I work a particular part of my body at once. But to ensure balance in strength development, I always start with the “opposite group” prior to the true workout. As the biceps is opposed to the triceps, pecs to upper back, abs to lower back, I make sure that I train both accordingly.
So when I’m doing upper back training, I’ll always do pecs-set too. So one set of 20 pushups to warm my body up for a full upper back workout. One set of 30 crunches, before I do my 3×12 deadlifts and 3×12, etc. And later in the week, it’ll be vice versa.
This means that I’ll train a bodypart extensively only once a week, albleit with a small “maintenance” set..
This is my usual schedule
Sunday: main course: upper back, casualty: pecs.
Monday: biceps, casualty: triceps. Abs-lower back
Wednesday: pecs, minor: upper back. Shoulders-obliques
Thursday: lower back-abs
Friday: legs, calves
Saturday: rest.
Sunday: one superset of squats, pushups, pullups and crunches
