Autonomic function
1. Time domain
Mean R-R interval (RRI) – Average time between peak of R-waves R-R interval standard deviation (RRISD) – Measure of vagal cardiac tone Baroreflex sensitivity (BRS) – Increase in RRI in response to increases in arterial pressure
Stroke Volume (SV), cardiac output (Q), and total peripheral resistance (TPR) – Estimated using arterial blood pressures on a beat-by-beat basis via the pulse contour method

MSNA - Integral of all sympathetic bursts for supine baseline rest period was determined and divided by the number of bursts occurring during rest to get an average control burst area. The area of each burst recorded henceforth was normalized by dividing it by the average control burst area

Sympathetic baroreflex gain – Ratio of decrease in SAP to increase in MSNA during phase II

Vagal baroreflex gain – Linear regression between RRI and SAP during phase IV overshoot

2. Frequency domain
RRI and SAP fast Fourier-based power spectral analysis – Low and respiratory powers were expressed as the area under the curve between 0.04-0.15 Hz and 0.15-0.40 Hz, respectively

Sympathovagal balance (SVB RRI) – Ratio of low to respiratory frequency power from the RRI spectrum as an index of sympathetic activity

Cross spectral analysis between SAP power and RRI power to calculate transfer function (alpha LF) via WinCPRS

VO2max Testing
VO2 - oxygen consumption: the difference between the volume of oxygen inhaled and exhaled
VO2 = (VI * FIO2) – (VE * FEO2)
VO2max = Maximum VO2 (measured during the last minute of testing)
Haldane Transformation
Assumes that the total volume of nitrogen inhaled is equal to that exhaled
FIN2 = 1 - FIO2 - FICO2 and FEN2 = 1 - FEO2 - FECO2
VE = (VI * FIN2) / FEN2
RER – respiratory exchange ratio: ratio of VCO2 to VO2
RER = VCO2 / VO2 (used to determine the body?s source of fuel -- fats vs. carbohydrates)

Statistical Analysis
We used repeated measures analysis of variance (ANOVA) with repeats on time (pre- vs. post-exercise).