Fluid intake restores retinal blood flow early after exhaustive exercise in healthy subjects

Purpose: It remains unclear whether rehydration restores retinal blood flow reduced by exhaustive exercise. We investigated the effect of fluid intake on retinal blood flow after exhaustive exercise. Methods: Blood flow in the inferior (ITRA) and superior temporal retinal arterioles (STRA) was measured before and after incremental cycling exercise until exhaustion in 13 healthy males. After the exercise, the subjects rested without drinking (control condition: CON) or with drinking an electrolyte containing water (rehydrate condition: REH) and were followed up for a period of 120 min. To assess the hydration state, the body mass was measured, and venous blood samples were collected and plasma volume (PV) was calculated. Results: Body mass decreased in CON after the trial [− 1.1 ± 0.1% (mean ± SE), p < 0.05]. PV was lower in CON than in REH during recovery. The ITRA and STRA blood flows decreased immediately after exercise from the resting baseline (ITRA; − 23 ± 4% in REH and − 30 ± 4% in CON, p < 0.05). The ITRA blood flow recovered baseline level at 15 min of recovery in REH (− 9 ± 3%, p = 0.5), but it remained reduced in CON (-14 ± 3%, p < 0.05). The STRA blood flow was higher in REH than in CON at 15 min (2 ± 3 vs. − 5 ± 3%, p < 0.05). Conclusions: The results of this study suggest that the reduction in retinal blood flow induced by exhaustive exercise can be recovered early by rehydration.