Abstract
This study was designed to measure changes in musculo-articular dissipative properties related to viscosity that were induced by passive cyclic and static stretching. Musculo-articular dissipative properties were assessed by calculating a dissipation coefficient using potential elastic energies stored and restituted during cyclic stretching. Eight subjects performed five passive knee extensions/flexions cycles on a Biodex dynamometer at 5 degrees . s (-1) to 80 % of their maximal range of motion before and after a static stretching protocol. Electromyographic activity from the hamstring muscles was monitored and remained constant during cyclic stretching and after static stretching (p > 0.05). The dissipation coefficient decreased during cyclic stretching (- 28.8 +/- 6.0 %, p < 0.001), while it was slightly increased after static stretching (+ 3.8 +/- 5.0 %, p = 0.037). The findings showed that energy stored and energy restituted decreased during cyclic stretching and after static stretching (p < 0.05). During unloading, passive torque remained constant during cyclic stretching, but was decreased after static stretching. The findings indicate that musculo-articular dissipative properties were primarily affected by a single cycle of motion, and were not influenced by static stretching procedures. The decrease in dissipation coefficient following cyclic motion indicates that the musculo-articular system displays thixotropic behavior.
Highlights
Passive stretching exercises are commonly performed in sports and rehabilitation
SEMG activity sEMG activity was not changed across cyclic stretches nor after static stretching with a mean and standard deviation of 0.97 ± 0.33%
Our results show that the DC and, viscosity was decreased during cyclic stretching
Summary
Passive stretching exercises are commonly performed in sports and rehabilitation. Both animal [20] and human data [6, 9 – 11,14,15] have indicated that the biomechanical properties (e.g., force, energy, stiffness) of passive muscle are altered immediately after passive stretching. The passive mechanical properties of a musculo-articular complex, including structures spanning the joint (i.e., muscles, tendons, skin, subcutaneous tissue, fascia, ligaments, joint capsule and cartilage) [18], can be assessed using passive loading and unloading torque (T) – angle (q) responses [6, 9 – 11,14,15,18] From these data, potential elastic energy stored by the musculoarticular complex during loading can be determined by calculating the area under the loading T-q relationship. Previous research by McNair et al [14] has shown that related elastic parameters such as stiffness are more affected by cyclic motion compared to static stretching These authors did not examine dissipative properties. The objective of this study was to compare the viscous changes that occur with static and cyclic stretching by quantifying the energy absorbed and dissipated during passive knee joint extension and flexion
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