Soleus — the deep calf muscle that can raise fat metabolism ~200–300%
Site for Steven · updated 12 Sep 2026 · videos + transcripts first · study & sources below
Video — Fat Metabolism 300%
The Muscle That Boosts Fat Metabolism 300% (You're Probably Ignoring It)
Tap a transcript line to seek the player. Full transcript is on this page.
Video — same claim in “10 Critical Muscles”
10 Critical Muscles You’re NOT Training (It’s Costing You YEARS of Progress!)
Soleus is #7. Transcript excerpt below starts at the soleus section; tap a line to seek.
Excerpt: soleus section only (~3:10–4:25).
Videos — Soleus Secret (anatomy / bent-knee)
Part 1 — The Soleus Secret (anatomy behind calf definition and volume)
Part 2 — The Soleus Secret (bigger & better calves)
Short answer The soleus is the deep plantar-flexor under the gastrocnemius. A 2022 iScience study (Hamilton et al., University of Houston) found that prolonged, low-effort soleus-dominant seated contractions (“soleus push-up”) can markedly raise local oxidative metabolism for hours, with large effects on postprandial glucose and insulin, and increased fat/carb oxidation — while the muscle is only ~1% of body mass and uses little glycogen.
Dr. Gains popularizes the takeaway as: bent-knee soleus work can raise whole-body fat metabolism on the order of ~200–300%. Treat video headlines as popularization; use the paper (below) for numbers. Videos and tap-to-seek transcripts are at the top of this page.
What the 2022 study actually reported
Marc T. Hamilton and colleagues published in iScience:
“A potent physiological method to magnify and sustain soleus oxidative metabolism improves glucose and lipid regulation.”
They developed a seated soleus push-up (SPU): heels rise while the forefoot stays planted, knees bent — soleus-dominant plantarflexion while sitting.
Local soleus oxidative metabolism could stay elevated for hours without fatigue; biopsies showed minimal glycogen use.
Systemic effects included roughly ~52% smaller postprandial glucose excursion and ~60% less hyperinsulinemia after a glucose drink.
Authors note they are unaware of pharmaceuticals that raise and sustain whole-body oxidative metabolism at this magnitude.
All ~600 skeletal muscles together normally contribute only ~15% of whole-body oxidative metabolism in the post-carbohydrate window they discuss — which is why a 1%-of-body-mass muscle doing this looks disproportionate.
Nuance The lab protocol is prolonged seated SPU activity (often discussed as hours with brief breaks), not a few hard gym sets. Dr. Gains maps the same biomechanics onto bent-knee / seated calf raises (gastrocnemius in active insufficiency). Related idea, different dose.
AnatomySoleus does not cross the knee (unlike gastroc). Bent knee (~≥90°) disadvantages gastroc → more load on soleus.
Fiber typeSoleus is extremely slow-twitch dominant (~80%+ Type I; Dr. Gains cites ~85–88%). Built for long, low-intensity work and fat/glucose oxidation more than glycogen sprints.