Heart rate control using first- and second-order models during treadmill exercise

Abstract

Heart rate control using first- and second-order models was compared using a novel control design strategy which shapes the input sensitivity function. Ten participants performed two feedback control test series on a treadmill with square wave and constant references. Using a repeated measures, counterbalanced study design, each series compared controllers C1 and C2 based on first- and second-order models, respectively. In the first series, tracking accuracy root-mean-square tracking error (RMSE) was not significantly lower for C2: 2.59\u2009bpm vs. 2.69\u2009bpm (mean, C1 vs. C2), p\u2009=\u20090.79. But average control signal power was significantly higher for C2: 11.29×10−4m2/s2 vs. 27.91×10−4m2/s2, p=3.1×10−10. In the second series, RMSE was also not significantly lower for C2: 1.99\u2009bpm vs. 1.94\u2009bpm, p\u2009=\u20090.39; but average control signal power was again significantly higher for C2: 2.20×10−4m2/s2 vs. 2.78×10−4m2/s2, p\u2009=\u20090.045. The results provide no evidence that controllers based on second-order models lead to better tracking accuracy, despite the finding that they are significantly more dynamic. Further investigation using a substantially larger sample size is warranted.