Use of dP/dt and rise time to estimate speed of shortening in muscle.
We examined the relationship between the maximum speed of shortening at zero load (Vmax) and two variables occasionally used to estimate Vmax: maximal rate of change of force during an isometric tetanic contraction [(dP/dt)max] and reciprocal of one-half rise time (RHRT), the time to achieve one-half the maximal force during an isometric tetanic contraction. The relationship was examined in two experiments on isolated toad sartorius muscle: the effect of temperature and the effect of changing pHe (extracellular pH) to test the hypotheses that (dP/dt)max or RHRT can be used to estimate the magnitude of the effect of experimental variables on Vmax. In the temperature experiment both (dP/dt)max and RHRT could be used to estimate changes in Vmax. The effect of pH on Vmax was markedly overestimated by (dP/dt)max, but there was no significant difference between the magnitude of the changes in Vmax and RHRT. Our results, taken with the results of others, suggest that it is inappropriate to assume that the magnitude of the effect of a particular experimental protocol on Vmax can necessarily be predicted by measuring (dP/dt)max or RHRT.
D000704:Analysis of Variance; D000818:Animals; D002025:Bufonidae; D006863:Hydrogen-Ion Concentration; D066298:In Vitro Techniques; D007537:Isometric Contraction; D009119:Muscle Contraction; D009132:Muscles / Q000502:physiology*; D013696:Temperature