Effects of Recumbent Angle during Cycling on Cerebral Blood Flow Velocity and Rate Pressure Product during Exercise and Recovery

The cerebral blood flow velocity (CBFV) and rate pressure product (RPP) have been reported to benefit hemodynamics more during exercise in the recumbent position than during that in the upright position. However, it is unclear which angle is of the greatest benefit to hemodynamics during exercise in the recumbent position. This study aimed to evaluate the effect of the recumbent angle on CBFV and RPP during exercise. Methods: In a balanced crossover study, 15 healthy volunteers (age, 18.71.1 years) were asked to perform the bicycle exercise four times in the upright and at recumbent angles of 67 (R), 47R, and 15R, with weekly intervals between each condition. The exercise intensity was set initially at 50 W and increased by 25 W every 2 minutes up to 150 W. CBFV in the middle cerebral artery (MCA) was measured using transcranial doppler sonography. All data were analyzed using two-way repeated-measures analysis of variance. Results: CBFV at 15R was significantly higher than that in the upright position and at 67R at 10 minutes recovery (6916 vs. 567 and 5810 cm/s, respectively; P<0.05). The RPP was significantly lower at 67R, 47R, and 15R than in the upright position immediately after exercise (17623, 17722, and 17326, respectively, vs. 24142 mmHgbeats/min10 -2 ; P<0.001). Conclusions: At an angle of less than 67R, exercise increases CBFV and reduces RPP, relative to those during exercise in the upright position. This hemodynamic effect was most prominent at 15R, where cerebral circulation was further increased in the recovery phase.