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Influence of a diaphragmatic fatigue protocol in healthy male population on muscle strength, respiratory function and
Marta de-la-Plaza-San-Frutos1,2, Alberto Sánchez Sierra1,2, Ángel González de la Flor1,2
1Department of Physiotherapy, Faculty of Medicine, Health and Sports, European University of Madrid, Madrid, Spain.
Background:
Inspiratory muscle fatigue has been shown to impair physical performance. This study investigated the impact of a specific inspiratory muscle fatigue protocol on lower limb muscle strength and cardiorespiratory outcomes in a cohort of physically active individuals.
Method:
A randomized controlled trial, adhering to CONSORT guidelines to ensure methodological rigor. Healthy male participants were randomly assigned to an inspiratory muscle fatigue group (EG) or control load group (CG). The EG performed a diaphragmatic fatigue protocol involving inspiratory exercises at 60 % of their maximal inspiratory pressure (MIP), while the CG performed two sets of 30 repetitions at 15 % of MIP. Measurements, including countermovement jump (CMJ), forced expiratory volume in 1 s (FEV1), forced vital capacity (FVC), FEV1/FVC ratio, half squat (HS), peripheral oxygen saturation (SpO2) and MIP, were collected before and immediately after the intervention.
Results:
Forty participants completed the study. Significant group-by-time interactions were found for CMJ (p < 0.001; η2p = 0.405), FEV1 (p = 0.030; η2p = 0.118), FEV1/FVC (p < 0.001; η2p = 0.279) and HS (p < 0.001; η2p = 0.332), all with moderate to large effect sizes. Post-hoc analysis revealed a significant decrease in CMJ in the EG (p < 0.001, -8.4 %), while the CG showed no significant change (p = 0.092). FEV1/FVC decreased significantly in the EG (p = 0.007, -5.3 %), while the CG showed a significant increase (p = 0.015, +4.7 %). Similarly, HS decreased significantly in the EG (p = 0.002, -6.3 %), while the CG showed a significant increase (p = 0.007, +5.4 %). No significant interactions were observed for SpO2, heart rate, MIP or FVC.
Conclusions:
Diaphragmatic fatigue significantly impairs lower limb strength in physically active individuals, potentially compromising athletic performance and increasing injury risk. These findings enhance understanding of the interplay between respiratory and muscular strength in athletes.
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