Temperature rise in human muscle during ultrasound treatments using flex-all as a coupling agent

To determine if Flex-all 454, as advertised, is effective as a thermal ultrasound couplant.

Research design was a one-factor analysis of variance. Subjects received three (alternating order) ultrasound treatments (1 MHz at 1.5 W/cm(2) for 10 minutes) using the following couplants: 50% Flex-all mixed with 50% ultrasound gel; 100% ultrasound gel; and sham ultrasound with 100% Flex-all. Data were collected in a ventilated laboratory.

Fifteen male and female students (mean age = 24.2 +/- 3.7 years).

Muscle temperature was measured via hypodermic microprobes inserted 3 and 5 cm deep in the medial triceps surae. A visual analogue scale was used to measure perceived heat.

At 3 cm, the increases for the gel, 50/50 mixture, and sham were 3.2 degrees C, 2.6 degrees C, and -0.82 degrees C, respectively. At 5 cm, the increases were 2.17 degrees C, 1.80 degrees C, and -0.50 degrees C, respectively. Subjects rated the sham treatment as mild heating (although the temperature dropped) and perceived treatments using the 50/50 mixture to be warmer than treatments using 100% gel couplant.

Ultrasound treatments delivered with a 50/50 Flex-all/gel couplant felt warmer to subjects; however, identical treatments with 100% ultrasound gel produced higher muscle temperatures. Clinicians desiring optimal thermal effects should use 100% ultrasound gel as the couplant.