this is a post of mine from long ago on another board:
[b]here's something i don't really understand: guys who divide their splits by muscle groups. i.e. chest and back day, arm day, leg day, and shoulder day.
how does this make sense when the best exercises are compound and hit many muscles at once? how can chest and back day really be chest and back day when doing chins, flat bench, rows, and dips? you're getting total arm involvement, hamstring and lower back tension, delt strain, etc...
doesn't make any sense.
that's why i look at my split in terms of movements or planes of motion. for example, i have 3 upper body days and 2 lower body days. on the upper body days i rotate my exercises every workout. one workout: horizontal plane of motion - upper body press , and upper body pull , the next workout: vertical plane of motion - upper body press and upper body pull
and i also do one lower body press and one lower body pull on my lower body days. i.e. deadlifts and front squats. and i'll hit calves every lower body workout as well.
i mean this is just the basic framework, there's a lot more to it, but i think the idea is clear. [/b]