What is the effect of long-term stretching?
It is well recognized that stretching is an effective method to increase long-term joint range of motion. However, the effects of stretch training on the muscle-tendon structural properties remain unclear. Published in the August 2017 edition of Scandinavian Journal of Medicine & Science in Sports, a group of researchers from Portugal, France, and Serbia conducted a systematic review to determine whether long-term stretching alters the structural properties of the muscle-tendon junction.
The authors searched through scientific publication databases for studies on longitudinal (long-term) stretching (static, dynamic and/or proprioceptive neuromuscular facilitation [PNF]) intervention (either randomized trial or not) in humans of any age and health status, with more than 2 weeks in duration and at least 2 sessions per week. Structural or mechanical variables from joint (maximal tolerated passive torque or resistance to stretch) or muscle-tendon unit (muscle architecture, stiffness, extensibility, shear modulus, volume, thickness, cross sectional area, and slack length) were extracted from those papers.
The authors found 26 studies with duration of stretching ranging from 3 to 8 weeks, and an average total time of stretching of 20 minutes per week. The review found that small effects were seen for maximal tolerated passive torque, but trivial effects were seen for joint resistance to stretch, muscle architecture, muscle stiffness, and tendon stiffness. Nevertheless, research findings also show a large heterogeneity for most of the investigated variables.
- The authors concluded that stretching interventions with 3-8 weeks duration do not seem to change either the muscle or the tendon properties. However, it increases the extensibility and tolerance to a greater tensile force, in other words, it “allowed” for great flexibility and range of motion.
- They further concluded that adaptations to long-term stretching protocols shorter than 8 weeks seem to mostly occur at a sensory level of the nervous system versus the mechanical properties of the muscle tendon complex itself.
Note: This blog post article was reproduced with permission from Terra Rosa