Passive hip flexion does not increase during or following ultrasound treatment of the hamstrings musculature

Abstract

The stretching window is a theoretical concept that refers to the period of maximum tissue temperature increase during and immediately following ultrasound treatment. This study was conducted to determine if an optimal time period exists for combining ultrasonic heat and stretching to obtain maximum joint range of motion; essentially, evaluate the existence of a stretching window. A 1 x 5 factorial design was used. The independent variable was time with 5 levels (5 min into treatment or 1½, 3½, 6, or 10 min following treatment). The dependent variable was maximum passive hip flexion range of motion (PHROM). Fifty healthy graduate and undergraduate students (27 males, 23 females) aged 24.1 y ±3.4 (s.d.), height 174.1 cm ± 16.2 (s.d.), and mass 74.1 kg ± 16.6 (s.d.) participated in the study. All subjects were free from significant lower extremity injury and had less than 90° PHROM. A range of motion pre‐test was measured for each subject. Each subject then had a range of motion post‐test taken 5 min into and at l½, 3½, 6, and 10 min following a 3 MHz ultrasound treatment of the hamstrings musculature using an electrogoniometer. A one‐way ANCOVA (with pre‐test ROM as the covariate) was used to determine if a difference in ROM existed between groups. No difference in PHROM existed between any of the 5 treatment groups (F(4, 44) = 0.28, P = 0.889). A theoretical stretching window possibly exists, since a maximum tissue temperature increase has been measured during and immediately following ultrasound treatment. However, this theoretical stretching window does not appear to translate into increased tissue extensibility in the hamstring musculature either during or following ultrasound treatment.