Moltubakk et al. (2021) examined the effects of 24 weeks of daily static stretching on the plantarflexors. They observed increased range of motion (ROM) and passive tendon elongation, but no changes in tendon stiffness, indicating that stretching can alter muscle-tendon behavior without necessarily increasing tendon stiffness.[1]
Su et al. (2008) investigated the effects of cyclic stretching on rat tendons and ligaments. They found that cyclic stretching significantly increased the ultimate stress and elastic modulus of both the patellar tendon and medial collateral ligament, suggesting enhanced mechanical properties with stretching.[2]
Kay et al. (2015) compared contract-relax (CR) stretching, static stretching (SS), and isometric contractions. They found that CR stretching and isometric contractions significantly reduced tendon stiffness, while static stretching did not. All interventions increased ROM, but the changes in muscle and tendon stiffness were distinct.[3]
[1] Moltubakk MM, Villars FO, Magulas MM, et al. Altered Triceps Surae Muscle-Tendon Unit Properties After 6 Months of Static Stretching. Medicine and Science in Sports and Exercise. 2021;53(9):1975-1986. doi:10.1249/MSS.0000000000002671.
[2] Su WR, Chen HH, Luo ZP. Effect of Cyclic Stretching on the Tensile Properties of Patellar Tendon and Medial Collateral Ligament in Rat. Clinical Biomechanics (Bristol, Avon). 2008;23(7):911-7. doi:10.1016/j.clinbiomech.2008.04.002.
[3] Kay AD, Husbands-Beasley J, Blazevich AJ. Effects of Contract-Relax, Static Stretching, and Isometric Contractions on Muscle-Tendon Mechanics. Medicine and Science in Sports and Exercise. 2015;47(10):2181-90. doi:10.1249/MSS.0000000000000632.
HOWEVER there is definitely ***some*** evidence suggesting that individuals who do not stretch may not be at a significant disadvantage compared to those who do, particularly in terms of injury prevention and muscle soreness.
A systematic review published in the BMJ concluded that stretching before or after exercise does not confer significant protection from muscle soreness or reduce the risk of injury.[1]
A randomized trial in the British Journal of Sports Medicine found that stretching did not produce clinically significant reductions in all-injury risk, although it did reduce the risk of experiencing bothersome soreness and injuries to muscles, ligaments, and tendons.[2]
A systematic review in Medicine and Science in Sports and Exercise indicated that static stretching (SS) and proprioceptive neuromuscular facilitation (PNF) stretching had no clear effect on all-cause or overuse injuries, and dynamic stretching (DS) produced small-to-moderate performance improvements when completed within minutes of physical activity.[3]
A review in Sports Medicine highlighted that stretching may not be necessary for injury prevention in sports with low-intensity stretch-shortening cycles (SSCs), such as jogging or cycling, where a compliant muscle-tendon unit is less critical.[4]
It comes down to the movement you're doing, how much, how often, and your own biophysics.
[1] Herbert RD, Gabriel M. Effects of Stretching Before and After Exercising on Muscle Soreness and Risk of Injury: Systematic Review. BMJ (Clinical Research Ed.). 2002;325(7362):468. doi:10.1136/bmj.325.7362.468.
[2] Jamtvedt G, Herbert RD, Flottorp S, et al. A Pragmatic Randomised Trial of Stretching Before and After Physical Activity to Prevent Injury and Soreness. British Journal of Sports Medicine. 2010;44(14):1002-9. doi:10.1136/bjsm.2009.062232.
[3] Behm DG, Blazevich AJ, Kay AD, McHugh M. Acute Effects of Muscle Stretching on Physical Performance, Range of Motion, and Injury Incidence in Healthy Active Individuals: A Systematic Review. Applied Physiology, Nutrition, and Metabolism = Physiologie Appliquee, Nutrition Et Metabolisme. 2016;41(1):1-11. doi:10.1139/apnm-2015-0235.
[4] Witvrouw E, Mahieu N, Danneels L, McNair P. Stretching and Injury Prevention: An Obscure Relationship. Sports Medicine (Auckland, N.Z.). 2004;34(7):443-9. doi:10.2165/00007256-200434070-00003.
