Self-biofeedback control of heart rate during exercise

To improve cardiac adjustment to exercise, we developed a new self-biofeedback heart rate (HR) controller. Using this device, we analyzed time courses of HR, running speed (RS), stride length (ST) and pitch of gait (PI) in response to various preset HR levels in 7 normal human subjects. When HR was preset at 80 bpm, HR increased rapidly in response to exercise and exceeded the preset level at 12. 1 s with overshoot. At the preset HRs of 100, 120, 140 and 160 bpm, the HRs increased to each preset level at 39.2, 64.5, 58.5 and 83.0 s after the onset of exercise, respectively, and the HRs were adjusted with a range of +/- 4%. For all preset HRs, RS, ST and PI increased more rapidly than the HR and reached the maximum values within 30 s. During exercise, RS, ST and PI remained constant within 1.5-5.5 min. HR, RS, ST and PI increased in proportion to the preset HR. The increases in PI against HR (DeltaPI/DeltaHR) decreased with the higher HR level, and at HRs of 160-170 bpm, HR and PI showed identical rhythm. The increases in RS were produced by 18-59% increases in PI and by 12-44% increases in ST. We concluded that, using our newly developed self-biofeedback HR control system, we could control HR to a given preset value by a change in RS due to PI and ST.