I have been walking up and down the 5 flights of stairs to my office each morning and lunchtime. I was told yesterday that I shouldn't walk down the stairs, only up the stairs, as it puts undue pressure on my knees and could be harmful. Could you please let me know if this is true? I recall in the book that you said you sometimes walk up the 14 flights of stairs to your office (I don't recall you saying you walk down).

I am an avid stair climber. I find that my usual workday is very sedentary--I can sit for hours at time if I am not careful. Whenever possible, I use the stairs to get my body moving. I advocate going both up and down. I find that going up targets my heart and thigh muscles and going down targets my bones! While there is no scientific evidence for a beneficial response of bone to going down stairs, there is reason to believe that it can only help. Bone reacts to high levels of force and when you go down stairs you are creating more force at the hip and spine then when you are going up stairs. There is one caveat here-if you have any orthopedic problems in your back, hips or knees then too much going down can exacerbate the problem. So, use your best judgment.