Microcomputer Servo‐controlled Bicycle Ergometer System for Psychophysiological Research

Abstract

Steady state exercise is widely used for psychophysiological studies in which a constant heart rate at a predetermined level is desired. We have developed a microcomputer servo-controlled bicycle ergometer system that can be used for administering steady state exercise. Fourteen healthy male subjects, with a wide range of fitness levels (measured by VO2max) were exercised to either a fixed workload (130 watts) or a predetermined heart rate level (servo-heart rate) of 122 bpm (i.e., 65% of maximum calculated heart rate for the sample). Servo-heart rate was implemented using a feedback loop that automatically adjusted workload to compensate for immediate variations in heart rate, resulting in a more consistent heart rate. Heart rate varied from the predetermined value by 17 bpm during fixed workload but only 3 bpm during servo-heart rate (p less than .05). Therefore, by using the microcomputer servo-controlled bicycle ergometer, heart rate was maintained at a predetermined level regardless of the subject's fitness level. VO2max and workload during servo-heart rate were significantly correlated (r = .85, p less than .05). Therefore, the workload necessary to maintain heart rate at a constant level may provide an approximate index of aerobic fitness level.

Model reference adaptive control of heart rate during wheelchair ergometry

“…5 6 years) while performing wheelchair ergometry. Four of the subjects were active wheelchair users (three of the subjects have paraplegia due to traumatic spinal cord injury, one subject had a unilateral traumatic amputation), the remaining eight subjects were unimpaired.…”

“…In the absence of an input, , the output model becomes rhr (5) The values obtained with the final value theorem for the mean and lumped models are given in (2) and (3), respectively. Positive and negative convergence of the models were tested using model initial conditions, , above and below the resting heart rate.…”

“…The second model will be referred to as the mean model. Prior to stepwise regression, it was assumed that both models would be over specified with a fifth-order difference model [5] rhr (1) where five second heart rate from interbeat interval; average speed over five second interval; shorthand notation for which is a multiple of the sample period ( s); five second beats per minute heart rate estimate from interbeat interval (subsequently the subscript is used to denote the mean models, whereas the subscript is used for the lumped models); rhr a constant to account for resting heart rate; model coefficients. The speed vectors were padded with zeros for sampling periods prior to the experiment, whereas the heart rate vector was padded with the resting heart rate values recorded prior to the start of testing.…”

“…Aerobic training also produces an increase in the rate of oxygen delivery to active tissues. Moreover, decreased oxygen and blood flow requirements by endurance trained skeletal muscle and more efficient glycolysis leads to a reduction in the amount of work required to be performed by the heart [5], [13], [14].…”

Design and testing of an MRI-compatible cycle ergometer for non-invasive cardiac assessments during exercise

“…Commercially available ergometers use 'fixed workloads', where the pedalling resistance is maintained regardless of pedalling frequency. This method provides the most accurate assessment of myocardial responses to a given external stress, but is not effective in controlling the heart rate at which images can be obtained [10]. In addition, exercising within the narrow diameter MRI bore is an issue.…”