The Science of Real Muscle Growth

Schoenfeld et al. (2017)^[5] found a graded dose response relationship: each additional weekly set increased hypertrophy by ~0.37%. The 2025 Pelland et al. meta analysis^[6] confirmed this with diminishing returns but no hard ceiling. Saying "4 sets per session is all you need" flies in the face of the largest body of meta analytic evidence we have.

Those meta analyses do support a weekly dose response trend. What they generally cannot tell us is whether all measured growth reflects the same mix of contractile and non contractile adaptations. Haun et al.^[3] raises that question in an extreme volume setting, but it should be treated as an important caution, not a universal refutation of higher volume training. Haun's lifters trained three times a week, so their result is a caution about huge, sudden volume increases, not about how often you train. Our separate point is practical. In a very long session the later sets are done tired, so spreading the same weekly sets over two or three sessions is usually easier to do well.

Elite bodybuilders routinely perform 20+ sets per muscle group in a session. If high volume didn't work, they wouldn't do it. Decades of real world results trump lab studies on untrained college students.

Three confounds. First, survivorship bias. We see the bodybuilders who succeeded despite (or because of) their genetics, not the thousands who burned out or got injured on the same programmes. Second, performance enhancing drugs change how much training a body can recover from and grow from, so drug assisted routines are a poor guide for natural lifters. Third, surveys suggest many competitive bodybuilders now train each major muscle about twice a week rather than once, though they still do more sets per session than the starting point suggested here. The argument here isn't "high volume doesn't work at all". It's that it's not optimal for natural trainees seeking the best return on time and recovery.

The Haun et al. study was only 6 weeks with extreme volume. Sarcoplasmic expansion may be a precursor to eventual myofibrillar growth. The cell expands first, then fills in with contractile proteins. Roberts et al. (2020)^[9] suggested exactly this: an early sarcoplasmic phase may help fibres "spatially, bioenergetically, and biosynthetically prepare" for adding new contractile protein.

This is a legitimate and important point. The 6 week timeframe is a genuine limitation, and the "priming" hypothesis from Roberts et al.^[9] is plausible. However, even if sarcoplasmic expansion eventually transitions to myofibrillar growth, the question remains: is that the most efficient path? Vann et al. (2020)^[14] point the same way: in 15 trained men, 10 weeks of heavy, lower volume training grew type II muscle fibres and raised squat strength, while sarcoplasmic protein and muscle fluid did not change and there were only small falls in actin and myosin. If you can get direct myofibrillar accretion from moderate volume at heavy loads without first going through a sarcoplasmic detour, the stimulus to fatigue ratio may still favour the lower volume, higher frequency approach. More research with longer durations and biopsy data is needed to fully resolve this.

Grgic et al.'s 2019 review^[8] found no significant difference between training a muscle once vs. multiple times per week when total weekly volume was equated. So spreading volume across the week doesn't inherently provide a growth advantage.

When weekly volume is equated, frequency often appears less important for hypertrophy itself. The practical case for higher frequency is more about execution quality, fatigue management, and adherence than about a guaranteed physiological advantage. By set 15 of a long session, performance is degraded, form is compromised, and the growth stimulus per set likely diminishes. Higher frequency allows the same weekly volume at consistently higher per set quality.

Damas et al.^[1][2] studied untrained people. The Alvarez et al. (2026)^[4] study you cite actually showed no persistent edema in trained lifters at any volume. So the edema confound is a non issue for the trained population that this article targets.

This is a fair and important criticism. The edema confound is most relevant to untrained populations and the early weeks of new programmes, and many foundational volume studies used exactly those populations. For trained individuals, Alvarez et al. (2026)^[4] does confirm that edema resolves rapidly. For trained lifters, the more relevant question comes from Haun et al. (2019).^[3] After six weeks of extreme, unfamiliar volume, the men whose fibres grew had less contractile protein per gram of muscle. The authors later noted that fluid shifts may also have played a part,^[9] so treat this as a caution about sudden huge volume, not proof that normal high volume training builds the wrong kind of muscle.

Morton et al. (2016)^[7], Schoenfeld et al. (2015)^[12], and others have shown that loads as light as 30 to 50% 1RM can produce similar hypertrophy to heavy loads when sets are taken to failure. The claim that 4 to 8 reps is "optimal" ignores this robust body of load equated evidence.

The load equated literature is real and robust. Lighter loads can produce significant hypertrophy when taken to or near failure. We do not dispute this. The recommendation for 4 to 8 reps as the primary range is based on efficiency, not exclusivity. Training at 30% 1RM to failure is brutally fatiguing systemically and metabolically, requires longer set durations, and makes progressive overload harder to track. For most people most of the time, the heavy range is the practical sweet spot. That said, including higher rep work (8 to 15) for isolation movements, joint friendly alternatives, or variety is entirely compatible with this model.