A study from Researchers at University of Colorado at Boulder showed leisurely walking for distance combined with low-impact cardiovascular activity appears to be useful for obese people.

Ray Browning, at CU-Boulder and lead author on the new study, said the results show that people who walk a mile at a leisurely pace burn more calories than if they walk a mile at their normal pace. In addition, those who walk at 2 miles per hour rather than 3 miles per hour reduce the loads on their knee joints by up to 25 percent.

" The message is that by walking more slowly, obese individuals can burn more calories per mile and may reduce the risk of arthritis or joint injury," he said.

Browning and his colleagues also found the number of calories burned per pound of body weight is similar for obese adults as normal sized adults walking at the same speed. Because obese people generally have heavier legs, wider stances and swing their legs in a wider arc, the researchers expected the cost of walking for obese people to be significantly higher.

" This was a surprise," said Browning. "The subjects probably are unwittingly altering their posture and walking with straighter legs, conserving calories in the process."

The CU-Boulder researchers based their expectations that obese adults would have a greater energy cost when walking on previous studies by Kram's lab team. In one study, energy expenditure increased by about 25 percent when normal-weight people walked with a deliberately wider stance, said Browning.

Other studies conducted in CU's Locomotion Laboratory have shown that normal weight people wearing "winged" shoes designed to force them to increase their lateral leg swing increased the metabolic cost of walking by 30 percent, Browning said.

"As people become gradually obese, they also seem to become particularly graceful," said Kram. "There appears to be some sort of a physiological drive for them to minimize the amount of energy they expend."

The researchers tested 20 men and 20 women on treadmills and sidewalks, half of whom were of normal weight and half classified as class 2 obese, meaning they have a body mass index, or BMI, of 30 to 40. A 5-foot 4-inch tall woman with a BMI of 30 weighs about 175 pounds, while a 6-foot man with a BMI of 30 weighs about 225 pounds.

The researchers measured each subject's body composition using an instrument known as a DEXA scanner to measure fat mass, lean tissue mass and bone mineral content of the total body. They also measured the oxygen consumption and carbon dioxide production of the test subjects to determine the energy and calories expended while walking.

The results show that brisk walking dramatically increases the knee joint forces, which can lead to a variety of problems including joint injuries and arthritis, the researchers said.

Because walking slowly may not significantly improve an obese person's level of cardiovascular fitness, performing other vigorous lower-impact activities like swimming, cycling, step routines and elliptical training workouts also are recommended, said Browning.

Source: University of Colorado, 2005


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