A university/government research team led by Peter Weyand of Southern Methodist University (SMU) in Dallas, Texas developed an equation to calculate exactly how much energy walkers expend based on walkers’ height, weight, and distance covered. Their findings and formula, which can be used in pedometers and biofeedback devices and for planning exercise regimens, are published in the 12 November 2010 issue of the Journal of Experimental Biology.
Weyand, joined by Maurice Puyau and Nancy Butte from the USDA’s Agricultural Research Service unit at the Baylor College of Medicine in Houston, Texas and SMU undergraduate Bethany Smith, measured the metabolic rates of children and adults, ranging from 5 to 32 years old to find out why larger people are more economical walkers than smaller people.
Weyand and colleagues filmed male and female volunteers as they walked on a treadmill at various speeds and measured the walkers’ oxygen consumption and carbon dioxide production rates to obtain their total metabolic rate. Next, the team calculated the amount of energy that each person used for walking by subtracting the basal metabolic rate (energy required to maintain the body’s basic metabolic functions) from the total metabolic rate measured while walking. Finally, the team compared the way each person walked, measuring the walkers’ stride lengths, stride durations, and the proportion of each stride they spent in contact with the ground to find out if large and small people walk differently.
The team found the walkers moved in much the same way regardless of their height, thus large people are not more economical in their use of energy because they walk differently from smaller people. The researchers then calculated the metabolic cost of a stride as each walker moved at their most economical pace and they discovered that walkers use the same amount of energy per stride regardless of their height.
The scientists plotted the walkers’ heights against their minimum energy expenditure and found walkers’ energy costs were inversely proportional to their heights. Thus, tall people walk more economically than shorter people because they have longer strides and have to take fewer steps to cover the same distance. And smaller people tire faster because each step costs the same and they have to take more steps to cover the same distance or travel at the same speed.
With these results, the group derived an equation to calculate the energetic cost of walking, using the walker’s height, weight, and distance walked to determine how many calories are burned.
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