Low skeletal muscle mass during young adulthood may impair diaphragm function, cognition, sleep, and psychological well-being. Inspiratory muscle training (IMT) has been shown to improve respiratory muscle performance; however, it remains unclear whether different IMT intensities produce differential effects on diaphragm morphology and function, cognition, sleep, anxiety, and health-related quality of life. The purpose of this randomized controlled trial is to compare the effects of high-intensity inspiratory muscle training (HI-IMT), moderate-intensity inspiratory muscle training (MI-IMT), and sham inspiratory muscle training in young adults with low skeletal muscle mass. A total of 69 participants with low skeletal muscle mass will be randomly assigned to one of three groups: (1) HI-IMT, (2) MI-IMT, or (3) sham IMT. Participants will complete a supervised 6-week intervention consisting of five training sessions per week. Participants allocated to the HI-IMT group will perform inspiratory muscle training at approximately 80% of maximal inspiratory pressure (MIP), whereas those in the MI-IMT group will train at approximately 50-60% of MIP. The sham group will perform low-intensity inspiratory muscle training at approximately 15% of MIP. Training intensity will be adjusted throughout the intervention according to repeated MIP assessments. Outcome assessments will be performed before and after the intervention. Primary outcomes will include diaphragm thickness, diaphragm thickening fraction, and diaphragm excursion assessed using ultrasonography. Secondary outcomes will include cognitive function assessed using the Montreal Cognitive Assessment (MoCA), sleep quality assessed using the Pittsburgh Sleep Quality Index (PSQI), daytime sleepiness assessed using the Epworth Sleepiness Scale (ESS), insomnia severity assessed using the Insomnia Severity Index (ISI), anxiety assessed using the State-Trait Anxiety Inventory (STAI), and health-related quality of life assessed using the Short Form-36 Health Survey (SF-36). The primary hypothesis is that both HI-IMT and MI-IMT will improve diaphragm morphology and function, cognition, sleep, anxiety, and health-related quality of life compared with sham IMT. It is further hypothesized that HI-IMT will produce greater improvements than MI-IMT because of the higher inspiratory training intensity.
Low skeletal muscle mass during young adulthood has become an increasingly recognized public health concern because it is associated with reduced physical performance, impaired metabolic health, and an increased risk of developing sarcopenia later in life. In addition to peripheral skeletal muscles, reduced muscle mass may affect diaphragm structure and function, potentially contributing to impaired respiratory mechanics as well as alterations in cognition, sleep, psychological well-being, and health-related quality of life. Although inspiratory muscle training (IMT) has been widely used to improve inspiratory muscle performance, the influence of different IMT intensities on diaphragm morphology and multidimensional health outcomes has not been fully established. This randomized, sham-controlled clinical trial is designed to compare the effects of high-intensity inspiratory muscle training (HI-IMT), moderate-intensity inspiratory muscle training (MI-IMT), and sham inspiratory muscle training in young adults with low skeletal muscle mass. The primary objective is to determine whether training intensity influences changes in diaphragm structure and function assessed by ultrasonography. Secondary objectives are to evaluate the effects of different IMT intensities on cognitive function, sleep quality, daytime sleepiness, insomnia severity, anxiety, and health-related quality of life. Participants aged 18-25 years with low skeletal muscle mass will be randomly assigned to one of three parallel groups using age- and sex-stratified block randomization. Participants allocated to the HI-IMT group will perform inspiratory muscle training at approximately 80% of maximal inspiratory pressure (MIP), whereas participants in the MI-IMT group will train at approximately 50-60% of MIP. Participants in the sham group will perform inspiratory muscle training using minimal resistance (approximately 15% of MIP). The intervention will last 6 weeks, with five training sessions per week. One session each week will be supervised by a physiotherapist, and the remaining sessions will be completed at home with regular monitoring. Outcome assessments will be performed before and after the intervention. Primary outcome measures will include diaphragm thickness, diaphragm thickening fraction, and diaphragm excursion assessed using ultrasonography. Secondary outcome measures will include body composition, cognitive function assessed using the Montreal Cognitive Assessment (MoCA), sleep quality assessed using the Pittsburgh Sleep Quality Index (PSQI), daytime sleepiness assessed using the Epworth Sleepiness Scale (ESS), insomnia severity assessed using the Insomnia Severity Index (ISI), anxiety assessed using the State-Trait Anxiety Inventory (STAI) and the Generalized Anxiety Disorder-7 (GAD-7), and health-related quality of life assessed using the Short Form-36 Health Survey (SF-36). The study is designed to evaluate whether different inspiratory muscle training intensities are associated with differences in diaphragm morphology and function, cognitive function, sleep, anxiety, and health-related quality of life in young adults with low skeletal muscle mass.
Study Type
INTERVENTIONAL
Allocation
RANDOMIZED
Purpose
TREATMENT
Masking
SINGLE
Enrollment
69
Participants performed a 6-week high-intensity inspiratory muscle training program using a threshold-loading inspiratory muscle trainer (POWERbreathe Classic Light Resistance). Training was conducted five days per week, consisting of one supervised session and four home-based sessions. The initial training intensity was set at approximately 80% of the predicted maximal inspiratory pressure (MIP) and was progressively adjusted weekly to maintain the target training intensity according to perceived exertion.
Participants performed a 6-week moderate-intensity inspiratory muscle training program using a threshold-loading inspiratory muscle trainer (POWERbreathe Classic Light Resistance). Training was conducted five days per week, consisting of one supervised session and four home-based sessions. The initial training intensity was set at 50-60% of the predicted maximal inspiratory pressure (MIP) and was progressively adjusted weekly to maintain the prescribed training intensity.
Participants completed a 6-week sham inspiratory muscle training program using the same threshold-loading inspiratory muscle trainer. The intervention followed the same schedule as the active groups (five sessions per week, including one supervised and four home-based sessions), while the resistance was maintained at 15% of maximal inspiratory pressure throughout the study to provide minimal inspiratory loading without an intended training effect.
Munzur University Faculty of Health Sciences
Tunceli, Turkey (Türkiye)
Change in Diaphragm Thickness Measured by Ultrasonography
Diaphragm thickness will be assessed using B-mode ultrasonography at functional residual capacity (FRC) and total lung capacity (TLC). The primary outcome is the change in diaphragm thickness from baseline to completion of the 6-week intervention. Measurements will be performed by a blinded radiologist using a standardized ultrasound protocol.
Time frame: Baseline and Week 6
Change in Diaphragm Thickening Fraction
Diaphragm thickening fraction measured by ultrasonography. The outcome is the change from baseline to Week 6.
Time frame: Baseline and Week 6
Change in Diaphragm Excursion
Diaphragm excursion (mobility) measured by ultrasonography. The outcome is the change from baseline to Week 6.
Time frame: Baseline and Week 6
Change in Montreal Cognitive Assessment (MoCA) Score
Cognitive function assessed using the Montreal Cognitive Assessment (MoCA). The Montreal Cognitive Assessment is a 30-point cognitive screening instrument with total scores ranging from 0 to 30. Higher scores indicate better cognitive function. The outcome measure is the change in total score from baseline to Week 6.
Time frame: Baseline and Week 6
Change in Pittsburgh Sleep Quality Index (PSQI) Score
Sleep quality assessed using the Pittsburgh Sleep Quality Index (PSQI). The Pittsburgh Sleep Quality Index is a 21-point questionnaire with total scores ranging from 0 to 21. Higher scores indicate poorer sleep quality. The outcome measure is the change in total score from baseline to Week 6.
Time frame: Baseline and Week 6
Change in Epworth Sleepiness Scale (ESS) Score
Daytime sleepiness assessed using the Epworth Sleepiness Scale (ESS). The Epworth Sleepiness Scale is a 24-point questionnaire with total scores ranging from 0 to 24. Higher scores indicate greater daytime sleepiness. The outcome measure is the change in total score from baseline to Week 6.
Time frame: Baseline and Week 6
Change in Insomnia Severity Index (ISI) Score
Insomnia severity assessed using the Insomnia Severity Index (ISI). The Insomnia Severity Index is a 28-point questionnaire with total scores ranging from 0 to 28. Higher scores indicate greater insomnia severity. The outcome measure is the change in total score from baseline to Week 6.
Time frame: Baseline and Week 6
Change in State Anxiety Inventory (STAI-State) Score
State anxiety assessed using the State-Trait Anxiety Inventory-State (STAI-State). The State-Trait Anxiety Inventory-State is a 20-item questionnaire with total scores ranging from 20 to 80. Higher scores indicate greater state anxiety. The outcome measure is the change in total score from baseline to Week 6.
Time frame: Baseline and Week 6
Change in Trait Anxiety Inventory (STAI-Trait) Score
Trait anxiety assessed using the State-Trait Anxiety Inventory-Trait (STAI-Trait). The State-Trait Anxiety Inventory-Trait is a 20-item questionnaire with total scores ranging from 20 to 80. Higher scores indicate greater trait anxiety. The outcome measure is the change in total score from baseline to Week 6.
Time frame: Baseline and Week 6
Change in Generalized Anxiety Disorder-7 (GAD-7) Score
Generalized anxiety symptoms assessed using the Generalized Anxiety Disorder 7-item Scale (GAD-7). The Generalized Anxiety Disorder 7-item Scale is a 7-item questionnaire with total scores ranging from 0 to 21. Higher scores indicate greater anxiety symptom severity. The outcome measure is the change in total score from baseline to Week 6.
Time frame: Baseline and Week 6
Change in Short Form-36 (SF-36) Total Score
Health-related quality of life assessed using the 36-Item Short Form Health Survey (SF-36). The 36-Item Short Form Health Survey generates a total score ranging from 0 to 100, with higher scores indicating better health-related quality of life. The outcome measure is the change in total score from baseline to Week 6.
Time frame: Baseline and Week 6
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