Relationship between blood pressure and cerebral blood flow during supine cycling: Influence of aging

Jonathan D. Smirl*, Keegan Hoffman, Yu Chieh Tzeng, Alex Hansen, Philip N. Ainslie

*Corresponding author for this work

    Research output: Contribution to journalArticlepeer-review

    7 Citations (Scopus)


    The cerebral pressure-flow relationship can be quantified as a highpass filter, where slow oscillations are buffered (<0.20 Hz) and faster oscillations are passed through relatively unimpeded. During moderate intensity exercise, previous studies have reported paradoxical transfer function analysis (TFA) findings (altered phase or intact gain). This study aimed to determine whether these previous findings accurately represent this relationship. Both younger (20-30 yr; n = 10) and older (62-72 yr; n = 9) adults were examined. To enhance the signal-to-noise ratio, large oscillations in blood pressure (via oscillatory lower body negative pressure; OLBNP) were induced during steady-state moderate intensity supine exercise (∼45-50% of heart rate reserve). Beat-to-beat blood pressure, cerebral blood velocity, and end-tidal P CO2 were monitored. Very low frequency (0.02- 0.07 Hz) and low frequency (0.07- 0.20 Hz) range spontaneous data were quantified. Driven OLBNP point estimates were sampled at 0.05 and 0.10 Hz. The OLBNP maneuvers augmented coherence to >0.97 at 0.05 Hz and >0.98 at 0.10 Hz in both age groups. The OLBNP protocol conclusively revealed the cerebrovascular system functions as a high-pass filter during exercise throughout aging. It was also discovered that the older adults had elevations (+71%) in normalized gain (+0.46 ± 0.36%/%: 0.05 Hz) and reductions (-34%) in phase (-0.24 ± 0.22 radian: 0.10 Hz). There were also age-related phase differences between resting and exercise conditions. It is speculated that these age-related changes in the TFA metrics are mediated by alterations in vasoactive factors, sympathetic tone, or the mechanical buffering of the compliance vessels.

    Original languageEnglish
    Pages (from-to)552-563
    Number of pages12
    JournalJournal of Applied Physiology
    Issue number5
    Publication statusPublished - 1 Mar 2016


    • Aging
    • Blood pressure
    • Exercise
    • Oscillatory lower body negative pressure
    • Transfer function analysis


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