After nine weeks of Nordic hamstring training, the nervous system activates muscle fibers at higher force levels, and the firing rate of those fibers returns to normal, suggesting that muscle...

Pro

Against

Mechanism

Synthesis from 1 study

How it works

At first, your nerves fire faster to make your muscles stronger, but after weeks of training, your muscles physically change so they can produce more force without needing faster nerve signals. Your muscles now turn on and off at higher levels of force because they’ve grown longer and more...

Most probable mechanism

In Simple Terms

Causal chain

High-force eccentric contractions activate sensory receptors in muscle and tendon, increasing excitatory input to spinal motor neurons.

Verified by multiple studies

which leads to

This elevates the firing rate of motor units in the early phase, boosting force output through increased neural drive.

Verified by multiple studies

which leads to

Repeated mechanical stress induces structural changes in muscle fibers, including sarcomerogenesis and increased fascicle length, altering the length-tension relationship.

Verified by multiple studies

which leads to

These structural changes increase the sensitivity of muscle spindles and shift the torque threshold required to recruit and sustain motor unit activity.

Verified by multiple studies

which leads to

As a result, motor units are recruited and de-recruited at higher torque levels, while discharge rate returns to baseline, indicating force production is now sustained by structural properties rather than neural drive.

Verified by multiple studies

Evidence from Studies

Supporting (1)

Community contributions welcome

Biceps femoris long-head motor unit discharge rates and recruitment thresholds vary across 9 weeks of eccentric training

Cohort Study

Human

2026 Apr 27

Contradicting (0)

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No contradicting evidence found

Gold Standard Evidence Needed

According to GRADE and EBM methodology, here is what ideal scientific evidence would look like to definitively prove or disprove this specific claim, ordered from strongest to weakest evidence.

Source Study

Biceps femoris long-head motor unit discharge rates and recruitment thresholds vary across 9 weeks of eccentric training

Score: 31

DOI: 10.1016/j.jshs.2026.101142

Similar Assertions

Performing Nordic hamstring exercises over several weeks leads to a measurable increase in the amount of force needed to activate muscle motor units, with greater increases seen after longer training periods.

89%

After nine weeks of Nordic hamstring exercises, the force required to stop muscle fibers from firing increases by 12%, but no change is seen after three weeks, suggesting that the nervous system's control of muscle activation adapts slowly over time.

88%

Performing Nordic hamstring exercises for three weeks leads to a 6% increase in the rate at which nerve signals activate the biceps femoris muscle, but this increase stops after nine weeks, suggesting that initial strength improvements are driven by nervous system changes that become less influential over time.

86%

After nine weeks of Nordic hamstring exercises, recreationally active men showed a 17% increase in knee flexor strength, with noticeable improvements starting at three weeks, indicating a gradual improvement in muscle force production.

77%

Doing two different hamstring exercises—Nordic curls and stiff-leg deadlifts—makes you stronger at both, even if your muscles don’t grow the same way, meaning muscle growth isn’t what’s making you stronger in the other exercise.

75%