Chronic stretching and muscle-tendon mechanical properties
The available evidence about the effect of stretching programs on the mechanical properties of muscles and tendons shows that - although small increases in extensibility and tensile force tolerance can be noted - interventions lasting 3-8 weeks do not seem to change the fundamental mechanical properties of muscles and tendons. Instead, adaptations tend to occur at a sensory level.
The efficacy of stretching programs in range of motion (ROM) increase is well established.
2 mechanisms are proposed to explain these changes: sensory and mechanical adaptations. The evidence regarding the effect of stretching programs on the structure of musculotendinous units (MTUs) is still conflicting.
Thus, this review aimed to systematically review the literature regarding the chronic effects of stretching interventions on the MTU structure. 26 studies with stretching programs ranging from 3-8 weeks were included. Average stretching time was 1165 s.
The authors found that chronic stretching (3-8 weeks) has a small effect on maximal tolerated passive torque, but no statistically significant effect on musculotendinous mechanical properties (joint resistance to stretch, muscle architecture, muscle stiffness, and tendon stiffness).
A large heterogeneity was observed for most variables. Structural changes may need a greater duration of the stretching interventions, since the observed effects seem to come from sensory, rather than mechanical, adaptations.
> From: Freitas et al., Scand J Med Sci Sports 28 (2018) 794-806 (Epub ahead of print). All rights reserved to John Wiley & Sons A/S. Click here for the online summary.