Ibuprofen Differentially Affects Supraspinatus Muscle and Tendon Adaptations to Exercise in a Rat Model

Abstract

Background Previous studies have shown that ibuprofen is detrimental to tissue healing following acute injury; however, the effects of ibuprofen when combined with non-injurious exercise are debated. Hypothesis We hypothesized that administration of ibuprofen to rats undergoing a non-injurious treadmill exercise protocol would abolish the beneficial adaptations found with exercise but have no effect on sedentary muscle and tendon properties. Study Design Controlled laboratory study Methods Rats were divided into exercise or cage activity (sedentary) groups and acute (a single bout of exercise followed by 24 hours of rest) and chronic (2 or 8 weeks of repeated exercise) time points. Half of the rats received ibuprofen to investigate the effects of this drug over time when combined with different activity levels (exercise and sedentary). Supraspinatus tendons were used for mechanical testing and histology (organization, cell shape, cellularity), and supraspinatus muscles were used for morphological (fiber CSA, centrally nucleated fibers) and fiber type analysis. Results Chronic intake of ibuprofen did not impair supraspinatus tendon organization or mechanical adaptations (stiffness, modulus, max load, max stress, dynamic modulus, or viscoelastic properties) to exercise. Tendon mechanical properties were not diminished and in some instances increased with ibuprofen. In contrast, total supraspinatus muscle fiber cross-sectional area decreased with ibuprofen at chronic time points, and some fiber type-specific changes were detected. Conclusions Chronic administration of ibuprofen does not impair supraspinatus tendon mechanical properties in a rat model of exercise but does decrease supraspinatus muscle fiber cross-sectional area. Clinically, these findings suggest that ibuprofen does not detrimentally affect regulation of supraspinatus tendon adaptions to exercise but does decrease muscle growth. Individuals should be advised on the risk of decreased muscle hypertrophy when consuming ibuprofen. This fundamental study adds to the growing literature on the effects of ibuprofen on musculoskeletal tissues and provides a solid foundation on which future work can build. Clinical Relevance Ibuprofen is a commonly used drug by sedentary individuals and athletes. This study suggests that ibuprofen has tissue-dependent effects that should be considered when prescribing the drug.

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“…Mechanical Testing. Supraspinatus-humerus complexes were isolated and prepared for mechanical testing, as described [45]. Briefly, muscle was fine dissected from the tendon and Verhoeff's stain lines were placed at the bony insertion site and 8 mm distally.…”

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