A maximal incremental effort alters tear osmolarity depending on the fitness level in military helicopter pilots

Effects and potential mechanisms of exercise and physical activity on eye health and ocular diseases

In the field of eye health, the profound impact of exercise and physical activity on various ocular diseases has become a focal point of attention. This review summarizes and elucidates the positive effects of exercise and physical activities on common ocular diseases, including dry eye disease (DED), cataracts, myopia, glaucoma, diabetic retinopathy (DR), and age-related macular degeneration (AMD). It also catalogues and offers exercise recommendations based on the varying impacts that different types and intensities of physical activities may have on specific eye conditions. Beyond correlations, this review also compiles potential mechanisms through which exercise and physical activity beneficially affect eye health. From mitigating ocular oxidative stress and inflammatory responses, reducing intraocular pressure, enhancing mitochondrial function, to promoting ocular blood circulation and the release of protective factors, the complex biological effects triggered by exercise and physical activities reveal their substantial potential in preventing and even assisting in the treatment of ocular diseases. This review aims not only to foster awareness and appreciation for how exercise and physical activity can improve eye health but also to serve as a catalyst for further exploration into the specific mechanisms and key targets through which exercise impacts ocular health. Such inquiries are crucial for advancing innovative strategies for the treatment of eye diseases, thereby holding significant implications for the development of new therapeutic approaches.

Maximal incremental exercise improves macular photostress recovery time and lowers intraocular pressure in healthy athletes

OBJECTIVES

Better visual performance in athletes compared to non-athletes could suggest improved macular function through physical exertion. The study aimed to investigate the effect of maximal incremental treadmill (MIT) exercise on macular function.

DESIGN

An interventional study comparing the effect of maximal incremental treadmill (MIT) exercise until volitional exhaustion between athletes (n = 26) and non-athletes (n = 26).

METHODS

Participants underwent an ophthalmological assessment involving repeated measurements of the photostress recovery time (PSRT) at baseline and post-exercise. PSRT was recorded after a 10-second exposure of the macular to an intense light source from an ophthalmoscope positioned 2 cm in front of the eye. Secondary outcome measures also recorded included the best-corrected visual acuity (BCVA) and the intraocular pressure (IOP).

RESULTS

Compared to the baseline, MIT exercise markedly improved the PSRT of athletes from 42.7 ± 1.6 s to 39.6 ± 1.4 s (P < 0.001), while having no significant changes in the PSRT of non-athletes. After adjusting for exercise duration, the exercise intervention showed significant effects on the PSRT improvement in the athletes compared to non-athletes after exercise [F(1,49) = 16.941, P < 0.001], with estimated marginal means of 3.00 s and 0.47 s, respectively. Also, the exercise intervention resulted in significant improvements in IOP (P < 0.001) and BCVA (P < 0.01) of both groups.

CONCLUSIONS

MIT exercise improves macular function, BCVA, and reduced IOP in healthy athletes. Maximal incremental exercise may be recommended for competitive sports athletes seeking optimal visual performance, as long as it does not adversely impact other relevant non-visual factors.

Effects of physical activity/exercise on tear film characteristics and dry eye associated symptoms: A literature review

PURPOSE

To conduct a review of the literature in order to identify the potential association between physical activity or exercise and the objective signs and/or subjective symptoms of dry-eye disease.

METHODS

A review of PubMed and Web of Science databases was performed, according to the PRISMA guidelines. The papers included in the review addressed the relationship of physical activity or exercise with dry-eye associated signs (changes in tear volume, osmolarity or biochemical composition) and/or subjective symptoms.

RESULTS

A total of 16 papers were included. In eight, the changes in tear film volume, osmolarity and/or biochemical composition were studied after a single, acute bout of aerobic exercise. In another eight, changes in dry-eye associated symptoms were studied in relation to the habitual practice of physical activity or to prescribed exercise programmes. Acute responses of the tear film to exercise included: a) an increase of tear volume, without an increase of the tear break-up time; b) a trend to increase tear osmolarity, although within its physiological range; and c) a reduced concentration of several cytokines, and other molecular markers of inflammation or oxidative stress. Long-term exposure to physical activity or exercise programmes was associated with relief of dry-eye associated symptoms and a trend to increased tear break-up time.

CONCLUSIONS

Despite a high heterogeneity in the studied population, study designs and methods, the current body of evidence suggests a potential role for physical activity as a modulatory stimulus for the proper functioning of the tear film and/or the relief of dry-eye symptoms.

Differential effect of maximal incremental treadmill exercise on tear secretion and tear film stability in athletes and non-athletes

The study investigated the differential response to a single bout of maximal incremental treadmill exercise between athletes and non-athletes without dry eyes regarding tear secretion, tear film stability, visual acuity (VA), and stereoacuity. Additionally, the study examined the effect of gender and the duration of exercise on exercise-induced changes. Study participants included young university students aged 18-25 years who were athletes (male/female: 13/13) or non-athletes (male/female: 17/9). Participants underwent an aerobic exercise session using a treadmill and following the laid down Bruce treadmill test protocol till exhaustion. Measurements were taken in the order of distance VA, stereopsis, non-invasive tear break-up time (TBUT), and phenol red thread test, at baseline and after the exercise regimen. Within- and between-subject analyses using multiple t-tests with correction for multiple comparisons were performed to determine differences before and after exercise in athletes and non-athletes. Subsequently, ANCOVA was used to assess the influence of gender and the duration of exercise. The mean age (SD) of the athletes and the non-athletes was 22.4 ± 2.1 years and 21.8 ± 2.1 years, respectively (p = 0.357). Before exercise, the athletes had higher TBUT than non-athletes (14.6 ± 2.9 s vs. 11.9 ± 3.8 s; p = 0.021), but no difference was observed in any other ocular measurements. After exercise, the athletes showed significant improvement in tear secretion with the basal tear secretion increasing from 22.3 ± 2.5 mm to 25.8 ± 1.7 mm (p < 0.001). The non-athletes on the other hand had a borderline increase in tear secretion from 21.42 ± 2.85 mm to 23.73 ± 2.68 mm (p = 0.08). Also, the TBUT was much improved in the athletes after exercise compared to the non-athletes (17.7 ± 2.7 s vs. 14.8 ± 2.9 s, p = 0.004). Additionally, exercise improved the VA indifferently between the groups, while stereoacuity was unchanged after exercise in either group. Gender had no influence on the differences in the tear function measures between athletes and non-athletes after exercise. The duration of exercise, however, showed a borderline effect on the tear film stability (p = 0.068) after exercise. Our findings support the differential effect of maximal incremental treadmill exercise on tear secretion and tear film stability between athletes and non-athletes. Thus, increased physical fitness and the duration of exercise might be crucial in the improvement of tear function through aerobic exercise.

Does Oxygen Uptake Before Physical Exercise Affect Tear Osmolarity?

Recently, it has been reported that tear osmolarity (Tosm) is correlated with plasma osmolarity and will increase during exertion. We aimed to assess whether inhaling oxygen-enriched air between exercises could significantly change the Tosm value. Thirty men aged 24.9 years were included in the study. A cycloergometer was used to perform the exercise protocol. We recorded the participants’ Tosm (mOsm/L), heart rate (HR, beats/minute), oxygen saturation, and blood pressure values. After the first exhaustive exercise (T1), participants inhaled oxygen in the experimental group and a placebo in the control group. After the second exercise (T2), another set of measurements was obtained. The Tosm value before exercise was 297.4 ± 1.21 and 296.53 ± 1.11 mOsm/L (p = 0.61718) and the HR was 72.6 ± 2.59 and 73 ± 2.59 beats/minute (p = 0.39949) in the study and the control group, respectively. At T1, Tosm was 303.67 ± 1.25 and 302.2 ± 1.25 mOsm/L (p = 0.41286) and the HR reached 178.04 ± 2.60 and 176.4 ± 2.60 beats/minute (p = 0.65832), respectively. At T2, Tosm in the study group reached 305.73 ± 0.86 mOsm/L (correlation with the use of oxygen: r = −0.3818), and in the control group, it was 308.4 ± 0.86 mOsm/L (p = 0.0373), while the HR reached 172.20 ± 2.53 beats/minute in the study group and 178.2 ± 2.53 beats/minute in the control group (p = 0.057). It was concluded that inhaling oxygen before and after exercise could increase the rate of recovery after exhaustive exercise.

Does Emotion Regulation Predict Gains in Exercise-Induced Fitness? A Prospective Mixed-Effects Study with Elite Helicopter Pilots

Emotion regulation (ER) is a strong predictor of different aspects of mental health and wellbeing. However, only recently has ER been examined in relation to physical activity and its effects on fitness. In the present study, 26 elite helicopter pilots, serving in the Spanish Air Force, were physically trained for 6 months, and their level of fitness (maximum oxygen consumption and time to exhaustion in a treadmill-running test) was assessed before and after that period. Additionally, two indices of emotion regulation (general adaptiveness of ER strategies, as measured by the Emotion Regulation Questionnaire (ERQ), and negative urgency, as measured by the UPPS-P questionnaire) measured at baseline were used as prospective predictors of fitness improvement. After controlling for individual features, baseline fitness, and type of training, better emotion regulation strategies (more cognitive reappraisal plus less expressive suppression) predicted larger fitness gains (p = 0.028). Incidental emotion regulation, as measured by the negative urgency index, failed to predict pre–post-fitness changes (p = 0.734). These results suggest that fostering emotion regulation skills may improve the effectiveness of fitness training programs.

Intraocular Pressure as an Indicator of the Level of Induced Anxiety in Basketball

SIGNIFICANCE

Our data demonstrate that intraocular pressure (IOP) is sensitive to anxiety manipulation in sport scenarios, specifically in a basketball free throw task. The present outcomes may be of special relevance because of its practical advantages for the objective control of athletes' anxiety levels.

PURPOSE

Athletes experience high levels of anxiety during sport competition, and IOP has demonstrated to reflect autonomous nervous system changes during mentally demanding situations. We tested whether different levels of induced anxiety during basketball free throw shooting alter IOP.

METHODS

We followed a repeated-measures design to test the effects of anxiety-induced manipulation during basketball free throw shooting on IOP, shooting performance, and perceived anxiety. Eighteen amateur basketball players performed three experimental sessions consisting of 100 free throws each. However, we gave three different instructions to participants regarding the score assigned to each free throw, allowing us to manipulate the level of induced anxiety (low, medium, and high).

RESULTS

Confirming a successful anxiety manipulation, basketball players reported more perceived anxiety with higher levels of induced anxiety (P < .001, η = 0.37). Our data show that higher levels of induced anxiety provoke an acute IOP rise (P < .001, η = 0.44), with the low-, medium-, and high-anxiety-induced conditions promoting an average IOP rise of 0.21, 1.63, and 18.46%, respectively. Also, there was a linear IOP rise over time in the high-anxiety-induced condition (r = 0.82). Nevertheless, we found no effect of anxiety-induced manipulation on basketball free throw performance (P = .93).

CONCLUSIONS

Intraocular pressure is sensitive to anxiety-induced manipulation during basketball free throw shooting, showing an increase in parallel with accumulated anxiety. Based on these findings, IOP may be considered a promising tool for the assessment of the level of anxiety in certain sport situations. Future studies are required to explore the generalizability of these results in other scenarios with different physical and mental demands.

Alteration of Blinking and Sex Differences During Physical Exercise Affect Tear Osmolarity

Physical exertion leads to the rise in tear osmolarity. However, previous studies have been conducted mostly on males and did not consider sex differences and the possible alteration in blinking during physical exercise. Sixteen women and 18 men aged 25.09 ± 1.70 were divided into equal groups with eyes open and shut. Participants performed 8-min medium-intensity exercise and 5-min intense exercise on a cycloergometer. Tear osmolarity (in mOsm/L) was evaluated before ( T0), after medium-intensity (T1) and intense exercise (T2). The blinking rate was assessed in a group with eyes open. Tear brake up time was measured in T0 and T1. With tear osmolarity measuring 305.72 ± 1.22 and 313.56 ± 1.90 for men and women, respectively, we observed significant differences in T1. In T2, tear osmolarity in men was 303.3 ± 1.28 vs. 310.87 ± 1.36 in women. The blinking rate decreased from 14.24 ± 2.54/min in T0 to 9.41 ± 2.83/min in T1. There was a statistically significant change in tear osmolarity in both groups, that is, in the group with eyes shut from 300.53 ± 1.37 in T0 to 308.06 ± 1.55 in T1 to 304.88 ± 1.54 in T2. In the group with eyes open, tear osmolarity increased from 300.29 ± 1.37 in T0 to 310.76 ± 1.55 in T1 and then dropped to 308.88 ± 1.54 in T2. Tear brake up time measured in T0 was 14.7 ± 1.43 vs. 13.53 ±1.48 in the open eyes condition. Due to physical exercise, short-term changes in tear osmolarity are partially caused by altered blinking. Sex differences in tear osmolarity in response to exertion may confirm the relationship between total body water and tear osmolarity.

Effect of a maximal treadmill test on intraocular pressure and ocular perfusion pressure: The mediating role of fitness level

Objectives:

We compared the impact of a maximal treadmill test on intraocular pressure and ocular perfusion pressure between trained and untrained individuals.

Methods:

Based on the maximal aerobic capacity (relative VO2 max), 31 military helicopter pilots were divided into groups of trained (n = 16; VO2 max = 57.06 ± 1.66) and untrained (n = 15; VO2 max = 43.42 ± 1.19) individuals. Intraocular pressure and blood pressure were collected before effort, just after volitional exhaustion and after 5 and 15 min of recovery.

Results:

The maximal treadmill test induced significant changes on intraocular pressure (p < 0.001, η2 = 0.52) and ocular perfusion pressure (p < 0.001, η2 = 0.60). Intraocular pressure and ocular perfusion pressure increased just after volitional exhaustion (effect size = 0.88 and 1.59, respectively), and these values returned to baseline levels after 5 (effect size = 0.87 and 1.26, respectively) and 15 (effect size = 1.23 and 1.91, respectively) min of recovery. The untrained group exhibited higher intraocular pressure and ocular perfusion pressure values in comparison with the trained group just after volitional exhaustion (effect size = 1.43 and 0.11 for intraocular pressure and effect size = 2.81 and 0.96 for ocular perfusion pressure). Five minutes of recovery was insufficient to reach baseline intraocular pressure and ocular perfusion pressure values only for the untrained group (effect size = 0.91 and 0.72, respectively).

Conclusion:

Our findings reveal that fitness level modulates the intraocular pressure and ocular perfusion pressure responses to a maximal treadmill test, being high fitness levels desirable in order to attenuate the impact of maximal efforts on these indices. These outcomes may be of clinical relevance for the management of glaucoma patients or those at risk, although future studies are needed to test these results in a clinical population.

Fitness Level Modulates Intraocular Pressure Responses to Strength Exercises

Purpose/Aim: The execution of strength exercises has demonstrated to increase the intraocular pressure (IOP) levels, and it may have a negative impact on the ocular health. We aimed to explore the influence of fitness level on the acute IOP response to strength exercises performed under different loading conditions, as well as to test whether the IOP responses differ between the bench press and jump squat when performed against the same relative loads.

MATERIALS AND METHODS

Forty military personnel males were divided in two subgroups (20 high-fit and 20 low-fit) based on their relative to body mass one-repetition maximum (1-RM). Participants performed an incremental loading test in the bench press and jump squat exercises, and IOP was assessed before and after each repetition by rebound tonometry.

RESULTS

IOP increased immediately after executing both exercises (p < 0.01 in both cases), being the magnitude of the IOP increment positively and linearly associated with the increment of the load in both groups (i.e., high-fit and low-fit) and in both exercises (R² range: 0.81-1.00). Higher fitness level attenuated the IOP rise produced by both exercises (p < 0.01 in both cases). The bench press induced higher IOP increments than the jump squat for both groups at relative loads of ~50%1-RM and ~60%1-RM (p < 0.01 in all cases).

CONCLUSIONS

These data indicate that IOP increases as a consequence of performing strength exercises, being the increment accentuated with the increase of the load and in the bench press compared to the jump squat exercise. Of special importance would be that the IOP responses were significantly reduced in high-fit individuals. These findings should be addressed in glaucoma patients.