Saniya Waghmare1, PT, Alicen A. Whitaker-Hilbig2, DPT, PhD, Mark Chertoff1, PhD, & Sandra A. Billinger1,3, PT, PhD

1University of Kansas Medical Center, Kansas City, Kansas; 2Medical College of Wisconsin, Milwaukee, Wisconsin; 3University of Kansas Alzheimer’s Disease Research Center, Fairway, Kansas

PURPOSE: With aging, studies have linked elevated beat-to-beat blood pressure variability (BTB BPV) with negative cardiovascular health. BTB BPV is a measure of the physiological autonomic nervous and cardiovascular systems interplay. The objective was to characterize mean arterial pressure BTB BPV response during high intensity interval exercise (HIIE, an exercise that repetitively switches between high intensity and active recovery) to determine the effect of aging on sympathetic nervous activity during a challenging exercise stimulus.

METHODS: Secondary analysis was performed on datasets of 25 young adults, 24.96 (1.64) years of age, 48% women and 25 sedentary older adults, 60.84 (13.84) years of age, 36% women. HIIE, alternated 1-minute bouts at 70% and 10% estimated Wattmax for 10 minutes, switching between high intensity and active recovery. Maximal watts were determined using a submaximal exercise test. Blood pressure was measured using finger photoplethysmography. Raw data sampled at 500 Hz was resampled at 10 Hz to obtain beat-to-beat blood pressure. We separated high-intensity and active recovery bouts, concatenating 5 minutes of data for each intensity. Low frequency power spectral density (LF PSD) of BTB BPV was obtained by Fast Fourier transform and cross spectral density, 100-s Hanning window, 50% superposition. LF PSD, reflecting sympathetic nervous activity influence, was summed within the BTB BPV spectral range of 0.04 – 0.15 Hz. We tested normality using Shapiro Wilk test and sphericity using Mauchly’s test. The Mann-Whitney U test was used for analysis between age groups.

RESULTS: LF PSD during the high-intensity bouts of HIIE for young adults was 1177.5 (662.3) mm2/Hg, and for older adults was 1274.4 (1348.2) mm2/Hg; Z = -0.84, p = 0.3. Average LF PSD during HIIE recovery for young adults was 1743.2 (1145.5) mm2/Hg, and for older adults was 1226.3 (1064.4) mm2/Hg; Z = -2.45, p < 0.05. CONCLUSION: BTB BPV reflected sympathetic activity measured by LF PSD did not differ with aging during the high intensity bouts of HIIE, LF PSD reduced in older adults during the recovery bouts. Future studies should examine the relationship between reduced sympathetic activity responsiveness during HIIE and changes in vascular structures, reduced baroreflex sensitivity and adrenergic sensitivity with aging.

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