Acute Changes in Muscle Thickness and Quality Following Dynamic Bodyweight Exercise in Recreationally Trained Adults

Musculoskeletal ultrasound imaging is a valid and reliable tool to measure muscle morphology, but minimal research explores its utility in assessing acute morphology changes after exercise in active populations. The purpose of this study was to assess changes in ultrasound-based measures of muscle thickness (MT) and quality (MQ) in response to a single bout of short-duration, high-intensity bodyweight exercise in the acute and postacute recovery timeframe.

Interventional study.

Nineteen healthy, recreationally active young men and women (27.1 [8.3] y) completed a dynamic bodyweight exercise circuit primarily focused on the lower body. B-mode ultrasound images were obtained of the rectus femoris in resting and contracted conditions preexercise, ∼15 minutes, and 24 hours postexercise. Knee-extensor strength and MQ (muscle strength [in newtons]/resting MT [in centimeters]) were also assessed at the same timepoints.

Resting and contracted MT increased (13.0%; 6.9%) from pre- to 15 minute postexercise, returning to baseline at 24 hours postexercise. Δ MT decreased (-24.5%) from pre- to 15 minutes postexercise and was not different from either 15 minutes postexercise or baseline by the 24-hour timepoint. Knee extension strength and MQ decreased (-15.6%; 24.2%) from pre- to 15 minutes postexercise and remained below baseline at 24 hours postexercise.

MT measures alone suggested faster recovery from an exercise circuit than knee-extensor strength or MQ, though the combined metric of MQ may be useful for longitudinal monitoring of muscle recovery timelines in rehabilitation programs.