Here is an interesting statement from a Psychology Today article:
Biking and rowing may get your heart racing, but a low-intensity stroll in the park 5-6 times a week is actually more effective in preventing obesity and eliminating heart risk factors including insulin sensitivity, total cholesterol, and blood pressure. Walkers trimmed their waistlines more and shed more weight.
The author recommends taking faster small steps, pushing off the back foot, and swinging the arms to set the pace.
I recommend walking and taking the stairs to all my patients -- both for easy stress reduction and for general health. Even for athletes, adding some meditative walking time can be helpful. Serious training is often stressful both to the mind and certainly to the body. Balancing that with easy walking and a quiet mind can be helpful.