The Carry-Over Effects of Diathermy and Stretching in Developing Hamstring Flexibility

OBJECTIVE: To compare the effects of low-load, short-duration stretching with or without high-intensity, pulsed short-wave diathermy on hamstring flexibility. DESIGN AND SETTING: We used a single-blind, repeated-measures design (pretest and posttest for all treatments) that included a placebo. The 3 independent variables were treatment mode, pretest and posttest measurements, and day. Treatment mode had 3 levels: diathermy and stretching, stretching alone, and control. The dependent variable was range of motion. Subjects were randomly assigned to the diathermy and stretching, stretching-only, or control group. Subjects were treated and tested each day (at approximately the same time) for 5 days, with a follow-up test administered 72 hours later. Hamstring flexibility was tested using a sit-and-reach box before and after each treatment. Diathermy and stretching subjects received a 15-minute diathermy treatment on the right hamstring at a setting of 7000 pulses per second, with an average pulse width of 95 μsec. Stretching-only subjects received a 15-minute sham diathermy treatment. Both diathermy and stretching and stretching-only subjects then performed three 30-second stretches (short duration) before being retested. Control subjects lay prone for 15 minutes before being retested. SUBJECTS: Thirty-seven healthy college students (11 men, 26 women, age = 20.46 +/- 1.74 years) volunteered. MEASUREMENTS: Hamstring flexibility was measured using a sit-and-reach box before and after each treatment. RESULTS: The average increases in hamstring flexibility over the 5 treatment days for the diathermy and stretching, stretching-only, and control groups were 6.06 cm (19.6%), 5.27 cm (19.7%), and 3.38 cm (10.4%), respectively. Three days later (after no treatment), the values for the diathermy and stretching, stretching-only, and control groups were 8.27 cm (26.7%), 6.83 cm (25.3%), and 4.15 cm (14.2%), respectively. No significant differences in hamstring flexibility were noted among the groups. CONCLUSIONS: Diathermy and short-duration stretching were no more effective than short-duration stretching alone at increasing hamstring flexibility. The effects of diathermy with longer stretching times need to be researched.