The training split debate is one of the most passionate and least productive arguments in fitness. People defend their preferred split like it is a political identity. PPL loyalists will tell you it is the only way to build a complete physique. Full body advocates insist that anything else is suboptimal. Upper/lower fans sit in the middle, quietly making gains while everyone else argues.
The truth, as it usually does, lives in the nuance. And the research on this topic is actually quite clear - just not in the way most people want it to be.
What the Science Says About Training Frequency
Before we compare specific splits, we need to understand the underlying variable that makes splits matter: training frequency. How often you train each muscle group per week is far more important than what you call your split.
Brad Schoenfeld's 2015 meta-analysis, published in Sports Medicine, examined the effects of training frequency on muscle hypertrophy. After pooling data from 10 studies, the conclusion was clear: training a muscle group at least twice per week was associated with significantly greater hypertrophy compared to training it once per week. The effect size was meaningful - not trivial.
This finding makes sense when you understand the biology. After a resistance training session, muscle protein synthesis (MPS) - the process by which your body builds new muscle tissue - is elevated for roughly 24 to 48 hours in trained individuals. In beginners, this elevation can last up to 72 hours. After that window, MPS returns to baseline, and your muscles are essentially just sitting there waiting for the next stimulus.
If you train chest on Monday with a traditional "bro split" and do not touch it again until the following Monday, you get one MPS spike per week. If you train chest on Monday and Thursday, you get two. Over the course of months and years, those extra synthesis windows add up to substantially more total muscle growth.
But Does Frequency Have a Ceiling?
A reasonable question: if two times per week is better than once, is three times per week better than two? The evidence here is less definitive. A 2019 study by Schoenfeld and colleagues compared training each muscle group three times per week versus once per week (with volume equated) and found similar hypertrophy outcomes. However, a later analysis by Grgic and colleagues (2018) suggested that there may be a small additional benefit to training each muscle three times per week, though the effect was not statistically significant in most comparisons.
The practical interpretation: hitting each muscle at least twice per week is clearly better than once. Going to three times per week may offer a small additional benefit, but it is not a game-changer if your total weekly volume and effort are adequate. The biggest jump in results comes from going from once per week to twice per week.
Breaking Down the Big Three Splits
Full Body Training (3 Days Per Week)
In a full body split, you train every major muscle group in each session, typically three days per week (Monday, Wednesday, Friday or similar). Each muscle group gets hit three times per week with relatively low per-session volume.
The case for it: Full body training naturally delivers high frequency, which aligns with the research on MPS optimization. It is also incredibly time-efficient - three gym sessions per week is all you need. For beginners and intermediates, it provides ample stimulus and recovery time. Studies like those reviewed by Schoenfeld (2015) frequently used full body protocols in their frequency comparisons, and the results consistently showed excellent hypertrophy outcomes.
The case against it: As you advance and need higher per-muscle-group volume to continue growing, full body sessions become extremely long and fatiguing. Trying to fit 16 sets of quads, 16 sets of back, 12 sets of chest, and accessory work for shoulders and arms into a single session is impractical. Exercise quality degrades as the session drags on, and systemic fatigue accumulates faster than local fatigue. By the time you get to your fourth or fifth movement, you are running on fumes.
Best for: Beginners, intermediates training 3 days per week, people who prioritize time efficiency, and lifters returning from a layoff.
Upper/Lower Split (4 Days Per Week)
Upper/lower alternates between upper body days and lower body days, typically run four days per week (upper Monday, lower Tuesday, rest Wednesday, upper Thursday, lower Friday). Each muscle group gets trained twice per week.
The case for it: This split hits the research-backed frequency sweet spot of twice per week per muscle group while keeping per-session volume manageable. You have enough time in each session to do meaningful work for each muscle without the session becoming a three-hour marathon. It also provides natural recovery days between sessions targeting the same muscles.
The case against it: Upper body days can become crowded. Chest, back, shoulders, biceps, and triceps all need attention, and fitting adequate volume for each into a single session requires careful exercise selection and prioritization. Some lifters find that their shoulder and arm work suffers because they are already fatigued from heavy pressing and rowing.
Best for: Intermediates and advanced lifters who can train 4 days per week, people who want a balance of frequency and per-session volume, and anyone who has outgrown full body but does not want to live in the gym.
Push/Pull/Legs (PPL) - 6 Days Per Week
PPL divides training into three days - push (chest, shoulders, triceps), pull (back, biceps, rear delts), and legs - typically run twice per week for six total sessions. Each muscle group gets trained twice per week.
The case for it: PPL allows you to dedicate serious time and energy to each muscle group without rushing. With only two or three muscle groups per session, you can do more exercises and sets for each without systemic fatigue becoming a limiting factor. The split also has a logical structure that minimizes overlap - you are not pre-fatiguing muscles you are about to train directly.
The case against it: It requires six days per week in the gym. For most working adults with families and careers, this is a significant commitment that may not be sustainable long-term. Adherence is the most important variable in training, and a perfect program you cannot stick to is worse than a good program you can execute every week. Additionally, the recovery demands of six training days per week are higher, requiring excellent nutrition and sleep habits.
Best for: Advanced lifters who need high volume, people with flexible schedules who genuinely enjoy daily training, and bodybuilders or physique competitors in serious growth phases.
The Variable Nobody Talks About: Volume Equating
Here is the finding that should end most of the debate: when researchers control for total weekly volume (same total sets, same total reps, same effort level), the differences between splits essentially disappear.
A 2018 systematic review by Grgic and colleagues examined multiple studies comparing different training frequencies and splits. Their conclusion: when weekly volume was equated, there were no significant differences in hypertrophy between different training splits.
Read that again. When you do the same total work across the week, it does not matter much whether you spread it across three full body sessions, four upper/lower sessions, or six PPL sessions. The total work and the frequency (at least twice per week) are what drive growth - not the name of the split.
This is profoundly liberating. It means the best split is not the one that wins internet arguments. It is the one that fits your schedule, aligns with your preferences, and allows you to consistently accumulate the right amount of high-quality training volume.
What Actually Matters More Than Your Split
Consistency and Adherence
A PPL split that you execute perfectly for three weeks before life gets busy and you miss sessions is worse than a full body split you run faithfully for twelve months straight. The most important factor in long-term results is showing up consistently. Choose a split that matches your realistic schedule - not your ideal one.
Progressive Overload
No split will produce results without progressive overload. Whatever split you choose, you need a structured plan to increase demands over time - more weight, more reps, more sets, or better execution. The split is the vehicle. Progressive overload is the engine.
Per-Session Volume Quality
Research by Dankel and colleagues (2017) has demonstrated that performance degrades as session length increases, particularly for muscle groups trained later in the workout. This means the practical advantage of any split is its ability to keep per-session volume at a level where every set is high quality. If your full body sessions have you doing productive back work when your quads are already toast from 8 sets of squats, that back work is compromised. A split that distributes volume to keep set quality high will outperform one that crams everything together.
Recovery and Life Context
A 6-day PPL split requires excellent recovery. If you sleep 5 hours a night, eat poorly, and have a high-stress job, you simply cannot recover from six training days per week. You will accumulate fatigue, performance will decline, and you will either burn out or get injured. Match your split to your actual recovery capacity, not to what an enhanced athlete does on Instagram.
Hybrid Approaches: The Best of All Worlds
In practice, the most effective programs for intermediate and advanced lifters often blend elements from multiple splits. Here are a few examples that work exceptionally well:
Upper/Lower/Full (3-Day Rotation)
Run an upper day, lower day, and full body day across the week. This gives every muscle group at least two hits per week, keeps sessions manageable, and only requires three to four training days.
Upper/Lower with a Specialization Day
Run a standard upper/lower four days per week, then add a fifth day targeting a lagging body part. If your arms need work, add an arm-focused day. If your quads are behind, add a quad specialization session. This lets you maintain balanced development while giving extra attention where it is needed.
Push/Pull/Legs/Upper/Lower (5-Day Rotation)
This hybrid gives you the focused sessions of PPL for three days and the balanced frequency of upper/lower for the other two. Every muscle group gets hit at least twice per week, session lengths stay reasonable, and you only need five training days.
How to Choose Your Split: A Decision Framework
Stop asking "which split is best?" and start asking these questions instead:
- How many days per week can you realistically train? Not want to - can. Factor in work, family, travel, and social commitments. Three days? Full body. Four days? Upper/lower. Five to six days? PPL or a hybrid.
- What is your training experience? Beginners respond to almost anything and benefit from the practice and motor learning that comes with full body training three times per week. Advanced lifters usually need more volume and more targeted sessions.
- How is your recovery? If you sleep well, eat enough protein, manage stress, and are generally healthy, you can handle more frequent training. If recovery is compromised, fewer sessions with higher quality is the smarter path.
- What do you actually enjoy? This matters more than most coaches will admit. If you hate full body workouts because they feel unfocused, you will eventually stop doing them. If you love the ritual of a dedicated chest day, that enthusiasm will drive better effort and consistency. Within the bounds of what is evidence-based, pick what you enjoy.
- Do you have lagging body parts? If specific muscle groups are not responding, consider a split that allows you to train them with higher frequency or volume. Sometimes the answer is not a new split but an extra session for a specific muscle group.
The Bottom Line
There is no universally "best" training split. The research is clear: when total weekly volume and frequency (at least twice per muscle per week) are equated, different splits produce similar outcomes. The bro split is the only clear loser, and only because it typically limits each muscle to one training day per week.
The best split is the one that matches your schedule, supports your recovery capacity, keeps session quality high, and - critically - that you will actually stick with for months and years. That might be full body. It might be upper/lower. It might be PPL. It might be a hybrid that does not have a catchy name.
Stop searching for the perfect split. Pick a good one, commit to it, progressively overload, and focus on the variables that actually drive results: consistency, effort, recovery, and time.