Purpose: A previous study observed a joint passive torque increase above baseline ~30 min after a high-intensity stretching. This study examined the effect of a high-intensity stretching on ankle dorsiflexion passive torque, medial gastrocnemius (MG) shear modulus, and plantar flexors maximal voluntary isometric force (MVIC).
Method: Participants (n = 11, age 27.2 ± 6.5 years, height 172.0 ± 10.0 cm, weight 69.5 ± 10.4 kg) underwent two stretching sessions with plantar flexors isometric contractions performed: (1) 5 min before, 1 min after, and every 10 min after stretching (MVC session); (2) 5 min before, and 60 min after the stretching (no-MVC session).
Results: In both sessions, no changes were observed for MG shear modulus (p > 0.109). In the no-MVC session, passive torque decreased 1 min after stretching (-7.5 ± 8.4 %, p = 0.015), but increased above baseline 30 min after stretching (+6.3 ± 9.3 %, p = 0.049). In the MVC session, passive torque decreased at 1 min (-10.1 ± 6.3 %, p < 0.001), 10 min (-6.3 ± 8.2 %, p = 0.03), 20 min (-8.0 ± 9.2 %, p = 0.017), and 60 min (-9.2 ± 12.4 %, p = 0.034) after the stretching, whereas the MVIC decreased at 1 min (-5.0 ± 9.3 %, p = 0.04) and 10 min (-6.7 ± 8.7 %, p = 0.02) after stretching.
Conclusion: The ankle passive torque increase 30 min following the stretch was not due to the MG shear modulus response; consequently, response may be due to changes in surrounding connective tissue mechanical properties.
Keywords: Ankle; Elastography; Flexibility; Intensity; Medial gastrocnemius; Torque.