Figure 2: (a) illustrates maximum amplitudes during contraction and the baseline between the contractions during distension. The closed symbols above the curve mark the phasic part (black line). The open symbols under the curve mark the tonic part (gray line). The pressures from the phasic and tonic parts were used to compute the total phasic and tonic stress. (b) illustrates an example of passive, total phasic, total tonic, phasic active, and tonic active stresses as function of strains from a normal animal. The passive and the total tonic stress increased exponentially as function of strain, whereas the total phasic stress increased in a polynomial way. The phasic and tonic active stresses were obtained by the total phasic and tonic stresses minus the passive stress.