The Science of Training Splits: How to Choose an Evidence-Based Routine
Brandon Hyatt, MS, CSCS
Dec. 04, 2024
A well-designed training split is a cornerstone of an effective fitness regimen, prompting the question: what does research indicate about the optimal approach to organizing weekly workouts? While proficiency in exercises is valuable, the critical question remains: what training split best integrates these movements into a concise, efficient routine?
A training split refers to the systematic division of muscle groups, movement patterns, or focus areas into a structured weekly plan—an organizational framework that enables progress tracking and alignment with specific fitness objectives.
Common Training Splits
Below are widely used training splits, presented in no particular order of effectiveness:
Individual muscle group: Chest, back, shoulders, arms, legs, abs (e.g., "arm day" or "leg day").
Upper/lower body: Divides sessions into upper-body (chest, back, shoulders, arms) and lower-body (legs, core) focus.
Antagonist/agonist pairing: Combines complementary muscle groups (e.g., chest + triceps, back + biceps) to optimize recovery.
Push/pull/legs (PPL): Organizes sessions by movement patterns: push (chest, shoulders, triceps), pull (back, biceps), legs.
Movement pattern: Breaks workouts into fundamental human movements (push, pull, hinge, squat) for functional focus.
Full-body: Trains all major muscle groups in every session.
Key Factors to Guide Split Selection
While research provides clarity on efficacy, individual needs must drive split choice. Two critical considerations:
1. Time Availability
The number of weekly training days is the most practical constraint. For example:
A 3-day/week routine favors full-body splits (e.g., train all muscles 3x/week).
A 5-day/week routine can accommodate individual muscle group splits (e.g., 1 day per muscle group).
Novices illustrate this point: a 5-day split with 60 minutes of chest work would overwhelm a beginner, leading to excessive soreness and poor recovery. A full-body split (1–2 days/week) is far more appropriate for building foundational strength.
2. Complementary Goals
Training splits must align with non-strength/hypertrophy objectives, as recovery and time allocation are interdependent. For instance:
- An individual targeting 12 weekly miles of running (3 sessions) would struggle with a 4–5 day strength split—recovery from running would compromise resistance training quality.
Research Comparisons: Full-Body vs. Split Routines
Most studies on training splits manipulate volume-equated training frequency—how often each muscle group is trained weekly, with total work (sets × reps × weight) held constant. Below is a synthesis of key findings:
Study 1: Novice Lifters (2021)
A study of 67 untrained young males compared an 8-week full-body routine (4 weekly sessions per muscle group) to a split routine (4 weekly sessions per muscle group). Strength was measured via 1-repetition maximum (1-RM) bench press/Smith machine squat; hypertrophy via ultrasound (biceps, triceps, vastus lateralis, rectus femoris).
Results: Both routines produced equivalent strength and hypertrophy gains.
Takeaway: Novices can use full-body or split splits interchangeably to build foundational fitness.
Limitations: Short intervention (8 weeks), unmonitored nutrition, and narrow muscle group focus (only arms/quads).
Study 2: Trained Lifters (2019)
A study of 36 trained young males evaluated a 10-week full-body routine (3 weekly sessions per muscle group) vs. a split routine (2 weekly sessions per muscle group). Outcomes mirrored Study 1 (1-RM strength, ultrasound hypertrophy).
Results: Training muscle groups 2–3 times weekly yielded identical strength/hypertrophy gains.
Takeaway: Trained lifters do not need to increase frequency beyond 2–3x/week to see progress.
Limitations: Small sample size, short duration, and exclusive focus on young men.
Study 3: Meta-Analysis (2024)
A systematic review of 14 studies (including women and all training levels) compared split and full-body routines. Outcomes included 1-RM strength (bench press, lower-body exercises) and hypertrophy (ultrasound, DXA, bioelectrical impedance).
Results: Robust evidence that split and full-body routines produce equivalent strength and hypertrophy when volume is standardized.
Takeaway: Split choice should prioritize personal preference and non-strength goals (e.g., time, sport-specific needs).
Final Recommendations: How to Choose
Research consistently demonstrates that full-body and split routines are equally effective for strength and hypertrophy—when volume is equated. The majority of splits fall into these two categories, so focus on:
Time: Match split to weekly availability (e.g., 3 days = full-body; 5 days = individual muscle groups).
Experience: Novices benefit from full-body splits to build foundational strength; advanced lifters may prefer splits to target specific muscles.
Goals: Prioritize complementary objectives (e.g., endurance training) that impact recovery and time allocation.
References
Evangelista AL, Braz TV, La Scala Teixeira CV, et al. Split or full-body workout routine: which is best to increase muscle strength and hypertrophy? Einstein (São Paulo). 2021 Aug 30;19:eAO5781. doi: 10.31744/einstein_journal/2021AO5781. PMID: 34468591; PMCID: PMC8372753.
Lasevicius T, Schoenfeld BJ, Grgic J, et al. Similar Muscular Adaptations in Resistance Training Performed Two Versus Three Days Per Week. J Hum Kinet. 2019 Aug 21;68:135-143. doi: 10.2478/hukin-2019-0062. PMID: 31531139; PMCID: PMC6724585.
Ramos-Campo DJ, Benito-Peinado PJ, Andreu-Caravaca L, et al. Efficacy of Split Versus Full-Body Resistance Training on Strength and Muscle Growth: A Systematic Review With Meta-Analysis. J Strength Cond Res. 2024 Jul;38(7):1330-1340. doi: 10.1519/JSC.0000000000004774.
