Incremental Ramp Load Protocol to Assess Inspiratory Muscle Endurance in Healthy Individuals: Comparison with Incremental Step Loading Protocol

Introduction: Protocols for obtaining the maximum threshold pressure have been applied with limited precision to evaluate inspiratory muscle endurance. In this sense, new protocols are needed to allow more reliable measurements. The purpose of the present study was to compare a new incremental ramp load protocol for the evaluation of inspiratory muscle endurance with the most used protocol in healthy individuals. Methods: This was a prospective cross-sectional study carried out in a single center. Ninety-two healthy individuals (43 men [22 +/- 3 years] and 49 women [22 +/- 3 years]) were randomly allocated to perform: (i) incremental ramp load protocol and (ii) incremental step loading protocol. The sustained pressure threshold (or maximum threshold pressure), maximum threshold pressure/dynamic strength index ratio, time until task failure, as well as difference between the mean heart rate of the last five minutes of baseline and the peak heart rate of the last 30 seconds of each protocol were measured. Results: Incremental ramp load protocol with small increases in the load and starting from minimum values of strength index was able to evaluate the inspiratory muscle endurance through the maximum threshold pressure of healthy individuals. Conclusion: The present study suggests that the incremental ramp load protocol is able to measure maximum threshold pressure in a more thorough way, with less progression and greater accuracy in the load stratification compared to the limited incremental step loading protocol and with a safe and expected cardiovascular response in healthy individuals.