In untrained men aged 25–70, changes in muscle strength relative to lean body mass after 12 weeks of blood-flow restricted resistance training are linked to the levels of certain signaling proteins...
Mechanism
Synthesis from 1 study
When you lift weights with your blood partially restricted, your muscles release signals that tell stem cells to repair and grow fibers, and turn up protein production. More of two signals (IL-4 and IL-6) means better strength gains for your muscle size, but if another signal (LIF) is already high,...
Most probable mechanism
When muscles are worked under restricted blood flow, they release signaling molecules that tell nearby muscle stem cells to multiply and join existing muscle fibers, while also turning up the production of new muscle proteins. Higher levels of two of these signals (IL-4 and IL-6) mean more stem cells and protein are made, leading to stronger muscles for their size. But if another signal (LIF) is already high before training, the muscles seem less able to respond, so strength gains are smaller.
Mechanical and metabolic stress from low-load resistance exercise under vascular restriction triggers skeletal muscle cells to secrete interleukin-4, interleukin-6, and leukemia inhibitory factor into the bloodstream.
Circulating interleukin-4 promotes the migration and fusion of muscle stem cells with existing muscle fibers, increasing fiber size without increasing total muscle mass.
Circulating interleukin-6 activates the STAT3 pathway in muscle stem cells to increase their proliferation and enhances mTOR signaling to boost muscle protein synthesis.
Leukemia inhibitory factor activates the same STAT3 and mTOR pathways to stimulate muscle stem cell activity and protein synthesis, but elevated baseline levels correlate with diminished capacity for further adaptation.
The net effect of increased myoblast fusion and protein synthesis elevates muscle strength relative to fat-free mass, with the magnitude of gain proportional to the integrated exposure to interleukin-4 and interleukin-6, and inversely proportional to leukemia inhibitory factor exposure.
Less supported by current evidence, but not ruled out
Exercise under restricted blood flow causes muscles to release a molecule called irisin, which increases a growth signal (IGF-1) and decreases a brake on muscle growth (myostatin), helping muscle fibers get bigger.
Mechanical and metabolic stress from low-load resistance exercise under vascular restriction triggers skeletal muscle cells to secrete irisin.
Irisin increases expression of insulin-like growth factor-1 in muscle tissue.
Irisin reduces expression of myostatin, a protein that limits muscle growth.
Increased IGF-1 and decreased myostatin enhance activation and proliferation of muscle stem cells and promote fusion into existing fibers.
Evidence from Studies
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