Jade Teta ND, CSCS
Walking and high-intensity exercise like intervals and weight training are synergistic in their actions. This is not a calorie phenomena but rather a hormonal one. In order for the body to recover properly, age well, build muscle and burn fat, it needs the correct balance of stress producing hormones (cortisol, adrenaline, noradrenaline) compared to growth promoting hormones (testosterone and human growth hormone (HGH)). During an exercise session the desirable effect is to raise all of these hormones together to maximize fat loss. It has been shown that cortisol added to elevated growth hormone drastically increases the fat burning potential of growth hormone by itself. Studies demonstrating this were published in 2000 out of the Journal of Clinical Endocrinology and Metabolism (Vol. 85 # 2) and in the March 2004 issue of the American Journal of Physiology, Endocrinology and Metabolism (Vol. 286). So, during intense workouts it is useful to workout at intensities high enough to elicit this beneficial hormonal response.
However, in the days and hours following an intense workout, it is most beneficial to maximize the levels of growth hormones while minimizing the levels of stress hormones. This is where walking comes in. Walking lowers cortisol levels. A 2007 article published in the Journal of Physiological Anthropology (Vol. 26 #2) showed that walking reliably and predictably lowers cortisol levels. This effect was magnified when the walking took place in a nature setting; what the Japanese call Shinrin-yoku. It is important to note that walking should be done at a leisurely pace. It is easy to turn walking into an “aerobic zone” workout which is not as beneficial. This is because moderate intensity aerobic exercise raises cortisol rather than lowers it and never reaches a high enough intensity to generate the growth promoting hormones. It is very easy to tip the scales towards stress production if aerobic exercise is all you do. This will lead to muscle loss just as readily as fat loss. Moderate intensity aerobics burns calories, but provides little hormonal advantage.
A workout program for optimal fat burning and slowed aging would combine high-intensity exercise like weight lifting, sprinting, and interval training with low intensity activity like leisure walking. We like to tell our clients that walking should not even be considered exercise but rather necessity. Leisure walking is done slowly at a relaxed pace allowing full and easy conversation (a speed of 3.5 or less on a typical treadmill) and should be done as much as feasible everyday. Adding 2-3 intense weight lifting sessions and 2-3 intense interval exercise sessions sprinkled throughout the week along with this walking is a great plan for body composition and healthy aging. Intense workouts should be kept short (less than 40 minutes) while leisure walking can be as long as you like. Shoot for at least 30 to 60 minutes a day or 5,000 to 10,000 steps. These can be all at once or spread throughout the day.