When you work more than one muscle simultaneously, you burn more calories and get more of a metabolic effect than you
do with isolation exercises.
By beginning your
workout with isolation exercises which, as the name implies, effectively isolate your chest fibers, you will be able to adequately fatigue your chest before moving on to the multi-joint presses which will engage the front delts and tri's as secondary muscle groups, allowing you to keep on pounding hard and heavy with the assistance of these fresh muscles.
If you want insanely big arms, or insanely strong arms, for that matter, you also need to hit your
arms with isolation exercises designed specifically for that — effectively isolating the target muscle so that you can hammer it with all you've got.
Sometimes he starts the workout
with an isolation exercise making his muscles accumulate a lot of lactic acid, like a single - arm dumbbell extension and then proceed with dips or close grip bench presses and at another workout he would do the exact opposite.
As with all isolation exercises, best results will be obtained by using this lift as an extra on top of compound lifts which work the whole of the legs, such as the leg press or squat.
You can also work your transverses abdominis, to pull your waist in tighter, by doing stomach vacuums but I suggest you don't work your abs
directly with isolation exercises, keep a strong core by performing compound movements and using free weights instead of machines.
For each muscle group it is a good idea to perform two compound movements as the main part of your workout then finish off
with an isolation exercise to fatigue the muscle.