The impact of damaging exercise on electromechanical delay in biceps brachii

Abstract 

Electromechanical delay (EMD) can be a useful tool in providing information on muscle function changes following a number of exercise interventions. The purpose of this investigation was to examine the effect of damaging exercise on EMD. Twelve volunteers completed 45 maximal lengthening contractions of the elbow flexors. Indices of muscle damage (maximum voluntary isometric torque and isokinetic torque (60s⁻¹ and 210s⁻¹), creatine kinase (CK), muscle soreness (DOMS)) were recorded pre-exercise, 48h and 96h post-exercise; electromyography was recorded from the belly of biceps brachii and EMD was determined during each contraction condition. Significant time effects were observed for all damage indices (P<0.05). Whilst muscle function was close to full recovery at 96h, both CK and DOMS were significantly (P<0.001) elevated above baseline. EMD was significantly greater at 96h for all contraction conditions (P⩽0.017), but not at 48h. Damaging exercise induces alterations in EMD beyond the apparent recovery of maximal voluntary contractions, which is likely to be a reflection of the changes in post-synaptic events. These data have applications for the use of EMD as a tool for exercise prescription and monitoring recovery following strenuous damaging exercise.

Keywords: Lengthening contractions, Electromyography, Post-synaptic events, Exercise-induce muscle damage