Training one arm doesn’t just make it stronger—it also makes the muscles fire more smoothly and steadily, even in the other arm, leading to more controlled movements.
Scientific Claim
Unilateral eccentric biceps training reduces motor unit firing variability (ISIv) by 4.6% in the untrained limb and improves force steadiness (CovF), indicating that neural adaptations enhance the precision of muscle control in both trained and untrained limbs.
Original Statement
“The untrained limb presented a significant decrease in ISIv following 4 weeks (∆ISIv = −3.9%) and 8 weeks (∆ISIv = −4.6%)... Lower interspike interval variability was also accompanied by enhanced force steadiness (lower CovF)”
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 repeated measures and statistical significance (p < 0.001) supports causal inference. The claim accurately reflects the observed changes without overextending to mechanisms.
Evidence from Studies
Supporting (0)
Contradicting (1)
Cross-education: motor unit adaptations mediate the strength increase in non-trained muscles following 8 weeks of unilateral resistance training
The study shows that training one arm can make the other arm stronger due to brain and nerve changes, but it didn’t measure whether the movements became more steady or consistent, which is what the claim says.