Within the last few years complex models of cardiovascular regulation and exercise fatigue have been presented and have been associated with nonlinear measures of heart rate variability (HRV) and ratings of perceived exertion (RPE), respectively. Until now, both measures have only been used separately to analyse cardiovascular regulation during fatiguing exercise and no direct link between HRV and RPE has been shown. Therefore, the purpose of the current study was to analyze the relationship between linear and nonlinear parameters of HRV and ratings of perceived exertion (RPE) during exhaustive cycling exercise. n = 19 cyctists (age: 25,1 ± 3,8 years, weight: 77,3 ± 8,4 kg, VO²max: 55,4 ± 5,4 ml/(kg*min)) performed a submaximal constant load test until exhaustion with the power exerted at the individual anaerobic threshold (IANS) that was determined previously. Besides heart rate (HR) and standard time domain HRV measures of SDNN and RMSSD (in ms), the short- and long-term fractal scaling exponent alpha1 and alpha2 of the detrended fluctuation analysis (DFA) were calculated for every five minutes. Additionally, perceived exertion (RPE, CR-10), blood lactate and oxygen uptake (VO²) were assessed for every five minutes. All measures were interpolated to 10% steps of time to exhaustion. Repeated measures ANOVA was used to detect effects of exercise duration, while relations with RPE were assessed by pearson's correlation coefficient. With time-to-exhaustion of 77.5 ± 15.3 min, RPE, HR, VO² an blood lactate rose significantly over time with highest values at exhaustion of RPE: 9±2 (RPE), blood lactate: 4.4 ± 1.7 mmol/l, HR: 182 ± 10 bpm, 95.8 ± 3.7 % HRmax and 79.9 ± 6.9% VO²max, while HRV-parameters declined strongly and significantly in amplitude and complexity. Besides strong positive correlations with RPE for HR (r = 0.75) and % HRmax (r = 0.70), strong negative relations were found for SDNN (r = -0.63,), alpha1 (r = -0.72) and alpha2 (r = -0.56). The results indicate a dramatic time dependent loss of variability and complexity of heart rate during exhaustive constant load exercise. Furthermore, a direct link between complexity measures of HRV and perceived exertion might offer new perspectives for the evaluation of complex models of exercise fatigue.
© Copyright 2011 Herzfrequenzvariabilität: Gesundheitsförderung - Trainingssteuerung - Biofeedback. Internationales Symposium am 29. und 30. Oktober.. Veröffentlicht von Feldhaus, Ed. Czwalina. Alle Rechte vorbehalten.