Influence of the breathing pattern during resistance training on intraocular pressure

Bidirectional causality of physical exercise in retinal neuroprotection

Physical exercise is recognized as an effective intervention to improve mood, physical performance, and general well-being. It achieves these benefits through cellular and molecular mechanisms that promote the release of neuroprotective factors. Interestingly, reduced levels of physical exercise have been implicated in several central nervous system diseases, including ocular disorders. Emerging evidence has suggested that physical exercise levels are significantly lower in individuals with ocular diseases such as glaucoma, age-related macular degeneration, retinitis pigmentosa, and diabetic retinopathy. Physical exercise may have a neuroprotective effect on the retina. Therefore, the association between reduced physical exercise and ocular diseases may involve a bidirectional causal relationship whereby visual impairment leads to reduced physical exercise and decreased exercise exacerbates the development of ocular disease. In this review, we summarize the evidence linking physical exercise to eye disease and identify potential mediators of physical exercise-induced retinal neuroprotection. Finally, we discuss future directions for preclinical and clinical research in exercise and eye health.

Acute intraocular pressure responses changes during dynamic resistance training in primary open-angle glaucoma patients and age-matched controls

BACKGROUND

Physical exercise has been proposed as a feasible strategy for preventing and managing glaucoma by modulating intraocular pressure (IOP) and ocular perfusion pressure (OPP). The primary objective of this cross-sectional study was to assess the IOP and OPP responses to dynamic resistance exercises (leg extension and biceps curl).

METHODS

Twenty-six patients with primary open-angle glaucoma (POAG) (age = 68.9 ± 8.1 years) and 18 healthy age-matched controls (age = 69.6 ± 5.9 years) were recruited. Participants performed one set of 10 repetitions of both exercises at low- (light bar) and moderate-intensity (15RM). IOP and blood pressure were measured at baseline and after 1 and 5 min of passive recovery. Additionally, IOP was measured during training after each of the 10 repetitions.

RESULTS

Our data showed a progressive IOP increase throughout the sets of leg extension and biceps curl exercises when performed at moderate intensity (p < 0.001). Remarkably, POAG patients showed a smaller IOP increase compared to controls (p = 0.048). The between-group differences for IOP changes were higher during the 10 exercise repetitions at moderate-intensity for both leg extension (average IOP rise: POAG = 0.3 ± 0.6 mmHg vs. control = 2.3 ± 0.7 mmHg) and biceps curl (average IOP rise: POAG = 1.4 ± 0.6 mmHg vs. control = 3.4 ± 0.8 mmHg) exercises. No changes in OPP were observed.

CONCLUSIONS

The findings of this study suggest that moderate-intensity dynamic resistance training is a safe intervention for potentially improving physical fitness in medically treated POAG patients.

Effects of Phenylcapsaicin on Intraocular and Ocular Perfusion Pressure During a 30-Min Cycling Task: A Placebo-Controlled, Triple-Blind, Balanced Crossover Study

The main objective of this placebo-controlled, triple-blind, balanced crossover study was to assess the acute effects of phenylcapsaicin (PC) intake (2.5 mg) on intraocular pressure (IOP), ocular perfusion pressure (OPP), and heart rate (HR) during a 30-min cycling task performed at 15% of the individual maximal power. Twenty-two healthy young adults performed the cycling task 45 min after ingesting PC or placebo. IOP was measured with a rebound tonometer before exercise, during cycling (every 6 min), and after 5 and 10 min of recovery. OPP was assessed before and after exercise. HR was monitored throughout the cycling task. We found an acute increase of IOP levels related to PC consumption while cycling (mean difference = 1.91 ± 2.24 mmHg; p = .007, ηp2=.30), whereas no differences were observed for OPP levels between the PC and placebo conditions (mean difference = 1.33 ± 8.70 mmHg; p = .608). Mean HR values were higher after PC in comparison with placebo intake (mean difference = 3.11 ± 15.87 bpm, p = .019, ηp2=.24), whereas maximum HR did not differ between both experimental conditions (p = .199). These findings suggest that PC intake before exercise should be avoided when reducing IOP levels is desired (e.g., glaucoma patients or those at risk). Future studies should determine the effects of different ergogenic aids on IOP and OPP levels with other exercise configurations and in the long term.

Acute Effects of Resistance Exercise on Intraocular Pressure in Healthy Adults: A Systematic Review

ABSTRACT

Hackett, DA, Li, J, Wang, B, Way, KL, Cross, T, and Tran, DL. Acute effects of resistance exercise on intraocular pressure in healthy adults: A systematic review. J Strength Cond Res 38(2): 394-404, 2024-Intraocular pressure (IOP) tends to fluctuate during a resistance exercise (RE). This systematic review examines the acute effects of RE on IOP in healthy adults and factors that influence changes in IOP. Five electronic databases were searched using terms related to RE and IOP. A strict inclusion criterion was applied, which included being 55 years or younger with no medical conditions and RE intensity needing to be quantifiable (e.g., based on a maximal effort). Thirty-four studies met the inclusion criteria for this review. Isometric and isotonic contractions produced similar changes in IOP during RE up to 28.7 mm Hg. Exercises that involved larger muscle mass, such as squats and leg press, were found to produce changes in IOP during exercise ranging from 3.1 to 28.7 mm Hg. Smaller changes in IOP during RE were found for exercises engaging less muscle mass (e.g., handgrip and bicep curls). Intraocular pressure was found to increase during RE when lifting heavier loads and with longer exercise durations (e.g., greater repetitions). The Valsalva maneuver (VM) and breath-hold during RE accentuated the change in IOP, with more extreme changes observed with the VM. However, most studies showed that postexercise IOP returned to baseline after approximately 1 minute of recovery. An acute increase in IOP is observed during RE in healthy adults with fluctuations of varying magnitude. Factors that independently increase IOP during RE include exercises involving larger muscle mass, heavy loads, greater set duration, and when the VM or breath-hold is performed.

The intraocular pressure lowering-effect of low-intensity aerobic exercise is greater in fitter individuals: a cluster analysis

This study aimed to determine the influence of physical fitness level and sex on intraocular pressure (IOP) during the low-intensity aerobic exercise. Forty-four participants (twenty-two men) cycled 30 minutes at low intensity (10% of the maximal power). Maximal power was determined by asking participants to perform maximal sprints of 6 seconds against 3-4 different resistances separated by 3 minutes of rest. The IOP was measured on 9 occasions (1) prior to the warm-up, (2) after the warm-up, (3-7) every 6 minutes during the low-intensity cycling task, and (8-9) 5 and 10 minutes after the cycling task. Low-intensity aerobic exercise had a lowering effect on IOP, being the beneficial effect more accentuated and prolonged in the High-fit group (IOP reduction compared to baseline lasted 30 minutes) than in the Low-fit group (IOP was only reduced at 6 minutes of exercise compared to baseline). Participants´ sex had no effect on the IOP behaviour at any time point (p = 0.453). These findings indicate that individuals who need to reduce IOP levels (i.e., glaucoma patients or those at risk) should increase or maintain a high fitness level to benefit more from the IOP lowering effect during low-intensity aerobic exercises.

Resistance Training with Blood Flow Restriction and Ocular Health: A Brief Review

Despite the many health benefits of resistance training, it has been suggested that high-intensity resistance exercise is associated with acute increases in intraocular pressure which is a significant risk factor for the development of glaucomatous optic nerve damage. Therefore, resistance training using a variety of forms (e.g., resistance bands, free weights, weight machines, and bodyweight) may be harmful to patients with or at risk of glaucoma. An appropriate solution for such people may involve the combination of resistance training and blood flow restriction (BFR). During the last decade, the BFR (a.k.a. occlusion or KAATSU training) method has drawn great interest among health and sports professionals because of the possibility for individuals to improve various areas of fitness and performance at lower exercise intensities. In comparison to studies evaluating the efficiency of BFR in terms of physical performance and body composition changes, there is still a paucity of empirical studies concerning safety, especially regarding ocular health. Although the use of BFR during resistance training seems feasible for glaucoma patients or those at risk of glaucoma, some issues must be investigated and resolved. Therefore, this review provides an overview of the available scientific data describing the influence of resistance training combined with BFR on ocular physiology and points to further directions of research.

Effect of wearing different types of face masks during dynamic and isometric resistance training on intraocular pressure

CLINICAL RELEVANCE

The use of face masks has demonstrated to be an effective strategy to prevent transmission of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2). Wearing face masks, mainly Filtering Face Piece 2 (FFP2) masks, during exercise practice has demonstrated to affect several physiological measures.

BACKGROUND

This study was aimed at assessing the intraocular pressure (IOP) behaviour during the execution of the dynamic and isometric biceps-curl exercise with a surgical and FFP2 face mask.

METHODS

Twenty two physically active young adults performed sets of 10 repetitions against the 10-RM (repetition maximum) load and 1-minute isometric effort against a load 15% lower than the 10-RM load with the FFP2 and surgical mask and without any mask. A total of six exercise sets (3 experimental conditions [FFP2, surgical and control] × 2 exercise modalities) were performed. A rebound tonometer was used to measure IOP before, during (10 measurements), and after (30-seconds of passive recovery) each training set.

RESULTS

At rest, there were not statistically significant IOP differences (p = 0.222). During dynamic exercise, there was a progressive IOP rise (p < 0.001), and a higher IOP response with the FFP2 than without the mask (corrected p-value = 0.003). For the isometric exercise, there was a greater IOP response as a function of accumulated effort (p < 0.001), which was dependent of the face mask used (FFP2> surgical>control; corrected p-values< 0.01).

CONCLUSIONS

The FFP2 masks cause a heightened IOP response during the execution of dynamic and isometric biceps-curl exercise, suggesting that, when possible, glaucoma patients should limit the use of FFP2 masks during resistance training.

Intraocular pressure fluctuation during resistance exercise

Objective

To evaluate the effect of weightlifting (leg press) on intraocular pressure (IOP).

Design

Prospective cohort study.

Subjects

A total of 24 participants met the inclusion criteria and completed the study procedures. Participants had an average age of 22.7±2.7 years and included nine women. The mean baseline IOP was 13.9 mm Hg (SD=2.4) with an average body mass index of 24.5 (SD= 3.1).

Methods

The maximum load for a single lift was found for each participant. Participants then performed three leg press regimens: one repetition using 95% of maximal load (1RM), six repetitions using 75% of maximal load (6RM) and isometric push against a weight much heavier than maximal load (ISO).

Main outcome measure

IOP was measured pre-exercise, during and immediately following the exercise using an iCare TA01i rebound tonometer. Blood pressure and HR were being monitored continuously during the lift. Optical coherence tomography images were obtained pre and postexercise session.

Results

The average maximum weight lifted by our participants was 331.9 Kg (SD=97.3). Transient increased IOP was observed across the 1RM, 6RM and ISO exercises with an average increase in 26.4 mm Hg (23.7 mm Hg to 28.7 mm Hg) to reach an average max IOP of 40.7 mm Hg (27.8 mm Hg to 54.2 mm Hg), with an absolute maximum of 70 mm Hg in one participant.

Conclusions

There is a transient and dramatic fluctuation in IOP with resistance training. This coupled with regular exposure to resistance training is potentially a significant risk factor for glaucoma. It should be noted that this study has been carried out in a healthy young population, and, thus, the external validity of these results in glaucoma participants requires further investigation.

Intraocular pressure responses to walking with surgical and FFP2/N95 face masks in primary open-angle glaucoma patients

Purpose

The use of face mask is globally recommended as a preventive measure against COVID-19. However, the intraocular pressure (IOP) changes caused by face masks remain unknown. The objective of this study was to assess the impact of wearing surgical and FFP2/N95 face masks during a 400-m walking protocol on IOP in primary open-angle glaucoma (POAG) patients.

Methods

Thirteen subjects diagnosed of POAG (21 eyes) were enrolled in this study. IOP was measured at baseline, during the 400-m walking protocol and after 5 min of passive recovery while POAG patients wore a surgical mask, FFP2/N95 mask and no mask in randomized order. From the 21 POAG eyes, we analyzed the IOP changes caused by physical exercise with two face masks and without wearing any face mask.

Results

At rest (baseline and recovery measurements), the use of the different face masks did not affect IOP levels (mean differences ranging from 0.1 to 0.6 mmHg). During physical activity, wearing an FFP2/N95 mask caused a small (mean differences ranging from 1 to 2 mmHg), but statistically significant, IOP rise in comparison to both the surgical mask and control conditions (Cohen’s d = 0.63 and 0.83, respectively).

Conclusion

Face masks must be used to minimize the risk of SARS-CoV-2 transmission, and POAG patients can safely use FFP2/N95 and surgical masks at rest. However, due to the IOP rise observed while walking with the FFP2/N95 mask, when possible, POAG patients should prioritized the use of surgical masks during physical activity.

Effects of Wearing the Elevation Training Mask During Low-intensity Cycling Exercise on Intraocular Pressure

PRCIS

Low-intensity aerobic exercise is recommended to reduce intraocular pressure (IOP) levels. However, this effect depends on several factors. We found that using an elevation training mask (ETM) during low-intensity aerobic exercise causes an IOP rise.

PURPOSE

The aim was to assess the influence of wearing an ETM on IOP during low-intensity endurance training.

METHODS

Sixteen physically active young adults (age=23.9±2.9 y) cycled during 30 minutes at 10% of maximal power production with and without an ETM in 2 different days and randomized order. A rebound tonometer was used to measure IOP at baseline, after a warm-up of 5 minutes, during cycling (6, 12, 18, 24, and 30 min), and recovery (5 and 10 min) by rebound tonometry.

RESULTS

The use of an ETM significantly affects the IOP behaviour during exercise (P<0.001, ηp²=0.66). In the ETM condition, there was an IOP increment during exercise (P<0.001, ηp²=0.28) whereas an IOP-lowering effect was observed in the control condition (P<0.001, ηp²=0.41). Post hoc comparisons showed that there were greater IOP values during exercise in the ETM condition in comparison to the control condition (average IOP difference=3.7±2.2 mm Hg; corrected P<0.01, and the Cohen d's >1.10, in all cases).

CONCLUSION

Low-intensity endurance exercise causes an increment in IOP when it is performed wearing an ETM and a decrease in IOP when the air flow is not restricted (control condition). Therefore, the ETM should be discouraged during low-intensity endurance exercise for individuals who need to reduce IOP levels (eg, glaucoma patients or those at risk). However, the external validity of these results needs to be addressed in future studies with the inclusion of glaucoma patients.

Effects of physical exercise on macular vessel density and choroidal thickness in children

We used swept-source (SS) optical coherence tomography (OCT) and OCT angiography (OCTA) to investigate the effects of moderate physical exercise on retinal and choroidal vessel densities (VDs) and thicknesses in children. One eye in each of 40 myopic children (mean age, 11.70 years) and 18 emmetropic children (mean age, 11.06 years) were included. SS-OCT 6 × 6-mm radial scans and SS-OCTA 3 × 3-mm images were centered on the macula. Heart rate (HR), systolic and diastolic blood pressure, and intraocular pressure (IOP) were recorded before and immediately after a 20-min stationary cycling exercise and after a 30-min rest. The subfoveal choroidal thickness (SFCT), choroidal thickness (CT), and VD at the superficial and deep retinal layers, choriocapillaris, and deeper choroidal vessels were determined. SFCT and CT were significantly lower at all locations immediately after exercise (p < 0.001) and did not fully recover after rest (p < 0.05). VD was lower in the deep retinal layer after exercise (p = 0.02) and higher in the superficial layer after rest (p = 0.03) in myopic eyes while it was higher in the superficial (p < 0.01) and deep layer (p < 0.01) after rest in emmetropic eyes. No significant exercise-related changes in the superficial retinal VD, choroidal VD, or IOP were observed. ΔCT% and ΔSFCT% were significantly correlated with increases in HR in myopic group (p = 0.04 and p = 0.03, respectively). Exercise increased retinal VD after rest in emmetropic eyes, and caused significant CT thinning that lasted for at least 30 min in both emmetropic and myopic eyes.

The intraocular pressure response to lower-body and upper-body isometric exercises is affected by the breathing pattern

We assessed the mediating role of the breathing pattern adopted during isometric exercise on the intraocular pressure (IOP) response in the back squat and biceps curl exercises. Twenty physically active young adults performed sets of 1-minute isometric effort against a load corresponding to 80% of the maximum load while adopting three different breathing patterns: (i) Constant breathing: 10 cycles consisting of 3 s of inhalation and 3 s of exhalation, (ii) 10-sec Valsalva: 3 cycles consisting of 10 s holding the breath and 10 s of normal breathing, and (iii) 25-sec Valsalva: 2 cycles consisting of 25 s of the Valsalva maneuver and 5 s of normal breathing. A rebound tonometer was used to semi-continuously assesses IOP during the six sets of 1-minute isometric effort (2 exercises × 3 breathing patterns). We found a progressive IOP rise during isometric effort (P < 0.001, ηp2 = 0.83), with these increases being greater when the breath was held longer (P < 0.001, ηp2 = 0.58; 25-sec Valsalva > 10-sec Valsalva = constant breathing). There was a trend towards higher IOP values for the back squat in comparison to the biceps curl, although these differences did not reach statistical significance for any breathing pattern (corrected P-value ≥ 0.146, d ≤ 0.69). These findings reveal that glaucoma patients or those at risk should avoid activities in which the breath is held, especially when combined with physical exercise modalities that also promote an increment in IOP values (e.g. isometric contractions).

Determinant Factors of Intraocular Pressure Responses to a Maximal Isometric Handgrip Test: Hand Dominance, Handgrip Strength and Sex

PURPOSE

To assess the mediating role of strength levels, hand dominance and participants´ sex on the intraocular pressure (IOP) behaviour during the execution of a maximal isometric handgrip test.

METHODS

One hundred and seventy-six sport science students (102 men and 74 women) performed a maximal isometric handgrip test with the dominant and non-dominant hands. A rebound tonometer was used to measure IOP before effort, during effort, and immediately after performing the handgrip test. Men and women were divided based on their handgrip strength in low- and high-strength groups using a median split analysis.

RESULTS

There was an acute IOP rise during effort, returning to baseline levels immediately after exercise cessation (P < .001, η_p ² = 0.79). A greater increase in IOP during the execution of the handgrip test was observed for the dominant-hand compared to the non-dominant hand (P = .004, d = 0.30) and for men compared to women (P = .001, d = 0.90). The main effect of strength level did not reach statistical significance (P = .266).

CONCLUSIONS

The IOP rise associated with a maximal isometric handgrip effort is affected by the participants´ sex (men > women) and hand dominance (dominant hand > non-dominant hand), but not on strength levels. These findings need to be corroborated in glaucoma patients.

Intraocular pressure increases during dynamic resistance training exercises according to the exercise phase in healthy young adults

PURPOSE

To determine the intraocular pressure (IOP) changes caused by the execution of lower body and upper body resistance training exercises leading to muscular failure depending on the exercise phase (concentric vs. eccentric). We also assessed the influence of the exercise type (back squat vs. biceps curl) and level of effort on the IOP response.

METHODS

Nineteen physically active young adults performed four sets (2 exercise type × 2 exercise phase) of 10 repetitions leading to muscular failure while adopting a normal breathing pattern. IOP was measured by rebound tonometry at baseline, after each of the ten repetitions, and after 1 min of recovery.

RESULTS

There was a main effect of the exercise phase (p < 0.001, η² = 0.56), observing greater IOP values in the eccentric condition of the back squat and concentric condition of the biceps curl. Also, greater IOP values were obtained for the back squat in comparison with the biceps curl (p < 0.001, η² = 0.61), and IOP progressively increases with the level of accumulated effort (p < 0.001, η² = 0.88; Pearson r = 0.97-0.98).

CONCLUSIONS

IOP fluctuates during the different phases of the repetition in dynamic resistance training exercises, being greater IOP values observed during the more physically demanding phases of the exercise (eccentric phase of the back squat and concentric phase of the biceps curl). A heightened IOP response is positively associated with muscle size (back squat > biceps curl) and with the level of effort (number of accumulated repetitions). Based on these findings, highly demanding dynamic resistance training should be avoided when maintaining stable IOP levels is desirable.

Impact of resistance training sets performed until muscular failure with different loads on intraocular pressure and ocular perfusion pressure

PURPOSE

The aim of this article is to investigate the acute effects of bench press sets leading to muscular failure with different loads on intraocular pressure and ocular perfusion pressure.

STUDY DESIGN

A randomized experimental study.

METHODS

Seventeen physically active young men performed four resistance training sets of bench press to muscular failure against different relative loads (65% one-repetition maximum vs 75% one-repetition maximum vs 85% one-repetition maximum vs 95% one-repetition maximum). Intraocular pressure was measured before and immediately after the execution of each of the four sets, and ocular perfusion pressure was also assessed before and after physical effort.

RESULTS

We found that intraocular pressure increased after reaching muscular failure (p < 0.001, ƞ²= 0.52), being also dependent on the interaction load × point of measure (p < 0.001, ƞ²= 0.33). Our data demonstrated that higher intraocular pressure increases were found when participants performed the bench press exercise against heavier loads, showing statistical significance for the 75% one-repetition maximum (p = 0.020, d = -0.63, mean change = 0.9 mmHg), 85% one-repetition maximum (p = 0.035, d = -0.56, mean change = 1.4 mmHg), and 95% one-repetition maximum (p < 0.001, d = -1.36, mean change = 2.9 mmHg) relative loads. For its part, ocular perfusion pressure showed a reduction after exercise (p = 0.009, ƞ²= 0.35), being these changes independent on the load used.

CONCLUSION

Bench press exercise leading to muscular failure provokes an acute intraocular pressure rise, with greater changes when heavier loads are used. Ocular perfusion pressure exhibited an acute reduction after exercise; however, its clinical relevance seems to be insignificant (lower to 4%). We argue that the use of heavy loads, when training to muscular failure, should be discouraged in order to avoid acute intraocular pressure fluctuations. Future studies should corroborate the generalizability of these findings in glaucoma patients.