Resistance-trained individuals frequently use non-steroidal anti-inflammatory drugs (NSAIDs) to manage muscle soreness and maintain training intensity. However, the long-term effects of NSAIDs on muscle adaptation are not fully understood. A 12-week, placebo-controlled study unexpectedly revealed that daily diclofenac ingestion in trained men boosted increases in muscle cross-sectional area and volume, especially later in the training period, without affecting strength gains. This hypertrophic effect was linked to specific changes in muscle gene expression, challenging prevailing ideas about the roles of inflammation and recovery in performance. This research review will examine the actual findings of the study and discuss the implications for both trainees and practitioners.
Overview
- What did they test? The study investigated the effect of daily NSAID consumption (75 mg diclofenac) on trained men undergoing 12 weeks of high-intensity resistance training. The researchers assessed changes in muscle size, strength, training workload, and muscle mRNA expression.
- What did they find? NSAID consumption resulted in enhanced muscle cross-sectional area and volume, with the most significant increases observed between weeks 4 and 12. These changes were accompanied by wider alterations in gene networks associated with muscle growth and metabolism. Despite these morphological differences, gains in strength and training work output were comparable between the NSAID and placebo groups.
- What does it mean for you? The prolonged administration of Nonsteroidal Anti-inflammatory Drugs (NSAIDs), such as ibuprofen or naproxen, might contribute to a modest increase in muscle volume during a training regimen; however, it has not been shown to enhance absolute strength or overall athletic performance. Furthermore, chronic use of these medications is associated with established health risks. Consequently, the routine use of NSAIDs for the sole purpose of augmenting training outcomes warrants a cautious approach.
What’s the Problem?
Non-steroidal anti-inflammatory drugs (NSAIDs) are widely and often routinely used by athletes and resistance-trained individuals to reduce pain, soreness, and perceived inflammation during training. This practice is frequently justified by the assumption that blunting pain allows greater training quality and workload, thereby enhancing muscle and strength adaptations. However, NSAIDs inhibit cyclo-oxygenase (COX) activity and prostaglandin production—pathways also involved in muscle protein synthesis, satellite cell activity, and hypertrophic signaling—raising concern that chronic use could impair, rather than enhance, training adaptations.
Complicating this issue, prior research has produced conflicting findings. Acute and short-term studies in young adults suggest NSAIDs may blunt anabolic signaling and hypertrophy, whereas longer-term studies in older adults report enhanced muscle growth with NSAID use during training. Whether chronic NSAID ingestion meaningfully alters muscle hypertrophy, strength, or the molecular response to resistance training in trained young men—and when these effects emerge over time—remains unclear, motivating the purpose and hypothesis of the present study.
Purpose
The aim of the present study was to determine whether daily ingestion of the NSAID diclofenac would positively impact resistance exercise training–induced increases in muscle cross-sectional area (CSA), muscle volume and strength over 12 weeks in young, trained men compared with a blinded placebo intervention.
Hypothesis
This was an exploratory study without an explicitly stated hypothesis where the researchers aimed to examine whether any outcomes observed were localized to a discernible time period of intervention and could be associated with NSAID-mediated changes in targeted muscle mRNA expression and/or training workload volume over time.
