Abstract
Abstract only Background Habitual exercise has previously been shown to alter the cerebrovascular response to hypercapnia. Similar to hypercapnia, increases in the brain’s metabolic activity result in local augmentation of cerebral blood flow; however, the mechanisms governing the cerebrovascular response to these two stimuli likely differ. Although, previous studies have examined the influence of aerobic exercise on the cerebrovascular response to hypercapnia, little is known about the influence of habitual resistance training on cerebrovascular function. Therefore, the purpose of this study was to evaluate the cerebrovascular response to both hypercapnia and a metabolic stimulus (cognitive challenge) in resistance trained (RT), aerobic trained (AT), and untrained (UT) adults. Methods We recruited 13 RT (women: n = 2, age: 24 ± 4 y), 12 AT (women: n = 2, age: 28 ± 6 y), and 13 UT (women: n = 2, age: 27 ± 5 y) healthy young adults. Middle cerebral artery velocity (MCAv), beat‐to‐beat mean arterial blood pressure (MAP) and end‐tidal carbon dioxide (ETCO 2 ) were continuously monitored during hypercapnia and a Stroop Color and Word Test. Cerebrovascular conductance index (CVCi) was calculated as MCAv/MAP. Reactivity to hypercapnia was calculated as the slope of the relationship between each variable of interest (MCAv or CVCi) and ETCO 2 . Responses to the Stroop test were calculated as the absolute change from baseline to the 3‐beat peak of each variable during the test. Results There were no significant differences in MCAv reactivity and CVCi reactivity to hypercapnia between groups. Despite all groups having a similar change in MAP and ETCO 2 during the Stroop test, RT individuals had a greater increase in MCAv (RT: 18.1 ± 1.9 cm/s, AT: 9.7 ± 1.5 cm/s, UT: 15.7 ± 2.0 cm/s; AT vs. RT p < 0.01; AT vs. UT p = 0.07) and CVCi (RT: 0.15 ± 0.02 cm/s/mmHg, AT: 0.08 ± 0.02 cm/s/mmHg, UT: 0.12 ± 0.02 cm/s/mmHg; AT vs. RT p = 0.05; AT vs. UT p = 0.28) compared with AT individuals during the Stroop test. While there was a positive association between the MCAv response to hypercapnia and the MCAv response to the Stroop test in AT individuals (r = 0.67, p < 0.05), and a trend for association in UT individuals (r = 0.49, p = 0.09), there was no relationship between the two variables in RT individuals (r = 0.18, p = 0.56). Conclusion While exercise modality did not influence the cerebrovascular response to hypercapnia, it did influence the response to a metabolic stimulus, such that RT individuals had a greater MCAv and CVCi response to a cognitive challenge, compared with AT individuals. Further, exercise modality may influence the mechanisms by which the cerebrovasculature of young adults responds to physiological stimuli. Support or Funding Information Supported by National Institute of Health grant HL118154