An examination of changes in skeletal muscle thickness, echo intensity, strength and soreness following resistance exercise

Abstract

It is suggested that changes in echo intensity (EI) measured through ultrasound can detect muscle swelling. However, changes in EI have never been examined relative to a non-exercise control following naïve exposure to exercise.

Purpose: Examine the changes in muscle thickness (MT), EI and isometric strength (ISO) before, immediately after, and 24, and 48 hr following biceps curls.

Methods: Twenty-seven non-resistance-trained individuals visited the laboratory four times. During visit 1, paperwork was completed and strength was measured. During visit 2, MT and ISO were measured before four sets of curls. Additional measures were taken immediately after exercise, as well as 24 and 48 hr post. Results are displayed as means (SD).

Results: For MT, there was an interaction (p < .001). For the experimental condition, MT increased from pre [2.88(0.64) cm] to post [3.27(0.67) cm] and remained elevated 48 hr post. There were no changes for MT in the control arm. In the experimental arm, EI increased from pre [22.9(9.6) AU] to post [29.1(12.3) AU] exercise and returned to baseline by 24 hr. For the control condition, EI was different between pre [24.8(10.2) AU] and 48 hr [21.5(10.7) AU]. The change in EI in the experimental condition was greater than the control condition immediately post (p = .039) and at 48 hr (p = .016). For ISO, there was an interaction (p < .001). In the experimental condition, ISO decreased from pre [40.6(14.7) Nm)] to post [24.8(9.4) Nm] and remained depressed.

Conclusions: Exercise produced a swelling response, which was elevated 48 hr post. Despite a sustained increase in MT, EI was only elevated immediately post exercise.

Keywords: B-mode ultrasound; echo intensity; muscle growth; muscle swelling; muscle thickness.