Schoenfeld Volume Meta-Analyses and the Junk-Set Question

The volume-vs-hypertrophy curve is the most-debated number in resistance training. Schoenfeld's lab has produced anchoring data on the relationship, with the 2017 dose-response meta-analysis and the 2019 volume trial at the centre of the modern conversation, alongside higher-volume work from other groups. This article walks through what the studies actually found, what the dose-response curve looks like in practice, and where the junk-volume boundary sits — taking care to report the published findings rather than invented precision.

The framework: what counts as a "set"

Set-volume math is sensitive to what counts. The published convention from Schoenfeld's work counts only working sets — sets taken close to or to failure — within the target rep range for hypertrophy (typically 6–20 reps). The convention excludes:

• Warm-up sets at sub-maximal effort.
• Sets below 50% of working intensity.
• Sets stopped well short of failure (more than 4 reps in reserve).
• Isolation work that is supplementary to compound movements.

This matters because lifters who count every set ("I did 25 sets for chest!") routinely double-count and over-state their actual hypertrophy-relevant working volume.

The Schoenfeld 2017 meta-analysis

The 2017 paper analysed 34 treatment groups drawn from 15 studies, regressing muscle-size change against weekly working-set volume. Its headline result was a significant, graded dose-response: more weekly sets produced greater hypertrophy (P = 0.002), with the relationship described as roughly linear across the studied range. The authors reported that each additional weekly set was associated with a small increment in effect size (on the order of a few tenths of a percent of additional gain per set), and suggested a near-maximal hypertrophy threshold in the region of about 10 sets per muscle per week.^[1]

Two cautions the authors themselves stressed: the dataset was heterogeneous, and few of the pooled trials pushed weekly volume far above ~20 sets per muscle, so the upper end of the curve is poorly characterised. The meta-analysis establishes the direction and rough threshold, not a precise per-volume-bracket percentage table.^[1]

The Schoenfeld 2019 trial

The 2019 trial ("Resistance Training Volume Enhances Muscle Hypertrophy but Not Strength in Trained Men") randomised 34 resistance-trained men to three volume conditions and trained them three times a week for eight weeks:

Group              Per session    Weekly sets per muscle
─────────────────────────────────────────────────────────
 Low volume        1 set/exercise        ~3
 Moderate volume   3 sets/exercise       ~9
 High volume       5 sets/exercise      ~15

The published result: all groups increased strength and endurance with no significant between-group differences, while hypertrophy showed significant advantages for the higher-volume conditions at several measured sites (elbow flexors, mid-thigh, and lateral thigh). In other words, extra weekly sets bought additional muscle size but not additional strength over this eight-week block.^[2]

That decoupling — more volume helping size but not strength — is the operational seed of the "junk volume" idea: past the point where strength stops responding, additional sets are working only the hypertrophy channel, at a recovery cost.

Where the junk-volume threshold sits

Pushing the volume question higher, the Heaselgrave 2019 trial compared 9, 18, and 27 weekly sets of elbow-flexor work over six weeks. It found growth continued as volume rose but with clearly diminishing per-set returns toward the top of that range, consistent with the idea that the curve flattens somewhere past the commonly cited 10–20 set band.^[3] The exact flattening point varies by individual and muscle group, so the honest reading is a region, not a single number:

Sets/muscle/wk    Practical read
─────────────────────────────────────────────────────────────────────
  under 10        likely sub-optimal for hypertrophy in trained lifters
  10 - 20         the commonly cited productive band
  20 - 27         growth can continue, but per-set returns diminish
  above ~27       little supporting data; recovery cost dominates

Below roughly 10 sets, hypertrophy is generally sub-optimal for trained men; in the 10–20 band the dose-response is reliable; above it the marginal gain shrinks and recovery and joint stress rise. The published trials do not support precise per-set percentage yields beyond this qualitative shape.^[3]

The strength-vs-hypertrophy divergence

The 2019 trial's most notable finding was the divergence between strength and hypertrophy: across its 3-to-15 weekly-set range, strength gains were statistically indistinguishable between groups while hypertrophy favoured higher volume. The higher-volume work kept feeding the size channel after strength had stopped responding. The mechanism is the published difference between neural and structural adaptation:

• Strength adaptation is primarily neural (motor unit recruitment, rate coding, intermuscular coordination). The neural system saturates at modest volume because the inputs are skill-rep-based, not work-volume-based.
• Hypertrophy adaptation is structural (protein turnover, fiber cross-section growth). The structural system responds to cumulative work signal, which keeps responding to additional volume well past the strength plateau.^[4]

Practical consequence: powerlifters and strength athletes can stay well below 15 weekly sets per muscle without losing strength outcomes. Bodybuilders and physique athletes benefit from pushing toward 20+ weekly sets where the marginal hypertrophy gain still exists despite no strength upside.

Bottom line: where to set weekly volume

1. Strength-focused lifters: 8–12 weekly sets per muscle. Plateau region for strength; additional volume costs recovery without benefit.
2. Balanced strength + hypertrophy: 12–18 weekly sets per muscle. Hits the productive band on both curves.
3. Hypertrophy-focused lifters: 16–22 weekly sets per muscle. Captures the hypertrophy-specific gains while staying inside sustainable recovery.
4. Advanced hypertrophy specialists in short blocks: 22–28 weekly sets per muscle, 4–6 week blocks with planned deload. Pushes the curve into the diminishing-returns zone for short-block productivity.
5. Above ~27 weekly sets: Sparsely studied; likely junk-volume territory for most trained lifters. The Heaselgrave trial's 27-set arm still grew but with the weakest per-set return, and such volumes are hard to recover from over multi-month blocks.^[3]

Where the methodology bends

Genetic variation

The dose-response curves above represent population averages. Individual lifters vary by ±20–30% in their response to volume; some lifters max out at 12 sets per muscle, others continue to gain at 28 sets. The published recommendation is to start at the population-mean range and adjust based on 8–12 week tracking results.^[1]

Compound vs isolation volume

Schoenfeld's "set per muscle" math counts both compound and isolation sets that recruit the muscle. A squat counts as a quad set, a glute set, and a hamstring set; a leg extension counts as a quad set. Lifters who run heavy compound programmes accumulate working sets per muscle faster than the simple session-count suggests.^[3]

Untrained subjects

The studies in the 2017 meta and 2019 trial were predominantly trained men. Untrained subjects gain hypertrophy at substantially lower volumes (4–8 sets per muscle/week) and respond differently to volume titration. The 10–20 set band does not apply to novices.^[4]

Worked weekly volume by muscle group

A concrete weekly volume plan for an intermediate hypertrophy-focused lifter:

Muscle group      Compound sets    Isolation sets    Total weekly sets
─────────────────────────────────────────────────────────────────────────
Chest             6 (bench)        6 (flyes, cable)   12
Back               8 (rows + pulls) 6 (face pulls)    14
Shoulders         4 (press)         8 (laterals)      12
Biceps            (4 from rows)    8                 12
Triceps           (4 from bench)   8                 12
Quads             6 (squat)        6 (leg ext)        12
Hamstrings        4 (RDL)          6 (curls)         10
Glutes            6 (squat + RDL)  4 (hip thrusts)   10
Calves            -                12                12

Every major muscle group lands in the 10–14 set band, comfortably inside the productive range from the 2017 meta. The structure splits compounds across major movements and adds targeted isolation to fill out volume on the muscles compounds under-stimulate (laterals, biceps, triceps, calves).

Lifters who push for more aggressive hypertrophy can add 2 sets per muscle group across 4–6 week blocks, landing at 16–18 sets per muscle. Above 20 sets per muscle group requires monitoring recovery markers (sleep quality, HRV, AMRAP performance) and dropping back to 12–14 sets every third or fourth week to reset the recovery debt before it accumulates into a missed-session pattern.^[3]

Cross-checking against related tools

The Junk Volume Detector implements the Schoenfeld curve to flag training programmes accumulating above-productive-band weekly sets. The Workout Volume Calculator handles the per-week set-counting math. The Progressive Overload Planner sequences volume across multi-week blocks.

Related reading: How Many Sets Per Week for Hypertrophy? for the 2026 dose-response curve turned into weekly set targets, Junk Volume Hypertrophy: From Your Log for the per-lifter junk-set diagnostic, Block vs DUP Periodisation for the volume-distribution debate, and Evidence-Based Programming 2026 for the broader framing.

FAQ

If more sets build more muscle, why call high volume "junk"?

Because the marginal cost-benefit flips. In the trials, the highest-volume groups kept adding hypertrophy but with shrinking per-set returns and no extra strength, while recovery demand kept climbing. Across a 12-month training year, that higher recovery cost typically forces missed sessions, lower training quality, or injury — so the net annual outcome can be worse than a more moderate volume.^[2][3]

How do I count compound exercises in the set total?

Count each compound set as a working set for every major muscle it heavily recruits. A squat counts as 1 set for quads, 1 for glutes, 0.5 for hamstrings (less direct work). The math is approximate; the goal is to land in the productive band, not to optimise to the third decimal.

What if I'm not training to failure?

Schoenfeld's curve was derived from sets taken to within 1–2 reps of failure (RIR 1–2). Sets stopped at RIR 4+ reduce the hypertrophy signal substantially; the published estimate is that an RIR-4 set produces roughly 60–70% of the hypertrophy stimulus of an RIR-1 set at the same weight. Lifters who consistently stop short of failure need to count their effective volume lower than their raw set count.^[1]

Should I increase volume slowly or jump to the optimal band?

Slowly. The published progressive-overload literature finds athletes who add 1–2 weekly sets per muscle every 2 weeks tolerate the new volume better than athletes who jump from 8 to 20 sets in one cycle. Recovery infrastructure (calories, sleep, joint conditioning) needs time to adapt to higher training demand.^[3]

References

1. 1 Dose-response relationship between weekly resistance training volume and increases in muscle mass: a systematic review and meta-analysis (Schoenfeld, Ogborn, Krieger) — Journal of Sports Sciences (2017)
2. 2 Resistance training volume enhances muscle hypertrophy but not strength in trained men (Schoenfeld et al.) — Medicine and Science in Sports and Exercise (2019)
3. 3 Dose-response relationship of weekly resistance-training volume and frequency on muscular adaptations in trained men (Heaselgrave et al.) — International Journal of Sports Physiology and Performance (2019)
4. 4 The effect of weekly set volume on strength gain: a meta-analysis (Ralston et al.) — Sports Medicine (2017)