The Study
Evidence for Simultaneous Muscle Atrophy and Hypertrophy in Response to Resistance Training in Humans
This study watched a small group of people do a 10-week workout program and measured their muscles. It can show that muscle size went up or down while they trained, but it cannot prove the workout caused those changes because there was no comparison group to see what would have happened without the workout.
Analysis score
Maximum 72 for a cohort study.
Where the score came from
A 10-week study tracked how muscles change when people do targeted resistance training. It found that while the worked muscles grew, some unworked muscles actually shrank. Eating more protein and calories helped prevent this shrinkage and supported overall muscle growth.
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 539 / 100
Quality score
Groups of people are followed over time to see who develops an outcome. Strong for identifying risk factors and associations, but cannot prove causation as firmly as RCTs.
Key takeaways
Summary
Based on the study abstract and findings.
- 1Yes, the findings are significant for humans as they demonstrate that resistance training can cause simultaneous muscle growth and shrinkage depending on the muscle group, and that nutrition plays a direct role in managing this trade-off.
- 2Targeted muscles grew by 2.2% to 17.7%.
- 3Untargeted adductor magnus and soleus muscles shrank by 1.5% and 2.4% respectively.
- 4Higher protein and calorie intake correlated with better muscle growth and less shrinkage.
Score breakdown, methodology, conflicts of interest, evidence analysis & raw study data
Publication
Journal
Medicine & Science in Sports & Exercise
Year
2024
Authors
K. Van Vossel, Julie Hardeel, Thibaux Van der Stede, Tom Cools, Jonas Vandecauter, Lynn Vanhaecke, Jan Boone, Silvia S. Blemker, E. Lievens, W. Derave
Related Content
Claims (5)
Eating more calories helps keep your leg muscles from shrinking, even the ones you aren't directly working out during strength training.
If you do targeted strength training for a few weeks, the muscles you work will grow bigger, but the muscles you don't use during those exercises might actually shrink a little bit. This happens because your body adapts specifically to the exact movements you're doing.
Eating more protein while lifting weights for 10 weeks is linked to bigger muscles and less muscle loss, specifically in the thigh muscle.
When you do strength training while not eating enough calories or protein, your body might build muscle in the areas you're working while actually shrinking muscle in the areas you're not. It's like your body is shifting resources from one place to another to cope with the stress and low fuel.
When people new to weightlifting don't eat enough calories, they actually lose muscle in body parts they aren't even working out. But if they eat enough food, their muscles stay the same size even in those untrained areas.
Not medical advice. For informational purposes only. Always consult a qualified healthcare professional before making health decisions.