Cooling of Lower Extremity Muscles According to Subcutaneous Tissue Thickness

Context: When using an ice bag, previous researchers recommended cooling times based on the amount of subcutaneous tissue. Unfortunately, many clinicians are unaware of these recommendations or whether they can be applied to other muscles. Objective: To examine if muscles of the lower extremity cool similarly based on recommended cooling times. Design: Crossover study. Setting: Athletic training laboratory. Patients or Other Participants: Fourteen healthy participants volunteered (8 men, 6 women; age = 21.1 +/- 2.2 years, height = 174.2 +/- 4.5 cm, weight = 74.0 +/- 7.5 kg). Intervention(s): Subcutaneous tissue thickness was measured at the largest girth of the thigh, medial gastrocnemius, and medial hamstring. Participants were randomized to have either the rectus femoris or medial gastrocnemius and medial hamstring tested first. Using sterile techniques, the examiner inserted a thermocouple 1 cm into the muscle after accounting for subcutaneous tissue thickness. After the temperature stabilized, a 750-g ice bag was applied for 10 to 60 minutes to the area(s) for the recommended length of time based on subcutaneous adipose thickness (0 to 5 mm [10 minutes]; 5.5 to 10 mm (25 minutes]; 10.5 to 15 mm [40 minutes]; 15.5 to 20 mm [60 minutes)]. After the ice bag was removed, temperature was monitored for 30 minutes. At least 1 week later, each participant returned to complete testing of the other muscle). Main Outcome Measure(s): Intramuscular temperature (degrees C) at baseline, end of treatment time (0 minutes), and posttreatment recovery (10, 20, and 30 minutes postintervention). Results: At the end of treatment, temperature did not differ by subcutaneous tissue thickness (10 minutes = 29.0 degrees C +/- 3.8 degrees C, 25 minutes = 28.7 degrees C +/- 3.2 degrees C, 40 minutes = 28.7 degrees C +/- 6.0 degrees C, 60 minutes= 30.0 degrees C +/- 2.9 degrees C) or muscle (rectus femoris- 30.1 degrees C +/- 3.8 degrees C, gastrocnemius = 28.6 degrees C +/- 5.4 degrees C, hamstrings 28.1 degrees C +/- 2.5 degrees C). No significant interaction was present for subcutaneous tissue thickness or muscle (P >= .126). Conclusions: Lower extremity muscles seemed to cool similarly based on the recommended cooling times for subcutaneous tissue thickness. Clinicians should move away from standardized treatment times and adjust the amount of cooling time by ice-bag application based on subcutaneous tissue thickness.