Acute effects of voluntary breathing patterns on postural control during walking

Breathing and postural control is reported to be both neuromuscularly and mechanically interdependent. To date, the effects of voluntary abdominal and thoracic breathing (VAB and VTB) on the EMG activity of muscles involved in both respiratory and postural functions, as well as gait biomechanics related to these breathing patterns, have not been investigated in young, healthy adults. The aim of the study was to evaluate the EMG responses of neck and trunk muscles, as well as the kinematic, stability, and kinetic parameters of gait induced by VAB and VTB compared to involuntary breathing (INB).

Twenty-four healthy, physically active participants (12 men and 12 females) were required to complete three two-minute walking sessions on an instrumented treadmill (e.g. devices with capacitive sensors embedded beneath the running belt) at 5.0 km h^-1, first with INB and then alternatively with VAB and VTB. A respiratory inductive plethysmography unit was used to provide real-time visual feedback of the breathing pattern performed by each participant. The EMG activity of the sternocleidomastoid (SCM), upper trapezius (UT), thoracic and lumbar erector spinae (TES and LES), as well as spatiotemporal (step width, stride length, stride time, stance phase, swing phase, and cadence), stability (anteroposterior and mediolateral center of pressure trajectory), and dynamic gait parameters (vertical ground reaction forces, vGRF) were recorded during each testing condition.

Our findings revealed that both voluntary breathing patterns significantly affected the EMG activity of the SCM (p < 0.01) and UT (p < 0.05), with the activity between these muscles, as expressed by the SCM:UT ratio, being more balanced during VAB (0.94) and VTB (1.05) compared to INB (0.73). Additionally, VAB walking led to a narrower step width (p < 0.01) and reduced vGRF over the forefoot (p < 0.01) compared to INB walking. Neither VAB nor VTB influenced the activation levels of the LES and TES, nor did they affect other spatiotemporal, stability, or dynamic gait parameters (p > 0.05).

Our findings suggest that certain gait parameters (e.g. step width, forefoot vGRFs) are primarily influenced by VAB compared to INB, likely due to the more balanced activation of the SCM and UT muscles. This balanced activation may enhance head stability and control during walking, thereby contributing to improved postural control.