The Study
Low-Load x High-Load Resistance Exercise: Greater Cell Swelling After a Training Session.
This study compared two ways of lifting weights and saw what happened right after—like how much your arm swelled up or how much lactic acid built up. It doesn't prove one way makes your muscles bigger over time, just what happens right after you lift.
Analysis score
Maximum 90 for a randomized controlled trial.
Where the score came from
When you lift weights and feel your muscles swell up (the 'pump'), it's because fluid rushes in — but this study shows that feeling the pump doesn't actually make your muscles grow bigger over time.
Where does this study sit?
Reviews of RCTs (Meta-analyses)
Max 100Randomized Trials
Max 90Reviews of Cohort Studies
Max 85Cohort Studies
Max 72Reviews of Case-Control Studies
Max 63Case-Control Studies
Max 58Cross-Sectional & Case Series
Max 50Expert Opinion
Max 559 / 100
Quality score
Participants are randomly assigned to treatment or control groups, minimizing bias. The gold standard for testing whether an intervention causes an effect.
Key takeaways
Summary
Based on the study abstract and findings.
- 1Even though the pump feels intense and happens with both light and heavy weights, it's just a temporary fluid shift — not a signal for long-term muscle growth.
- 2After lifting, muscles swelled 11.5–18.9% and blood lactate rose 105–164% in both light and heavy lifting, with light lifting causing slightly more swelling and more reps.
Score breakdown, methodology, conflicts of interest, evidence analysis & raw study data
Publication
Journal
International journal of exercise science
Year
2023
Authors
G. I. Agentilho, E. D. de Lucena, L. Teixeira, V. V. Boas, I. Ribeiro, R. Barroso, B. Schoenfeld, M. Uchida
Related Content
Claims (7)
High-volume resistance training leads to muscle swelling due to fluid buildup, and this swelling can last for up to 72 hours after the workout.
After resistance training, muscle thickness increases temporarily due to fluid shifts inside muscle cells caused by metabolic byproducts and the length of mechanical stress, but this does not mean the muscle will grow permanently.
That muscle 'pump' you feel when lifting weights? It might feel like growth, but this claim says it doesn't actually cause your muscles to get bigger over time.
In well-trained adult males, resistance training with light weights and heavy weights, when performed with the same total work, increases elbow muscle thickness and blood lactate levels within 10 minutes after exercise, with light weights producing a greater increase in both measures.
In trained males, blood lactate levels rise by 105–164% after resistance training, whether using light or heavy weights, as long as the total amount of work is the same, and the increase is not different between the two conditions.
In trained men, resistance training causes a measurable increase in muscle thickness between 11.5% and 18.9%, whether heavy or light weights are used, and this change occurs alongside consistent swelling within muscle cells during exercise.
Not medical advice. For informational purposes only. Always consult a qualified healthcare professional before making health decisions.