In the body building world, split routines have become to go to for maximizing the amount of training allowed in a week. A split routine consists of targeting specific muscle groups every day rather than working all major lifts at one time. A common example is Day 1 – Legs, Day 2 – Chest + back, Day 3 – Shoulders + Biceps + Triceps, Day 4 – Rest, performing multiple exercises for each group on the specified day. This cycle allows for 6 days of work per week rather than the traditional 3 days associated with full body sets. This month, a group of researchers out of Lehman published an analysis of the effects of split training versus those of full body training to The Journal of Strength and Conditioning Research. The full article can be found here.
In this study, 20 participants were randomly assigned to one of two groups. The first group was assigned to a full body workout routine in which they exercised three times per week working each muscle group once per session. The second group was assigned to a split routine in which the worked out three times per week but only worked 2-3 muscle groups per session but worked those groups multiple times. Progress for both groups was assessed by one repetition maximums and muscle size. After 8 weeks, researcher found no correlation between training style and one rep maxes or forearm hypertrophy (muscle growth). They did find increased muscle size in the biceps and triceps of the split group, however the relative growth was so small (1.1mm, 1.3mm respectively) the application is questionable.
What this study reveals is that ultimately total volume is more important than the specific splits or routines. That being said, split routines typically do allow for more weekly volume than full body routines. On a split routine you can hit the same muscle groups six times per week in with standard one hour workouts. For a full body routine, you are limited by recovery days and would most likely need two hour sessions to reach the same amount of volume. But if the total volume is held constant, this study tells us that there is not magic benefit to either a split or a full body routine. Routine should be determined by what allows the most volume in your schedule on a consistent basis.