Am J Physiol Heart Circ Physiol 315: H492–H501, 2018
Jaimie L. Ward,1* X Jesse C. Craig,2* Yumei Liu,1 Eric D. Vidoni,3 Rebecca Maletsky,4 David C. Poole,2 and Sandra A. Billinger1
1 Department of Physical Therapy and Rehabilitation Science, University of Kansas Medical Center, Kansas City, Kansas;
2 Department of Kinesiology and Department of Anatomy and Physiology, Kansas State University, Manhattan, Kansas;
3 University of Kansas Alzheimer’s Disease Center, Fairway, Kansas;
and 4Lawrence, Kansas
Ward JL, Craig JC, Liu Y, Vidoni ED, Maletsky R, Poole DC, Billinger SA. Effect of healthy aging and sex on middle cerebral artery blood velocity dynamics during moderate intensity exercise.Am J Physiol Heart Circ Physiol 315: H492–H501, 2018. First published May 18, 2018;doi:10.1152/ajpheart.00129.2018.—Blood velocity measured in the middle cerebral artery (MCAV) increases with finite kinetics during moderate-intensity exercise, and the amplitude
and dynamics of the response provide invaluable insights into the controlling mechanisms. The MCAV response after exercise onset is well fit to an exponential model in young individuals but remains to be characterized in their older counterparts. The responsiveness of vasomotor control degrades with advancing age, especially in skeletal muscle. We tested the hypothesis that older subjects would evince a slower and reduced MCAV response to exercise. Twenty-nine healthy
young (25 1 yr old) and older (69 1 yr old) adults each performed a rapid transition from rest to moderate-intensity exercise on a recumbent stepper. Resting MCAV was lower in older than young
subjects (47 2 vs. 64 3 cm/s, P 0.001), and amplitude from rest to steady-state exercise was lower in older than young subjects (12 2 vs. 18 3 cm/s, P 0.04), even after subjects were matched for work rate. As hypothesized, the time constant was significantly longer (slower) in the older than young subjects (51 10 vs. 31 4 s, P 0.03), driven primarily by older women. Neither age-related
differences in fitness, end-tidal CO2, nor blood pressure could account for this effect. Thus, MCAV kinetic analyses revealed a marked impairment in the cerebrovascular response to exercise in older individuals. Kinetic analysis offers a novel approach to evaluate the efficacy of therapeutic interventions for improving cerebrovascular function in elderly and patient populations.
NEW & NOTEWORTHY Understanding the dynamic cerebrovascular response to exercise has provided insights into sex-related cerebrovascular control mechanisms throughout the aging process. We report novel differences in the kinetics response of cerebrovascular blood velocity after the onset of moderate-intensity exercise.The exponential increase in brain blood flow from rest to exercise revealed that 1) the kinetics profile of the older group was blunted compared with their young counterparts and 2) the older women demonstrated a slowed response.
