Ibuprofen and acetaminophen: effect on muscle inflammation after eccentric exercise

Area of Science:

• Exercise physiology
• Muscle biology
• Pharmacology

Background:

• Eccentric contractions induce muscle damage and inflammation.
• Neutrophils and macrophages are key inflammatory cells involved in muscle repair.
• Non-steroidal anti-inflammatory drugs (NSAIDs) and acetaminophen are commonly used to manage exercise-induced inflammation and pain.

Purpose of the Study:

• To investigate the effects of ibuprofen and acetaminophen on muscle neutrophil and macrophage concentrations after eccentric exercise.
• To determine if therapeutic doses of these analgesics modulate the inflammatory response in skeletal muscle.

Main Methods:

• Twenty-four males underwent knee extensor eccentric contractions.
• Participants received maximal over-the-counter doses of ibuprofen, acetaminophen, or placebo.
• Vastus lateralis muscle biopsies were analyzed for neutrophil and macrophage concentrations using immunohistochemistry before and 24 hours after exercise.

Main Results:

• Macrophage concentrations significantly increased 24 hours post-exercise (1.5- to 2.5-fold).
• Neutrophil concentrations did not show a significant increase post-exercise.
• Neither ibuprofen nor acetaminophen treatment affected muscle inflammatory cell concentrations compared to placebo.

Conclusions:

• Maximal therapeutic doses of ibuprofen and acetaminophen do not alter muscle neutrophil or macrophage concentrations 24 hours after novel eccentric contractions.
• These common analgesics do not appear to modulate the early inflammatory cell response in skeletal muscle following eccentric exercise.