Washio Takuro, Vranish Jennifer R, Kaur Jasdeep, Young Benjamin E, Katayama Keisho, Fadel Paul J, Ogoh Shigehiko
Department of Biomedical Engineering, Toyo University, Kawagoe-shi, Saitama, Japan.
Research Fellow of Japan Society for the Promotion of Science, Tokyo, Japan.
Physiol Rep. 2018 Oct;6(20):e13886. doi: 10.14814/phy2.13886.
The mechanism(s) for the increased occurrence of a grayout or blackout, syncope, immediately after heavy resistance exercise are unclear. It is well-known that orthostatic stress increases the occurrence of postexercise syncope. In addition, previous findings have suggested that hypo-perfusion, especially in the posterior cerebral circulation rather than anterior cerebral circulation, may be associated with the occurrence of syncope. Herein, we hypothesized that the postexercise decrease in posterior, but not anterior, cerebral blood flow (CBF) would be greater during orthostatic stress. Nine healthy subjects performed 3-min isometric handgrip (HG) at 30% maximum voluntary contraction without (CONTROL) and during lower body negative pressure (LBNP; -40 Torr) while vertebral artery (VA) blood flow, as an index of posterior CBF, and middle cerebral artery blood velocity (MCAv), as an index of anterior CBF, were measured. Immediately after HG (0 to 15 sec of recovery phase), mean arterial pressure decreased but there was no difference in this reduction between CONTROL and LBNP conditions (-15.4 ± 4.0% and -17.0 ± 6.2%, P = 0.42). Similarly, MCAv decreased following exercise and was unaffected by the application of LBNP (P = 0.22). In contrast, decreases in VA blood flow immediately following HG during LBNP were significantly greater compared to CONTROL condition (-24.2 ± 9.5% and -13.4 ± 6.6%, P = 0.005). These findings suggest that the decrease in posterior CBF immediately following exercise was augmented by LBNP, whereas anterior CBF appeared unaffected. Thus, the posterior cerebral circulation may be more sensitive to orthostatic stress during the postexercise period.
在进行大强度抗阻运动后立即出现意识模糊或昏厥、晕厥的发生率增加的机制尚不清楚。众所周知，直立位应激会增加运动后晕厥的发生率。此外，先前的研究结果表明，灌注不足，尤其是在后脑循环而非前脑循环中，可能与晕厥的发生有关。在此，我们假设在直立位应激期间，运动后后脑而非前脑的脑血流量（CBF）下降会更大。九名健康受试者在最大自主收缩的30%强度下进行3分钟的等长握力（HG）运动，分别在无（对照）和下体负压（LBNP；-40 Torr）条件下进行，同时测量椎动脉（VA）血流（作为后脑CBF的指标）和大脑中动脉血流速度（MCAv）（作为前脑CBF的指标）。在HG运动后立即（恢复阶段的0至15秒），平均动脉压下降，但对照和LBNP条件下的这种下降没有差异（-15.4±4.0%和-17.0±6.2%，P=0.42）。同样，运动后MCAv下降，且不受LBNP施加的影响（P=0.22）。相比之下，与对照条件相比，LBNP期间HG运动后立即出现的VA血流下降明显更大（-24.2±9.5%和-13.4±6.6%，P=0.005）。这些发现表明，运动后立即出现的后脑CBF下降因LBNP而加剧，而前脑CBF似乎未受影响。因此，在运动后期间，后脑循环可能对直立位应激更敏感。
