The Study
Muscle fiber typology is associated with the incidence of overreaching in response to overload training.
This study shows a link between the type of muscles in runners' legs and how they respond to heavy training. It doesn’t prove one causes the other — just that they tend to go together. Think of it like noticing that kids who eat more vegetables are often taller, but not knowing if veggies made them grow or if something else is going on.
Analysis score
Maximum 72 for a cohort study.
Where the score came from
Some runners get too tired to run well after lots of hard training, while others bounce back stronger. This study checked what makes the difference.
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 545 / 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, this matters because it shows that your muscle type might affect how well you handle hard training and recover.
- 212 out of 24 runners performed worse after heavy training.
- 3These runners had higher muscle carnosine levels, which means more fast-twitch muscles.
- 4Runners with lower carnosine (more slow-twitch muscles) kept their performance and improved more after rest.
Score breakdown, methodology, conflicts of interest, evidence analysis & raw study data
Publication
Journal
Journal of applied physiology
Year
2020
Authors
Phillip M Bellinger, B. Desbrow, W. Derave, E. Lievens, C. Irwin, S. Sabapathy, Ben Kennedy, Jonathan Craven, Evan N Pennell, Hal Rice, C. Minahan
Related Content
Claims (4)
Elite middle-distance runners with more fast-twitch muscle fibers (based on certain chemical levels) might be more likely to get overtrained after intense training, while those with more slow-twitch fibers tend to recover better and perform stronger after rest.
When 24 top middle-distance runners did a tough 3-week training plan, half got so worn down that their performance dropped, while the other half felt tired but still performed well — showing that people respond very differently to intense training.
Elite middle-distance runners with more of a certain muscle chemical (carnosine) tend to get worse, not better, after intense training and rest—meaning their performance drops instead of improving.
People with more fast-twitch muscles or who are older may bounce back slower after workouts and are more likely to get overtrained than younger people or those with more slow-twitch muscles.
Not medical advice. For informational purposes only. Always consult a qualified healthcare professional before making health decisions.