Development of a servo-controller of heart rate using a treadmill

Although treadmill exercise involves a more familiar range of motions and i s thus more physiological in terms of daily activity than cycle ergometer e xercise, difficulties in controlling the exercise intensity have limited it s utility. As heart rate (HR) has been used as a measure of exercise intens ity, controlling HR should allow for the proper control of exercise intensi ty during treadmill exercise. Thus, a servo-controller framework was applie d to regulate HR during treadmill exercise. After estimating an averaged tr ansfer function from speed command to HR, feedback parameters were optimize d via a computer simulation in order to achieve a quick and stable HR respo nse. The performance of the servo-controller of HR was then examined in 10 healthy subjects. Standard deviations of the steady-state difference betwee n the target and measured HRs were 2.7+/-0.9 and 5.0+/-1.4 beats/min in the stepwise and ramp target HR protocols, respectively. The rise time to reac h 90% of the target HR was 93+/-20 s in the stepwise protocol. It was concl uded that a treadmill implemented with a negative feedback mechanism made i t possible to precisely regulate HR and thus exercise intensity.