Effect of repeated endurance exercise on intraocular pressure in healthy subjects: a prospective pilot study based on a 500-km swim relay

CORRESPONDING AUTHOR Robert Gajda, Center for Sports Cardiology at the Gajda-Med Medical Center, 23/29 Piotra Skargi St., 06-100 Pułtusk, phone: +48 604 286 030, fax: +48 23 692 01 99, e-mail: gajda@gajdamed.pl INTRODUCTION Glaucoma is the leading cause of blindness worldwide. Importantly, it is an avoidable visual impairment; therefore, potential prevention strategies are crucial [1-3]. The primary risk factor for glaucoma development is an elevated intraocular pressure and associated fluctuations that lead to gradual dysfunction of the optic nerve [1-3]. Of late, interest in participation in intense endurance exercise has been increasing globally. The popularity of sports events such as running marathons, ultramarathons, and triathlons is systematically rising, with thousands of participants gathering for every event. As opposed to regular moderate physical activity (PA), which has well-known beneficial effects, exhaustive prolonged exercise may have a negative impact on health, particularly in susceptible individuals. Muscle damage, electrolyte fluctuations, hemostatic disorders, and even sudden cardiac death are among the most common detrimental effects of intensive PA [4, 5]. Several studies have also investigated the potential relationship between exercise and intraocular pressure (IOP), although the obtained results are inconsistent. The majority of studies show that PA may reduce IOP, although the decrease is transient and the pressure shortly returns to its baseline value [6, 7]. In contrast, some studies have shown that exercise induces a transient increase in IOP [8]. Interestingly, IOP fluctuations may be associated with the habitual PA level and physical fitness. Dane et al. obtained different responses to submaximal exercise in athletes and sedentary subjects [9]. However, most previous studies examined the effects of short ABSTRACT Aim of the study: To investigate exercise-related changes in the intraocular pressure (IOP) in healthy participants of a 500-km swim relay. Material and methods: A group of 12 well-trained amateur swimmers aged 13-67 years participated in a 500-km swim relay in the Warta River, Poland. Each participant underwent detailed clinical examinations, including IOP and central corneal thickness measurements, 2-3 weeks before the relay (baseline) and at peak effort (10 min after the last shift). A baseline maximal treadmill exercise test was also conducted for measurement of the maximal oxygen consumption (VO2) and metabolic equivalent of task (MET) values. Results: None of the athletes (12 eyes) exhibited significant changes in IOP at peak effort (mean change from 14.3 to 15.4 mmHg, p > 0.05). Six male subjects exhibited an exercise-induced mean increase in IOP at peak effort, from 15.6 to 18.5 mmHg (6 eyes, p < 0.05). In six female subjects, the peak effort was not associated with significant IOP changes; IOP mean declined slightly from 13.0 to 12.3 mmHg (6 eyes, p > 0.05). IOP parameters, including the pressure at rest, pressure at peak effort, and pressure change, showed no significant correlations with cardiorespiratory aerobic fitness determined by VO2 and MET. Conclusions: This pilot study did not reveal changes in IOP among well-trained amateur athletes in response to prolonged vigorous swimming. These results, as well as sex-specific differences, in IOP changes at peak effort due to the small sample size must be confirmed by examinations in a larger group.