Objective: To investigate the effect of isometric biceps brachii contraction and neck flexion on the time course of threshold sural amplitude.
Design: 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.
Results: 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).
Conclusion: 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.