Viscoelasticity is the ability to return of a material to return to a position after an extended force application. Dynamic tissues (muscles, tendons, ligaments) possess viscoelastic structures.
The ideal mechanism and benefits of stretching are uncertain, but previous work suggests constant-torque is more beneficial than constant-angle for improving muscle creep, resulting in a decrease in stiffness. This creep is the physiological deformation of a tissue after the application of a constant load.
Ryan et al studied the viscoelastic creep responses during repeated constant-torque stretching exercises using stretching durations (2 min of time under stretch) which is commonly performed in athletic and clinical settings.
What was done
Twelve participants performed two trials, the first a familiarization and the second an experimental. During the familiarization, each participant practiced the 30-s stretches and determined the maximal passive torque threshold.
The experimental trial used four 30-s constant torque stretches with a 20-s rest period between each stretch and a maximal voluntary contraction (MVC) of the plantar flexors performed following the four stretches.
The stretches were performed to the plantar flexors in the supine position.
A significant change was noted in the stretches. The results indicated that increases in joint angle were similar for all four stretches over the entire 30 s, but the third and fourth stretches started and ended at the same joint position.
The largest increase in the stretch was noted at the 0 – 5s time period.
Overall, the findings indicate that four consecutive 30-s constant-torque stretches resulted in the same viscoelastic creep response.
The amount of viscoelastic creep appears to be unaffected during four 30-s constant-torque stretches. This suggests this form of stretching is not required for more than one bout of 30-s. However, the indications of stretches are still uncertain and potentially negligible. Constant-torque stretching appears no more beneficial compared to regular static stretching, however, both appear to have many benefits for swimmers.
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- Ryan ED, Herda TJ, Costa PB, Walter AA, Cramer JT. Dynamics of viscoelastic creep during repeated stretches. Scand J Med Sci Sports. 2012 Apr;22(2):179-84. doi: 10.1111/j.1600-0838.2010.01285.x. Epub 2011 Mar 1.