Sorry, for comparative studies:
Mahieu et al. (2007) conducted a study comparing static and ballistic stretching to a control group over six weeks. They found that static stretching significantly decreased passive resistive torque without changing Achilles tendon stiffness, while ballistic stretching significantly decreased Achilles tendon stiffness without affecting passive resistive torque
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.
