Background: A transient reduction in intraocular pressure (IOP) after an aerobic exercise is found time and again across studies in literature. It has been suggested that systemic dehydration could be a possible mechanism driving these hypotensive effects of exercise. However, IOP reduction never had been examine in hyper versus hypo-hydration conditions for a same group of participants. The purpose of this study is to examine the influence of hyper and hypo hydration conditions on exercise-induced fluctuations in intraocular pressure.
Methods: Thirteen participants rode an ergocycle in a temperate room for 90 minutes, at 59% of their maximal aerobic capacity, in a state of both hyper and hypo-hydration. IOP was measured at 0, 5, 30, 60 and 90 minutes, and 30 minutes after exercise. Reduction in body weight was measured at 0, 30, 60 and 90 minutes.
Results: There is an initial drop in IOP under both conditions followed by a rise in IOP at 30 minutes that is nearly equal to the baseline. From that point on, IOP hovers around baseline values in the hypo-hydrated condition and increases until the end of the exercise protocol in the hyper-hydrated condition. A repeated-measures ANOVA showed a significant interaction between time and condition F(5,60) =3.99, P=0.003, as well as a main effect of time F(5,60) =7.90, P<0.001, and a main effect of condition F(1,12) =5.83, P=0.033.
Conclusions: The results of this study, when taken with others that looked specifically at factors of exercise, hydration and IOP suggest that fluctuations in IOP during exercise are likely a homeostatic response related fluid intake and not because of any specific benefit incurred through exercise.
