Soft tissue thermodynamics before, during, and after cold pack therapy

BACKGROUND: Cold packs are commonly used by clinicians, trainers, and others, often as an interim treatment for many acute conditions, but the extent of temperature change associated with this form of treatment remains poorly understood. METHODS: In 16 healthy male and female volunteers aged 25.4 +/- 3.6 yr, we monitored skin temperature, and recorded the temperature of the quadriceps muscle at 1, 2, and 3 cm depths below the skin, before, during, and after 20 min of cold pack treatment. RESULTS: The results revealed a slight rise in temperature at all four levels during the 5 min pretreatment period, but significant temperature falls at the skin and 1 cm levels beginning from 8 min of treatment (P < 0.001). There was no significant change in tissue temperature at the 2.0 cm or 3.0 cm depths throughout treatment. However, after treatment, cutaneous temperature and the temperature at 1.0 cm depth rose rapidly, returning to baseline levels at variable intersubject times. As these superficial temperatures rose, there were concurrent falls in the temperatures at the 2.0 cm and 3.0 cm levels. Thus, the deeper tissues lost heat (cooled) simultaneously as the superficial tissues rewarmed; to the extent that 40 min after treatment, the deeper levels were cooler than the cutaneous and 1.0 cm levels. CONCLUSION: 1) Cold pack therapy produces significant temperature falls in cutaneous and subcutaneous superficial tissues without directly changing the temperature of tissues at or more than 2.0 cm below the skin; and 2) the temperature gradients of both layers of tissue reverses after treatment, indicating that the deep tissue beneath is at least one of the sources of heat used to rewarm the cooled superficial tissue. The latter finding underscores the importance of the hemodynamic interchange between superficial and deep tissues, and offers an explanation for the reduction of pain, muscle spasm, and edema observed with cold therapy in several clinical situations.