Increased threshold sural amplitude after upper limb isometric contractionin complete paraplegics

Objective: To determine whether the enhancement of threshold sural sensory nerve action potentials (SNAPs) occurred in patients with spinal cord injur y after upper limb isometric contraction. Design: This prospective study, in which ten paraplegic patients with spina l cord injury were recruited from the Harris County community and served as his/her own control, was performed in the electromyography laboratory at H arris County Hospital District Quentin Mease Hospital. The baseline SNAP wa s established using ten threshold, signal-averaged stimuli to the sural ner ve. With the same stimulus strength, the SNAP was recorded while the subjec ts' arms were pulled apart against a force gauge at 50% and 100% maximum fo rce. Responses were recorded every 4 min until the values returned to basel ine, Results: Results showed an increase in the SNAP amplitude after 50% and 100 % maximum force. The mean preexercise SNAP amplitude was 4.0 +/- 0.6 (SE) m uV. At 50% force, the SNAP amplitude was 7.57 +/- 1.2 muV; at 100% force, i t was 7.29 +/- 1.2 muV. The post hoc analysis of the data revealed P = 0.00 9 and P = 0.01 for 50% and 100% maximum force, respectively, Conclusions: The threshold SNAP of the sural nerve was enhanced after isome tric exercise in paraplegic patients with spinal cord injury.