After performing heavy bicep curls with the shoulder extended, the lower part of the long head of the biceps muscle shows a larger decrease in stiffness compared to other parts of the muscle,...
Mechanism
Synthesis from 1 study
When you lift a heavy weight with your arm stretched back, the bottom part of your biceps gets pulled extra tight. That extra pull tears tiny parts inside the muscle fibers there, making that spot softer than the rest. That’s why it shows up as a bigger drop in stiffness after the workout.
Most probable mechanism
When you bend your elbow with your shoulder pulled back, the lower part of your biceps gets stretched tighter than other parts. This extra stretch, especially when you're lowering a heavy weight, tears tiny structures inside the muscle fibers there. These tears make that part of the muscle softer and less stiff, which is why it shows up as a bigger drop in stiffness after the workout.
Shoulder extension elongates the biceps brachii, increasing passive tension in its elastic components, particularly in the distal long head region
High-load eccentric elbow flexion under elevated passive tension imposes excessive mechanical strain on sarcomeres in the distal long head, which is biomechanically vulnerable due to its anatomical position and fiber orientation
Mechanical strain disrupts sarcomeric Z-disks and cytoskeletal proteins, reducing tissue integrity and stiffness as measured by shear modulus
Evidence from Studies
Supporting (1)
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Biceps brachii regional shear modulus following elbow flexion exercises at different muscle lengths.
Contradicting (0)
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