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Updated: Apr 18, 2026

Human Skeletal Muscle Biopsy Procedures Using the Modified Bergström Technique
Published on: September 10, 2014
Quantitative and qualitative adaptations of muscle fibers to glucocorticoids
Marco Alessandro Minetto1, Rizwan Qaisar2, Valentina Agoni2
1Division of Endocrinology, Diabetology and Metabolism, Department of Medical Sciences, University of Turin, Corso Dogliotti, 14, 10126, Turin, Italy.
Introduction:
The aim of this study was to understand the effects of short-term glucocorticoid administration in healthy subjects.
Methods:
Five healthy men received dexamethasone (8 mg/day) for 7 days. Vastus lateralis muscle biopsy and knee extension torque measurement were performed before and after administration. A large number of individual muscle fibers were dissected from the biopsy samples (pre-administration: n = 165, post-administration: n = 177).
Results:
Maximal knee extension torque increased after administration (∼ 13%), whereas both type 1 and type 2A fibers had decreased cross-sectional area (type 1: ∼ 11%, type 2A: ∼ 17%), myosin loss (type 1: ∼ 18%, type 2A: ∼ 32%), and loss of specific force (type 1: ∼ 24%, type 2A: ∼ 33%), which were preferential for fast fibers.
Conclusion:
Short-term dexamethasone administration in healthy subjects elicits quantitative and qualitative adaptations of muscle fibers that precede (and may predict) the clinical appearance of myopathy in glucocorticoid-treated subjects.
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