"Junk Volume" is Real: The 2025 Meta-Regression That Should Change How You Train

TL;DR on the data: A new meta-regression from Remmert et al. (2025) analyzed the dose-response of per-session volume and found that the point of undetectable outcome superiority (PUOS)—the volume where additional sets stop producing measurable benefits—occurs at approximately 11 "fractional" sets for hypertrophy and a shockingly low ~2 "direct" sets for strength. The relationship shows diminishing returns, not linear growth. Your "20-set chest day" is likely metabolic theatre.

The Mechanistic Underpinnings of Volume Economics

The fitness industry has been running on a flawed assumption for decades: that volume and results share a linear relationship. More sets = more gains. Push harder. Add volume until you can't. It's the kind of bro-science that sells "extreme" workout programs and keeps physical therapists in business.

The physics here is actually pretty simple: biological systems don't scale linearly. They follow dose-response curves with thresholds, plateaus, and—if you push far enough—negative returns via excessive fatigue and recovery debt.

Enter Remmert, Pelland, Robinson, Hinson, and Zourdos (2025). Their meta-regression, published on SportRxiv, represents one of the most rigorous attempts to quantify the per-session volume ceiling. And the numbers are going to upset people who measure their masculinity by their set count.

The PUOS: Where Additional Sets Become Statistical Noise

The researchers introduced a concept that every 1% trainee needs to tattoo on their program spreadsheet: the Point of Undetectable Outcome Superiority (PUOS). This is the per-session set volume where additional work has less than a 50% probability of producing a difference exceeding the smallest detectable effect size.

In plain English: past this point, you're doing sets that don't statistically matter.

The PUOS findings:

Let that sink in. For pure strength development, the data suggests diminishing returns kick in hard after approximately 2 direct sets per session. For hypertrophy, you've got more runway—about 11 fractional sets—but even that caps out far lower than the "30 sets per muscle per session" protocols floating around Instagram.

Direct vs. Fractional: The Set-Counting Distinction That Matters

Here's where most trainees (and honestly, most coaches) get sloppy: they don't distinguish between direct and indirect volume.

The researchers classified sets as:

• Direct sets (1.0): The exercise directly measures the outcome (e.g., squatting when testing squat 1RM)
• Fractional sets (0.5): The exercise contributes to but doesn't directly measure the outcome (e.g., leg pressing when measuring squat 1RM)
• Indirect sets (0): Minimal or no contribution to the measured outcome

This distinction is critical. When you do 5 sets of squats and 5 sets of leg presses, that's not "10 sets of quad volume" for strength purposes—that's 5 direct + 5 fractional = 7.5 effective sets. And if you're training for squat strength specifically, those leg press sets barely move the needle.

(This is why "total volume" arguments on Reddit devolve into chaos—people are using different accounting methods and don't realize it.)

The Diminishing Returns Curve: What the Data Actually Shows

The posterior probability of the marginal slope exceeding zero was 100% for both hypertrophy and strength. Translation: yes, volume does work. More sets generally produce more gains—up to a point.

But—and this is the crucial "but"—both models showed diminishing returns as per-session volume increased. And critically, strength gains showed more strongly diminishing returns than hypertrophy.

This aligns with what we know about the underlying biology:

• Hypertrophy is driven by cumulative mechanical tension, metabolic stress, and muscle damage across a broader time window. You can accumulate more effective volume before hitting the ceiling.
• Strength is highly specific to neural adaptations, motor unit recruitment patterns, and technical proficiency. Past a low threshold, additional volume primarily increases fatigue without proportional neural adaptation.

Why Your "Junk Volume" is a Metabolic Leak

Let's run the numbers on a typical "chest day" I see in commercial gyms:

• Barbell Bench Press: 4 sets × 8 reps
• Incline Dumbbell Press: 4 sets × 10 reps
• Cable Flyes: 4 sets × 15 reps
• Machine Chest Press: 3 sets × 12 reps
• Dips: 3 sets × failure

That's 18 sets. If we're being generous and calling everything "fractional" pec volume (it's not—dips are mostly anterior delt/tricep for most people), you're at 18 fractional sets.

The PUOS for hypertrophy? ~11 fractional sets.

Those last 7 sets? Junk volume. They're not producing measurable additional hypertrophy. What they are producing is:

• Excessive central nervous system (CNS) fatigue
• Extended recovery time
• Increased injury risk as form degrades
• Opportunity cost—you could have trained that muscle again 48 hours later instead of waiting 96+ hours to recover from your "massacre"

The BS-Meter: Red Flags in Volume Recommendations

When evaluating training programs, watch for these "major leaks in the metabolic bucket":

Practical Application: The 1% Trainee Protocol

Here's how to apply the Remmert et al. findings to your programming:

For Hypertrophy:

• Target 8-11 fractional sets per muscle per session
• Train each muscle 2-3× per week (frequency compensates for lower per-session volume)
• Prioritize direct sets for lagging muscle groups
• Stop when you hit the target—don't "chase the pump" into junk volume territory

For Strength:

• Limit to 2-4 direct sets per lift per session
• Increase frequency (3-4× per week) rather than per-session volume
• Focus on technical quality and RPE management over set accumulation
• Remember: strength is specific. Your squat 1RM doesn't care about your leg press PR.

The Caveats: What This Study Doesn't Prove

Intellectual honesty demands we acknowledge the limitations:

1. Insufficient data at very high volumes: The researchers noted there's limited data on per-session volumes exceeding ~15 sets. We can't say for certain whether there's a true "attenuation point" where more volume becomes actively harmful, or if the curve simply flattens indefinitely.
2. Individual variation exists: Meta-analyses show population averages. Your personal PUOS may differ based on recovery capacity, training age, sleep quality, and stress levels.
3. Drug-free vs. enhanced: The dataset includes mixed populations. Anabolic assistance changes recovery dynamics and potentially shifts the PUOS ceiling.

But here's the thing: absence of evidence is not evidence of absence. Until we have data showing clear benefits of 20+ set sessions, the prudent approach is to respect the PUOS threshold and optimize frequency instead.

The Bottom Line

The "no pain, no gain" crowd isn't going to like this. The supplement companies selling intra-workout carbs to fuel your "epic 30-set arm day" really aren't going to like this. But the data is the data.

Remmert et al. (2025) provides the strongest evidence yet that per-session volume has a ceiling of practical utility. Past ~11 fractional sets for hypertrophy and ~2 direct sets for strength, you're accumulating fatigue faster than you're accumulating adaptations.

The solution isn't to train less overall—it's to redistribute that volume across more frequent sessions, prioritize direct work for your goals, and stop treating every workout like a CrossFit competition.

Your recovery budget is finite. Spend it wisely.

Sources:

• Remmert, J. F., Pelland, J. C., Robinson, Z. P., Hinson, S. R., & Zourdos, M. C. (2025). Is There Too Much of a Good Thing? Meta-Regressions of the Effect of Per-Session Volume on Hypertrophy and Strength. SportRxiv. https://doi.org/10.51224/SRXIV.537
• Pelland, J. C., Remmert, J. F., Robinson, Z. P., Hinson, S. R., & Zourdos, M. C. (2024). The Resistance Training Dose-Response: Meta-Regressions Exploring the Effects of Weekly Volume and Frequency on Muscle Hypertrophy and Strength Gain. SportRxiv.

Correction & Optimization Policy: If subsequent research contradicts or refines these findings, I will issue a formal correction. Science evolves. Protocols should too.

Now, go apply it.