Evaluation of Locomotor-Respiratory coupling (LRC) using the motion analysis system

A breathing strategy to improve the endurance of the respiratory muscles during exercise is the synchronization between the respiratory and the locomotor muscles, named Locomotor-Respiratory Coupling (LRC). LRC refers to the frequency and the phase locking of running and breathing so that the same number of steps occur during each breath. This study aimed to find a way to exclusively utilize the motion analysis system to analyze LRC. Optoelectronic Plethysmography provides measurement of breathing ventilation and the gait events were detected by the acceleration signals from one marker placed on the trunk. Ten subjects (7 males, age 24.1 ± 1.3 years) were tested during 5 tasks of 5 effective minutes of exercise on a treadmill: walking at 4 km/h and at 6 km/h (W04, W06), uphill walking with 12% of slope at 4.5 km/h (S12) and running at 8 and 10 km/h (R08, R10). These 5 tasks were performed twice: with the individual breathing freely (SB) and with an imposed 2:1 LRC (CO). No correlation between the phase and frequency coupling and the type of activity was observed. Coupling had mostly an impact on time-related ventilatory parameters such as respiratory rate and minute ventilation by reducing their variability. The adaptation to this coupled rhythm could improve the control of ventilation during exercise leading to a more regular and efficient respiration and reducing the respiratory stress and fatigue during performance. We have shown that the motion analysis system can be used as a unique method for the evaluation of LRC.