Subjectivity, lack of precision, and accuracy are the challenges in the spasticity clinical measurement. One of the causes is the unwell standardization of the measurements that cause temporary changes in muscle resistance termed as muscle thixotropy. This temporary changes can
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Subjectivity, lack of precision, and accuracy are the challenges in the spasticity clinical measurement. One of the causes is the unwell standardization of the measurements that cause temporary changes in muscle resistance termed as muscle thixotropy. This temporary changes can affect the accuracy of the result that may lead to a wrong diagnosis. Unfortunately, resting period between the measurements, as one of the factors generating the thixotropic effect, is still not well considered. The present study investigates the effect of resting period on the short-range stiffness and the resting torque in muscle thixotropy around the human ankle joint. Twenty participants were seated on a chair with the foot placed onto the footplate connected to the Achilles Rehabilitation Device(ARD). The experimental procedure was done using segmental passive slow movements (v=5° /s) applied to the ankle with each segment consisting of multiple dorsi-plantarfexion cycles (Amplitude 15° in dorsiflexion direction) controlled by the ARD. Six different resting period durations (1s, 2s, 4s, 8s, 16s, 32s) were applied to the segments with Balance Latin Square randomization rule. The results clearly showed the time dependency of the Short-range stiffness (SRS) (RM ANOVA, F(1.702,32.399)=210.776, p<0.0005) and the resting torque (RM ANOVA, F(1.709,32.472)=210.776, p<0.0005) with a negative exponential pattern. We suggested that the most responsible structures for SRS and resting torque were the cross-bridges. We found that the resting torque was significantly affected by the multiple movements in the primary procedure (Wilcoxon Signed-Rank test, Z=-3920, p<0.0005) which had not recovered to its initial value. However, the insignificant effect was found in SRS (dependent t-test, t(19)=1.512, and p=0.147). We suggested that the SRS was generated as long as having enough resting period whereas resting torque was not. Our interpretation is that the resting torque was influenced by the mechanical-history of both dorsi- and plantar flexor muscles. The compliance of the tendon and the parallel connective tissue of plantarflexors, as well as the stiffness recovery of the dorsiflexor muscles, caused the slow resting torque recovery even though the cross-bridges in plantarflexors already started reforming.