Carol C. Spelman was a spy for science.
She wanted to know whether walkers did what exercise experts counted on them to do--walk at a pace associated with health benefits.
So she watched them, covertly.
Spelman sought to nail down a key detail in exercise studies. Researchers had already estimated from laboratory work how hard a person must walk to achieve metabolic changes associated with better health.
The question was whether people outside a lab normally did it.
"Nobody had ever done something like this before," said Spelman, program coordinator at Westchester Cardiac Rehabilitation, a clinic in Scarsdale, N.Y.
Spelman did her experiment while a graduate student at the University of South Carolina. Results were published in the American College of Sports Medicine journal Medicine and Science in Sports and Exercise.
Spelman looked at 29 healthy walkers whose ages averaged 35. They were given questions on mood state to answer before and after they walked.
That, however, was just a cover.
"They didn't have any idea we were looking at things like pace," Spelman said.
If the walkers had known, they might have consciously or unconsciously changed their pace, she said.
The questioning was an excuse for Spelman to visit them where they walked, so she could spy out their normal route.
"I found a spot where I could see them, and they couldn't see me, and I timed them between two spots," Spelman said. "I measured that distance, and I came up with a pace."
The average was about 4 m.p.h., the study said.
After the self-selected outside pace was determined, the walkers entered the lab to walk on a treadmill at the same pace. Researchers then measured the energy the walkers expended at that pace.
The average burn, expressed as a percent of maximal heart rate, was about 70, although the range was wide--from 56 to 89, the study said.
The rates were within the ACSM's recommended range for cardiorespiratory fitness, 55% to 90% of maximal, the study said.
Although percent of maximal heart range is commonly used by exercisers, it is not the most accurate measure of how hard you are working out.
A more precise standard for energy used, which looks at how much oxygen the exerciser consumes, showed three of the exercisers falling below the ACSM's cardiorespiratory target.
By and large, the exercise walkers Spelman studied were working hard enough to make the experts happy, she concluded.
Even those who fell below the cardiorespiratory target probably were still working hard enough to get important health benefits in such areas as lower blood pressure and better cholesterol levels, Spelman said.
Researchers also computed energy expended during the week based on the estimated calories burned per exercise session and the number of days of exercise. On that, the results don't look as good, Spelman said.
The average was 1,100 calories per week--slightly above the 1,000 that other researchers have found healthful, Spelman said.
But several apparently fell below that level, indicating some were not walking often enough.
This underlines the need for regular exercise--not just a couple of days a week, Spelman said.
The study supports the idea that walking is a good health practice, said another researcher on walking, Dr. James M. Rippe, director of the Exercise Physiology and Nutrition Center in Shrewsbury, Mass.
People tend to walk about 3 m.p.h. doing errands, so adding 1 m.p.h. can turn them into exercisers, the cardiologist said.
Spelman's method of field study did raise eyebrows among other exercise researchers, she conceded.
Watching secretly and misdirecting subjects about the experiment's true purpose are accepted in psychological research.
However, that is not traditional in physiology.
Spelman replies that her design does have one point in its favor--it worked.