Age Alters Integrated Cerebrovascular and Cardiovascular Dynamic Responses to Exercise: Insights from a Systems Modeling Approach

Figures

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  Figure 1.. Middle cerebral artery blood velocity (MCAv) response to moderate-intensity exercise. Exercise onset (dashed line at 0 s). 1a Group average MCAv (cm*s−1) across the entire sample (n = 164). 1b MCAv response stratified by age group: young (black), middle-aged (gray), and older adults (light gray). 1c MCAv response stratified by sex: males (black) and females (gray).

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  Figure 2.. Mean arterial pressure (MAP) response to moderate-intensity exercise. Exercise onset (dashed line at 0 s). 1a Group average MAP (millimeters of mercury; mmHg) across the entire sample (n = 164). 1b MAP response stratified by age group: young (black), middle-aged (gray), and older adults (light gray). 1c MAP response stratified by sex: males (black) and females (gray).

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  Figure 3.. Heart rate (HR) response to moderate-intensity exercise. Exercise onset (dashed line at 0 s). 3a Group average HR (beats per minute, bpm) across the entire sample (n = 164). 3b HR response stratified by age group: young (black), middle-aged (gray), and older adults (light gray). 3c HR response stratified by sex: males (black) and females (gray).

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  Figure 4.. End tidal carbon dioxide (PETCO2) response to moderate-intensity exercise. Exercise onset (dashed line at 0 s). 3a Group average PETCO2 (millimeters of mercury, mmHg) across the entire sample (n = 164). 3b PETCO2 response stratified by age group: young (black), middle-aged (gray), and older adults (light gray). 3c PETCO2 response stratified by sex: males (black) and females (gray).

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  Figure 5:. Estimated system VAR(9) model of physiological data. Each panel shows the estimated effect of one physiological factor from the past 9 lags (4.5 seconds) on the immediate level of another physiological factor (e.g. PETCO2->HR indicates the effect of PETCO2 level on HR). Bonferroni-corrected 95% confidence intervals of the estimates are plotted, as well as stars indicating the level of statistical significance testing whether the corresponding true effect is nonzero after applying Bonferroni correction across all 144 tests.

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  Figure 6:. Estimated coefficients for VAR(9) model of physiological data for each subject, split by age. Each panel shows the estimated effect of one physiological factor from the past 9 lags (43.5 seconds) on the current level of another physiological factor (e.g. PETCO2->HR indicates the effect of PETCO2 level on HR), for each subject colored by their age. Stars indicate the level of statistical significance testing whether there was a difference in the effect between age groups (young, middle-age, and older) after applying a Bonferroni correction for 144 tests.