Soreness is not an indicator of growth. But it can be used as a diagnostic tool if you’re not getting growth. If you’re not growing and you’re not sore, that could be an indicator that you’re not training hard enough (intensity or volume). But if you’re sore and you’re not growing that could be an indicator you’re training too hard or too much or a recovery issue etc. Then you add drugs into the mix and you might not get sore at all and grow like crazy. Running a marathon will have your legs sore for days, is running a marathon great for Leg growth?