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

ABSTRACT

BACKGROUND: 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, 18.7±1.1 years) were asked to perform the bicycle exercise four times in the upright and at recumbent angles of 67° (R), 47°R, and 15°R, 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 15°R was significantly higher than that in the upright position and at 67°R at 10 minutes recovery (69±16 vs. 56±7 and 58±10 cm/s, respectively; P<0.05). The RPP was significantly lower at 67°R, 47°R, and 15°R than in the upright position immediately after exercise (176±23, 177±22, and 173±26, respectively, vs. 241±42 mmHg×beats/min×10⁻²; P<0.001). CONCLUSIONS: At an angle of less than 67°R, exercise increases CBFV and reduces RPP, relative to those during exercise in the upright position. This hemodynamic effect was most prominent at 15°R, where cerebral circulation was further increased in the recovery phase.