Acetaminophen and Impaired Musculoskeletal Adaptations to Exercise Training

The commonly used pain relievers acetaminophen and ibuprofen may impair musculoskeletal adaptations to progressive resistance exercise training by inhibiting exercise-induced muscle protein synthesis.

To test the hypothesis that acetaminophen and ibuprofen would diminish training-induced increases in fat-free mass, untrained men (n=26) aged ≥ 50 years participated in 16 weeks of high-intensity progressive resistance exercise training and bone-loading exercises and were randomly assigned to take ACET (1000 mg), ibuprofen (400 mg) or placebo 2 hours before each exercise session.

The primary outcome was the change in total body fat-free mass measured by dual-energy X-ray absorptiometry (DXA) at baseline and week 16. Our primary interest was in the comparison of the acetaminophen and placebo groups.

Inclusion criteria

• average use of acetaminophen and non-steroidal anti-inflammatory drugs (NSAIDs) [including aspirin] less than 3 days per month
• not currently engaged in moderate-to-vigorous weight-lifting exercise
• non-smoker
• willing to participate in a supervised exercise program for 9 months

Exclusion criteria

• relative or absolute contraindications to regular use of acetaminophen or NSAIDs including known allergy or intolerance to either drug,history of peptic ulcer or GI bleeding, anemia, asthma with bronchospasm induced by aspirin or other NSAIDS, moderate or severe renal impairment, known hepatobiliary disease
• contraindications to exercise testing and training including congestive heart failure class III or IV, uncontrolled hypertension and unstable cardiovascular disease
• thyroid dysfunction
• orthopedic problems that limit the ability to perform vigorous exercise or increase the likelihood of the use of pain medications
• drugs known to alter bone metabolism
• allergy to lidocaine
• diabetes mellitus requiring pharmacologic therapy