Effect of cooling on thixotropic position-sense error in human biceps muscle.

Muscle temperature affects muscle thixotropy. However, it is unclear whether changes in muscle temperature affect thixotropic position-sense errors. We studied the effect of cooling on thixotropic position-sense errors induced by short-length muscle contraction (hold-short conditioning) in the biceps of 12 healthy men. After hold-short conditioning of the right biceps muscle in a cooled (5.0°C) or control (36.5°C) environment, subjects perceived greater extension of the conditioned forearm at 5.0°C. The angle differences between the two forearms following hold-short conditioning of the right biceps muscle in normal or cooled conditions were significantly different (–3.335 ± 1.680° at 36.5°C vs. –5.317 ± 1.096° at 5.0°C; P = 0.043). Induction of a tonic vibration reflex in the biceps muscle elicited involuntary forearm elevation, and the angular velocities of the elevation differed significantly between arms conditioned in normal and cooled environments (1.583 ± 0.326°/s at 36.5°C vs. 3.100 ± 0.555°/s at 5.0°C, P = 0.0039). Thus, a cooled environment impairs a muscle's ability to provide positional information, potentially leading to poor muscle performance. Muscle Nerve, 2007