How Your Bones Change With Exercise: anatomy video with implications for weight training
(www.youtube.com)https://www.youtube.com/watch?v=1gToyjm4NNAI'm lifting weights because I'm over sixty, in poor health, and trying to avoid becoming frail. I've got a little routine with dumbbells, nine different exercises, mostly trying to cover all the complicated muscles and tendons that hold the shoulder joint together.
I've been picking a weight light enough that I can manage 7 repetitions. Work my way up to 12. Then go back to 7 but with a slightly heavier weight. I've made a little progress. With several of my exercises I can manage 12 repetitions quite comfortably.
Should I (1)go for more repetitions (for stamina) or (2)down to 7 but heavier, (for strength) or (3)save my energy for gardening/life/whatever?
This video provides an answer: the range, seven to twelve repetitions, is heavy enough to set the osteoblasts to work and maintain bone density. If you can manage more than twelve repetitions, your weight is a little light for promoting bone density.
That gives me my answer. I'm trying to set the osteoblasts to work, so it is option 2 - a little heavier.
Gore tag because of the anatomical specimens. No blood, broken bones, or fatalities, so not gore if you can overlook the flayed corpses.