Stretch-induced Calcium Release

[Martinelli]

Good evening Mark,
What did you think of the Amazon women's morning weightlifting session in the Olympics?

Anyway, I have a technical question concerning the relation between muscle stretch and force production. It isn't anything that will directly affect training, but it's just so I might have a basis for justifying exercises involving the most ROM (i.e., dips versus the decline bench press). It will also help me with arguing with the camp of lifters who advocate 90-degree bench presses and shoulder presses in order to place more tension on the muscle over at the Bodybuilding.com forum (but you know, their pictures don't lie; the guys who are proponents of this style of training do have the shape to back it, so it does make me wonder).

My knowledge of the specific mechanisms are a little cloudy, but please affirm or correct my progressive logic. I did search this extensively on google, but no articles are as nit-picky as I am. Here it goes.

A greater degree of muscle stretch equates to a greater degree of calcium release from muscular sarcoplasmic reticulum (SR), equating to a longer duration of the cycling (formation and breaking down of) of myosin-actin cross bridges, equating to greater contractility of the muscle, which equates to greater force production. My understanding is that the greater the ROM, the stronger the muscle contraction. In a comparison between the dip and the decline bench press, the exercise with more eccentric stretch (the dip) will result in greater force production. Did I describe the process correctly?

A second, simpler question I have is if there is any risk that either deadlifts or squats may cause myelopathy (kinking of the nerves that run along the spine, akin to a tangling of one's garden hose)?

Thanks,
Martin

[Mark Rippetoe]

As I remember it -- I don't work with contractile physiology on a daily basis -- this is a good assessment of the process. Perhaps Dr. Kilgore will weigh in. And I am aware of absolutely no research that links lifting weights with any form of myelopathy.