Acute changes in hamstrings musculo-articular dissipative properties induced by cyclic and static stretching.

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.