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The effects of threshold inspiratory muscle training in patients with obstructive sleep apnea: a randomized experimental study



Patients with obstructive sleep apnea (OSA) (an obstructed airway and intermittent hypoxia) negatively affect their respiratory muscles. We evaluated the effects of a 12-week threshold inspiratory muscle training (TIMT) program on OSA severity, daytime sleepiness, and pulmonary function in newly diagnosed OSA.


Sixteen patients with moderate-to-severe OSA were randomly assigned to a TIMT group and 6 to a control group. The home-based TIMT program was 30–45 min/day, 5 days/week, for 12 weeks using a TIMT training device. Their apnea-hypopnea index (AHI), Epworth sleepiness scale (ESS), and forced vital capacity (FVC) scores were evaluated pre- and post-treatment. Polysomnographic (PSG) analysis showed that 9 TIMT-group patients had positively responded (TIMT-responder group: post-treatment AHI < pre-treatment) and that 7 had not (TIMT non-responder group: post-treatment AHI > pre-treatment).


Post-treatment AHI and ESS scores were significantly (both P < 0.05) lower 6% and 20.2%, respectively. A baseline AHI ≤ 29.0/h predicted TIMT-responder group patients (sensitivity 77.8%; specificity 85.7%). FVC was also significantly (P < 0.05) higher 7.2%. Baseline AHI and FEV6.0 were significant predictors of successful TIMT-responder group intervention. OSA severity and daytime sleepiness were also significantly attenuated.


Home-based TIMT training is simple, efficacious, and cost-effective.

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Fig. 1
Fig. 2



Aerobic exercise


Apnea-hypopnea index


Apnea-hypopnea index during non-rapid eye movement (NREM) sleep


Apnea-hypopnea index during rapid eye movement (REM) sleep


American Thoracic Society


Body mass index




Epworth sleepiness scale

FEV1.0 :

Forced expiratory volume in 1 s

FEV6.0 :

Forced expiratory volume in 6 s


Forced vital capacity


Inspiratory muscle training


Non-rapid eye movement


Obstructive sleep apnea


Pulmonary function test




Pittsburgh sleep quality index


Physical therapist


Rapid eye movement


Repetition maximum


Receiver operating characteristic


Rating of perceived exertion


Threshold inspiratory muscle training program


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We thank Professor Yu-Wen Chen, Grace Chen, and the sleep medicine center staff members at National Cheng Kung University Hospital and Tainan Hospital who participated in the study.


This study was funded by Shu-Zen Junior College of Medicine and Management, under contract SZPT10403008, and by the Gary & Amy Foundation, and by National Cheng-Kung University Hospital (grant number NCKUH-10802018).

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Correspondence to Cheng-Yu Lin.

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The authors declare that they have no conflict of interest.

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All procedures performed in studies involving human participants were approved by the Institutional Review Board of National Cheng Kung University (IRB No. A-ER-103-168).

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Lin, H., Chiang, L., Ong, J. et al. The effects of threshold inspiratory muscle training in patients with obstructive sleep apnea: a randomized experimental study. Sleep Breath (2019). https://doi.org/10.1007/s11325-019-01862-y

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  • Obstructive sleep apnea
  • Threshold inspiratory muscle training
  • Apnea-hypopnea index
  • Forced vital capacity