Training only one limb can increase strength in the untrained limb due to a central neural adaptation. What is this phenomenon called?

Training only one limb can increase strength in the untrained limb due to a central neural adaptation. What is this phenomenon called?

• A. Bilateral transfer
• B. Cross-education
• C. Mirror training
• D. Cross-activation

Answer: (B)

Cross-education is the phenomenon where training a muscle on one side leads to strength gains in the opposite, untrained limb. This happens through central nervous system adaptations—changes in the brain and spinal pathways that improve neural drive, motor unit recruitment, and coordination for both limbs via interhemispheric connections. The untrained limb gets stronger not because its muscles hypertrophy, but because the nervous system becomes more efficient at activating them. Other terms can describe related ideas, but they don’t capture the full mechanism as precisely. Bilateral transfer is a broader label for effects that transfer between limbs, cross-activation refers to neural activity in the untrained limb during training, and mirror training relies on visual feedback. The strongest, most specific fit for unilateral training yielding contralateral strength gains through CNS changes is cross-education.

Cross-education is the phenomenon where training a muscle on one side leads to strength gains in the opposite, untrained limb. This happens through central nervous system adaptations—changes in the brain and spinal pathways that improve neural drive, motor unit recruitment, and coordination for both limbs via interhemispheric connections. The untrained limb gets stronger not because its muscles hypertrophy, but because the nervous system becomes more efficient at activating them.

Other terms can describe related ideas, but they don’t capture the full mechanism as precisely. Bilateral transfer is a broader label for effects that transfer between limbs, cross-activation refers to neural activity in the untrained limb during training, and mirror training relies on visual feedback. The strongest, most specific fit for unilateral training yielding contralateral strength gains through CNS changes is cross-education.