A reflex hammer for accurate measurement of reflex latency.

Abstract A hammer equipped with a piezo-electric crystal is suitable to measure fast tendon jerk latencies more accurately than a hammer equipped with a mechanical switching device. Measurements show that the hammer supplied with a piezo-electric crystal gives a pulse within 50 μsec — at least 10 times faster than hammers supplied with a mechanical switch — which is negligible in comparison with the latency of any reflex response.