| | Author & year | Country | Gender (M/F) | Sample size (T/C) | Intervention | Control | Treatment duration | Main outcome |
| | Gounden, 1990 | South Africa | 32/8 | 20/20 | Resistive EMT | Usual care | 8 w | VC, MEP | | Xu, 2018 | China | 95/5 | 50/50 | Respiratory resistance training | Usual care | 2 m | FVC, FEV1, MVV | | Van Houtte, 2008 | Belgium | 12/2 | 7/7 | Normocapnic hyperpnea training | Sham | 8 w | FVC, PEM, MVV | | Litchke, 2011 | USA | NR | 9/7 | (a) Concurrent flow resistance
(b) Concurrent pressure threshold | Usual care | 9 w | MVV, MIP | | Mueller, 2013 | Netherlands | 18/6 | 16/8 | (a) Isocapnic hyperpnea training
(b) Inspiratory resistance training | Sham | 8 w | MVV, MIP, VC, FEV1, MEP | | Derrickson, 1992 | USA | 9/2 | 6/5 | Resistive IMT | Usual care | 7 w | FVC, MVV, | | West, 2014 | UK | 9/1 | 5/5 | Resistive IMT | Sham | 6 w | FVC, MVV, FEV1, MEP | | Litchke, 2007 | USA | 9/0 | 4/5 | Respiratory resistance training | Usual care | 10 w | MVV, MIP | | Liaw, 2000 | China | 16/4 | 10/10 | Resistive IMT | Usual care | 6 w | FVC, MIP, FEV1, | | Loveridge, 1989 | Canada | NR | 6/6 | Resistive IMT | Usual care | 8 w | FVC | | Postma, 2014 | Netherlands | 35/5 | 19/21 | Resistive IMT | Usual care | 8 w | MVV, MIP, FVC, FEV1 | | Roth, 2010 | USA | 22/7 | 16/13 | Resistive EMT | Sham | 9 w | FVC, MIP, FEV1 | | Tamplin, 2013 | Australia | NR | 13/11 | Therapeutic singing training | Music appreciation | 12 w | VC, FVC, MIP, FEV1 | | Kim, 2017 | Korea | 22/15 | 25/12 | (a) Integrating training
(b) Respiratory muscle training | Sham | 8 w | FVC, FEV1 | | Zhang, 2016 | China | 27/11 | 19/19 | Resistive IMT | Usual care | 4 w | MIP | | Soumyashree, 2018 | India | 22/5 | 15/12 | Resistive IMT | Usual care | 4 w | MEP, MIP |
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