Quote Originally Posted by velogirl View Post
I guess my question is this. Neither Han's friend nor Tulip's story are scientific control group studies -- they are anecdotal. Would Han's friend or the step instructors have had a hip replacement if they chose a different line of work? We don't know that...
Anecdotal evidence can be quite valuable. These people are in their 40s (that's young, BTW), healthy except for their obsessive exercise behaviors over decades (like hours a day, every single day, no rest days--fitness instructors these days would not encourage this), no RA, not overweight (perhaps underweight). I would wager that experts here and elsewhere would agree that the methods used in the 80s--high impact routines with poor equipment, inadequate training and rest over decades--can also cause joint problems. Hell, I can't even run on a regular basis because of shinsplints, so I ride a bike and I swim when I can find a pool. Lots of people who do high impact sports have to ease up after years and decades of such impact--runners, basketball players, tennis players, iceskaters...Would their knees go out if they didn't play sports? We don't know.

I would add to Velo's list that obsessive, repetitive exercise over decades can also lead to physical problems. I don't think anyone here is blasting fitness instructors, far from it. Han is a fitness instructor. But we know alot more now than we did when the aerobics dance craze was going on. And thank goodness there are those of you out there who do know better and can instruct the rest of us on the right way to do things--on both ends of the scale.