Context:Research on therapeutic ultrasound has not focused on the duration needed to cause thermal change with various ultrasound intensities.Objective:To analyze triceps surae intramuscular temperature using 4 intensity levels after a 10-min 1-MHz continuous ultrasound treatment at a depth of 4 cm.Design:1 × 4 repeated measures. Independent variable: intensity of 4 levels—0.5, 1.0, 1.5, and 2.0 W/cm2. Dependent variable: peak intramuscular temperature.Setting:Research laboratory.Participants:19 volunteers with no lower leg pathologies.Intervention:Treatment order was balanced via Latin square and performed 24 hr apart.Main Outcome Measures:Peak intramuscular temperatures.Results:The only significant difference detected was that the mean temperature after the 1.0-W/cm2 treatment (37.3 °C) was greater than that at 2.0-W/cm2 intensity (36.1 °C). No treatment reached the desired 4° increase needed for therapeutic efficacy.Conclusions:Treatments at 1.0 W/cm2 increased tissue temperatures more than those at 2.0 W/cm2.
