Evaluating the results of resistance training using ultrasound or flexed arm circumference: A case for keeping it simple?

backgroundThe present study aimed to compare changes in muscle size when measured by ultrasound (US) muscle thickness (MT) and arm circumference (AC) using data from young men.

methodsThe investigation involved data from three previous studies involving a total of 67 young men who performed resistance training (RT) for 10-12 weeks. Before and after the training period, elbow flexor MT was evaluated by US and AC was measured. We conducted two-stage individual patient data random-effects meta-analyses using both Frequentist and Bayesian hypothesis testing. One-sample analyses examined the absence or presence of a change in both MT and AC, and paired analyses examined whether these differed from one another or equivalent.

resultsOne-sample analysis supported that both AC (+4.9%; tp=0.0002; BF10=6,255,759,515) and MT (+3.9%;

conclusionBoth MT and AC are able to detect RT-induced changes in muscle size of the upper arm, but that the magnitude of changes may differ. Thus, care should be taken when comparing or combining estimates using either approach. RELEVANCE FOR PATIENTS: The use of AC might be considered as a practical and low-cost alternative to detect changes in muscle size.