Changes in stress hormone levels with the application of vibrations before resistance exercises at different intensities

[Purpose] The purpose of the present study was to determine whether vibrations should be applied before resistance exercises by examining changes in stress hormone levels with vibrations applied before different exercise intensities. [Subjects] Eighteen male subjects in their 20s were included, and were randomly divided into one-repetition maximum (1RM) 50% group (50% RMG, n = 6), 1RM 70% group (70%RMG, n = 6), and 1RM 90% group (90% RMG, n = 6). [Methods] Three sets of Smith squats were performed at 1RM 50%, 70%, and 90% according to resistance intensities, and vibrations were applied for 1 min at a fixed frequency of 30 Hz before each set. Epinephrine, norepinephrine, and dopamine stress hormone levels were analyzed. [Results] Epinephrine levels were significantly higher immediately after exercise than at rest in the 50%RMG; however, no significant changes were noted in the 70%RMG and 90%RMG. Norepinephrine levels were significantly higher immediately after exercise than at rest in all three groups. However, no significant changes in dopamine levels were noted in the three groups. [Conclusion] The application of vibrations at a frequency of 30 Hz before 70%RM and 90%RM resistance exercises suppressed increases in the stress hormone epinephrine levels immediately after exercise.