The peripheral origin of tap-induced muscle contraction revealed by multi-electrode surface electromyography in human vastus medialis

Abstract

It is well established that muscle percussion may lead to the excitation of muscle fibres. It is still debated, however, whether the excitation arises directly at the percussion site or reflexively, at the end plates. Here we sampled surface electromyograms (EMGs) from multiple locations along human vastus medialis fibres to address this issue. In five healthy subjects, contractions were elicited by percussing the distal fibre endings at different intensities (5-50 N), and the patellar tendon. EMGs were detected with two 32-electrode arrays, positioned longitudinally and transversally to the percussed fibres, to detect the origin and the propagation of action potentials and their spatial distribution across vastus medialis. During muscle percussion, compound action potentials were first observed at the electrode closest to the tapping site with latency smaller than 5 ms, and spatial extension confined to the percussed strip. Conversely, during tendon tap (and voluntary contractions), action potentials were first detected by electrodes closest to end plates and at a greater latency (mean ± s.d., 28.2 ± 1.7 ms, p < 0.001). No evidence of reflex responses to muscle tap was observed. Multi-electrode surface EMGs allowed for the first time to unequivocally and quantitatively describe the non-reflex nature of the response evoked by a muscle tap.

Physical and electrophysiological motor unit characteristics are revealed with simultaneous high-density electromyography and ultrafast ultrasound imaging

“…The often implicit assumption in these studies is that EMGs with high amplitude are associated with excitation of a spatially localised site underlying the electrode array 23 . The presumptive logic associating local changes in EMG amplitude with local changes in muscle excitation has been substantiated in simulated conditions 24 , 25 and, more recently, by local EMG responses to muscle percussion 26 , 27 . The study of the association between the properties of the EMG amplitude distribution and the location of tissue excitation within the muscle requires a method to assess in vivo muscle tissue displacement associated with the activation of a spatially localized group of fibers.…”

High Velocity Passive Stretching Mimics Eccentric Exercise in Cerebral Palsy and May Be Used to Increase Spastic Muscle Fascicle Length

“…Muscle was considered as “inhibited” if any increased ARV activity dropped back to the baseline in any epoch of 60 ms. Muscle was considered as “deactivated” if the ARV dropped below the baseline by 25% (i.e., <baseline − 25% baseline) in any epoch of 60 ms. We expected that TD-EG would not show any increased quadriceps activity during knee flexion at any velocity of knee rotation hence we did not record EMG in this group [ 28 ], while reflex contraction would be observed during knee flexion in the spastic muscles. We did not make any prediction if the reflex contraction would be maintained or inhibited/deactivated throughout the flexion phase in this group.…”

Self-made 3D-printed encapsulation of thin-film transducers for reliable force measurement in biomedical applications

“…Thin-film force sensors are versatile and can potentially be employed in a wide range of applications. For example, due to their low thickness, they have been adopted for the measurement of force and pressure exerted on different body parts [1,2,3,4,5] as well as clenching force [6,7,8,9]. However the behavior of film sensors is strongly influenced by test conditions, e.g., area and nature of the contact surfaces, load direction, etc.…”