Performance is usually assessed by simple indices stemming from cardiac and respiratory data measured during graded exercise test. The goal of this study is to characterize the indices produced by a dynamical analysis of HR and VO 2 for different effort test protocols, and to estimate the construct validity of these new dynamical indices by testing their links with their standard counterparts. Therefore, two groups of 32 and 14 athletes from two different cohorts performed two different graded exercise testing before and after a period of training or deconditioning. Heart rate (HR) and oxygen consumption (VO 2) were measured. The new dynamical indices were the value without effort, the characteristic time and the amplitude (gain) of the HR and VO 2 response to the effort. The gain of HR was moderately to strongly associated with other performance indices, while the gain for VO 2 increased with training and decreased with deconditioning with an effect size slightly higher than VO 2 max. Dynamical analysis performed on the first 2/3 of the effort tests showed similar patterns than the analysis of the entire effort tests, which could be useful to assess individuals who cannot perform full effort tests. In conclusion, the dynamical analysis of HR and VO 2 obtained during effort test, especially through the estimation of the gain, provides a good characterization of physical performance, robust to less stringent effort test conditions. Characterization of Heart Rate (HR) and oxygen consumption (VO 2) related to mechanical power (i.e., speed or power) during standardized graded exercise test (GET) is an unavoidable step in current athlete's performances assessment 1. These two measurements are also classically used in the scientific field of sport studies as one of the main physiological outputs to characterize evolution of athlete's performance over time 2-4. Current analysis of these parameters is based on two radically different approaches. The first is the use of standard techniques, easily applicable and extensively used. The most common index to characterize the HR recovery is the Heart Resting Rate (HRR) 5 , commonly defined as the difference between HR at the onset of recovery and HR one minute after. This characterization is known to be a good predictor of cardiac problems in medicine 5 , and is an interesting indicator of physical condition and training 6. The maximum rate of HR increase (rHRI) is a recent indicator showing correlation with fatigue and training in various studies 6. This first type of approaches to characterize HR dynamics suffers from two important drawbacks. First, these measurements mix the amplitude of the HR response to effort with its temporal shape. For instance, someone reaching a maximum heart rate of 190 beat/minute and decreasing to 100 beat/min in one minute will have the same HRR as another person reaching 150 beats/minute and decreasing to 60 beats/minute in one minute, although the HR dynamic is different. Secondly and more importantly, they use only a small fraction of the inf...
Heart rate during effort test has been previously successfully adjusted with a simple first order differential equation with constant coefficients driven by the body power expenditure. Although producing proper estimation and yielding pertinent indices to analyze such measurement, this approach suffers from its inability to model the saturation of the heart rate increase at high power expenditure and the change of heart rate equilibrium after effort. The objective of the present study is to improve this model by considering that the amplitude of the heart rate response to effort (gain) depends on the power expenditure value. Therefore, heart rate and oxygen consumption of 30 amateur athletes were measured while they performed a maximum graded treadmill effort test. The proposed model was able to predict 99% of the measured heart rate variance during exercise. The gains estimated at the different power expenditures were constant but noisy before the first ventilatory threshold, stable and decreasing slightly with power increase between the two ventilatory thresholds, before decreasing in a more pronounced manner after the second ventilatory threshold. The slope of the decrease of heart rate gain .
Performance is usually assessed by simple indices stemming from cardiac and respiratory data measured during graded exercise test. The goal of this study is to test the interest of using a dynamical analysis of these data. Therefore, two groups of 32 and 14 athletes from two different cohorts performed two different graded exercise testing before and after a period of training or deconditioning. Heart rate (HR) and oxygen consumption (VO2) were measured. The new dynamical indices were the value without effort, the characteristic time and the amplitude (gain) of the HR and VO2 response to the effort. The gain of HR was moderately to strongly associated with other performance indices, while the gain for VO2 increased with training and decreased with deconditioning with an effect size slightly higher than VO2 max.Dynamical analysis performed on the first 2/3 of the effort tests showed similar patterns than the analysis of the entire effort tests, which could be useful to assess individuals who cannot perform full effort tests. In conclusion, the dynamical analysis of HR and VO2 obtained during effort test, especially through the estimation of the gain, provides a good characterization of physical performance, robust to less stringent effort test conditions.
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