 Muscle Sympathetic Nerve Activity. Muscle sympathetic nerve activity MSNA was directly recorded from the peroneal nerve using the technique of microneurography Roveda et al., 2003; Ueno et al., 2009. Muscle sympathetic bursts were identified by visual inspection by a single investigator, blinded to the study protocol, and were expressed as burst frequency bursts per min and burst per 100 heart beats. 