Questions for dumbbell users?

for what?

arms?

shoulders?

back?

for biceps

no more then 4 sets 6-8 reps for size

but barbells build mass, dumbbells build peak and isolate muscles

1) the same as you would do when using a barbell or machine (but be careful, just because you can bench 200 pounds doesnt mean you can just go ahead and grab the same weight in dumbells, I can bench 145 with a barbell but only use 60 pound dumbells)

2) 1 minute to 1 minute and thirty seconds

3) Id say 4 sets on your big movements that use alot of different muscles (Benchpress, shoulder press, squats, deadlifts, pull ups, bent over rows etc) and 3 sets of isolation movements (like bicep curls, and tricep pushdowns.

I can only answer Q1 as my dad also uses Dumbell and he tells me how many reps he did per go.

About 5-10 if you can. My dad did 8!