An Examination Of Changes In Echo Intensity Following Resistance Exercise Using Various Regions Of Interest

Abstract

Echo intensity (EI) is often used to examine exercise induced muscle damage, acute muscle swelling, muscle quality, and pre and post-exercise stores of intramuscular glycogen. PURPOSE: To compare changes in EI using different areas of interest (small box, large box and muscle trace) immediately following naïve exposure to exercise as well as 24 and 48 hours following an exercise bout. METHODS: 20 non-resistance trained individuals visited the laboratory 4 times. During visit 1, paperwork and maximum strength were measured. During visit 2 (2-7 days later) participant’s muscle thickness was measured in both arms before performing 4 sets of biceps curls. Additional measures of muscle thickness were taken immediately after exercise, as well as 24 and 48 hours after following the exercise bout. EI of muscle thickness images was measured using three different techniques: 1) Trace around the muscle to include the entire musculature, without any surrounding tissue; 2) Small box placed in the middle of the muscle (2 x 2 cm); 3) Maximal rectangular box that includes as much muscle as possible without surrounding tissue. Results are displayed as means (SD). RESULTS: A total of 20 non-resistance trained men (n = 11) and women (n = 9) completed the study. For EI there was no condition x time interaction (p = 0.174). However, there were main effects for condition (p = 0.001) and time (p = 0.001). EI increased from pre [23.9 (10.4) AU] to post exercise [30.7 (13.6) AU, p = 0.005] and returned to baseline 24 [21.0 (10.5) AU, p = 0.242] and 48 hours [23.0 (11.8) AU, p = 0.722] post exercise. In addition, EI values were different amongst the different methods. EI values were higher when comparing the small box method [26.3 (13.4) AU] to the large box method [24.7 (11.5) AU, p = 0.019] and when comparing the small box to the full trace method [22.9 (9.9) AU, p = 0.001]. In addition, the full trace method demonstrated lower values compared to large box method (p < 0.001). CONCLUSIONS: Results of the present study demonstrate that similar changes in EI are detected when using different areas of interest for analyzing the EI of an ultrasound image. When larger regions of interest are examined, EI values appear to be lower. The results of the present study suggest that the region of interest chosen may not have an appreciable effect on the ability to detect changes in EI.