Breathing vibration - can it make us stronger?

Introduction
Acute vibration stimulation enhances skeletal muscle activity and strength performance (Issurin & Tenenbaum, 1989; Bosco et al., 1999; Mileva et al., 2006). Vibration stimulation has also been applied to the respiratory musculature with demonstrable increases in respiratory activity in rabbits (Jammes et al., 2000), reduced breathlessness at rest in healthy humans (Edo et al., 1998), and reduced breathlessness during exercise in chronic obstructive pulmonary disease patients (Fujie et al., 2002).
We therefore investigated whether a vibration stimulus applied through air as it passes into the airways elicits increments of maximal breathing performance.

Methods
We recruited 12 healthy subjects (8 female, 4 male; 22-50 years old) from the University and they completed 3 maximal inspirations followed by 10 inspirations against a vibration stimulus (VIB; youbreathe, Exoscience Ltd., London, UK), an inspiratory resistive-load training device (RES) or resting breathing (CON; no load). 3 forced inspirations were repeated and compared to pre-training for maximal breathing power.

Results
Maximal breathing power was significantly greater (15%) after 10 breaths of vibrated resistance (VIB) when compared to PRE (VIB) and POST control (CON) and POST resistive-loading training device (RES). There was no effect of either resistance or control breathing on maximal breathing power.

Discussion
10 breaths of vibration lead to increased maximal breathing power suggesting that applying a vibration stimulus increases the voluntary force generating capacity of the inspiratory muscles, in a similar manner observed when vibration is applied to other skeletal muscles (Mileva et al., 2006).
The mechanisms underlying the changes in maximal breathing power require further study, however mechanisms such as shifts in neuromuscular recruitment via increases in stretch reflex sensitivity may have a role (Cardinale, 2003). This would enhance recruitment of higher-threshold motor units and the activation of previously inactive motor units. Confirmation of the mechanisms involved will require the acquisition of respiratory muscle EMG, transcranial magnetic stimulation and testing of peripheral reflexes.
Thus, vibration leads to an increased maximal breathing power suggesting there is an increase in neural inspiratory drive possibly via upregulation of the respiratory motoneurones.