Which method is used to measure inhibition by comparing voluntary contraction to an evoked response?

Which method is used to measure inhibition by comparing voluntary contraction to an evoked response?

• A. Burst Superimposition Testing
• B. Central Activation Ratio
• C. Electromyography
• D. Isokinetic testing

Answer: (B)

Central Activation Ratio measures how completely the brain is driving the muscle by comparing what you can voluntarily produce to what an external stimulus elicits during that same maximal effort. In practice, you have the person perform a maximal voluntary contraction and deliver a supramaximal stimulus to evoke an additional twitch during the effort. You then calculate CAR as the voluntary force divided by the sum of voluntary force and the evoked twitch force, times 100. If activation is full, the stimulus doesn’t recruit much more muscle, so the evoked response adds little or nothing, and CAR is near 100%. If there’s central inhibition, the stimulus recruits additional motor units, the evoked force adds more to the total, and CAR drops. This makes CAR a direct, quantitative gauge of central activation or inhibition. Electromyography or isokinetic testing don’t provide this specific ratio of voluntary to evoked activation during a maximal effort, and burst superimposition, while related, is typically described in terms of the presence of a superimposed twitch rather than the explicit central activation ratio.

Central Activation Ratio measures how completely the brain is driving the muscle by comparing what you can voluntarily produce to what an external stimulus elicits during that same maximal effort. In practice, you have the person perform a maximal voluntary contraction and deliver a supramaximal stimulus to evoke an additional twitch during the effort. You then calculate CAR as the voluntary force divided by the sum of voluntary force and the evoked twitch force, times 100.

If activation is full, the stimulus doesn’t recruit much more muscle, so the evoked response adds little or nothing, and CAR is near 100%. If there’s central inhibition, the stimulus recruits additional motor units, the evoked force adds more to the total, and CAR drops. This makes CAR a direct, quantitative gauge of central activation or inhibition.

Electromyography or isokinetic testing don’t provide this specific ratio of voluntary to evoked activation during a maximal effort, and burst superimposition, while related, is typically described in terms of the presence of a superimposed twitch rather than the explicit central activation ratio.