Declines in skeletal muscle quality vs. size following two weeks of knee joint immobilization

Rob J MacLennan; Michael Sahebi; Nathan Becker; Ethan Davis; Jeanette M Garcia; Matt S Stock

doi:10.7717/peerj.8224

Declines in skeletal muscle quality vs. size following two weeks of knee joint immobilization

PeerJ. 2020 Jan 13:8:e8224. doi: 10.7717/peerj.8224. eCollection 2020.

Authors

Rob J MacLennan¹, Michael Sahebi¹, Nathan Becker¹, Ethan Davis¹, Jeanette M Garcia², Matt S Stock¹

Affiliations

¹ School of Kinesiology and Physical Therapy, University of Central Florida, Orlando, FL, United States of America.
² Department of Health Sciences, University of Central Florida, Orlando, FL, United States of America.

Abstract

Background: Disuse of a muscle group, which occurs during bedrest, spaceflight, and limb immobilization, results in atrophy. It is unclear, however, if the magnitude of decline in skeletal muscle quality is similar to that for muscle size. The purpose of this study was to examine the effects of two weeks of knee joint immobilization on vastus lateralis and rectus femoris echo intensity and cross-sectional area.

Methods: Thirteen females (mean ± SD age = 21 ± 2 years) underwent two weeks of left knee joint immobilization via ambulating on crutches and use of a brace. B-mode ultrasonography was utilized to obtain transverse plane images of the immobilized and control vastus lateralis and rectus femoris at pretest and following immobilization. Effect size statistics and two-way repeated measures analyses of variance were used to interpret the data.

Results: No meaningful changes were demonstrated for the control limb and the rectus femoris of the immobilized limb. Analyses showed a large increase in vastus lateralis echo intensity (i.e., decreased muscle quality) for the immobilized limb (p = .006, Cohen's d = .918). For vastus lateralis cross-sectional area, no time × limb interaction was observed (p = .103), but the effect size was moderate (d = .570). There was a significant association between the increase in vastus lateralis echo intensity and the decrease in cross-sectional area (r = - .649, p = .016).

Conclusion: In female participants, two weeks of knee joint immobilization resulted in greater deterioration of muscle quality than muscle size. Echo intensity appears to be an attractive clinical tool for monitoring muscle quality during disuse.

Keywords: Disuse; Muscle; Neuromuscular; Physical therapy; Quadriceps; Ultrasound.

Grants and funding

Funding support for this study was provided by the De Luca Foundation Research Scholarship program to Mr. Rob MacLennan, as well as the University of Central Florida’s Advancement of Early Career Researchers program to Dr. Matt Stock. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.