So, it looks like my theory is one of several out there, but the exact mechanism has not been elucidated yet.
from PHYS THER
Vol. 85, No. 10, October 2005, pp. 1053-1060
Can Mental Practice Increase Ankle Dorsiflexor Torque?
Ben Sidaway and Amy (Robinson) Trzaska
“Possible mechanisms of these neural adaptations include the extent of motor unit activation, improved coordination, and decreased co-contraction of antagonist muscles.”
Apparently, the number of motor units one can activate with maximal effort is related to the size of the area of the brain in which the muscle involved is represented. In muscles which have large cortical representation (e.g. fine motor muscles of the hand) it is possible to stimulate most or all motor units with maximal voluntary effort. However, is muscles less well-represented (such as thoses for extending the ankle), maximal force cannot be voluntarily generated. Howevere, training (actual or imaginary) seems to increase the area of the cortex devoted to controlling the muscle, which then increases the strength one can generate. But, as the quote above indicates, there are other theories.
As far as the relative effect of muscle vs nerve/brain on muscle strength, an interesting study involved artificially imobilizing a limb for 4 weeks and determining the relative effects of neurological and muscle changes on the loss of strength. the conclusion was:
“These findings suggest that unweighting induces plastic changes in neural function that appear to be spatially distributed throughout the nervous system. In terms of the relative contribution of neural and muscular factors regulating strength loss, we observed that neural factors (primarily deficits in central activation) explained 48% of the variability in strength loss, whereas muscular factors (primarily sarcolemma function) explained 39% of the variability. “
J Appl Physiol 101: 264-272, 2006. Adaptations in human neuromuscular function following prolonged unweighting: II. Neurological properties and motor imagery efficacy
Brian C. Clark,1 Todd M. Manini,1 Stanley J. Bolanowski,2, and Lori L. Ploutz-Snyder1
Several studies have also looked at the effect of imaginary activity or imaginary suppression of activity in various muscles on the neural input to these muscles and have found, generally, a significant effect. You can increase or decrease brain and spinal cord activity relevant to a specific movement by imagining doing or supressing the movement. Cool!
Clearly, the brain (and the mind, which of course are essentially the same thing) has a powerful role in determining what the body does, and it is possible to imagine such things as increasing muscle strength by thinking about moving the muscle without any mystical mumbo-jumbo. And, of course actual use of the muscle shows even greater effects in all the studies even before enough time has passed for true muscle changes to occur. This is interesting theoretically, but it obviously has some implications for people with deficits in the relationship between mind and body. Some of the changes with imagined movement we’ve been talking about turn out not to happen in an organized, reliable way in patients with Parkinson’s Disease, for example. So maybe ” meditation” (defined quite loosely) would help these patients. But maybe you’d be better off just lifting weights :wink:
Sorry if this is too much info. Sort of in my field, so I get carried away.