From The New York Times:
Is it better to walk a human or to walk a dog?
New research from the University of Missouri has found that people who walk dogs are more consistent about regular exercise and show more improvement in fitness than people who walk with a human companion. In a 12-week study of 54 older adults at an assisted living home, 35 people were assigned to a walking program for five days a week, while the remaining 19 served as a control group. Among the walkers, 23 selected a friend or spouse to serve as a regular walking partner along a trail laid out near the home. Another 12 participants took a bus daily to a local animal shelter where they were assigned a dog to walk.
To the surprise of the researchers, the dog walkers showed a big improvement in fitness, while the human walkers began making excuses to skip the workout. Walking speed among the dog walkers increased by 28 percent, compared with just a 4 percent increase among the human walkers.