Shear Modulus of Triceps Surae After Acute Stretching

Stretching programs are frequently used in order to reduce or avoid the risk of injury, in addition to promoting a gain in flexibility. Dynamic elastography technique (Supersonic ShearWave Imaging (SSI)) was used to analyze the changes in the shear modulus (µ) of the triceps surae tissue, in vivo, after an acute stretching maneuver. Some studies have analyzed the µ of the medial gastrocnemius (MG) and lateral gastrocnemius (LG) after an acute stretching, but data from the Achilles tendon (AT) seems to be absent. Therefore, the aim of the study is to analyze the µ of the MG, LG and the AT immediately after an acute stretch of the plantar flexors. Eight healthy young performed two stretching exercises for the triceps surae, e 3 sets of one minute were performed for each exercise. Range of motion (ROM) was measured pre and post stretching, as well as the elastographic images, for GM, GL and AT. After acute stretching, there was a significant increase in ROM (p-value = 0.033; mean pre: 34.75°; mean post: 38.50°), however, no significant difference in µ was observed for the muscles and tendon structures (GM mean pre: 5.81 ± 2.85 kPa, mean post: 7.25 ± 2.37 kPa, p = 0.200. LG mean pre: 4.89 ± 1.74 kPa, mean post: 6.49 ± 3.18 kPa, p = 0.255. AT mean pre: 128.12 ± 26.66 kPa, mean post = 108.06 ± 41.79 kPa, p = 0.168). We concluded that the stretching protocol applied in this study resulted in a significant increase in the range of motion, however, it seems not to be due to changes in the mechanical properties of the triceps surae muscle and tendon structures.