In our former attempts to obtain a measure of human muscle tonus in quantitative terms,1 we found that the resistance of apparently resting muscles to stretching forces was extremely variable from time to time in many of the persons tested. This variability occurred in numerous subjects in whom no reasonable doubt could be entertained as to their desire to cooperate in releasing their muscles from conscious control during the testing. We deduced, therefore, that mechanisms other than simple tissue elasticity or relatively unvarying innervations of muscles were often at play. One's thoughts naturally turn to the possibility of demonstrating the presence of voluntary or reflex activities in muscles being stretched in a search for an explanation of these fluctuations. Few comments are required to dispose of the literature as far as pertinence to our present problem is concerned.
Wertheim Salomonson2 has made the following statement:
We may observe
McKINLEY JC, BERKWITZ NJ. ELECTRIC ACTION POTENTIALS IN MUSCLES DURING RECORDING OF MECHANICAL TONUS TRACINGS. Arch NeurPsych. 1933;29(2):272-286. doi:10.1001/archneurpsyc.1933.02240080062006