Should I train all muscles or concentrate on some muscles in each session?

Question

Say I train 3 times a week. Which alternative is better:

• Just train all target muscles in each session, no focus on any muscles on any session, or
• Dedicate each session to some muscles. For example: Tuesday for leg and shoulders, Friday for abs and back, Sunday for chest and arms

I'm a beginner and my goal is increase my muscle size. However it would be useful if the answer provided more general guidelines.

So can anyone explain whether I should train all muscles or focus on some muscle groups for a well balanced workout?

PS: I'm a beginner, and the goal is size. However I think it will be useful to explain also how the answer varies depending on the person.

Answer 1

According to the ACE Personal Training Manual (American Council on Exercise (2003). ACE Personal Trainer Manual (3rd ed.). San Diego, CA: American Council on Exercise.):

Because the muscle rebuilding process typically requires about 48 hours, strength workouts should be scheduled on an every-other-day basis. Clients who prefer to train more frequently should avoid working the same muscles groups on consecutive days.

The ASCM (see "Frequency") recommends weight training 3 days per week if doing a total-body workout and 4 days per week if doing a split routine (different muscles on different days, to work each muscle group twice a week).

So, if you know you want to weight train 3 times per week, I would apply this information by recommending you leave 48 hours between each workout and do a full body workout every time. If you work different muscles groups during each of your three workouts, you may not end up meeting the recommendation to hit each muscle group 2-3 times per week.

For completeness, the ACE manual also mentions that more stressful training sessions may require a longer recovery period. In these cases, a split routine (targeting different muscle groups on different days) could be justified.

Answer 2

I love to cite reams of scientific journals and studies to support this but unfortunately most of what I know about effective training comes through the certifications I received, working with successful trainers, and years of training clients myself. What I found in that experience is that beginners benefit the most from full body workout routines. There is a learning period when you first begin weight training and your body is primed to respond by building muscle mass - a lot of phenomenal gains you see comes from people training the first time, and it seems that full body workouts using compound movements (bench, squat, dead-lift, etc.) can provide the best base for this.

As your experience grows, you'll find you can start to break out and working on muscle groups and eventually very experienced trainers (5 - 10 years) find that focusing on specific muscles and even breaking it down by segment (i.e. arms one session, back one session, shoulder one session) provides value. The most successful long term trainers I know phase their training to accommodate all of these models using periodicity - so they'll have a phase of strength that focuses on full-body and compound movements, and another phase they'll call "sculpting" but is really just a focus on specific body parts and perhaps more isolation movements.