Do nonsteroidal anti-inflammatory drugs (NSAIDs) affect muscle hypertrophy and strength gains in healthy adults?

NSAIDs May Impair Muscle Growth in Healthy Adults

Based on the most recent and highest-quality evidence, high-dose NSAIDs (specifically ibuprofen at 1200 mg/day) significantly impair muscle hypertrophy and strength gains during resistance training in young, healthy adults, while moderate doses (400 mg/day) appear safe. However, a 2025 study challenges this by showing enhanced hypertrophy with diclofenac, creating a complex clinical picture.

The Evidence Landscape

High-Dose NSAIDs: Clear Negative Impact

The strongest evidence comes from a 2018 randomized controlled trial 1 demonstrating that maximal over-the-counter doses of ibuprofen (1200 mg/day) reduced muscle hypertrophy by approximately 50% compared to low-dose aspirin (75 mg/day) over 8 weeks of resistance training. Specifically:

• Muscle volume increase: 3.7% with ibuprofen vs. 7.5% with aspirin (difference of 34 cm³, p=0.029)
• Strength gains were also attenuated in the ibuprofen group, particularly with maximal effort training
• The mechanism appears independent of traditional hypertrophy pathways (mTOR signaling, satellite cells, myonuclear accretion remained similar between groups) 2

Moderate-Dose NSAIDs: Likely Safe

In stark contrast, a 2008 study 3 found that moderate-dose ibuprofen (400 mg/day) had no negative effect on muscle hypertrophy or strength gains during 6 weeks of resistance training. Both arms showed similar increases in muscle thickness (8%) and strength (25%).

The 2025 Paradox: Enhanced Hypertrophy?

Most recently, a 2025 study 4 reported that diclofenac (75 mg/day) actually increased muscle hypertrophy MORE than placebo during 12 weeks of resistance training:

• Muscle CSA increase: 8.6% with diclofenac vs. 3.9% with placebo at 84 days (p=0.038)
• The enhanced hypertrophy occurred predominantly between days 28-84
• However, strength gains were identical between groups (~40-50% increase in both)
• Multiple gene networks related to muscle mass regulation were more altered with diclofenac

Clinical Interpretation: The Dose-Response Relationship

The evidence suggests a critical dose-dependent threshold:

• ≤400 mg/day ibuprofen: No impairment of muscle growth 3
• 1200 mg/day ibuprofen: Significant impairment (~50% reduction in hypertrophy) 1
• 75 mg/day diclofenac: Possible enhancement of hypertrophy but without functional strength benefits 4

The Disconnect Between Size and Function

The 2025 diclofenac study reveals a crucial caveat: enhanced muscle size does NOT translate to enhanced performance 4. This dissociation between hypertrophy and strength suggests that NSAID-induced muscle growth may be qualitatively different—potentially involving edema, altered protein composition, or non-functional tissue expansion rather than true contractile protein accretion.

Practical Recommendations

For Athletes and Individuals Seeking Muscle Growth:

Avoid chronic NSAID use during resistance training programs, particularly at high doses. The risk-benefit ratio is unfavorable:

• High-dose NSAIDs (≥1200 mg/day ibuprofen) clearly impair muscle adaptation 1
• Even if some NSAIDs increase muscle size, they don't improve strength 4
• Athletes commonly overuse NSAIDs 5, which also increases gastrointestinal complications 6

Specific Guidance:

1. If pain management is needed during training:

   • Use acetaminophen as first-line (up to 3000 mg/day in divided doses)
   • If NSAIDs are necessary, limit to ≤400 mg/day ibuprofen
   • Use for shortest duration possible (days, not weeks)

2. For acute sports injuries:

   • NSAIDs are appropriate for short-term use (≤7 days) 7, 8
   • Topical NSAIDs may provide localized benefit with less systemic exposure 9, 8
   • Discontinue once acute inflammation resolves

3. Avoid NSAIDs:

   • During structured hypertrophy training phases
   • In the pre-competition period for athletes 5
   • In individuals with history of GI bleeding, cardiovascular disease, or renal impairment 6, 10

Common Pitfalls to Avoid

1. Chronic "preventive" NSAID use: Many athletes take NSAIDs prophylactically before training—this practice should be strongly discouraged 5

2. Assuming all NSAIDs are equivalent: The evidence shows different effects between agents and doses; diclofenac may behave differently than ibuprofen 4, 1

3. Ignoring the strength-hypertrophy disconnect: Larger muscles without greater strength provide no performance benefit and may indicate pathological adaptation 4

4. Overlooking GI and CV risks: NSAIDs cause 3-5 fold increased risk of serious GI complications 6 and cardiovascular events 10, risks that persist throughout use

The Bottom Line

For healthy adults engaged in resistance training to maximize muscle growth and strength, chronic NSAID use—particularly at high doses—should be avoided. The 2018 evidence 1 showing ~50% reduction in hypertrophy with high-dose ibuprofen is compelling and clinically significant. While the 2025 diclofenac study 4 suggests possible hypertrophy enhancement, the absence of functional strength gains makes this finding clinically irrelevant for performance and potentially concerning for muscle quality.

When NSAIDs are medically necessary, use the lowest effective dose for the shortest duration, and consider acetaminophen or topical NSAIDs as alternatives. The widespread overuse of NSAIDs in athletic populations 5 represents a modifiable factor that may be limiting training adaptations in countless individuals.