The nerves don’t become more sensitive to signals—they just fire more often and start earlier, which is how the untrained arm gets stronger without the brain sending stronger commands.
Scientific Claim
Unilateral eccentric biceps training does not alter the input-output gain of motoneurons in either limb, indicating that the neural drive to muscles becomes more efficient through changes in discharge rate and recruitment, not through altered sensitivity to synaptic input.
Original Statement
“The input-output gain of motoneurons, measured as the association between the change in discharge rate and exerted force during the ramp-up phase of contractions, was not altered by resistance training in both limbs for the intervention group (p > 0.05)”
Evidence Quality Assessment
Claim Status
appropriately stated
Study Design Support
Design supports claim
Appropriate Language Strength
definitive
Can make definitive causal claims
Assessment Explanation
The RCT design with precise measurement of input-output gain allows definitive conclusions about the absence of change. The claim accurately reflects the null result without overinterpretation.
Evidence from Studies
Supporting (1)
Cross-education: motor unit adaptations mediate the strength increase in non-trained muscles following 8 weeks of unilateral resistance training
Training one arm made the other arm stronger too, not because the nerves became more sensitive, but because the nerves sent stronger and more frequent signals to the muscles.