Graduate School of Human-Environment Studies, Kyushu University , Kasuga, Fukuoka, Japan ; Graduate School of Decision Science and Technology, Tokyo Institute of Technology , Ookayama, Meguro, Japan.
Graduate School of Decision Science and Technology, Tokyo Institute of Technology , Ookayama, Meguro, Japan.
J Sports Sci Med. 2014 Jan 20;13(1):172-9. eCollection 2014 Jan.
The hypothesis that heat stress reduces the ocular blood flow response to exhaustive exercise was tested by measuring ocular blood flow, blood pressure, and end- tidal carbon dioxide partial pressure (PETCO2) in 12 healthy males while they performed cycle ergometer exercise at 75% of the maximal heart rate at ambient temperatures of 20°C (control condition) and 35°C (heat condition), until exhaustion. The blood flows in the retinal and choroidal vasculature (RCV), the superior temporal retinal arteriole (STRA) and the superior nasal retinal arteriole (SNRA) were recorded at rest and at 6 and 16 min after the start of exercise period and at exhaustion [after 16 ± 2 min (mean ± SE) and 24 ± 3 min of exercise in the heat and control condition, respectively]. The mean arterial pressure at exhaustion was significantly lower in the heat condition than in the control condition at both 16 min and exhaustion. The degree of PETCO2 reduction did not differ significantly between the two thermal conditions at either 16 min or exhaustion. The blood flow velocity in the RCV significantly increased from the resting baseline value at 6 min in both thermal conditions (32 ± 6% and 25 ± 5% at 20°C and 35°C, respectively). However, at 16 min the increase in RCV blood flow velocity had returned to the resting baseline level only in the heat condition. At exhaustion, the blood flows in the STRA and SNRA had decreased significantly from the resting baseline value in the heat condition (STRA: -19 ± 5% and SNRA: -30 ± 6%), and SNRA blood flow was lower than that in the control condition (-14 ± 6% vs -30 ± 6% at 20°C and 35°C, respectively), despite the finding that both thermal conditions induced the same reductions in PETCO2 and vascular conductance. These findings suggested that the heat condition decreases or suppresses ocular blood flow via attenuation of pressor response during exhaustive exercise. Key PointsThe ocular (retinal and choroidal) blood flow response to exhaustive exercise with heat stress is unknown.We hypothesized that the heat stress decreases ocular blood flow response to exhaustive exercise, since cerebral flow, which is regulated similarly to ocular flow, was reported to decrease during heat stress.To test this hypothesis, ocular blood flow was measured during exhaustive exercise at 20°C (control condition) and 35°C (heat condition).At exhaustion in the heat condition, the ocular flow response was suppressed or decreased with an attenuated pressor response.It is suggested that the heat condition decreases or suppresses the ocular blood flow to exhaustive exercise via attenuation of pressor response.
假设热应激会降低剧烈运动时的眼部血流反应，本研究通过测量 12 名健康男性在环境温度为 20°C（对照条件）和 35°C（热条件）时，以最大心率的 75%进行踏车运动时的眼部血流、血压和呼气末二氧化碳分压（PETCO2），直到力竭。在休息时以及运动开始后 6 分钟和 16 分钟时记录视网膜和脉络膜血管（RCV）、颞上视网膜小动脉（STRA）和鼻上视网膜小动脉（SNRA）的血流，以及力竭时的血流[在热条件和对照条件下分别运动 16±2 分钟和 24±3 分钟后力竭]。在热条件下，力竭时的平均动脉压明显低于对照条件下的 16 分钟和力竭时。在 16 分钟和力竭时，两种热条件下的 PETCO2 降低程度无显著差异。在两种热条件下，RCV 的血流速度均在 6 分钟时从静息基线值显著增加（20°C 和 35°C 时分别为 32±6%和 25±5%）。然而，在 16 分钟时，只有在热条件下，RCV 血流速度的增加才恢复到静息基线水平。在力竭时，热条件下的 STRA 和 SNRA 血流均明显低于静息基线值（STRA：-19±5%和 SNRA：-30±6%），并且 SNRA 血流低于对照条件（20°C 和 35°C 时分别为-14±6%和-30±6%），尽管两种热条件均导致 PETCO2 和血管传导相同程度的降低。这些发现表明，热应激通过减弱压力反应来降低剧烈运动时的眼部血流。关键点：剧烈运动时眼部（视网膜和脉络膜）血流对热应激的反应尚不清楚。我们假设热应激会降低剧烈运动时的眼部血流反应，因为类似地调节眼部血流的脑血流据报道在热应激时会减少。为了验证这一假设，在 20°C（对照条件）和 35°C（热条件）下进行剧烈运动时测量了眼部血流。在热条件下的力竭时，压力反应减弱，眼血流反应受到抑制或降低。这表明，热应激通过减弱压力反应来降低剧烈运动时的眼部血流。
