Peak Cardiac Mechanical and Haemodynamic Responses During Incremental Exercise Are Temporally Associated With Ventilatory Thresholds: Novel Insight Into the Coordination of Integrative Physiological Responses to Exercise

ABSTRACT Background Maximal aerobic capacity (VO 2 peak) is traditionally attributed to limitations in oxygen transport and utilization. However, it remains unclear whether peak cardiac mechanical and haemodynamic responses occur in temporal association to ventilatory thresholds during incremental exercise, and whether these relationships vary with cardiorespiratory fitness. Methods Eighteen healthy, recreationally active adults (26 ± 3.18 years VO 2 peak 41.87 ± 4.76 mL·kg·min −1 ) completed two incremental supine cycling tests to exhaustion, with breath‐by‐breath gas exchange analysis, exercise echocardiography, and continuous blood pressure monitoring. Plateau timing (PT) was defined as the relative heart rate (%HRmax) at which each cardiovascular variable reached its peak or plateau response. Associations between cardiovascular PTs, VO 2 peak, and the first (VT1) and second ventilatory thresholds (VT2) were examined using correlation analysis. Exploratory k‐means clustering was used to descriptively visualize plateau‐timing distributions. Results VT1 significantly correlated with PT–ejection fraction (EF) and PT–vascular conductance, whereas VT2 correlated with deformation‐based parameters including PT–apical circumferential strain, PT–apical rotation, and iCarT ( p < 0.05). VO 2 peak was positively associated with PT–twist and PT–apical rotation ( p < 0.05), and negatively associated with PT–EF ( p < 0.05). Exploratory clustering yielded two descriptive clusters which differed in VO 2 peak ( p < 0.05) and were characterized by differences in volumetric and rotational plateau‐timing distributions. Conclusions During exercise, different cardiac parameters are temporally associated with ventilatory thresholds 1 and 2. Cardiorespiratory fitness may influence interindividual differences in the temporal organization of response patterns during incremental exercise.