Sample Entropy Analysis of Cardiac and Respiratory Responses during Four Limbs Exercise

This study was aimed to elucidate the effects of exercise on sample entropy of beat-to-beat (RR) intervals (SampEn-RR) and breath-to-breath (BB) intervals (SampEn-BB). A four limbs-based exercise equipment was used for the experiment and a wireless wearable respiration and heart rate monitoring system was used for recording the RR and BB intervals during lower limbs (LL), upper limbs (UL), and all four limbs (AL) exercises. A significant increment in both SampEn-RR and S ampEn-BB was observed during exercises when compared with pre and post-exercise states. Further comparisons of statistical parameters during AL and UL exercises showed the highest and the lowest mean of S ampEn values. Moreover, the comparison between exercise duration and the linear trend line gradients obtained from both S ampEn-RR and SampEn-BB during exercise revealed an inversely proportional relationship between them. Thereby, this work supports analysis of trend line gradients of SampEn would be helpful to determine the fatigue level during exercise.