Primary objective To evaluate the effects of an unsupervised inspiratory muscle training
(IMT) protocol on the behavior of ventilatory variability.

Secondary objective Evaluate the effects of IMT on, respiratory muscle strength,
pulmonary function, quality of life, peripheral muscle strength, functional capacity and
adverse effects and adherence.

Material and methods Type of study and location of research This randomized, controlled,
double-blind, parallel, two arm clinical trial will be conducted at the Laboratory of
Health Assessment Measures (LABMAS), Department of Physiotherapy of the Federal
University of Rio Grande do Norte (UFRN).

I The subjects included in the research will undergo three assessment stages:
pre-training (Initial), post-training (6 weeks). Assessments in the pre-training period
will be carried out in 1 day. After recruitment, participants will be invited to attend
the UFRN Physiotherapy Department to carry out the first day of assessment by a
previously trained evaluator blind to the intervention allocation group and will include
anamnesis and physical examination, with measurement of vital signs. , anthropometric
measurements, spirometry, respiratory muscle strength (manovacuometry), functional
capacity (6-minute step test) and analysis of ventilatory variability (portable
ventilator), assessment of peripheral muscle strength (dynamometry), quality of life
(SF-36) .

The sample will be automatically randomized through the website www.randomization.com and
allocated into two distinct groups: Experimental Group (GE): inspiratory muscle training
and Sham Group (G2): IMT without load. Three evaluators will participate in the research:
researcher 1 will be responsible only for the evaluations, researcher 2 for respiratory
muscle training with weekly load adjustment and researcher 3 for randomization. The study
will be double-blind, as researcher 1 and participants will not be aware of the
allocation of subjects into groups, nor of the effects of the intervention.

After the initial assessment, all volunteers will receive a POWERbreathe® classic light
resistance device (POWERbreathe®, Nsc, Brazil), to carry out the training, and will be
individually guided on how to use it and how to complete the protocol. They will perform
a trial session to familiarize themselves with the device that will not be considered for
analysis. Every week, volunteers will receive a telephone call from researcher 2, who
will not participate in the evaluation, to confirm whether the exercise with the
POWERbreathe® will be performed appropriately at the recommended frequency, intensity,
and duration and whether there are any questions regarding the protocol. At the end of
each week, participants will receive a video call from researcher 2 to adjust the device
according to G1's weekly load progression.