Impact of Resisted Inspiratory Training Using the NU SpiroBreath Device on Diaphragmatic Muscle Activity: A Randomized Crossover Trial in Healthy Adults

ABSTRACT Background and Purpose The NU SpiroBreath device was developed as a novel respiratory training tool to support post‐operative recovery in cardiac and thoracic surgery patients. While previous studies have demonstrated its safety and user acceptability, its effect on diaphragmatic muscle activation during resisted inspiratory maneuvers has not been fully characterized. The aim of this study was to assess diaphragmatic muscle activity during deep inspiratory breathing with and without resistance using the NU SpiroBreath device in healthy adults. Methods Twelve healthy male participants (aged 20–30 years) participated in a single‐blind, randomized, two‐period crossover trial. Participants performed deep inspiratory breathing maneuvers using the NU SpiroBreath device under two conditions: 0 cm H 2 O (sham) and 10 cm H 2 O (resistance), with a 2‐week washout period between sessions. Each session included a 5‐min baseline control followed by three sets of 10 deep inspiratory efforts (DI1–DI3), separated by 1‐min rest intervals. Diaphragm muscle activity was assessed using high‐resolution surface electromyography (sEMG) recorded at 4000 Hz, filtered (20–500 Hz), and analyzed using root mean square (RMS) values. Results Significant increases in diaphragmatic muscle activity were observed from baseline at both resistance levels ( p 0.05), suggesting that even minimal resistance elicits robust diaphragmatic recruitment in untrained healthy individuals. Discussion Inspiratory training using the NU SpiroBreath device significantly enhances diaphragmatic muscle activation regardless of resistance level. These findings support its utility as a safe, low‐burden respiratory training tool.