Pinneo, L. R. (1961). The effects of induced muscle tension during tracking on level of activation and on performance. Journal of Experimental Psychology, 62(5), 523-531.
http://dx.doi.org/10.1037/h0047245
38 male college students were trained in an auditory tracking task. Physiological measures were obtained during training and while squeezing a hand dynamometer to a predetermined level of muscle tension during tracking. "Results clearly showed close agreement between amount of tension induced and the level of activity in all physiological measures. These results were considered in support of a theory that the proprioceptive return from the induced muscle tension produces generalized behavioral and physiological effects indirectly by increasing activity in the reticular activating system." (15 ref.) (PsycINFO Database Record (c) 2016 APA, all rights reserved)