The relationship between body height extremes and the conditioned patellar tendon reflex response.

The purpose of this study was to determine the effects of extreme body heights on the conditioned patellar tendon reflex response in an attempt to differentiate between the contributions of supraspinal and spinal mechanisms on long-latency reflex facilitation. Unilateral and conditioned right patellar tendon reflexes were assessed in 10 extremely short males and females and 10 extremely tall males and females. The conditioning stimulus was a contralateral patellar tendon tap and the conditioning intervals were 10, 15, 25, 50, 60, 75, 100, 150, and 300 ms. There was a long-latency facilitation of quadriceps excitability beginning at the 75 ms conditioning interval regardless of the height of the subject. It is hypothesized that the similar conditioned patellar tendon recovery profiles in the extremely short subjects and the extremely tall subjects reflects the activation of a spinal polysynaptic pathway as the predominant mechanism for our long-latency reflex facilitation.