The interference effect is real but wildly overstated. Concurrent training research shows meaningful interference only when conditioning is high-volume, high-impact, and stacked directly against leg training. Managed properly, a bigger engine makes you a better lifter: faster recovery between sets, more work capacity, better nutrient partitioning.
The hierarchy for lifters: low-intensity comes first. 2-3 weekly sessions of 30-45 minutes of zone 2 work—incline walking, cycling, sled dragging—build the aerobic base with essentially zero recovery cost. This is the foundation, and most lifters skip it because it isn't impressive on camera.
High-intensity work is a spice, not a meal. One or two sessions weekly of 10-15 minutes: bike sprints, hill runs, sled pushes. Keep them short, keep them away from leg day by at least 24 hours, and stop while you could still do one more round.
Modality matters. Cycling and sled work interfere least with lifting because there's no eccentric damage. Running interferes most—every stride is a small eccentric hit your legs must recover from alongside your squat volume. If you love running, run; just count it as leg work.
The payoff compounds: lifters with a real aerobic base recover faster between sets, handle more weekly volume, and stay leaner at higher calories. Build the engine. Keep the armor.