Sarcolemmal Excitability Properties of the Trapezius.

Introduction/aims: The sarcolemma can be probed in vivo using muscle excitability recordings. These techniques have been applied to the tibialis anterior and brachioradialis muscles in healthy and diseased states. We aimed to study and validate the trapezius as a more proximal muscle to be used for myopathic conditions.

Methods: Muscle velocity recovery cycles (MVRCs) and frequency ramp recordings were performed on the trapezius of 29 healthy controls. These recordings were compared to tibialis anterior recordings from 74 healthy controls.

Results: Overall, the recorded MVRC and frequency ramp recordings were similar between the trapezius and tibialis anterior. The mean relative refractory period (MRRP) was shorter in the trapezius (3.29 vs. 3.71 ms), but this is explained by differences in muscle temperature.

Discussion: The trapezius demonstrates similar MVRC and frequency ramp parameters to the more commonly studied tibialis anterior. The trapezius is technically easy to study using muscle excitability techniques and therefore presents itself as a promising muscle to study sarcolemmal properties in conditions that preferentially affect the proximal musculature.