Organization of segmental reflexes in trained dancers.

Unilateral and conditioned Achilles tendontap reflex (ATR) characteristics were examined in a group of skilled dancers and a group of sedentary, untrained subjects (n = 7/group). For the conditioned reflex, the right ATR was conditioned by a tap to the left Achilles tendon using intervals of 10, 40, 70, 100, 130, 160 and 190 ms. Peak isometric force, contraction time and half-relaxation time were examined on each trial. The results indicated that the trained dancers exhibited less unilateral isometric force and longer half-relaxation times (p less than 0.05) than the untrained subjects. Moreover, the contralateral conditioning stimulus caused a more marked short-latency facilitation as well as a long-latency inhibition in the reflex force characteristics for the trained dancers when compared with the untrained subjects. These differences in both simple and conditioned reflexes in individuals trained for dance activities may reflect differences in muscle stiffness, tissue compliance or neural organization.