Time-course recovery of cerebral blood velocity metrics post aerobic exercise: a systematic review

Currently, the standard approach for restricting exercise prior to cerebrovascular data collection varies widely between 6 and 24 h. This universally employed practice is a conservative approach to safeguard physiological alterations that could potentially confound one's study design. Therefore, the purpose of this systematic review was to amalgamate the existing literature examining the extent and duration of postexercise alterations in cerebrovascular function, measured via transcranial Doppler ultrasound. Furthermore, an exploratory aim was to scrutinize and discuss common biases/limitations in the previous studies to help guide future investigations. Search strategies were developed and imported into PubMed, SPORTDiscus, and Medline databases. A total of 595 records were screened and 35 articles met the inclusion criteria in this review, which included assessments of basic cerebrovascular metrics (n = 35), dynamic cerebral autoregulation (dCA; n = 9), neurovascular coupling (NVC; n = 2); and/or cerebrovascular reactivity (CVR-CO2; n = 1) following acute bouts of aerobic exercise. Across all studies, it was found that NVC was impacted for 1 h, basic cerebrovascular parameters and CVR-CO2 parameters for 2 h, and dCA metrics for 6 h postexercise. Therefore, future studies can provide participants with these evidence-based time restrictions, regarding the minimum time to abstain from exercise prior to data collection. However, it should be noted that other physiological mechanisms could still be altered (e.g., metabolic, hormonal, and/or autonomic influences), despite cerebrovascular function returning to baseline levels. Thus, future investigations should seek to control as many physiological influences when using cerebrovascular assessments, immediately following these time restraints. The main limitations/biases were lack of female participants, cardiorespiratory fitness, and consideration for vessel diameter.