The claimEvidence B · meta-analysis
Cardio kills the muscle you built
The evidence
The interference effect is real but oversold: it shows up mainly with high endurance volume, running more than cycling, and sequencing plus spacing keep the loss small.
The mechanism, in brief
Want both strength and a strong heart — do the two get in each other's way? Yes, but only a little. This is the interference effect: when you do a lot of endurance training at the same time, strength and muscle grow more slowly.
Sources (2)
- Wilson, J. M., Marin, P. J., Rhea, M. R., Wilson, S. M., Loenneke, J. P., & Anderson, J. C. (2012). Concurrent training: A meta-analysis examining interference of aerobic and strength exercises. Journal of Strength and Conditioning Research, 26(8), 2293-2307.
- Hickson, R. C. (1980). Interference of strength development by simultaneously training for strength and endurance. European Journal of Applied Physiology and Occupational Physiology, 45(2-3), 255-263.