As a personal trainer, I have found a few of my female clients complaining about certain limitation with some of the exercises I set for them. They blame these limitations on the fact that they are female and are thus not as capable as their male counterparts. I always knew that there were areas in which the average male could out perform the average female, but I never knew to what extent. So thus began my investigation into gender differences in endurance and performance training.
Let us start at endurance capabilities and lung and heart capacity. The data presented below is for the average men and the average woman. There is no questioning that The “typical” young untrained male will have an absolute VO2 max of 3.5 liters/min, while the typical same-age female will be about 2 liters/min. This is a 43% difference! Well first, much of the difference is due to the fact that males are bigger, on average, than females. Us humans are all geometrically similar, so heart size scales in proportion to lean body size . If we divide VO2 by body weight, the difference is diminished (45 ml/min/kg Vs 38 ml/min/kg) to 15 to 20%, but not eliminated.
If we compare average body fat in males and females, we find part of the answer. Young untrained women average about 25% body fat compared to 15% in young men. So, if we factor out body composition differences by dividing VO2 by lean body mass (Body weight minus estimated fat weight)) the difference in maximal O2 consumption decreases to perhaps 7-10.
To find an explanation for the remaining 10% difference we must go back to the key limitation on VO2 max, oxygen delivery. On average females have a lower blood hemoglobin content than males, up to 10% lower. Finally, there is some evidence, that the female heart is slightly smaller relative to body size than the male heart. Recent ECG and echocardiographic studies also suggest that the young female heart exhibits less enlargement in response to either endurance or resistance training than the male heart (George et al, 1995) This may be due to differences in androgen receptor density in the female heart. A smaller heart would be expected to be a less effective pump.
Slightly lower oxygen carrying capacity of the blood (lower hemoglobin levels) plus a somewhat smaller or less adaptive heart are sufficient to account for the gender differences in maximal oxygen consumption that are independent of body size and fat percentage.
It is worth noting here the results of a 1993 study by Spina et al. Their data suggested that in previously sedentary older men and women (60 to 65 years old) who trained for 9 months to a year, both men and women increased their VO2 max by the same amount (an average of 20%). However, the mechanism of improvement was different. The men improved primarily by increasing maximal cardiac output due to higher stroke volume.
However, the older women did not demonstrate any increase in cardiac performance, but rather increased oxygen consumption by improving oxygen extraction by the working muscles, due to greater capillarization and more mitochondria. This data supports previous studies in 60+ year old women that show no cardiac hypertrophy in response to endurance training.
The Lactate Threshold
This is the point during exercise intensity that lactic acid begins to build up in the blood stream at levels above baseline values. The general consensus on this area is there is hardly any difference between the 2 genders. The fiber distribution is no different and women and men seem to respond similarly when exercising. However during long very long distance running, women probably have the edge on men due to the fact that they have more slow twitch fiber percentage. So the larger the distance they will be covering, the more the higher percentage of slow twitch fibers becomes an advantage.
Efficiency can be an ambiguous measure, as it really depends on the sport in question. Differing research has found women to be more, less and equally efficient compared to men! When we talk about running, the efficiency differences between men and women can be minimal as here they are more a product of an individual’s running efficiency regardless of their gender. This leaves the debate to focus on other sports where body shape, body mass and anthropometric differences are more important. Interestingly, in sports such as running and cycling body shapes of women would be more advantageous with narrower upper bodies meaning less wind drag however in other sports such as football and swimming the gender advantage may reverse.
Muscle Strength and Power
Females, on average, have less total muscle mass than males. As a result, maximal strength measures as well as maximal power measures (power = force/time) are reduced. Gross measures of upper body strength suggest an average 40-50% difference between the sexes, compared to a 30% difference in lower body strength. So, what about power? Maud and Schultz compared 52 men and 50 women, all roughly 21 years old using a maximal power test on a bicycle ergometer. Their peak power was about 60% lower for the females when comparing absolute values. Although, the men were heavier. Peak power per kg body weight was more similar, 9.3 watts/kg Vs 7.9 watts/kg for the women, an 18% difference.
Finally, when power outputs were adjusted for fat-free mass, the values were 10.4 watts/kg and 9.9 respectively. This 5% difference was not statistically different. Various other studies using different techniques have demonstrated to us that when you just look at muscle quality, male and female muscle is not different. Within the accuracy of current comparative techniques, it appears that the strength and power differences between the sexes are a function of muscle quantity only. Biomechanical differences probably play a role in some situations, but this will be very sport specific.
So there are many studies, which demonstrate that men do outperform their female counterparts when it comes to endurance training and measuring their maximum oxygen consumption. There are several studies that have been conducted that can disprove and confirm with what I have mentioned, I must stress that this is a generalization and does not affect athletes on either end of the spectrum.
However anyone who trains regularly and trains hard knows that pushing yourself is not usually a matter of physical boundaries but MENTAL BOUNDARIES. It is about finding out how much we can take mentally, how much we can endure psychologically. After all, 30% of training is physical and 70% is mental.