We show (again) that: Resistance training load does not determine...
Stuart Phillips (he/him)@mackinprof
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Jan 01, 2026
~2 min read
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We show (again) that: Resistance training load does not determine resistance training‐induced hypertrophy across upper and lower limbs in healthy young males physoc.onlinelibrary.wiley.com/doi/10.1113/JP…
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New paper in The Journal of Physiology:
Resistance training load does NOT determine hypertrophy when effort is matched.
Heavier ≠ better for muscle growth. 🧵👇
Resistance training load does NOT determine hypertrophy when effort is matched.
Heavier ≠ better for muscle growth. 🧵👇
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20 young men trained their arms and legs unilaterally for 10 weeks.
• One limb: heavy load (70–80% 1RM, 8–12 reps)
• Other limb: light load (30–40% 1RM, 20–25 reps)
All sets to volitional fatigue.
20 young men trained their arms and legs unilaterally for 10 weeks.
• One limb: heavy load (70–80% 1RM, 8–12 reps)
• Other limb: light load (30–40% 1RM, 20–25 reps)
All sets to volitional fatigue.
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Muscle size was assessed in every way possible:
DXA lean mass
Ultrasound CSA & thickness
Muscle biopsies (type I & II fibre CSA)
Strength testing
This wasn’t a single-measure study.
Muscle size was assessed in every way possible:
DXA lean mass
Ultrasound CSA & thickness
Muscle biopsies (type I & II fibre CSA)
Strength testing
This wasn’t a single-measure study.
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The result?
👉 No differences in hypertrophy between heavy and light loads
Arms or legs.
Whole muscle or fibres.
If effort is high, load doesn’t determine growth.
The result?
👉 No differences in hypertrophy between heavy and light loads
Arms or legs.
Whole muscle or fibres.
If effort is high, load doesn’t determine growth.
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But here’s the real insight:
Hypertrophy was far more consistent within an individual than between individuals.
If you respond well in one limb, you tend to respond well everywhere.
But here’s the real insight:
Hypertrophy was far more consistent within an individual than between individuals.
If you respond well in one limb, you tend to respond well everywhere.
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Translation:
Inter-individual variability ≫ training-variable manipulation.
Your biology matters more than whether you lift “heavy” or “light.”
Translation:
Inter-individual variability ≫ training-variable manipulation.
Your biology matters more than whether you lift “heavy” or “light.”
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Myofibrillar protein synthesis (measured with D₂O):
• Increased early in training
• Blunted later with training adaptation
• No difference between heavy vs light loads at any point
Myofibrillar protein synthesis (measured with D₂O):
• Increased early in training
• Blunted later with training adaptation
• No difference between heavy vs light loads at any point
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Strength gains?
Also, similar between loads, unless you practice the test itself.
Heavier training mostly improves 1RM because you rehearse heavy lifting.
Strength gains?
Also, similar between loads, unless you practice the test itself.
Heavier training mostly improves 1RM because you rehearse heavy lifting.
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Important myth check:
More load ≠ more muscle
More pain ≠ more growth
More complexity ≠ better results
Effort-to-fatigue (and volume) are the key drivers.
Important myth check:
More load ≠ more muscle
More pain ≠ more growth
More complexity ≠ better results
Effort-to-fatigue (and volume) are the key drivers.
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Practical takeaway:
Lift loads you can tolerate.
Train close to failure.
Accumulate volume.
Progress over time.
Stop obsessing over “optimal” load.
Practical takeaway:
Lift loads you can tolerate.
Train close to failure.
Accumulate volume.
Progress over time.
Stop obsessing over “optimal” load.
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This study reinforces a growing conclusion:
Resistance training adaptations are largely governed by endogenous biology, not gym dogma.
If your program works for you, stick with it.
If it doesn’t, changing load alone probably isn’t the answer.
Full paper here 👇
physoc.onlinelibrary.wiley.com/doi/epdf/10.11…
This study reinforces a growing conclusion:
Resistance training adaptations are largely governed by endogenous biology, not gym dogma.
If your program works for you, stick with it.
If it doesn’t, changing load alone probably isn’t the answer.
Full paper here 👇
physoc.onlinelibrary.wiley.com/doi/epdf/10.11…
