Resting muscle sympathetic nerve activity (MSNA) demonstrates high intra-individual reproducibility when sampled over 5-30 minute epochs, though shorter sampling durations are commonly used prior to, and during, a stress to quantify sympathetic responsiveness. The purpose of the present study was to examine the intra-test validity and reliability of MSNA sampled over 2-minute, 1-minute, 30-second, and 15-second epoch durations. We retrospectively analyzed 68 resting fibular nerve microneurographic recordings obtained from 53 young healthy participants (37 males; 23±6 years of age). From a stable 7 minute resting baseline, MSNA (burst frequency and incidence, normalized mean burst amplitude, total burst area) was compared between each epoch duration and a standard 5-minute control. Bland-Altman plots were used to determine agreement and bias. Three sequential MSNA measurements were collected using each sampling duration to calculate absolute and relative reliability (coefficients of variation and intra-class correlation coefficients). MSNA values were similar between each sampling duration and the 5-minute control (All p>0.05), highly correlated (r = 0.69-0.93, All p<0.001), and demonstrated no evidence of fixed bias (All p>0.05). A consistent proportional bias (p<0.05) was present for MSNA burst frequency (all sampling durations) and incidence (1-minute, 30-second, and 15-second) such that participants with low and high average MSNA underestimated and overestimated the true value, respectively. Reliability decreased progressively using the 30-second and 15-second sampling durations. In conclusion, short 2-minute, 1-minute, and 30-second sampling durations can provide valid and reliable measures of MSNA, though increased sample size may be required for epochs ≤30 seconds due to poor reliability.
- Muscle sympathetic nerve activity
- Copyright © 2016, Journal of Applied Physiology