The Effects of Strength Training Volume, Intensity, and Breathing Techniques on Intraocular Pressure and Retinal Blood Vessels

NCT07326462 | Not Yet Recruiting

• 1 other identifier: LithuanianSportsU-27
• Study Type: interventional
• Target: 60
• Locations: 0 countries
• Sites: N/A

Brief Summary

This study aims to determine the effects of different breathing patterns on ocular vasculature and intraocular pressure (IOP) during isokinetic and isometric strength exercises. It is hypothesized that higher ocular microcirculation changes and IOP values will be observed during the Valsalva maneuver compared to normal breathing in both exercise types. Additionally, ocular microcirculation and IOP changes are expected to be more pronounced during isometric exercises than during isokinetic exercises. The results will help establish optimal strength training strategies for both professional athletes and physically active individuals.

Conditions

Healthy Participants

Keywords

intraocular pressure; exercise; Valsalva maneuver; retinal vessels

Outcome Measures

Primary Outcomes (9)

• 1. Intraocular Pressure (IOP)

  Tool: Icare portable tonometer (Icare, Tiolat Oy, Helsinki, Finland). Description: Measures the pressure inside the eye, caused by the aqueous humor pressing against the eye wall. Rationale: IOP is a key factor in glaucoma development and progression. Monitoring fluctuations during exercise and different breathing techniques is critical. Timing: Baseline (before exercise), immediately post-exercise, and at 5, 10, 15 minutes after exercise.

  3 days

• 2. Retinal Microcirculation

  Tool: Aurora handheld non-mydriatic fundus camera (Optomed, Finland). Description: Digital fundus photography to measure retinal vessel diameters (arterioles and venules) in the superior and inferior temporal quadrants, near the optic disc margin. Rationale: Retinal vessel diameter is a biomarker for cardiovascular health and provides insights into ocular blood flow changes during stress. Timing: Same schedule as IOP (before, immediately after, and 5, 10, 15 minutes post-exercise).

  3 days

• 3. Blood pressure (BP)

  Tool: Omron BP742N automatic arm blood pressure monitor (Omron Healthcare, Japan). Description: Monitors systolic and diastolic blood pressure levels. Rationale: To capture systemic cardiovascular responses during isometric vs. isokinetic exercise and different breathing conditions. Timing: Baseline, immediately after, 5, 10, and 15 minutes post-exercise.

  3 days

• 4. Oxygen Saturation (SpO₂)

  Tool: Pulse oximeter (Omron). Description: Monitors peripheral blood oxygen levels. Rationale: Evaluates systemic oxygen delivery and breathing effects (especially relevant with Valsalva maneuver). Timing: During the exercise protocol (exact points not deeply detailed in file but implied to match BP).

  3 days

• 5. Eye Dryness

  Tool: Schirmer Test (TearFlo strips). Description: Filter paper strips placed inside the lower eyelid for 5 minutes; length of wetting indicates tear production. Rationale: Assesses ocular surface health, as exercise and breathing methods may influence tear production and comfort. Timing: At baseline (before experimental trials).

  3 days

• 6. Anthropometric Data

  Tools: Leicester Height Metre for height. Tanita TBF-300 body composition scale for weight and body fat %. Derived Measurement: Body Mass Index (BMI = weight/height²). Rationale: Provides participant characteristics for standardization and analysis.

  3 days

• Questionaire no. 1

  Validated Baecke questionnaire → Physical activity level. Rationale: Captures subjective perception of workload alongside physiological measures.

  3 days

• Questionnaire no.2

  Fatigue assessment questionnaires → Subjective fatigue. Rationale: Captures subjective perception of fatigue alongside physiological measures.

  3 days

• Questionnaire no. 3

  Rating of Perceived Exertion (RPE) → Subjective exercise intensity. Rationale: Captures subjective perception of exertion alongside physiological measures.

  3 days

Study Arms (2)

Isokinetic exercise arm

EXPERIMENTAL

Protocol: Participants perform a 1-minute maximal voluntary isometric contraction of the knee extensors using a BIODEX dynamometer. Load setting: The maximum isometric load that each individual can sustain for 1 minute is determined during familiarisation. In the main session, participants work at 80% of their predetermined maximum load to avoid premature muscle failure. Nature of exercise: Static contraction (muscle generates force without changing length).

Diagnostic Test: Normal Breathing; Diagnostic Test: Valsalva maneuver

Isometric exercise arm

EXPERIMENTAL

Protocol: Participants perform 1 minute of repeated isokinetic knee extensions and flexions at a controlled angular velocity on the BIODEX dynamometer. Velocity settings: Knee extension at 30°/s and knee flexion at 60°/s within the 0°-90° range of motion (0° = full extension). Nature of exercise: Dynamic contraction (muscle changes length while producing force against constant velocity resistance).

Diagnostic Test: Normal Breathing; Diagnostic Test: Valsalva maneuver

Interventions

Normal Breathing DIAGNOSTIC_TEST

Participants perform the isometric or isokinetic exercise while following a controlled breathing rhythm: Inhale for 3 seconds Exhale for 3 seconds Breathing remains steady and continuous throughout the 1-minute exercise. Rationale: Represents a natural and safe breathing pattern during physical exertion, serves as the physiological baseline condition.

Isokinetic exercise arm; Isometric exercise arm

Valsalva maneuver DIAGNOSTIC_TEST

Participants perform the same isometric or isokinetic exercise but finish the trial with a 10-second breath-hold at the end of the 1-minute exercise. This maneuver increases intrathoracic and intra-abdominal pressures, which are transmitted to ocular and vascular systems. Rationale: Common in athletic performance, but may cause significant intraocular pressure and retinal vascular fluctuations.

Isokinetic exercise arm; Isometric exercise arm

Eligibility Criteria

• Age: 18 Years - 40 Years
• Sex: all
• Healthy Volunteers: Yes
• Age Groups: Adult (18-64)

You may qualify if:

• Subjects 18-40 years old
• Peak IOP \<21 mmHg in the modified DTC
• Open angle at gonioscopy
• Optic disc with cup-to-disc ratio \<0.6 with no signs of glaucomatous neuropathy
• Not currently taking any medication
• Non-smokers, no physical and mental disabilities
• Blood pressure up 120/80 mmHg and heart rate (HR) 60-90 rpm at rest
• BMI (18.5-34.8) kg/m2

You may not qualify if:

• Presence of any ocular disease (with the exception of refractive errors)
• Anxiety or depressive disorders
• History of ocular trauma or surgery
• Pregnancy
• Use of any kind of oral/topical steroids
• Any diagnosed chronic health condition such as cardiovascular disease including hypertension and or previous physical injuries that could impact their safe participation
• Evidence of ocular pathology due to narrow anterior chamber angles, elevated IOP greater than or equal to 21mm Hg, optic nerve or retinal pathology, cup: disc ratio of greater than 0.6 or asymmetry of cup: disc ratio of greater than 0. 2.
• Refractive error more than ±4.00 diopters, astigmatism greater than 3.00 diopters.

Sponsors & Collaborators

• Lithuanian Sports University: lead

MeSH Terms

Conditions

Motor Activity

Interventions

Valsalva Maneuver

Condition Hierarchy (Ancestors)

Behavior

Intervention Hierarchy (Ancestors)

Heart Function Tests; Diagnostic Techniques, Cardiovascular; Diagnostic Techniques and Procedures; Diagnosis; Respiratory Function Tests; Diagnostic Techniques, Respiratory System; Hemodynamics; Cardiovascular Physiological Phenomena; Circulatory and Respiratory Physiological Phenomena; Respiratory Physiological Phenomena

Study Officials

• Vytautas Streckis, phD, Prof.

  Lithuanian Sports University

  STUDY DIRECTOR

Central Study Contacts

Monika Vieversyte-Dvyliene, MD

CONTACT

069031331; monikavieversyte@gmail.com

Study Design

• Study Type: interventional
• Phase: not applicable
• Allocation: RANDOMIZED
• Masking: TRIPLE
• Who Masked: PARTICIPANT, INVESTIGATOR, OUTCOMES ASSESSOR
• Masking Details: Triple (Participant, Investigator, Outcomes Assessor)
• Purpose: BASIC SCIENCE
• Intervention Model: PARALLEL
• Sponsor Type: OTHER
• Responsible Party: SPONSOR

Model Details: This is a crossover experimental study with 60 healthy adults, where each participant completes two exercise arms (isometric vs. isokinetic) under two breathing interventions (normal vs. Valsalva), separated by 2-3 days. The design allows controlled comparison of ocular and systemic responses to exercise and breathing techniques within the same individuals.

Study Record Dates

• First Submitted: December 17, 2025
• First Posted: January 8, 2026
• Study Start: January 1, 2026
• Primary Completion: April 1, 2026
• Study Completion: May 1, 2026
• Last Updated: January 8, 2026

Record last verified: 2026-01