Evaluating peripheral neuromuscular function with brief movement-evoked pain.

Movement-evoked pain is an understudied manifestation of musculoskeletal conditions that contributes to disability, yet little is known about how the neuromuscular system responds to movement-evoked pain. The present study examined whether movement-evoked pain impacts force production, electromyographic (EMG) muscle activity, and the rate of force development (RFD), during submaximal muscle contractions. Fifteen healthy adults (9 male, age = 30.3 ± 10.2; range = 22-59) performed submaximal isometric first finger abduction contractions without pain (baseline) and with movement-evoked pain induced by laser stimulation to the dorsum of the hand. Normalized force (% maximal voluntary contraction) and RFD decreased by 11% (p<0.001) and 15% (p=0.003), respectively, with movement-evoked pain, without any change in normalized peak EMG (p=0.77). Early contractile RFD, force impulse, and corresponding EMG amplitude computed within time segments of 50, 100, 150, 200ms relative to the onset of movement were also unaffected by movement-evoked pain (p>0.05). Our results demonstrate that movement-evoked pain impairs peak characteristics and not early measures of submaximal force production and RFD without affecting EMG activity (peak and early). Possible explanations for the stability in EMG with reduced force includes antagonist coactivation and a reorganization of motoneuronal activation strategy, which will be discussed herein.