Endurance activates and resistance activates , and the two cross-inhibit inside the cell, the molecular basis of the concurrent training interference effect.Endurance activates (energy sensor → mitochondrial biogenesis); resistance activates (nutrient/mechanical sensor → MPS). These cross-inhibit intracellularly — AMPK phosphorylates and inhibits ; mTOR negatively feeds back to AMPK. This is the molecular basis of the concurrent training interference effect.
2 · Magnitude · running vs cycling
show interference is real but moderate: concurrent training yields about 10-30% less strength and hypertrophy than resistance alone, and running interferes more than cycling. (Wilson 2012, Coffey 2017) show interference is real but moderate: concurrent training produces ~10-30% less strength and hypertrophy than resistance alone. Running > cycling — eccentric lower-limb work (running) creates more interference. Effect grows with volume and frequency.
3 · How to mitigate
Separating sessions by more than 6 hours, doing resistance before endurance, choosing low-intensity steady-state cardio, periodizing and eating enough protein and carbs after training all reduce interference.① Temporal separation: >6h between sessions (ideally AM/PM). ② Order: resistance before endurance ( window first). ③ Mode: LISS interferes less than . ④ Periodization: don't peak both simultaneously. ⑤ Nutrition: adequate protein+carbs post-training to support MPS.
4 · Don't skip cardio because of this
For 99% of people, interference costs far less than skipping cardio does, and only advanced trainees chasing strength or muscle peaks need to manage it carefully.For 99% of people, the practical impact of interference is far smaller than the cost of skipping cardio (cardiovascular health, metabolic health, body fat management). Only advanced trainees (>2 years systematic training) chasing strength/hypertrophy peaks need to carefully manage interference. For most, concurrent benefits >> losses.