Study design: A randomized, counterbalanced 2x3x5 repeated-measures design.
Objective: To compare changes in hamstring flexibility after treatments of pulsed shortwave diathermy and prolonged stretch, sham diathermy and prolonged stretch, and control.
Background: Heat and stretch techniques have been touted for years. To date, the effect of shortwave diathermy and hamstring stretching has not been studied. Because diathermy heats a large area and penetrates deep into the muscle, use of this device prior to or during hamstring stretching may increase flexibility.
Methods and measures: Thirty college-age students (mean age, 21.5 years) with tight hamstrings (inability to achieve greater than 160 degrees knee extension at 90 degrees hip flexion) participated. Subjects were assigned to 1 of 3 groups: diathermy and stretch, sham diathermy and stretch, and control). Range of motion was recorded before and after each treatment for 5 days and on day 8. A straight leg-raise stretch was performed using a mechanical apparatus. Subjects in the diathermy-and-stretch group received 10 minutes of diathermy (distal hamstrings) followed by 5 minutes of simultaneous diathermy and stretch, followed by 5 minutes of stretching only. Subjects in the sham-diathermy-and-stretch group followed the same protocol, but with the diathermy unit turned off. Subjects in the control group lay on the table for 20 minutes. Data were analyzed using an ANOVA and post hoc t tests.
Results: Mean (+/- pooled SE) increases in knee extension after 5 days were 15.8 degrees 2.2 degrees for the diathermy-and-stretch group, 5.2 degrees +/- 2.2 degrees for the sham-diathermy-and-stretch group, and -0.3 degrees +/- 2.2 degrees for the control group. Seventy-two hours after the last treatment, the diathermy-and-stretch group lost 1.9 degrees +/- 2.2 degrees, the sham-diathermy-and-stretch group lost 3.0 degrees +/- 2.2 degrees, and the control group changed -0.4 degrees +/- 2.2 degrees.
Conclusion: These results suggest that hamstring flexibility can be greatly improved when shortwave diathermy is used in conjunction with prolonged stretching.