It has long been recognized that volume is a key mediator of muscle growth. Thus, from a muscle growth perspective, the idea of using high volumes has some merit. Considering that mechanical tension, muscular damage, and metabolic stress appear to be the primary drivers of hypertrophy, increasing volume should in theory contribute to greater muscular damage and potentially more metabolic stress compared to low volume protocols. Furthermore, one indicator of muscular damage is delayed onset muscle soreness (DOMS). This has led many to judge the effectiveness of a program based on the DOMS achieved by the workout.
This thinking has led many to follow a body-part split (“bro split”), allowing a full workout to be dedicated to targeting usually 1-3 muscle groups in a day. This allows for large amounts of part-specific volume to be achieved and often results in increased DOMS. The downside is that using a split routine means that in order to train the entire body, one must workout for 3-4 days. Furthermore, the muscle groups often go an entire week before being trained again.
Going this long between workouts is problematic for one main reason. Muscle protein synthesis (MPS), an indicator of how much muscle is being synthesized in the body, typically increases about 50% at 4 hours post-workout, 109% by 24 hours, and returns to baseline by 36 hours post workout. Some people return to baseline sooner, some later. Essentially the anabolic stimulus of the workout has a time-frame of effectiveness before needing to be repeated. Waiting too long between training a muscle group could compromise muscular growth.
One alternative to this approach is to perform full-body workouts. The downside to this approach is that each workout results in less training volume per muscle per workout. The upside is that the workouts may be performed more frequently because the lower training volume results in faster recover and less DOMS. This conceivably would allow for a more optimal time course of elevated MPS. Moreover, a similar level of total weekly volume could be accomplished compared to a split routine when considering the increased workout frequency.
Schoenfeld and colleagues (2015) compared a group performing a traditional “bro split” to a volume-equated full-body split. Each group trained 3 days per week and did the same exercises. The subjects were trained bodybuilders. Interestingly, the results indicated a slight superiority in muscular growth in the full-body group.
Another newly published 8-week study compared lean mass and strength gains between a once a week high volume (9 sets per muscle group) and a 3 times per week low volume (3 sets per muscle group). Groups differed only in daily workout volume; however, total weekly volume was the same. The results indicated that there were no differences between the two protocols for strength and size gains.
Although the results may be surprising and someone ambiguous, there are a number of potential explanations. Further analysis of the subjects in the first study reveals that most were previously using a body part split. Thus, there may be a novelty factor at play. Another explanation could be that the increased frequency of training may have resulted in a more favorable elevation in the MPS curve. Of course, the results from the second study does not appear to be in agreement. In fact, the “bro split” group had equal muscle and strength gains, despite not obtaining the same volume-load due to muscle group fatigue.
All together, the best recommendations I can give regarding what type of split to choose would be this:
- Consider the novelty factor. If you’ve been using a particular split for a while, try changing it up.
- Keep the elevated MPS time-frame in mind when designing your program.
- Consider finding a happy medium between full body workouts and single muscle workouts. Find what works best for you.
- Consider how many days you can dedicate to training. If you only have 3 days a week to lift, a full body program might be your best bet. If you can dedicate 6-7 days a week to training, using more of a split plan may offer more bang for your buck and help prevent overtraining.
- Use self-experimentation. If you don’t notice improvements from a particular program, switch it up.
- Always aim for progress through progressive overload.