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J. V. Lovasik, H. Kergoat, M. Parent; Neurovascular Coupling in Long-Term Joggers Versus Healthy Non-Joggers. Invest. Ophthalmol. Vis. Sci. 2007;48(13):2273.
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Professional athletes outperform normal individuals in their sport mainly because of greater muscle strength and faster reflexes. While regular exercise improves cardiovascular function and muscle tone, the transfer of superior physiological conditioning to the coupling between neural activation and vascular response at the retinal level has not been examined. In the present study we compared the vasomotor responses of retinal vessels elicited by flicker stimulation of the retina in healthy adults and long-term long distance runners. We hypothesized that superior physical conditioning would also be manifest in some form at the retinal level.
A Zeiss Retinal Vessel Analyser (RVA) was used to quantify the vasomotor responses of the peri-papillary retinal vessels during three consecutive cycles of 60s 12.5Hz diffuse green flicker delivered through a Zeiss fundus camera and a 60s recovery interval. The targeted vessels included paired arteries and veins within 1 disc diameter of the optic nerve head. The RVA provided real time measurements of changes in vessel caliber in a 1mm vessel segment. The vessel reactivity was accumulated for a cohort of 10 adults who were long distance joggers for a minimum of 5 years (range 5-20 years), and a group of 10 healthy adult volunteers. The vessel diameter and dynamics of vessel caliber change were averaged across subjects within each test group to derive population statistics.
Flicker initially elicited a rapid dilation that was followed by a slower near linear increase towards a maximal dilation of ~ 8%. At the end of flicker, vessel dilation was quickly replaced by constriction that proceeded at a rate that was some 30% lower than the initial rate of dilation. This response profile characterized the arteries and veins in both test groups; however, arteries dilated less than veins in either group of subjects. Furthermore, even though venous dilation was the same in runners and controls, arterial dilation was ~2.3% lower in our cohort of long-term runners (ANOVA, p< 0.05). The degree of flicker-induced vessel dilation was not correlated with the caliber of arteries or veins.
Inasmuch as the arterial response was lower in joggers versus control subjects, we conclude that the vascular system in joggers was more efficient in meeting the metabolic demand of the retina caused by photic stimulation. How a lower level of arterial retinal perfusion (joggers vs non-joggers) could satisfy a heightened retinal metabolism remains unknown.
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