Combined Inspiratory Muscle Training and Functional High-Intensity Interval Training in Boys With Obesity (IMT and HIIT)

September 3, 2026 updated by: Coşkun YILMAZ, Gümüşhane Universıty

Combined Inspiratory Muscle Training and Functional High-Intensity Interval Training Promote Respiratory, Diaphragmatic, and Aerobic Adaptations in Children With Obesity

Childhood obesity is associated with reduced cardiorespiratory fitness, impaired exercise tolerance, and altered respiratory mechanics. This randomized controlled trial investigated whether combining inspiratory muscle training with functional high-intensity interval training improves diaphragm morphology, respiratory muscle strength, pulmonary function, aerobic fitness, and functional exercise capacity in boys with obesity. Fifty boys aged 10-12 years were randomly assigned to six weeks of combined inspiratory muscle training and functional high-intensity interval training or usual activity.

Study Overview

Status

Status

Indicates the current recruitment status or the expanded access status.
Not yet recruiting

Conditions

Conditions

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Intervention / Treatment

Intervention / Treatment

A process or action that is the focus of a clinical study. Interventions include drugs, medical devices, procedures, vaccines, and other products that are either investigational or already available. Interventions can also include noninvasive approaches, such as education or modifying diet and exercise.

Detailed Description

This prospective, two-arm, randomized controlled trial investigated the effects of a six-week combined inspiratory muscle training and functional high-intensity interval training program in boys aged 10-12 years with obesity.

Fifty participants were randomly allocated in a 1:1 ratio to either a combined training group or a usual-activity control group. The intervention consisted of progressive inspiratory muscle training performed five days per week and functional high-intensity interval training performed three non-consecutive days per week for six weeks.

Inspiratory muscle training was performed using a threshold pressure-loading device. Training commenced at 30% of maximal inspiratory pressure and increased by 5% each week, reaching 55% of maximal inspiratory pressure in week 6. Each session consisted of two sets of 30 inspiratory efforts.

Functional high-intensity interval training was performed three times per week. Each approximately 35-40-minute session consisted of a standardized warm-up, a functional high-intensity interval circuit, and a cool-down. The circuit included wall sit, incline push-up, seated knee-to-chest exercise, shadow boxing, Superman exercise, and low-step-up exercise. Training intensity was progressively increased by manipulating work-to-rest ratios and circuit volume.

The control group continued habitual daily activities without participating in structured exercise or respiratory muscle training during the six-week study period.

Primary outcomes were diaphragm thickening fraction, inspiratory diaphragm thickness, and expiratory diaphragm thickness. Secondary outcomes included maximal inspiratory pressure, maximal expiratory pressure, forced vital capacity, forced expiratory volume in one second, FEV₁/FVC ratio, six-minute walk distance, estimated VO₂max, body composition, and perceived exertion.

Assessments were performed at baseline and after the six-week intervention under standardized laboratory conditions between 15:00 and 17:00. Diaphragm ultrasonography was performed by a radiologist blinded to group allocation

Study Type

Study Type

Describes the nature of a clinical study. Study types include interventional studies (also called clinical trials), observational studies (including patient registries), and expanded access.
Interventional

Enrollment (Estimated)

Enrollment

The number of participants in a clinical study. The "anticipated" enrollment is the target number of participants that the researchers need for the study.
50

Phase

Phase

The stage of a clinical trial studying a drug or biological product, based on definitions developed by the U.S. Food and Drug Administration (FDA). The phase is based on the study's objective, the number of participants, and other characteristics. There are five phases: Early Phase 1 (formerly listed as Phase 0), Phase 1, Phase 2, Phase 3, and Phase 4. Not Applicable is used to describe trials without FDA-defined phases, including trials of devices or behavioral interventions.
  • Not Applicable

Contacts and Locations

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Study Contact

Study Contact

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Study Locations

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Eligibility Criteria

The key requirements that people who want to participate in a clinical study must meet or the characteristics they must have. Eligibility criteria consist of both inclusion criteria (which are required for a person to participate in the study) and exclusion criteria (which prevent a person from participating). Types of eligibility criteria include whether a study accepts healthy volunteers, has age or age group requirements, or is limited by sex.

Ages Eligible for Study

  • Child

Accepts Healthy Volunteers

Yes

Description

Inclusion Criteria:

  • Male sex.

  • Age 10-12 years.

    *Obesity according to World Health Organization age- and sex-specific BMI reference criteria.

  • No regular participation in structured exercise training during the preceding six months.
  • Medical clearance to participate in moderate-to-vigorous physical activity.

Exclusion Criteria:

  • Diagnosed cardiovascular, neuromuscular, orthopaedic, or metabolic conditions that could interfere with exercise participation.
  • Chronic respiratory disease, including asthma requiring regular medication.

  • Impaired pulmonary function defined as FEV₁/FVC <75%.

    *Upper respiratory tract infection within the preceding two weeks.

  • Medication use that could affect respiratory function or exercise capacity.
  • Previous thoracic surgery.
  • Inability to complete the testing procedures.

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

  • Primary Purpose: Supportive Care
  • Allocation: Randomized
  • Interventional Model: Parallel Assignment
  • Masking: Single

Arms and Interventions

Participant Group / Arm

Participant Group / Arm

A group or subgroup of participants in a clinical trial that receives a specific intervention/treatment, or no intervention, according to the trial's protocol.
Intervention / Treatment

Intervention / Treatment

A process or action that is the focus of a clinical study. Interventions include drugs, medical devices, procedures, vaccines, and other products that are either investigational or already available. Interventions can also include noninvasive approaches, such as education or modifying diet and exercise.
Experimental: Combined IMT + Functional HIIT
Participants received six weeks of combined inspiratory muscle training and functional high-intensity interval training in addition to their usual daily activities. Inspiratory muscle training was performed five days per week, and functional high-intensity interval training was performed three non-consecutive days per week.
Other: Inspiratory Muscle Training
Inspiratory muscle training was performed using a threshold pressure-loading device (POWERbreathe). Participants trained once daily, five days per week, for six consecutive weeks. Each session consisted of two sets of 30 inspiratory efforts. Training began at 30% of maximal inspiratory pressure in week 1, with the training load progressively increased by 5% each week to reach 55% of maximal inspiratory pressure in week 6. Training pressure was reassessed weekly, and all sessions were supervised by a certified exercise specialist.
Other: Functional High-Intensity Interval Training
Functional high-intensity interval training was performed three times per week on non-consecutive days for six weeks. Each session lasted approximately 35-40 minutes and consisted of an approximately 8-minute warm-up, a functional high-intensity interval circuit, and an approximately 5-minute cool-down. The circuit included wall sit, incline push-up, seated knee-to-chest exercise, shadow boxing, Superman exercise, and low-step-up exercise. Training intensity was progressively increased by manipulating work-to-rest ratios and the number of circuit cycles. Perceived exertion was monitored using the Borg CR-10 scale.
No Intervention: Usual Activity Control
Participants continued their habitual daily activities throughout the six-week study period and did not participate in structured exercise or respiratory muscle training. They were instructed not to initiate a new exercise program until study completion.

What is the study measuring?

Primary Outcome Measures

Primary Outcome Measures

In a clinical study's protocol, the planned outcome measure that is the most important for evaluating the effect of an intervention/treatment. Most clinical studies have one primary outcome measure, but some have more than one.
Outcome Measure
Measure Description
Time Frame
Inspiratory Diaphragm Thickness
Time Frame: 6 weeks
Inspiratory diaphragm thickness (DTins) was measured by ultrasound at the end of maximal inspiration at the zone of apposition of the right hemidiaphragm. Three measurements were obtained and averaged. The measurement represents an ultrasound-derived index of diaphragm morphology.
6 weeks
Diaphragm Thickening Fraction
Time Frame: 6 weeks
Diaphragm thickening fraction (DTf) was assessed using diaphragm ultrasonography and calculated as [(end-inspiratory diaphragm thickness - end-expiratory diaphragm thickness) / end-expiratory diaphragm thickness] × 100. Measurements were obtained from the right hemidiaphragm at the zone of apposition. Three measurements were obtained in each respiratory phase and averaged for analysis.
6 weeks
Expiratory Diaphragm Thickness
Time Frame: 6 week
Expiratory diaphragm thickness (DTexp) was measured by ultrasound at the end of maximal expiration at the zone of apposition of the right hemidiaphragm. Three measurements were obtained and averaged. The measurement represents an ultrasound-derived index of diaphragm morphology.
6 week

Secondary Outcome Measures

Secondary Outcome Measures

In a clinical study's protocol, a planned outcome measure that is not as important as the primary outcome measure for evaluating the effect of an intervention but is still of interest. Most clinical studies have more than one secondary outcome measure.
Outcome Measure
Measure Description
Time Frame
Maximal Inspiratory Pressure
Time Frame: 6 week
Maximal inspiratory pressure (MIP) was measured using a handheld mouth pressure meter according to ATS/ERS recommendations. Measurements were performed from residual volume, and the best reproducible values were recorded in cmH₂O.
6 week
Maximal Expiratory Pressure
Time Frame: 6 week
Maximal expiratory pressure (MEP) was measured using a handheld mouth pressure meter according to ATS/ERS recommendations. Measurements were performed from total lung capacity, and the best reproducible values were recorded in cmH₂O.
6 week
Forced Vital Capacity
Time Frame: 6 week
Forced vital capacity (FVC) was measured using spirometry according to ATS/ERS recommendations.
6 week
Forced Expiratory Volume in One Second
Time Frame: 6 week
Forced expiratory volume in one second (FEV₁) was measured using spirometry according to ATS/ERS recommendations.
6 week
FEV₁/FVC Ratio
Time Frame: 6 week
The FEV₁/FVC ratio was calculated from spirometric measurements obtained according to ATS/ERS recommendations.
6 week
Six-Minute Walk Distance
Time Frame: 6 week
Functional exercise capacity was assessed using the Six-Minute Walk Test. Participants walked for six minutes along a pre-measured, flat, straight corridor at a self-selected comfortable pace. The total distance covered in meters was recorded.
6 week
Estimated VO2max
Time Frame: 6 week
Estimated maximal oxygen uptake (VO₂max) was calculated from six-minute walk distance and body mass index using the validated prediction equation developed for children and adolescents with obesity: VO₂max = 26.9 + (0.014 × 6MWD [m]) - (0.38 × BMI [kg/m²]). VO₂max values were estimated and were not directly measured by cardiopulmonary exercise testing.
6 week
Body Mass Index
Time Frame: 6 week
Body composition was assessed using a multi-frequency bioelectrical impedance analyzer. Body mass index (BMI) and BMI z-score were assessed according to standardized procedures.
6 week
Rating of Perceived Exertion
Time Frame: 6 week
Perceived exercise intensity was assessed using the Borg Category Ratio-10 Rating of Perceived Exertion scale. Participants were familiarized with the scale before the intervention, and RPE was recorded immediately after each functional HIIT session throughout the six-week intervention period.
6 week
Height
Time Frame: 6 Week
Body composition was assessed using a multi-frequency bioelectrical impedance analyzer. Height was assessed according to standardized procedures.
6 Week
Weight
Time Frame: 6 Week
Body composition was assessed using a multi-frequency bioelectrical impedance analyzer. Weight was assessed according to standardized procedures.
6 Week

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

Sponsor

The organization or person who initiates the study and who has authority and control over the study.
Gümüşhane Universıty

Publications and helpful links

The person responsible for entering information about the study voluntarily provides these publications. These may be about anything related to the study.

General Publications

Study record dates

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Study Major Dates

Study Start (Estimated)

Study Start

The actual date on which the first participant was enrolled in a clinical study. The "anticipated" study start date is the date that the researchers think will be the study start date.
October 20, 2026

Primary Completion (Estimated)

Primary Completion

The date on which the last participant in a clinical study was examined or received an intervention to collect final data for the primary outcome measure. Whether the clinical study ended according to the protocol or was terminated does not affect this date. For clinical studies with more than one primary outcome measure with different completion dates, this term refers to the date on which data collection is completed for all the primary outcome measures. The "anticipated" primary completion date is the date that the researchers think will be the primary completion date for the study.
December 15, 2026

Study Completion (Estimated)

Study Completion

The date on which the last participant in a clinical study was examined or received an intervention/treatment to collect final data for the primary outcome measures, secondary outcome measures, and adverse events (that is, the last participant's last visit). The "anticipated" study completion date is the date that the researchers think will be the study completion date.
December 20, 2026

Study Registration Dates

First Submitted

First Submitted

The date on which the study sponsor or investigator first submitted a study record to ClinicalTrials.gov. There is typically a delay of a few days between the first submitted date and the record's availability on ClinicalTrials.gov (the first posted date).
September 1, 2026

First Submitted That Met QC Criteria

First Submitted That Met QC Criteria

The date on which the study sponsor or investigator first submits a study record that is consistent with National Library of Medicine (NLM) quality control (QC) review criteria. The sponsor or investigator may need to revise and submit a study record one or more times before NLM's QC review criteria are met. It is the responsibility of the sponsor or investigator to ensure that the study record is consistent with the NLM QC review criteria.
September 3, 2026

First Posted (Actual)

First Posted

The date on which the study record was first available on ClinicalTrials.gov after National Library of Medicine (NLM) quality control (QC) review has concluded. There is typically a delay of a few days between the date the study sponsor or investigator submitted the study record and the first posted date.
September 9, 2026

Study Record Updates

Last Update Posted (Actual)

Last Update Posted

The most recent date on which changes to a study record were made available on ClinicalTrials.gov. There may be a delay between when the changes were submitted to ClinicalTrials.gov by the study's sponsor or investigator (the last update submitted date) and the last update posted date.
September 9, 2026

Last Update Submitted That Met QC Criteria

Last Update Submitted That Met QC Criteria

The most recent date on which the study sponsor or investigator submitted changes to a study record that are consistent with National Library of Medicine (NLM) quality control (QC) review criteria. It is the responsibility of the sponsor or investigator to ensure that the study record is consistent with the NLM QC review criteria.
September 3, 2026

Last Verified

Last Verified

The most recent date on which the study sponsor or investigator confirmed the information about a clinical study on ClinicalTrials.gov as accurate and current. If a study with a recruitment status of recruiting; not yet recruiting; or active, not recruiting has not been confirmed within the past 2 years, the study's recruitment status is shown as unknown.
September 1, 2026

More Information

Terms related to this study

Keywords

Additional Relevant MeSH Terms

Other Study ID Numbers

Other Study ID Numbers

Identifiers or ID numbers other than the NCT number that are assigned to a clinical study by the study's sponsor, funders, or others. These numbers may include unique identifiers from other trial registries and National Institutes of Health grant numbers.
  • 2026/025

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

NO

IPD Plan Description

Individual participant data will not be publicly shared. The raw data supporting the conclusions of the study will be made available by the authors upon reasonable request, subject to applicable ethical, institutional, and data-protection requirements.

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

No

Studies a U.S. FDA-regulated device product

No

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