After resistance training, the thickening of the vastus lateralis muscle in young men is not the same along its length: the part closer to the knee grows more than the part closer to the hip.
Mechanism
Synthesis from 1 study
When you do leg exercises, the part of your thigh muscle closest to the knee gets stretched more and works harder, so it grows more. This happens because your body naturally recruits the strongest muscle fibers there when you lift heavy. Other factors like blood flow or connective tissue might...
Most probable mechanism
When you lift weights, your body uses different muscle fibers depending on how hard you push. The part of the muscle near the knee gets worked harder during knee extensions because it's easier for the nerves to activate those fibers when the muscle is stretched. This means more force is generated there, which triggers more growth in that area compared to the part near the hip.
High-load resistance training recruits high-threshold motor units preferentially in distal regions of the vastus lateralis due to greater mechanical demand and muscle length during knee extension
Increased mechanical tension in distal muscle fibers activates intracellular signaling pathways such as mTOR, leading to elevated muscle protein synthesis
Sustained net positive muscle protein balance results in greater myofibrillar accretion and fiber enlargement in distal regions compared to proximal regions
Less supported by current evidence, but not ruled out
When blood flow is partially blocked during light lifting, waste products build up more in some parts of the muscle, especially near the knee, which may cause swelling and trigger growth signals more strongly in those areas.
Blood flow restriction during low-load resistance training causes metabolite accumulation and cellular swelling, with greater accumulation in distal regions due to anatomical constraints on venous outflow
Metabolite accumulation activates anabolic signaling pathways (e.g., mTOR, MAPK) and increases satellite cell activity in regions with higher metabolite retention
Enhanced anabolic signaling leads to greater muscle protein synthesis and fiber hypertrophy in distal regions compared to proximal regions
The connective tissue around the muscle thickens after training, and this might allow the part near the knee to expand more easily than the part near the hip, shaping where growth happens.
Resistance training induces mechanical strain on the fascia surrounding the vastus lateralis, triggering fibroblast activation and collagen deposition
Regional differences in fascial thickness or stiffness may alter the mechanical environment for muscle fiber expansion, favoring distal growth
Remodeled fascia may provide structural support that enables greater distal hypertrophy by limiting proximal expansion or enhancing force transmission distally
Evidence from Studies
Supporting (1)
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Contradicting (0)
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