Friday, March 12, 2010

Weight bearing exercise

Conventional wisdom tells us that weight training increases bone density (ex. here and here). The force of your muscles moving a load stresses the bones slightly and causes them to grow back stronger. That's a decidedly good thing, at least assuming that you don't do anything really (excuse the pun) bone-headed like lift weights you're not ready for or do exercises with terrible technique. Imagine my surprise when I catch this bit of news: "Weight-bearing exercise does not prevent increased bone turnover."

My response to that headline was a bafflement. I thought there was going to be some crap study on how weight bearing exercise didn't do anything for your bone health. Turns out that it's a study about how jogging and walking don't mitigate the increased bone turnover that occurs during weight loss. Apparently, you have increased bone remodeling when you lose a lot of body weight. This makes inherent sense: less weight = less load on the bones = less stimulation for bone growth. The thing that bothers me with the study is how "load-bearing" exercises are defined. I guess getting my ass up and walking around is technically putting a load on my bones. But it's as much of a load bearing exercise for a healthy person as is picking up a remote to change the channel on the idiot box. I'm not sure when "walking" and "light jogging" became considered "load-bearing" exercises. Have we became that sedentary that everyday activities have become tough exercise?