Fig. 2. A typical twitch record, chosen as it has kinetics close to the mean values obtained. Time to peak twitch tension T_peak was measured as the time from baseline force to peak force during activation. The time taken for the muscle force to decline from its peak to 50% of its peak (RT_50%) and to 10% of its peak (i.e. a 90% decline in force; RT_90%) were used as indices for the rate of relaxation.