After twelve weeks of either lengthened state eccentric training or Nordic hamstring training, maximum eccentric knee flexion torque increases by about 17% and 11%, respectively, and the improvement...
Mechanism
Synthesis from 1 study
Both exercises make the hamstrings stronger at slowing down the leg, but they do it in different ways. One stretches the muscle longer while lifting, making the whole muscle and its connecting tissue bigger. The other shifts the work to smaller knee muscles, making them stronger instead. Either...
Most probable mechanism
When the hamstrings are stretched and contracted under heavy load while lengthened, the muscle fibers and their connecting tissue grow larger and stronger, allowing them to produce more force during slow, controlled bending of the knee. This happens even if different parts of the muscle grow in different ways, because the overall ability to resist force improves through structural changes in both muscle and connective tissue.
Eccentric contractions performed with the hip flexed elongate the biarticular hamstrings across both the hip and knee joints, generating high mechanical tension along the entire muscle-tendon unit.
High mechanical tension activates intracellular signaling pathways that increase muscle protein synthesis and reduce protein breakdown, leading to addition of sarcomeres in series and radial growth of muscle fibers.
Mechanical strain is transmitted to the proximal aponeurosis of the biceps femoris long head, stimulating fibroblast activity and collagen remodeling, which increases aponeurosis area and width.
Increased muscle volume and enlarged aponeurosis improve force transmission efficiency, allowing greater torque production during eccentric knee flexion regardless of which specific muscle subunits hypertrophy.
Less supported by current evidence, but not ruled out
When the body performs Nordic hamstring training, the hip stays extended, reducing stretch on the long head of the biceps femoris and shifting the load to shorter knee-only muscles. These muscles grow larger and become more active during knee bending, which increases the overall ability to resist force during eccentric movement.
Hip extension during Nordic hamstring training limits passive stretch on biarticular hamstrings, reducing their mechanical contribution to the movement.
Reduced activation of biarticular hamstrings increases relative recruitment of monoarticular knee flexors such as the short head of the biceps femoris and semimembranosus.
Eccentric loading of monoarticular knee flexors under body weight stimulates localized muscle protein synthesis, leading to hypertrophy of these specific fibers.
Increased size and neural drive of monoarticular knee flexors enhance torque production during eccentric knee flexion, compensating for reduced contribution from biarticular muscles.
Evidence from Studies
Supporting (1)
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Hamstrings Hypertrophy Is Specific to the Training Exercise: Nordic Hamstring versus Lengthened State Eccentric Training
Contradicting (0)
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