Temporal effects of isometric contraction maneuvers on threshold sural amplitude.

Abstract

To investigate the effect of isometric biceps brachii contraction and neck flexion on the time course of threshold sural amplitude. Twelve healthy subjects, who were asked to lie supine on an examination bench, performed 1 min of muscle contraction. The sural sensory nerve action potential was recorded before, immediately after, and at 2-min intervals after muscle contraction. The preexercise level of stimulus intensity remained unchanged for sural readings throughout the entire course of the experiment. The temporal changes in sensory nerve action potential amplitudes for both maneuvers were similar (P = 0.9734, two-way interaction). The mean sural amplitude after neck flexion increased from 6.0 +/- 2.9 microV (SD) to 10.6 +/- 6.6 microV (SD) 10 min after contraction. Similarly, mean sural amplitude increased from 6.5 +/- 1.8 microV (SD) to 14.5 +/- 9.7 microV (SD) 8 min after biceps brachii contraction. Statistical analysis performed using repeated measures with post hoc least significant difference showed a significant temporal effect in the two groups (P = 0.04). The temporal responses of threshold sural amplitudes after isometric biceps brachii contraction and central reinforcement neck flexion maneuvers are nearly identical with regard to increase in the amplitude.