Research Paper Volume 14, Issue 9 pp 3910—3920

Figure 1. Representative cerebral hemodynamic response during a maximal handgrip strength test. BOV (amplitude or SD of oxyhemoglobin-to-total hemoglobin ratio) increases mildly during a 10-repeated maximal voluntary muscle exertion in adults aged 25 y (A) and 75 y (B). BHV (amplitude or SD of total hemoglobin) elevated substantially during the maximal contraction task in adults aged 25 y (C) and 75 y (D). To maintain stable oxygenation (A, B), the adult at age 75 y shows much vigorous cerebral hemodynamic response (scale increases ~100 folds) than the young counterpart at age 25 y, suggesting a huge compensatory cost of vascular control (vasoconstriction/ vasorelaxation) in the brain during muscle exertions. Abbreviations: SD: standard deviation of the 300 optical data in 30 sec; BOV: brain oxygenation variability; BHV: brain hemodynamic variability.