Training one arm with heavy weights three times a week for six weeks can improve the endurance of the opposite, untrained arm, allowing it to perform about 5 to 11 more repetitions in a strength...
Mechanism
Synthesis from 1 study
Training one arm hard teaches the brain to send stronger signals to both sides of the body. Even the unused arm gets better at doing repeated movements because its muscles receive more command signals from the brain, letting it push longer before tiring.
Most probable mechanism
When one arm is trained with heavy weights, the brain's movement control center becomes more active and sends stronger signals to the opposite side of the brain, which then tells the unused arm's muscles to work harder and more efficiently. This lets the unused arm perform more repetitions before getting tired, even though it never lifted any weights.
High-load resistance training induces neuroplastic changes in the primary motor cortex of the trained hemisphere, increasing its output signal strength.
Enhanced activity in the trained motor cortex increases transcallosal signaling to the contralateral motor cortex, altering excitatory-inhibitory balance in the untrained hemisphere.
The contralateral motor cortex increases corticospinal drive to the untrained limb's motor neurons, improving the recruitment and firing rate of motor units.
Increased motor unit recruitment and firing efficiency in the untrained limb allows sustained force production during repetitive contractions, delaying fatigue and increasing the number of repetitions completed.
Evidence from Studies
Supporting (1)
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Unilateral High-Load Resistance Training Increases Absolute but Not Relative Muscular Endurance in the Contralateral Untrained Limb
Contradicting (0)
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