Stretching Not Shown To Improve Muscle Length
Static stretching, involving holding a muscle at end of its’ length for a sustained period of time, is a common component of most individual’s exercise programs but its’ useful compared to other forms of exercise including aerobic and strength training is questionable. Research is unclear on the benefits of static stretching for most individuals, as well as, the ideal parameters for the most effective stretch. Conversely, utilization of mobility or dynamic warm up activities has been shown to improve subsequent performance and reduce an individual’s injury risk.
Our understanding behind the benefits of static stretching has evolved over the years due to research indicating flexibility gains are more likely due to changes in stretch tolerance (neural adaptations) vs. changes in length (muscular adaptations). Thus, individuals who stretch reduce their sensitivity to the tensile load and in turn are able to stretch beyond previous sensory barriers. A recent review of the literature shines further light on this area of exercise and further questions previously held beliefs.
Freitas and colleagues reviewed the available evidence on the impact of stretching on muscle and tendon tissue (Scand J Med Sci Sports. 2018). Authors reviewed 26 studies for their review of the literature. They reported stretching programs ranged from 3 to 8 weeks with an average of 20 minutes of exercise per week. Consistent with our current understanding participants demonstrated improvements in tolerance to passive stretch after training, but no changes were noted in muscle or tendon mechanical properties. This indicates the flexibility gains which followed the exercise programs were primarily due to an improvement in the ability to tolerate a stretch (desensitization). Thus, the authors concluded benefits experienced under 8 weeks are most likely to occur at the sensory level. Those without a specific mobility need (ex. post operatively or post immobilization) are advised to strength train through a complete range of motion to maintain and improve their current flexibility.