Dear all

Here is a summary of the replies relating to high impact exercises and the bone strength for the list. There were numerous interesting replies concerning high impact exercises and the bone strength. Sadly none of these evaluated calcitonin or calcitonin secretion. (Nor were there any comments on the effects on the allegedly beneficial effects of high magnesium levels in the diet for calcium uptake or the allegedly detrimental effects of high intakes of salt and coffee). However there were more replies on exercise and bone density and strengthening than you could safely point a stick at. Here is a summary of the very best (roughly in order from smallest to largest).

Matt Patterson and Cor-Jan Tolkamp provided some very thought-provoking comments. Matt Patterson (Kinematics Researcher) noted that it is very strange that it is commonly thought necessary to reduce impacts in training order to improve it and reduce injury rates when research suggests that our bodies are made for impacts and that they work better when they are stimulated that way. He speculated that expensive shoes with lots of shock absorption might be causing more problems than they are preventing. He provided this comment; "I remember taking an undergrad course taught by Stu McGill at the University of Waterloo. I recall that he talked about a research study on bone density in spines of prison inmates who did a lot of free squat training. They found that bone density and inter-bone structure in the spine were much stronger than a normal population."

Cor-Jan Tolkamp (Managing Director Tolkamp Business Development) told me that there have been studies about this topic relating to the martial arts. He raised this interesting topic "Maybe the most interesting study would be for practitioners of 'le parkour' ". Apparently this is an " extreme sport" that has been promoted by David Belle; it is an extreme form of gymnastics on the street where a person can jump from a height of 4 stories (about 12 meters), land an their feet, make a head-roll and run on.

Two of the replies related to the same research centre. Gary Christopher, Texas Woman's University told me that Christine Snow and some of her students in the Bone Research Laboratory at Oregon State University have published some articles about increased bone density in children following a jumping exercise program. Virginia Klausmeier (who is at the Bone Research Laboratory) told me that she has done research on this specific topic. Virginia mentioned that a height of about 1.5 feet is osteogenic for children. She provided this website for the lab;

Three people provided references. These kind souls were Chris Geiser, Timo Jamsa and (last but not least!) Kevin McQuade.

Chris Geiser (Program Director, Athletic Training Education Marquette University) said that in a Milgrom study (ref below) the subjects with a history of jumping sports (higher impact) minimized their stress fracture incidence and the same history was noted in the Hoffman study However regular physical activity was not protective; it took impact type activity. He provided these references;

* Milgrom, C., Simkin, A., Eldad, A., Nyska, M., & Finestone, A. (2000), "Using bone's adaptation ability to lower the incidence of stress fractures", American Journal of Sports Medicine, 28(2), 245-251.

* Hoffman, J. R., Chapnik, L., Shamis, A., Givon, U., & Davidson, B, (1999), "The effect of leg strength on the incidence of lower extremity overuse injuries during military training", Military Medicine, 164(2), 153-156.

Timo Jamsa (Department of Medical Technology, University of Oulu, Finland) provided a few references on his research on quantifying the intensity level of impact that has an osteogenic effect. The research showed that quite a low number of impacts is enough (