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Place · Level 3
肌肉不是只会收缩 · 它是代谢炉、内分泌器官、神经训练场
synergy · 3
↔Bone
Muscle pull is the mechanical signal for bone remodeling — sarcopenia and osteoporosis co-occur in aging (osteosarcopenia). Resistance training targets both simultaneously.
Compound lifts drive both mechanical tension and neural recruitment simultaneously across multi-joint chains — the origin of whole-body training adaptation.
Exercise-induced muscle releases BDNF + irisin → enters blood → crosses BBB or acts at periventricular regions → neuroplasticity + cognition + antidepressant effect. The molecular basis of 'exercise is the best antidepressant.'
cofactor · 3
Leucine is sensed inside the muscle cell and flips mTORC1, the master switch for protein synthesis. A meal of 25-40 g of quality protein captures most of the available response; larger doses still add something, and last longer (100 g drives a bigger, >12-hour response than 25 g — Trommelen 2023), just with diminishing returns. What actually builds muscle is the daily total (rising benefit up to roughly 1.6 g/kg — Morton 2018), not policing a per-meal ceiling.
The moment an action potential arrives, the sarcoplasmic reticulum dumps its stored calcium into the cytosol; calcium clicks onto troponin, and only then does myosin's binding site come into view. No calcium, no cross-bridge.
The pump that returns calcium to the sarcoplasmic reticulum burns an ATP-magnesium complex on every trip — without magnesium, ATP is unusable and calcium never gets back to the store. But a mechanism holding up doesn't mean the supplement works: Cochrane found no effect on cramps in the general population.
regulates · 6
Motor neurons → neuromuscular junction → muscle contraction. Loss of innervation causes disuse atrophy within weeks; Mg²⁺ plugs NMDA receptors contributing to neuromuscular excitability control.
Sarcopenia = muscle mass ↓ + strength ↓ + performance ↓ (EWGSOP2 2019 triad). Fiatarone 1994 NEJM (N=100, mean 87 yo, 10 wk × 80% 1RM): knee-extension strength +174% vs control +9% — atlas's canonical 'frailty ≠ destiny' proof.
Muscle is an organ AND an endocrine organ: contraction releases myokines (IL-6, irisin, BDNF, FGF21) → distal metabolic effects. The mechanism behind exercise's whole-body benefits. Sedentary = muscle silent = whole-body metabolism muted.
Weeks 1-4 of RT see 80% of strength gain from neural drive (recruitment + rate coding + synchronisation + coordination), not muscle. This is why strength and muscle size can dissociate.
Eccentric contractions cause Z-disc microdamage → 24-72h inflammation sensitising C-fiber nociceptors. DOMS is an adaptation signal, not 'lactate accumulation' (lactate clears in 30 min). The repeated bout effect halves DOMS on the same workout 2 weeks later.
Schoenfeld 2017 volume meta: 10-20 sets/wk/muscle is the hypertrophy sweet spot. <10 progressive, >20 plateau + junk volume. Frequency allocates, volume drives.