How regular is your heart beat during exercise?

It is easy to measure the number of heart beats per minute. Clearly, this number increases with exercise intensity. But how regular is your heart beat during exercise? And what does this imply potentially? In a recent work with my colleagues Esa Räsänen, Matti Molkkari and Giorgio Angelotti, we have studied the fluctuations of the human heart beat during physical exercise. We developed a dynamical approach to analyze the time evolution of heart beat correlations in running across various training and racing events under real-world conditions. In particular, we introduced a method from statistical physics (dynamical detrended fluctuation analysis and dynamical partial autocorrelation functions), which are able to detect real-time changes in the scaling and correlations of the beats. We related these changes to the exercise intensity quantified by the heart rate. Beyond a certain intensity, the heart beats show multiscale anticorrelations with both universal and individual scale-dependent structure that is potentially affected by the running stride frequency. These preliminary results are encouraging for future applications of the dynamical statistical analysis in exercise physiology and cardiology, and the presented methodology is also applicable across various disciplines. Our publication is available here.