Influence of an inspiratory muscle fatigue protocol on older adults on respiratory muscle strength and heart rate variability. A randomized controlled trial - Ladriñán-Maestro, Arturo; Sánchez-Infante, Jorge; Martín-Vera, Daniel; Del-Blanco-Muñiz, José Ángel; Merino-Andrés, Javier; Sánchez-Sierra, Alberto (Frontiers in Neuroscience, 2024)