This study investigated the effects of normobaric hypoxia on mechanical cardiac function during resting and short-term moderate intensity exercise. The cardiac contraction force and ventricular twist of eleven healthy male participants (24±5 years, 176±3cm, 76±9kg) were assessed using seismocardiography (SCG). The SCG was placed superficially to the sternum, 1 cm above the Xiphoid process. An isometric squat-stand maneuver performed at 0.05 Hz for 5 minutes was used as the exercise stimulus. Participants began by resting supine for 30-minutes under normobaric normoxia (712mmHg, 577m, 19.8% oxygen), followed by the squat-stand maneuver. Participants repeated the supine and squat-stand maneuver in a normobaric hypoxic (712mmHg, ~2750m, 14.8% oxygen) environmental simulation chamber. SCG was measured for 30 seconds at the end of normoxic rest (T1), end of normoxic squat-stands (T2), end of hypoxic rest (T3), and end of hypoxic squat-stands (T4). An average of 5 cardiac beats from the SCG were analyzed to determine contraction force and ventricular twist (milligravity, mG). No significant differences were found under resting conditions between T1 and T3 (13±2, 15±3 mG). Furthermore, no significant differences were found comparing squat-stands between normoxia (T2, 35±6 mG) and hypoxia (T4, 45±9 mG), although there were trends showing an increase in contraction force during hypoxia (p=0.2). Ventricular twist mechanics showed similar responses. These results suggest that acute shortduration normobaric hypoxia had no significant effect on the contractility and ventricular twist mechanics of the heart after a moderate-intensity squat-stand exercise. This shows that mechanical cardiac function can be assessed using SCG.
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