Walking doesn't build muscle - study
Women who walk at least 10,000 steps a day have no greater muscle strength and perform no better on tests of balance and agility than women who walk fewer than 7500 steps, according to a new study.
Researchers did find, however, that extra walking each day is tied to favourable measures of body fat, weight and endurance.
"This tells me more is better in terms of body composition and fitness," said Catrine Tudor-Locke, a professor at Pennington Biomedical Research Center, who was not involved in this study.
But "none of us think that if you walk a huge amount that you're going to have huge muscles".
The researchers, led by professor Mylène Aubertin-Leheudre at the University of Quebec in Montreal, tracked the walking habits of 57 women between 50 and 70 years old.
Women wore pedometers for a week to tally how many steps they took in day that occurred from any walking periods lasting longer than three minutes.
The women were split pretty much equally among three activity groups: low activity women walked fewer than 7500 steps a day, the medium activity group walked between 7500 and 10,000 steps and the high activity group walked more than 10,000 steps each day.
The researchers also measured the women's body weight, fat and muscle mass; muscle strength through hand grip and knee extension exercises; and balancing and functional skills by exercises such as standing on one leg or jumping onto a step with both feet.
The women who walked the most weighed less and had a smaller percentage of body fat.
"This is good for the prevention of cardiovascular risk factors," said Aubertin-Leheudre.
The highest activity group, for instance, had an average body mass index (BMI) - a measure of weight compared to height - of 25, which is considered normal weight.
The other two groups had BMI numbers in the overweight range.
Muscle strength and the percentage of muscle mass on the body were the same among the three groups, however.
Women also performed similarly on the balance and physical ability tests regardless of how much they walked.
Aubertin-Leheudre said she had expected to see women who walked more perform better on these tests because inactivity is known to weaken muscles.
"Maybe we don't walk the way we need to walk" to see any muscle benefits, Aubertin-Leheudre said. "I always see the postmenopausal women in my study sliding more than walking."
Perhaps a more proper stride or a more intense walk - one that would make it difficult to talk while walking - would have made a bigger impact on women's strength and abilities, she added.
DOES '10,000 STEPS A DAY' NEED REVISION?
Her team did not measure the quality or intensity of the walking, but it is working on future studies to measure whether higher-impact walking could make a difference.
Health advocacy groups have tossed around 10,000 steps as a daily walking goal to keep people fit.
Aubertin-Leheudre said that recommendation might need to be revised to specify the impact of the activity so that women gain some muscle benefit.
Tudor-Locke said she expects that if the researchers had compared truly sedentary women - those who walk fewer than 3000 steps per day - to the super walkers, they would likely have seen a difference.
"Maybe there is such a relationship where you get the biggest bang for your buck in this lower end (of activity) and maybe any additional walking is not going to add any extra muscle strength," Tudor-Locke said.