Life / Health

Women have a mysterious superpower: moderate exercise

A new University of Waterloo study shows females have a "remarkable" ability to direct oxygen to their muscles

In the brisk-walking treadmill test, women seem to have an edge.

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In the brisk-walking treadmill test, women seem to have an edge.

Remember the old playground taunt “Girls rule, boys drool”? Well, there may be some truth to it — at least when it comes to aerobic exercise.

A new study from researchers at the University of Waterloo has found women can transfer oxygen from their blood to their muscles about 29 per cent faster than men during moderate exercise.

The rate the body consumes oxygen, also called VO2 or oxygen uptake, is a major measure of cardiorespiratory fitness. Muscles need oxygen to burn fuel for energy. We absorb it from our lungs into the haemoglobin in our red blood cells and finally into the muscles.

But at some point during intense exercise – depending on how hard your heart muscle can pump, your haemoglobin levels and a few other factors – your VO2 maxes out. There’s only so much extra breathing you can do.

By this point, your muscles are burning more fuel anaerobically, or without oxygen, causing a build-up of by-products like lactic acid in the major muscles you’re working. The result is burning sensation, soreness, exhaustion and giving up (especially in people who don’t particularly care to “feel the burn.”)

As a rule, men max out at a higher VO2 than women do. In measures of their maximum aerobic power, they beat women by about 15 per cent on average, according to the paper.

But when it comes to everyday exercise, like the brisk-walking treadmill test in this experiment, women seem to have an edge.

And that was the exact opposite of the expected result, study author and U of W kinesiologist Thomas Beltrame said.

“We were pretty sure that men were more athletic, that their system would be more fit,” he said.

The study was small — nine men and nine women in their 20s, with similar fitness levels — but the results were so dramatic and consistent the researchers felt confident in the finding, Beltrame added.  

The study subjects did several bouts of power-walking on a treadmill, stopping when their heart rates reached about 80 per cent of the maximum. The researchers used a technique called near-infrared spectroscopy to measure how fast their red blood cells transferred oxygen to their muscles.

Women were “remarkably” more efficient at it, the paper says.

Why? “We still don’t know,” Beltrame said, but it might have to do with women having a different mix of muscle fibres, or changes in muscular blood flow at different times in the menstrual cycle.

Regardless of the reason, it matters, because it relates to an activity almost all of us do every day: walking. And it could change the way future research is carried out, Beltrame said..

“We usually put men and women together in the same group when we’re testing something. Now we know it’s important to split the groups. They might have different responses to disease treatment, exercise training, or even medication.”

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