Effective training split: what does the science say?
One of the biggest decisions individuals have to make when starting a workout routine is choosing what workout split (or “workout schedule”) they’re going to use. Simply put, this means how you’re going to schedule your exercises throughout the week. There are advantages and disadvantages to split training, which most of us know through experience. Therefore, let’s examine this with some science.
Training split routines are highly popular and discussed just as often as most performance and nutrition topics. A primary benefit of a split routine is the ability to increase per-workout volume while affording ample recovery between sessions.
A study by Hackett, Johnson & Chow surveyed 127 competitive bodybuilders and found that every respondent trained with a split routine. Every single one! In addition, 2/3 of respondents trained each muscle group only once per week — commonly known as a “bro split” — and none worked a muscle more than twice weekly. The main premise behind such routines is that growth is maximized by training a muscle with multiple exercises from multiple angles and then allowing long periods of recovery.
If you look into the old school training from the 1960’s and 70’s, you’ll often find bodybuilders doing total body routines, working all muscles each session over three-consecutive days a week. Historically, these methods have been largely based on anecdote and previously long-held beliefs. Surprisingly, up until the last 3-4 years, little research has been carried out on the topic, and no study had directly compared muscle growth in a total-body routine versus a bro split.
So the question is: should you do the bro split and work out five days a week? Should you split up your routine into upper and lower body rotations and work out four days a week?
Alternatively, should you do a full body workout three days a week?
Let’s highlight some science about training frequency.
A recent meta-analysis by Schoenfeld et al. (2016) examined when volume is matched, training each muscle at least 2x per week results in significantly greater muscle growth than training each muscle just once per week as you do in a bro split.
In a previous study by Schoenfeld et al. (2015), they examined nineteen young men with an average of more than four years lifting experience and were randomly assigned to a resistance training program using either a total-body or split-body routine (2-3 muscle groups worked per session).
The program consisted of 21 different exercises spread out over three days per week training cycle. The volume of the routines were matched so that both groups performed an equal number of sets and reps over the course of each week. All subjects performed three sets of 8-12RM per exercise. Training was carried out for eight weeks. Furthermore, subjects were tested pre- and post-study and the researchers used a B-mode ultrasound to measure the thickness of the biceps, triceps, quads, and assessed maximal strength via 1RM for the back squat and bench press. In addition, subjects were advised to consume their normal diets and they monitored food intake by analysis of a self-reported diary.
What did they find?
Subjects in both groups significantly increased hypertrophy in the arm and leg muscles. Interestingly enough, muscle mass increased significantly more in the biceps/brachialis for the group performing total body training compared with those in the split routine group. There was a trend for greater increases in the quads (i.e. vastus lateralis) and the effect size highly favored the total body group. Although no significant between-group differences were found in tricep thickness, the effect size again showed an advantage to total body training.
With respect to strength, both groups significantly increased 1RM performance in the bench press and squat from baseline. There were no significant between-group differences in either of these measures, although the effect size for the bench press did seem to favor the total body group.
The downside of higher frequency is that you may feel obligated to train more, like 4–6 times per week. However, more is not necessarily better. In fact, a 2018 study by Yue et al. showed that training each muscle two times a week is better for muscle growth vs. training four times a week.
Lastly, another recent paper by Ochi et al. found that training each muscle 3x per week as you do in a full-body split, is not only more effective at improving strength in untrained individuals when compared to lower training frequencies.
On the surface it would seem that a total-body routine from Schoenfeld et al. (2015) is superior to a one-muscle-per-week bro split for building muscle. All of the muscles investigated showed greater growth from a higher training frequency. For the biceps, these results were “statistically significant,” but could also be biologically or practically significant too. While results in the quads and triceps did not reach “significance,” other statistical measures indicate a pretty clear advantage for the higher frequency routine. These results would seem to be consistent with the time-course of muscle recovery and regeneration, which lasts approximately 48 hours (depending on lifting experience).
However, let’s go down the next layer.
It’s important to remember that the study equated volume between conditions. This was done to isolate the effects of frequency on muscular adaptations. Due to the split routines ability to provide ample time between sessions to increase or maintain workout volume, there is a clear dose response relationship between volume and hypertrophy, total weekly volume needs to be factored into all workouts. Certainly it’s possible that a split routine with a higher weekly volume would have performed as well or even better than the total body routine. Or perhaps not, as these questions have still not yet been thoroughly answered with large consensus. Perhaps, participants in the total body group benefited from the unconventional method of higher frequency training, per this study.
Application and take aways
It’s no surprise that benefits exist to training more frequency in order to maximize strength and hypertrophy. Therefore, it’s best to directly work each muscle at least twice a week; any less and you’re probably not stimulating protein synthesis frequently enough to optimize muscle hypertrophy. Training each muscle group three times a week, at least for periods of time, can often provide additional benefits. However, the return on investment from increased frequency can often backfire as adequate recovery between training sessions is significantly reduced.