Background: It is important to identify the low-cost complementary treatments that help improve the asthma control and quality of life of these individuals. Inspiratory muscle training (IMT) may be a good alternative to complement traditional drug therapy. Previous studies have shown a significant increase in inspiratory muscle strength, as well as a reduction in the degree of dyspnea and β2 agonist consumption. For such gains to occur, IMT prescribing should consider the principles of training, including the basic principles of overload, specificity and reversibility. Objective: To investigate the principles of intensity, specificity and reversibility of IMT on respiratory muscle strength, asthma control, quality of life, degree of dyspnea, functional capacity, inspiratory muscle electromyography and lung function in people with asthma. Methods: This was a double-blind randomized controlled trial. The sample consisted of 29 people with asthma divided into two groups: 14 participants in the low load group (L15%) and 15 in the moderate load group (L50%). IMT was performed 5 days a week for 6 weeks with POWERbreathe® device. The sessions consisted of 30 repetitions twice a day. The L15% group trained with a load of 15% of maximal inspiratory pressure (MIP), while L50% group trained with 50% of MIP. Initially, the participants were submitted to lung function assessments. Then, the Asthma Quality of Life Questionnaire (AQLQ) and Asthma Control Questionnaire (ACQ) were applied. Surface electromyography of inspiratory muscles was recorded during quiet breathing and during deep inspirations. Respiratory muscle strength was obtained by MIP and by maximal expiratory pressure (MEP). Finally, the Borg CR10 scale and the distance walked in six-minute walk test (6MWD) were used to assess degree of dyspnea and functional capacity, respectively. Assessments were performed at baseline, after 6 weeks of training and six weeks after cessation of training. Parallel to the experimental study, a systematic review was developed in partnership with the Cochrane Collaboration on Respiratory Muscle Training (TMR) in people with neuromuscular diseases (NMD). Results: MIP increased about 20 cmH2O (24%) in the L15% group, while the L50% group showed a gain of approximately 33 cmH2O (35%). In addition, the L50% group exhibited an increase in the MEP of 10 cmH2O (10%) and there was an improvement of 8.1 cmH2O (9%) in the L15% group after the training. Both groups promoted a clinically relevant improvement in quality of life. This improvement was observed in the activity limitation and emotional function domains in the L15% group and in all AQLQ domains in the L50% group. Moderate-load training also reduced the degree of dyspnea. Small changes were observed after the training in the control of asthma, functional capacity and pulmonary function, after IMT. In the systematic review, 7 studies involving 151 participants with DNM were included. However, the studies included in the meta-analysis failed to demonstrate an enhancement after RMT. The trials included in this review did not report the number of unscheduled hospitalisations for acute exacerbations of chronic respiratory failure or other adverse events related to RMT. Conclusions: In people with asthma, IMT with low and moderate loads increases the strength of respiratory muscles and improves quality of life. In addition, moderate-load training reduces the degree of dyspnea. The systematic review concluded that in people with neuromuscular diseases, there is a very low quality of evidence that respiratory muscle training improves respiratory muscle strength and quality of life.