When lifting for a range of 4-6 reps, you would need to lift more than 60% of your 1RM. My post was in reference to lifting less than 60% of your 1RM would deliver hardly any, if any strength improvements. Lifting in the 4-6 rep range is lifting moderately heavy and should deliver good gains in strength. If you lift 4-6 reps, make sure your lifting HARD and HEAVY. I usually spread out my rep range. Starting at 10-12, finishing at 4-6, weight increases every set for up to 4 sets for compound exercises.