Coordination between Respiration and Motion during Running by a Wearable System

Entrainment in human motion can be defined as the phase coupling between two periodical events. In the case of running, entrainment can be studied as the coordination between respiration and motion and can potentially improve running efficiency. In such context we aimed to verify whether wearable devices, providing multi-parametrical acquisitions to detect both movement and respiration-related signals, could be used to study entrainment. Ten male subjects were enrolled and instructed to run on a treadmill at predefined velocities using a wearable system embedding resistive stretchable sensors and inertial measurement units (IMUs) to detect respiration and vertical body acceleration respectively. The acquired data were analyzed to detect the distribution of delays between the respiration transition from expiration to inspiration or the vice- versa and the nearest foot-strike instant. The delay distribution provided the most and least frequent coupling patterns, from which a corresponding temporal parameter called T50 was used to numerically quantify respiration transition time during running. From the statistical analysis of a normalized aggregated dataset, it was demonstrated how T50s associated to the most frequent intervals chosen by each subject were significantly lower compared to the least frequent ones. Additionally, the strides per breath ratio (SPBR) of running regimes with entrainment had generally lower values, close to 2:1 (2.31 with respect to 2.4), even though the difference was not significative. Entrainment was more frequent during running regimes with constant speed and longer duration (29 cases for long regimes against 13 cases for shorter ones). The results suggest that subjects were likely to develop entrainment when the right conditions of velocity and time for adaptation were given and that the most frequently chosen coupling patterns were the ones characterized by a shorter respiration transition time.