This study was designed to assess the effect of inspiratory and expiratory muscle training in the same cycle on respiratory muscle strength, pulmonary functions, perception of asthma symptoms in children with bronchial asthma. Fifty-one children with bronchial asthma were randomly allocated to the unloaded respiratory muscle training (Placebo training group; n = 17), inspiratory muscle training alone (inspiratory muscle training group; n = 17), or combined inspiratory and expiratory muscle training in the same cycle (combined training group; n = 17). All groups were assessed for respiratory muscle strength, pulmonary functions, and asthma symptoms.

Fifty-one children with bronchial asthma were recruited from King Khalid Hospital, Al-Kharj, Saudi Arabia. The study included children who had a confirmed diagnosis of bronchial asthma according to the Global Initiative for Asthma guidelines, aged 12-18 years, identified as being stable cases, had a baseline percent-predicted value of the peak expiratory flow rate of 60-80%, sustained stale doses of medications in the past three months. Children who had unstable asthma or exacerbated asthma symptoms, history of thoracic surgery, or cardiopulmonary comorbidities were excluded.

Outcome measures

1. Respiratory muscle strength: assessed by measuring the maximal inspiratory and expiratory pressure using an electronic respiratory pressure meter.
2. Pulmonary function: The forced vital capacity (FVC), forced expiratory volume in the first second of expiration (FEV1), and FEV1/FVC ratio, were measured in a pulmonary function test through a spirometry analyzer.
3. Control of asthma symptoms: Asthma symptoms were assessed using a translated version of the asthma control test.

All groups received the conventional respiratory re-training program, three times a week, for 12 weeks in succession. The placebo group additionally received unloaded respiratory muscle training, the inspiratory muscle training group received respiratory muscle training alone, and the combined group received combined inspiratory and expiratory muscle training in the same cycle. Interventions were conducted by a licensed physical therapist who had experience of more than 10 years of respiratory training.

Inclusion Criteria:

• Confirmed diagnosis of asthma according to Global Initiative of Asthma guidelines.
• Age between 12 and 18 years.
• Clinically stable asthma.
• Stable doses of medications in the last three months
• A percent-predicted value of the peak expiratory flow rate of 60-80%
• No activity limitation due to asthma

Exclusion Criteria:

• Unstable asthma
• Exacerbation of asthma symptoms
• History of thoracic surgery
• Cognitive/behavioral problems
• Cardiopulmonary co-morbidities

The outcome assessor was blinded to the treatment allocation