it has been widening again since the 1980s. Men are now nine to 13 per cent faster than women across all events.

How do male and female animals compare on running speed? Pauline Entin, North Arizona University, has carried out a study on gender differences in running speed in horses and dogs. Horse racing in the US is segregated by gender whereas greyhound racing is not, and Entin expected to find a difference between the sexes in horses but not in dogs.

Thoroughbred and standardbred horses were studied. A total of 330 thoroughbred flat races were analysed. Race distance was divided by winning time to give the winners' average velocity in metres per second. The races were divided into two categories before analysis - less than or equal to one mile and greater than one mile.

The standard distance for standardbred harness racing is one mile. Some 191 record-holding times were used and the velocity calculated in metres per second. In all, 169 greyhound races were analysed and the average speed calculated in metres per second.

The results showed that in all cases the males were slightly faster than the females, although this result was not statistically significant for dogs. However, the difference between male and female animals was small, no greater than 1.2 per cent compared with the 10 per cent gender gap in peak running speeds between men and women.

Running is powered by expending the energy we generate by burning food in our bodies. Technically, this burning of food is oxidation, and so an important parameter affecting the body's capacity to carry out endurance running is the maximum rate at which the body can use oxygen to produce energy (VO2 max). VO2 max is significantly greater in men than in women, even when differences in body mass are taken into account.

The physiological differences between the sexes that contribute to men's athletic advantage include: (a) cardiac output (pumping oxygen-carrying blood) in a women is about 10 per cent less than in a similarly-sized man; (b) a woman has about 20 per cent less blood volume than a man of the same body weight; (c) for the same volume of blood, women have about 10 per cent less blood haemoglobin (which carries oxygen) than men; (d) the average female has about 10 per cent more body fat than the male.

It is important to note that these are average differences. Many individual women have significantly higher VO2 max values than average men. However, when you compare the best with the best these differences persist. For example, the highest VO2 max recorded by Norwegian male national team cross-country skiers was 90 millilitres/min/kilo, whereas the best Norwegian woman skier has been measured at 77 millilitres/min/kilo. This woman will outperform 99.9 per cent of all men, but she will not outperform the national male team.

Why is the gender running speed difference in horses and dogs so much less than in humans? The horse evolved as a prey species and the dog as a predatory species. Running speed is of great importance to all members of predator and prey species, so natural selection would have operated pretty much equally on both males and females of these species.

On the other hand, it seems that as long as one million years ago our human ancestors used tools and may have had gender-specific tasks. Natural selection may not have worked on running speed in human females as assiduously as it did in males. It is also true that racehorses and greyhounds have been selectively bred for speed in both genders for hundreds of years whereas humans rarely select mates based on running ability. It appears, then, that physiology dictates that athletics should remain segregated on a gender basis.

William Reville is Associate Professor of Biochemistry and Director of Microscopy at UCC