Abdominal Air Pressure Resistance Versus Abdominal Weight Training Versus Breathing Exercise for Improving Diaphragmatic Strength, Endurance, and Physiological Responses in Young Healthy Adults: A Study Protocol for RCT

This study aims to compare the effects of abdominal air pressure resistance training, abdominal weight training, and breathing exercises on diaphragmatic strength, endurance, and physiological responses in young healthy adults.

Forty-two healthy adults aged 18-35 years will be randomly allocated to one of three groups: abdominal air pressure resistance training, abdominal weight training, or breathing exercises. Participants will complete supervised training sessions three times per week for eight weeks, with standardized breathing cadence, training volume, and therapist contact time across groups.

This trial will provide the first direct comparison of a programmable pneumatic abdominal loading method with traditional abdominal weight loading and standard breathing exercises in healthy young adults. The findings will help determine the relative effectiveness, tolerability, and safety of these interventions for enhancing diaphragmatic function. The results may contribute to the development of evidence-based respiratory muscle training strategies for rehabilitation, health promotion, and performance enhancement.

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Key information

Conditions

Diaphragm Thickness Dyspnea Dyspnoea Pathological Conditions, Signs and Symptoms Respiration Disorders Respiratory Tract Diseases Signs and Symptoms Signs and Symptoms, Respiratory

Age range

18 year–35 year

Sex eligibility

All sexes

Study type

Interventional

Phase

Not applicable

Who can participate

Healthy volunteers accepted: Yes

Only the study team can determine whether someone qualifies for participation.

Inclusion criteria

males and females with a body mass index (BMI) between 18.5 and 29.9 kg/m²
non-smokers
have not participated in structured respiratory muscle training within the previous six months
able to understand the study procedures
provide written informed consent.

Exclusion criteria

have a known cardiopulmonary, neuromuscular, or significant metabolic disease
experience a respiratory infection or respiratory symptoms within the preceding 2-3 weeks
pregnant
have undergone major abdominal or thoracic surgery within the previous six months
have uncontrolled hypertension, significant gastroesophageal reflux disease (GERD), or any other condition that could make abdominal loading unsafe, as determined during the screening process.

Treatment and study plan

Abdominal Air Pressure Resistance Training

Other

In the AAPR group, resisted diaphragmatic breathing will be performed using a pneumatic abdominal garment or cuff capable of delivering quantifiable air pressure. Training will be initiated at a pressure level that elicited a moderate perceived breathing effort, corresponding to a Borg Rating of Perceived Exertion (RPE) of approximately 4-5, or within a predefined pressure range (e.g., 5-10 cmH₂O), depending on device capability. Progressive overload will be applied through weekly increases of 1-2 cmH₂O, provided predefined symptom tolerance criteria were satisfied. Each session consisted of 4-6 sets of resisted diaphragmatic breathing, with each set lasting 2-3 minutes and separated by rest periods of 1-2 minutes. During each session, the applied pressure, perceived exertion, and symptom responses will be recorded.

Abdominal Weight Training (AWT)

Other

In the AWT group, diaphragmatic breathing will be performed with an external load applied to the anterior abdominal wall using a standardized sandbag or weight pack, with participants positioned in supine crook-lying. Load prescription will be implemented using a pre-specified method, which included either a fixed initial load of 2-5 kg with weekly increments of 0.5-1 kg as tolerated, an initial load corresponding to 3-5% of body mass with weekly progression, or load titration based on perceived exertion targeting a Borg RPE of 4-5 during training sets. Training volume, set duration, and rest intervals will be matched to those of the AAPR group. For each session, the load applied, perceived exertion, and symptom responses will be documented.

Breathing Exercise Control (BE)

Other

In the BE control group, standardized diaphragmatic breathing combined with paced slow deep breathing will be performed without the application of external resistance. Training duration, breathing cadence, number of sets, and rest intervals will be matched to those used in the loaded intervention groups. Perceived exertion and symptom responses will be documented during each session.

Primary outcomes

Diaphragm thickening fraction

Time frame: pre and post intervention, 8 weeks

Diaphragm thickness will be assessed using a portable ultrasound device (VERSANA PREMIER) operating in B-mode with a 10-MHz linear transducer. Standardized imaging settings, including gain, depth, and focus, were maintained throughout all examinations. Ultrasound measurements were conducted by a trained assessor who was blinded to participants' group assignments. With participants positioned supine, the transducer was placed over the right hemidiaphragm at the zone of apposition, located between the anterior and mid-axillary lines at the eighth to ninth intercostal space. Care was taken to apply minimal pressure with the probe to prevent compression of underlying tissues. Diaphragm thickness measurements were obtained at end-expiration, corresponding to residual volume (RV), and at end-inspiration, corresponding to total lung capacity (TLC). Each measurement was repeated three times with a minimum rest period of 30 seconds between trials, and the mean value was used for analysis.

Secondary outcomes

Borg Rating of Perceived Exertion (RPE) scale

Time frame: pre and post intervention, 8 weeks

To evaluate the acute physiological response to the intervention perceived exertion were monitored during a standardized 2-3-minute breathing task.

Sponsors and collaborators

Lead sponsor

University of Sharjah

Other

Registry information

Official study title

Abdominal Air Pressure Resistance Versus Abdominal Weight Training Versus Breathing Exercise for Improving Diaphragmatic Strength, Endurance, and Physiological Responses in Young Healthy Adults: A Study Protocol for Randomized Controlled Trial

Important dates

Study start: 2026
Primary completion: 2026
Study completion: 2026
First posted: Aug 31, 2026
Registry last updated: Aug 31, 2026

OpenTrials presents study information sourced from ClinicalTrials.gov. The official registry record should be consulted for the latest information.

View the official ClinicalTrials.gov record (opens in a new tab)

This listing is for discovery and informational purposes only. It is not medical advice, does not guarantee that a study is recruiting, and does not determine eligibility. Contact the study team and a qualified healthcare professional when considering participation.

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