Sun, 17 Feb 2002 11:24:35 -0500 Hilary McClure <[log in to unmask]>
wrote:

>Don, thanks for the great article. One question, though. Just
>wondering why you don't specifically mention weight-lifting, or
>other strength-building exercise for building bone. It sounds
>like you're saying that walking or jogging, through calcitonin,
>cause a general systemic deposition of bone mineral. I've also
>read that direct stress on the bone causes local bone build-up.
>That as muscles increase in size and strength the tendons also
>strengthen and the bones they are attached to strengthen, but
>I don't know how reliable the source was. Do you know anything
>about that?

Insight into bone mineral density and stress-induced calcitonin
production came, in part, from the dramatic bone mineral losses
experienced by astronauts over very short periods (a matter of
days). The assumption in what I've read has consistently been
that it was the absence of gravitational stress that resulted
in these losses. Perhaps a case could also be made for the
relative lack of exercise imposed by spending time in the
cramped confines of a space craft. I haven't followed this
research. Do you know if training programs use simulations that
reduce or eliminate gravity for training purposes yet still
involve vigorous exercise? If so, and if they are monitoring
bone density throughout such training (which seems likely) the
data might offer some guidance on this point.

Ron Hoggan, M.A.
Co-author of Dangerous Grains
Published by Penguin-Putnam-Avery August 2002