Effect of superficial heat, deep heat, and active exercise warm-up on the extensibility of the plantar flexors.

BACKGROUND AND PURPOSE Warm-up prior to static stretching enhances muscle extensibility. The relative effectiveness of different modes of warm-up, however, is unknown. The purpose of this study was to evaluate the effectiveness of superficial heat, deep heat, and active exercise warm-up prior to stretching compared with stretching alone on the extensibility of the plantar-flexor muscles. SUBJECTS Ninety-seven subjects (59 women, 38 men) with limited dorsiflexion range of motion (ROM) were randomly assigned to 1 of 5 groups. Female subjects had a mean age of 27.6 years (SD=7.68, range=17-50), and male subjects had a mean age of 26.8 years (SD=6.87, range=18-48). METHODS The first group (group 1) was a control group and did not perform the stretching protocol. The 4 experimental groups (groups 2-5) performed a stretching protocol 3 days per week for 6 weeks. Group 2 performed the static stretching protocol only; group 3 performed active heel raises before stretching; group 4 received 15 minutes of superficial, moist heat to the plantar-flexor muscles before stretching; and group 5 received continuous ultrasound for 7 minutes before stretching. Dorsiflexion ROM measurements were taken initially and after 2, 4, and 6 weeks. RESULTS All experimental groups increased active and passive range of motion (AROM and PROM). The mean AROM/PROM differences at 6 weeks were 1.11/1.39 degrees for group 1, 4.10/6.11 degrees for group 2, 4.16/4.21 degrees for group 3, 4.38/4.90 degrees for group 4, and 6.20/7.35 degrees for group 5. The group receiving ultrasound before performing the stretching protocol (group 5) displayed the greatest increase in both AROM (6.20() and PROM (7.35(). DISCUSSION AND CONCLUSION Among the modalities tested, the use of ultrasound for 7 minutes prior to stretching may be the most effective for increasing ankle dorsiflexion ROM.