Krank definitely knows his shit and while I agree that muscles don’t know the difference between cables,bands,dumbbells,barbells,weight stack machines,plate loaded machines as stress is stress. Yet at the same time I have to agree with Hankins as to free weight curls whether with dumbbells or barbells definitely seem to build more muscle. There have been times I train hard as hell using bands or machines and my arms actually shrink a bit then when I go back to free weight they grow again. But wtf do I know? Just my personal experience.