Female and male performance times

Female and male athletes seem to respond to training in a comparable manner. As the quantity or intensity of training increases, aerobic capacity (VO2max) shoots upward, body fat tends to decrease, and performance improves, regardless of gender.

In spite of these parallel responses, males frequently achieve better performance times than similarly trained females. Part of the reason for this is that males routinely engage in a perfectly legal, natural form of 'blood doping'. The key male sex hormone - testosterone - promotes the production of haemoglobin, the oxygen-carrying protein found inside red blood cells, and testosterone also increases the concentration of red cells in the blood. The key female sex hormone, oestrogen, has no such effect. As a result, each litre of male blood contains about 150-160 grams of haemoglobin, compared to only 130-140 grams for females. The bottom line is that each litre of male blood can carry about 11 per cent more oxygen than a similar quantity of female blood.

Strangely enough, male world records at distances from 800 metres all the way up to the marathon are also about 11 per cent faster than female world marks. Is that just a coincidence, or does the 11 per cent enhancement of blood oxygen in males produce the 11 per cent improvement in running speeds? Since oxygen is needed to furnish most of the energy required for endurance running, some scientists have suspected that the 11 per cent oxygen difference is indeed the key factor behind male-female performance variation.

Take out a litre of blood

To gain insight into this question, Kirk Cureton, Ph.D., and his colleagues at the Human Performance Laboratory at the University of Georgia removed just under a litre of blood from each of 10 male athletes so that their blood haemoglobin concentrations would be the same as those found in 11 female athletes. Three days after the bloodletting, both males and females were tested for V02max and endurance capacity ('Sex Difference in Maximal Oxygen Uptake,' European Journal of Applied Physiology, vol. 54, pp. 656-660, 1986).

The blood removal caused haemoglobin concentrations in males to drop to 134 grams per litre, exactly the same as in the female athletes' blood. In addition, male V02max values plunged by 7 per cent and became approximately equivalent to female values (lowering haemoglobin also lowers V02max, because it reduces the amount of oxygen which can be delivered to the muscles). However, although male endurance capability declined by about 5 per cent, males continued to fare better than females during an endurance test which involved pedalling an exercise bicycle for as long as possible against steadily increasing resistance. In other words, making male and female haemoglobin levels the same cut into only about half of the difference in performance between the sexes.

Is it extra body fat?

Actually, Dr. Cureton and a co-researcher, Dr. Phil Sparling of the Department of Physical Education at the Georgia Institute of Technology, had known for several years that higher haemoglobin wasn't the whole story behind faster male performances. Cureton and Sparling knew that the key male sex hormone, testosterone, also stimulated muscle mass development, while the principal female hormone, oestrogen, tended to enhance the accumulation of fat. Cureton and Sparling were aware that female runners tended to be eight to 10 percentage points fatter than male runners and wondered how that disparity influenced performance times.

So, in experimental work involving 34 male and 34 female runners who were similarly trained (average running distance for both sexes was 25-30 miles per week), Sparling and Cureton tested each runner for V02max, percent body fat, and running economy, and then asked all 68 individuals to run as far as possible in 12 minutes ('Biological Determinants of the Sex Difference in 12-Minute Run Performance,' Medicine and Science in Sports and Exercise, vol. 15(3), pp. 218-223, 1983).

Males did significantly better on the test, running an average of almost 3300 metres in 12 minutes, while females covered just 2750 metres. Although male performances were about 20 per cent better, males didn't run more economically than the females, and male V02max values were only slightly (5 per cent) higher. What caused the big difference in performance?

As it turned out, percent body fat averaged 20 per cent in the females but only 11 per cent in the males. When Sparling analysed the data, he found that 74 per cent of the variation between male and female performances could be accounted for by the difference in body fatness, while a much smaller amount (20 per cent) of the difference was determined by the males' higher V02max values. The higher amounts of body fat in the female runners acted as 'dead weight', increasing the energy cost of running and making quality running paces seem more strenuous.

If the 'dead weight' of body fat is the key factor separating male and female running speeds, attaching weights to the bodies of male runners should nearly equalise the performance times of the two sexes. Ingeniously, Sparling and Cureton collaborated in 1980 on a study in which weight-bearing harnesses were strapped over the shoulders of 10 male distance runners ('Distance Running Performance and Metabolic Responses to Running in Men and Women with Excess Weight Experimentally Equated,' Medicine and Science in Sports and Exercise, vol. 12(4), pp. 288-294,1980).

The idea was to make the percentage of excess weight lugged around by the male runners absolutely equal to the percent body fat of 10 female distance runners who also took part in the study. From five to 23 pounds were added to the individual male runners, depending on their leanness (to simulate greater fatness, leaner male runners had more weight added to their harnesses).

In a test in which the athletes ran as far as possible in 12 minutes, males ran 568 metres further than females when not wearing weights, but only 395 metres further when wearing the weighted harnesses. In a second test in which the athletes ran for as long as possible on a treadmill, males ran four minutes longer without weights but only 2.7 minutes longer with added weight. The gap between weighted males and females would have been even narrower, except that the males in the study happened to be more economical runners than the females. The better male economy meant that even when males and females were carrying around similar amounts of excess weight (fat plus attached weight for the males, fat only for the females) a particular running pace felt easier for the males. This improved economy in the male distance runners was an anomaly; most studies carried out since then have found similar economies in the two sexes.

What about muscle composition?

Some scientists have speculated that key differences in muscle composition or metabolism might also slow females down a bit. However, recent tests have determined that male and female runners have about the same percentages of 'fast-twitch' and 'slow-twitch' muscle fibres, and other research has documented that 'fuel burning' (actually, the rates of fat and carbohydrate oxidation) is very similar in males and females. Although it is true that non-endurance-trained women tend to burn more fat while running than non- trained men, well-trained male and female athletes break down fat at about the same relative rate during long-distance running ('Energy Metabolism and Regulatory Hormones in Women and Men during Endurance Exercise,' European Journal of Applied Physiology, vol. 59, pp. 1-9,1989).

That means that when just two things (percent body fat and V02max) are equalised between the sexes, the running performances of similarly trained males and females become pretty much the same.

Russ Pate, Ph.D., an exercise physiologist at the University of South Carolina, recently found that eight male and eight female runners with equivalent V02max values and nearly equal amounts of body fat (around 17 per cent) had nearly identical finishing times in a 15-mile race ('A Physiological Comparison of Performance-Matched Female and Male Distance Runners,' Research Quarterly of Exercise and Sport, vol. 56, pp. 245-250, 1985).

At a typical week-end IOK race, you can expect the average male finishing time to be about 45 minutes and the average female time to be around 50 minutes, almost a minute per mile slower. That might make females appear to be less speedy than males, but remember that such races are not 'handicapped' properly. If you simply added the appropriate amount of fat to the males' bodies (to make them comparable in fatness to the females) and drained away a bit of male haemoglobin to equalize V02max values between the two sexes, finishing times would be essentially identical for males and females with similar training programmes.

Performance measurement

If you use a fairer scale - 'heights', not metres - then the women are really quicker than the men
Are men really faster than women? If you compared absolute times over fixed distances, of course they are. But is that really fair? Men are taller than women and therefore take longer strides. Since studies have shown that elite male and female athletes in Olympic competition have very similar stride rates, isn't the male superiority simply due to their height and not their ability? What would happen if we compared men and women with a fairer scale, not just on the basis of overall time per distance?

Well, it is possible to use a different scale. Since being taller seems to give men an unfair advantage, why not compare male and female athletes' performances based on their heights? This means that fixed race distances must be converted into units of competitor height. A competitor's race velocity is then reckoned by dividing the race distance in 'heights' - not in metres - by the total elapsed time for the race.

For example, as mentioned in the preceding article, women finish lOK races in an average of 50 minutes, while men cross the finish line in about 45 minutes. This makes men look superior, but let's divide the race course into heights, not metres. An average woman would stand about 5'5-3/4' tall, which is 1.67 metres. We convert the length of the race into heights by dividing race length by height: 10,000 meters/1.67 meters = 6000 heights. We can then figure velocity for the average woman by dividing heights by time: 6000 heights/50 minutes = 6000 heights/3000 seconds = 2 heights per second.

Assuming that the average man in the lOK is about 5'11-3/4' tall (1.82 metres), we know that average race distance for men is 10,000/1.82 = 5494 heights. In other words, men are running a shorter race (only 5494 heights - versus 6000 female heights)! Race velocity for men would be 5494 heights/45 minutes = 5494/2700 seconds = 2.03 heights per second, a negligible difference from the female pace of 2 heights per second!

What about the top athletes?

That's great, but aren't men still faster if we look at the very top-level athletes? Let's compare two of the 'hottest' Kenyan runners - Paul Tergat, current world cross country champion, and Tegla Loroupe, winner of the 1994 New York Marathon and an assortment of other major races. Paul is 1.82 metres tall and has run the half-marathon (21 . 1 K) in about 60 minutes. Tegla is just 1.5 metres in height and covers the half-marathon in 68 minutes. Paul's pace for the half-marathon is about 11,593 heights/3600 seconds = 3.22 heights per second. Tegla's tempo is 14,067 heights/4080 seconds = 3.45 heights per second. Tegla is actually faster than the world champion male!

What about world record performances? Certainly you would think that the very best male sprinter would be faster than the topmost female. Leroy Burrell, who stands 6 feet tall, currently holds the men's world record for 100 metres with a clocking of 9.85 seconds, which turns out to be a velocity of 5.55 heights per second. Florence Griffith-Joyner, who stands 5'6-1/2' tall, holds the women's world record for 100 metres with a time of 10.49 seconds, which is a speed of 5.64 heights per second. Using fair velocity comparisons (in heights per second, not metres per second), the fastest woman in the world is almost 2 per cent faster than the quickest man !

Such comparisons are even more striking when you consider that women are usually not as encouraged to go into sports as men are. As a result, Tegla Loroupe comes from a smaller 'pool' of distance runners in Kenya than Paul Tergat does (there are far more male runners in Kenya than female runners, because males get more assistance and overall support). Thus, Tegla may not in fact be the best-possible female runner from Kenya (better runners may have easily become discouraged and dropped out of the sport), while it's easy to argue that Tergat is currently the best long-distance harrier from the tiny country in the horn of Africa, since almost all Kenyan males give the sport a try. Likewise, Florence Griffith-Joyner comes from a smaller sample of athletes compared to Leroy Burrell, and is less likely to be the best-possible representative of fast running for her sex, in the world.

It's true for swimmers, too

Although topnotch male runners don't look so great when compared to topnotch female runners, surely men should fare better in a sport like swimming, which emphasizes outstanding upper-body strength (compared to females, males can usually add much greater bulk to their arms and shoulders). Men's longer legs should also provide a more powerful 'kick' in the pool. In 1993, Janet Evans, the 5'5' women's world record holder at the 1500-metre freestyle, swam the distance in 15:52.1 minutes. Vladimir Salnikov, the men's record holder, zipped through the same distance in just 14:54.76 minutes. However, Salnikov's velocity was actually just .926 heights per second, while Evans steamed through the water at .949 heights per second. Evans was 2.5 per cent faster!

Other studies support the idea that women are equal to or better than men as long as fair comparisons are made. For example, many studies have attempted to determine whether there are differences between men and women in the use of stored elastic energy (USEE). Elastic energy is stored in a muscle when it is stretched; this energy can help a muscle contract powerfully by elastic 'recoil', without a need for the muscle to use up lots of fuel to actively contract. USEE is thus a measure of how ECONOMICALLY muscles can work, because excellent USEE means that more fuel can be conserved, and then used during the late stages of prolonged exercise. USEE can be a key indicator of resistance to fatigue; endurance athletes with high USEE tend to perform better than similarly trained athletes with lower USEE values. Some studies have suggested that males have better USEE than females, but the problem with this research is that the males are often more highly trained than the females. More appropriate research suggests that in fact - when men and women are equivalently trained - USEE is actually identical between the sexes.

What about muscle power? One way to measure leg-muscle power is to look at maximal vertical jumping ability. Usually, tests show that men jump better than women, but this is not surprising when you consider that men are generally much bigger in stature and therefore have larger leg muscles. When vertical jumping ability is expressed per unit of body weight, however, male and female jumping performances tend to be absolutely equivalent, even when heavy packs are placed on the backs of the performers.

The bottom line? In comparing male and female performances, it's important to make FAIR comparisons. Sorry, chaps, but when that is done, female efforts are actually equivalent to - or better than - the male.

('It's Mostly a Matter of Metric,' in Women and Sport: Interdisciplinary Perspectives, D. Margaret Costa and Sharon R. Guthrie, Eds., pp. 143-162, Human Kinetics Press, 1994.)

Owen Anderson