Subcutaneous Adipose Tissue Thickness Alters Cooling Time During Cryotherapy Jeffrey W. Otte, MS, Mark A. Merrick, PhD, Christopher D. Ingersoll, PhD, Mitchell L. Cordova, PhD Brian, Julianne, Anna

Research Question/ Hypothesis The purpose of this study was to examine the effects of subcutaneous adipose tissue thickness on the cryotherapy duration necessary to produce a standardized intramuscular cooling effect. The researchers hypothesized that there would be an indirect relationship between adipose tissue thickness and time to cool IM tissue.

Clinical Applicability of Hypothesis: This study could be used to determine the specific amount of time needed to reach a standard IM temperature with cryotherapy according to the amount of adipose tissue at the location of application. If, in other studies, a standard optimal IM temperature is determined that decreases secondary hypoxic and enzymatic injury (as well as inflammation, pain, and muscle spasm), then this study will determine the amount of time needed to attain this temperature.

Sample/Subjects: Forty-seven healthy volunteers with anterior thigh skinfold measurement of less than 40mm Study Design: A 4-group, between-groups comparison IV = skinfold thickness (0-10, 11-20, 21-30, 31-40mm) DV = cooling time (treatment duration required to decrease intramuscular temperature 7°C from baseline)

Experimental Procedure: The vertical mid-anterior thigh measurement was taken using skin calipers with the subject in supine. The measurement was then divided in half to estimate the thickness of the adipose tissue. The hair was removed and the skin was cleaned from the anterior thigh halfway between the ASIS and the superior pole of the patella. The IM thermocouple receptor was inserted to a distance 1 cm deeper than the thickness of the adipose tissue and taped to hold in place. A 2 minute baseline reading of temperature was taken and then a 750g bag of ice with air removed was placed on the anterior thigh and temperature recordings were taken every 30 seconds. This continued until the temperature reached 7  below baseline and stayed there for 60 seconds.

Results: Analysis of variance revealed that mean time to cool IM tissues by 7  C differed across all groups with cooling time increasing as adipose thickness increased.

Strengths: This study focused solely on the relationship between adipose tissue thickness and IM cooling time so all variance was due Weaknesses: The study looked at “ typical ” effect of a 7°C drop and not an “ optimal ” effect of cryotherapy, because this optimal effect has not yet been defined.

Potential Impact on Clinical Practice The study found that different thickness of adipose tissue did affect the amount of time that it took to cool structures under the tissue. When standard times are used for icing, some patients will not receive the same amount cooling in the desired tissue due to their adipose thickness. Individuals with varied thickness of adipose tissue need more or less time cooling to get the same resulting decreased temperature.