depends on the muclegroup. i might do i or 2 machine movments if i feel that it will help develpe a muscle. like for instance low pulley rows for back, pushdowns for triceps, lex ext for quads, leg curls for hams, calf raise for (suprise) calves. people who are saying machine movments arent worth shit are wrong. they may not require as much help from other muscles, both they do help you focus one that one musclegroup.