When trained individuals exercise biarticular muscles with their joints in positions that stretch the muscles more, those muscles grow larger than when exercised in positions where the muscles are...
Mechanism
Synthesis from 4 studies
When you stretch a muscle while lifting, the fibers pull harder, which tells the muscle to build more protein and get bigger, especially in the parts that stretch the most. This happens even in people who already train regularly.
Most probable mechanism
When a muscle is stretched while under load, the fibers and surrounding structures experience more pull, which triggers signals inside the muscle cells to build more protein and grow thicker, especially in the parts of the muscle that are stretched the most.
Training at longer muscle lengths increases passive tension in the sarcomeres and extracellular matrix during both concentric and eccentric contractions.
Elevated mechanical tension activates mechanotransduction pathways including mTORC1, FAK, and integrin signaling, which upregulate ribosomal biogenesis and muscle protein synthesis.
Biarticular muscles experience greater strain gradients in distal regions near tendon insertions during lengthened contractions, leading to localized anabolic signaling and satellite cell activation.
Increased muscle protein synthesis exceeds breakdown, resulting in net accretion of contractile proteins and radial hypertrophy, most pronounced in the distal regions of the muscle.
Less supported by current evidence, but not ruled out
Stretching a muscle under load increases oxygen deprivation and waste buildup in the tissue, causing small tears that trigger repair processes that add more muscle protein.
Training at longer muscle lengths increases metabolic stress due to reduced blood flow and greater fiber recruitment, leading to lactate accumulation and hypoxia.
Metabolic stress and mechanical strain cause microdamage to muscle fibers and sarcolemma, activating inflammatory and repair pathways.
Muscle damage and metabolic signals increase IGF-1 expression and satellite cell proliferation, contributing to protein accretion and hypertrophy.
Evidence from Studies
Supporting (4)
Community contributions welcome
Exercise Selection Differentially Influences Lower Body Regional Muscle Development
Triceps surae muscle hypertrophy is greater after standing versus seated calf-raise training
Triceps surae muscle hypertrophy is greater after standing versus seated calf-raise training
Contradicting (0)
Community contributions welcome
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