Effects of caffeine consumption on intraocular pressure during low‐intensity endurance exercise: A placebo‐controlled, double‐blind, balanced crossover study

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.

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.

Effect of caffeine on superficial retinal vasculature of the macula in high myopes using optical coherence tomography angiography - A pilot study

PURPOSE

To monitor effect of caffeine on vasculature of the inner retina of high myopes METHODS: This was a crossover, self-control, randomized trial. Healthy young high myopes were recruited to take 200 mg of caffeine capsule and placebo capsule, randomly assigned in two visits separated by at least one week. Superficial retinal vasculature in terms of vessel length density (VD) and perfusion area density (PD) was captured and monitored using a spectral domain optical coherence tomography angiography (OCTA) machine. After baseline measurements, blood pressure (BP), intraocular pressure (IOP), and subfoveal choroidal thickness (ChT) were also monitored at 30-min intervals till 3 h.

RESULTS

Eighteen subjects (6 male, 24.3 ± 3.1 years) completed the study. After taking the caffeine capsule, there was a significant increase in BP (p < 0.01), and reduction in ChT (p < 0.01), with no change in IOP (p = 0.36). VD demonstrated a trend of reduction at the central 1-mm circle, and 1-3 mm annulus (p < 0.01) following the ETDRS grid. Reduction trend of PD appeared at the central 1-mm circle, 1-3 mm annulus, and the entire 3-mm circle (p < 0.01). Compared with baseline, VD and PD reductions were significant 180 min after taking the caffeine capsule at the central 1-mm circle, but the reduction was small (VD: by 1mm^-1; PD: by 1%). Changes in other regions were not significant.

CONCLUSIONS

The current study found significant reduction in VD and PD after taking 200 mg of caffeine capsule. Such a small amount of alteration may be clinically irrelevant.

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.

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.