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
'I want both muscular strength and good cardio — will they fight each other?' This is the famous 'interference effect', discussed since Hickson's 1980 observation.
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. Concurrent endurance work attenuates strength and hypertrophy gains (modality- and volume-dependent); running interferes more than cycling.
- 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. The original 'interference effect' study: 10-week combined training group plateaued in strength at week 8, while strength-only kept gaining.