Effects of Inspiratory Training on Respiratory Function in Swimming

Condition(s) studied

Investigational drug(s) / intervention(s)

Placebo: The control group will use the same device without resistance, maintaining the same breathing frequency and volume to control for the placebo effect.

Inspiratory training: The experimental group will perform an eight-week home-based training program using the POWERbreathe EX1-MR device, individually calibrated according to MIP. Participants will complete 30 deep inspirations per session, twice daily, seven days a week, with progressive intensities: 30% of initial MIP during weeks 1-2, 50% of the new MIP during weeks 3-4, 60% during weeks 5-6, and 70% of MIP during weeks 7-8, with the aim of familiarizing participants with the device and progressively adapting the diaphragm to increasing loads.

Study summary

Introduction:

The diaphragm is the primary inspiratory muscle and plays a key role in ventilation, trunk stability, and exercise efficiency. Its dysfunction is associated with early fatigue, increased respiratory work, and reduced performance. Inspiratory muscle training (IMT) has been shown to improve respiratory function and exercise tolerance. Swimming, due to its specific characteristics, imposes an additional demand on the respiratory muscles.

Objective:

To evaluate the effects of an IMT program on diaphragmatic function, respiratory variables, cardiorespiratory response, and performance in swimmers.

Methods:

A randomized, parallel, double-blind clinical trial with 34 swimmers. The experimental group will perform an 8-week IMT program with progressive loads, while the control group will use a sham device without resistance. Diaphragmatic function will be assessed using ultrasound (thickness and excursion), along with respiratory variables (MIP, FEV₁, MEP, FVC), cardiovascular variables (heart rate, HRV), metabolic variables (lactate), and performance (100 m test).

Expected results:

IMT is expected to improve diaphragmatic function, increase inspiratory muscle strength, enhance ventilatory efficiency, and reduce respiratory fatigue, leading to improvements in performance and physiological responses to exercise.

Conclusion:

IMT could be an effective strategy to enhance respiratory function and swimming performance. This study provides a novel approach by incorporating ultrasound assessment of the diaphragm in an aquatic exercise context.

Eligibility

Primary outcome measure(s)

• Sport performance — This measurement will be carried out from the randomization process until 8 weeks after the start of the inspiratory training program.
  Total time and split times for completing 100 m freestyle.
• Maximal inspiratory pressure. — This measurement will be carried out from the randomization process until 8 weeks after the start of the inspiratory training program.
  Inspiratory variables: Inspiratory muscle strength was assessed by measuring MIP using the POWERbreathe Smart Adaptor device. The participant was seated and used a mouthpiece with a leak hole to minimize activation of the orofacial musculature. The procedure consisted of a maximal expiration to residual volume, followed by a maximal inspiration sustained against the device for at least 2 seconds. Three attempts were performed with rest periods of at least 1 minute, and the highest value was selected.
• Maximal espiratory pressure. — This measurement will be carried out from the randomization process until 8 weeks after the start of the inspiratory training program.
  Expiratory variables: Pulmonary function was assessed using forced spirometry, recording FEV₁, MEP, and FVC with the MIR Spirobank Oxi Portable Spirometer device. For a manoeuvre to be acceptable, the subject had to perform a maximal inspiration followed by a rapid and continuous forced expiration, without coughing during the first second and with a smooth flow-volume curve, without leaks. The expiration had to last at least 6 seconds or until a volume plateau was reached. Manoeuvres with interruptions, false efforts, or closed glottis were discarded. Three acceptable manoeuvres were performed, and results were considered valid when the two best FEV₁ and FVC values differed by less than 150 mL. If this variability criterion was not met, additional attempts were performed until reproducible results were obtained.

Trial sites (1)

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