Repeated static stretching was more effective for increasing range of motion and decreasing passive stiffness than a combination of a thermal agent with static stretching.

Combining static stretching (SS) and thermal agents could be beneficial for improving range of motion (ROM) and passive stiffness. However, in many previous studies, combining SS and thermal agents resulted in a longer intervention time than SS alone. Therefore, it is unclear whether the effects of SS alone and combining SS and thermal agents are similar when the total intervention time is standardized. This study aimed to compare the effects of SS alone and combine SS with thermal agents when the intervention time is standardized for 10 minutes. The participants were 14 healthy sedentary males (21.0 ± 0.4 y) in three conditions: 1) 120 s SS (480 s rest+120 s SS), 2) Heat+120 s SS (480 s thermal agent+120 s SS), and 3) 120 s SS × 4 times (120 s SS × 4 repetitions+40 s rest{ × 3 times}) conditions. The ankle dorsiflexion (DF) ROM, passive torque at DF ROM, passive stiffness, and plantar flexors maximal voluntary isometric contraction (MVIC) torque were measured before (PRE) and immediately after the intervention (POST). Two-way repeated-measures analysis of variance showed significant interaction effects in DF ROM and passive stiffness but not in passive torque at DF ROM and MVIC. Post-hoc tests showed that DF ROM in the 120 s SS × 4 times condition was significantly higher than in the 120 s SS condition, and the decrease in passive stiffness in the 120 s SS × 4 times condition was significantly higher than in the 120 s SS and the Heat+120 s SS conditions. In conclusion, repeating SS induced greater ROM increases and passive stiffness decreases than combining SS with thermal agents in a standardized intervention lasting 10 minutes.