Hot-Pack and 1-MHz Ultrasound Treatments Have an Additive Effect on Muscle Temperature Increase
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Triceps muscle tissue temperature at depths of 1 and 3 centimetres was tested after superficial heating, and then after adding ultrasound. The muscle was anaesthetized, and the temperature was taken with a fine needle probe.
With a “primer” of superficial heat, ultrasound increased tissue temperature more and more quickly. An interesting incidental finding is the effect of superficial heating alone: 15 minutes of superficial heat increased tissue temperature by 3.8 at 1cm depth and .74 deg at 3cm depth.
original abstract†Abstracts here may not perfectly match originals, for a variety of technical and practical reasons. Some abstacts are truncated for my purposes here, if they are particularly long-winded and unhelpful. I occasionally add clarifying notes. And I make some minor corrections.
OBJECTIVE: Therapeutic ultrasound is an effective deep heating modality commonly applied alone or after cooling or heating of the treatment area. The purpose of this study was to examine the tissue temperature rise in the human triceps surae muscle group after ultrasound with prior heating via a silicate gel hot pack.
DESIGN AND SETTING: This study was designed as a 2 x 2 x 3 factorial with repeated measures on two factors (depth and time). Independent variables were temperature of pack (hot and room temperature), depth of measurement (1 cm and 3 cm), and time (beginning, after pack application, and after ultrasound). The dependent variable was tissue temperature. Subjects were assigned to one of two treatment groups: ultrasound preceded by a 15-minute hot pack treatment or ultrasound preceded by a 15-minute application with a silicate gel pack at room temperature. Measurements were taken while subjects were treated in a university training room.
SUBJECTS: Twenty-one uninjured male and female college student volunteers were randomly assigned to one of the two pack groups.
MEASUREMENTS: The hot packs were stored in 75 degrees C water. A 1-MHz ultrasound treatment was administered for 10 minutes at an intensity of 1.5 W/cm(2). Tissue temperature was measured every 30 seconds using 23-gauge hypodermic microprobes interfaced with a telethermometer and inserted 1 and 3 cm below the surface of anesthetized triceps surae muscle.
RESULTS: At both tissue depths, there was a 0.8 degrees C greater increase in tissue temperature with hot packs and ultrasound. At 1 cm, ultrasound increased temperature 3.5 degrees C after a 0.5 degrees C rise during the room temperature-pack application, but only 0.6 degrees C after a 3.8 degrees C increase during hot-pack application. At 3 cm, ultrasound increased temperature 3.85 degrees C following a slight (-0.26 degrees C) decrease during the room temperature-pack application and 3.68 degrees C after a 0.74 degrees C increase during hot-pack application.
CONCLUSIONS: Vigorous increases in deep muscle temperature (>/=4 degrees C) can be reached with 2 to 3 minutes less total sonation time when preheated with a hot pack. Thus, ultrasound and hot packs have an additive effect on intramuscular temperature, but the characteristics of the additive effect are different, primarily because there appears to be a tissue temperature plateau.
related content
These two articles on PainScience.com cite Draper 1998 as a source:
- PS Heat for Pain — When and how to apply heat for therapy … and when not to!
- PS Icing, Heating & Tissue Temperature — How much do ice packs and heating pads change the temperature of muscle and joints?
