Hill plots of muscles bathed in hypertonic solutions

The velocity of muscle contraction is found to decrease as the osmotic pressure increases for constant load. Vmax evaluated from computer fitted load/velocity curves shows two distinct activation processes when plotted against the reciprocal of absolute temperature. Hill's equation proves to be an accurate descriptor of the experimental P/V curves for each osmotic pressure and temperature. The area under the P/V curves was found to provide a more reliable parameter representing the overall muscle response than Vmax. When the bathing solution is made sufficiently hypertonic only one activation process remains. These effects are found to be reversible. The results are explained in terms of the inhibition of ATP splitting during the crossbridge power stroke.