The use of arterial spin labeling to measure cerebral blood flow (CBF) after acute
exercise has not been reported. The aims of this study were to examine: (1) the optimal
inversion time to detect changes in CBF after acute exercise and (2) if acute exercise
alters CBF in the motor cortex at rest or during finger-tapping. Subjects (n=5) performed
30 min of moderate intensity exercise on an electronically braked cycle ergometer
(perceived exertion 'somewhat hard'). Before and after exercise, relative CBF was
measured using multiple inversion time (TI) pulsed arterial spin labeling (PASL).
Two multiple TI runs were obtained at rest and during 4 Hz finger-tapping. Four inversion
times (675, 975, 1275, and 1,575 ms) were acquired per run, with 20 interleaved pairs
of tag and control images per inversion time (320 s run). The results indicated that
global CBF increased approximately 20% following exercise, with significant differences
observed at an inversion time of 1,575 ms (p<.05). Finger-tapping induced CBF in the
motor cortex significantly increased from before to after exercise at TI=1,575 ms
(p<.01). These findings suggest changes in human cerebral blood flow that result from
acute moderate intensity exercise can be detected afterwards using PASL at 3T with
an inversion time of 1,575 ms. The effect of prior acute exercise to increase motor
cortex CBF during the performance of a motor task suggests future use of indices of
functional activation should account for exercise-induced changes in cardio-pulmonary
physiology and CBF.
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