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A comparison of acute changes in muscle thickness between A-mode and B-mode ultrasound
Tayla E Kuehne1, Noam Yitzchaki1, Matthew B Jessee2
1USF Muscle Lab, Exercise Science Program, University of South Florida, Tampa, FL, United States of America.
Objective:
The purpose of this study was to compare acute changes in muscle thickness (MT) between A-mode and B-mode ultrasound before and after four sets of biceps curls.
Approach:
Participants visited the laboratory on two separate occasions. The first visit consisted of paperwork and one repetition maximum (1RM) strength assessment. During the second visit, participants performed four sets of biceps curls to volitional failure using an exercise load equal to 70% of 1RM or a time-matched non-exercise control. MT measurements were taken before and immediately after exercise. MT measures were taken using both A-mode and B-mode ultrasound.
Main Results:
Results are displayed as mean (SD). A total of 49 resistance-trained men (n = 24) and women (n = 25) completed the study. There was no group (experimental versus control) by mode (A-mode versus B-mode) by time interaction (p = 0.442). However, there was a group (experimental versus control) × time (pre versus post) interaction (p < 0.001). Muscle thickness increased from pre (3.61 (0.86) cm) to post exercise (4.06 (0.92) cm) in the experimental group (p < 0.001). However, there was no change from pre (3.46 (0.78) cm) to post (3.48 (0.78) cm) in the time-matched control group (p = 0.237). There was a main effect for ultrasound mode (A-mode versus B-mode) (p < 0.001). Muscle thickness values as measured by A-mode ultrasound were lower than those measured by B-mode ultrasound pre (A-mode = 3.43 (0.79) cm versus B-mode = 3.63 (0.84) cm) and post (A-mode = 3.67 (0.87) cm versus B-mode = 3.83 (0.91) cm) intervention.
Significance:
MT measurements taken using A-mode ultrasound are lower than those of B-mode ultrasound. Despite this difference, it appears A-mode can detect similar acute changes in MT following resistance exercise when compared to B-mode ultrasound. These results suggest that A-mode ultrasound can serve as a useful tool when examining acute changes in MT.
