On heart rate regulation in cycle-ergometer exercise

© 2014 IEEE. In this paper, we have focused on the issue of regulating the human heart rate (HR) to a predefined reference trajectory, especially for cycle-ergometer exercise used for training or rehabilitation. As measuring HR is relatively easy compared to exercise intensity, it has been used in the wide range of training programs. The aim of this paper is to develop a non-model-based control strategy using proportional, integral and derivative (PID) controller/relay controller to regulate the HR to track a desired trajectory. In the case of using PID controller, the controller output signal is interpreted as a voice or auditory command, referred to as biofeedback, which can be heard by the exercising subject as a part of the control-loop. Alternatively, the relay controller output signals can be converted to some special words which can be recognised by the exerciser. However, in both cases, to effectively communicate to the user a change in exercise intensity, the timing of this feedback signal relative to the positions of the pedals becomes quite critical. A feedback signal delivered when the pedals are not in a suitable position to efficiently exert force may be ineffective and may lead to a cognitive disengagement of the user form the feedback controller. In this paper we examine the need and the consequence of synchronising the delivery of the feedback signal with an optimal and user specific placement of the pedal

МЕТОД И СИСТЕМА ОЦЕНКИ ФИЗИОЛОГИЧЕСКИХ РЕЗЕРВОВ СПОРТСМЕНА ВО ВРЕМЯ ТРЕНИРОВОК

Introduction. An assessing of the sportsman's physiological reserve (PR) and its dynamics is important when planning and carrying out a training, forecasting sportsman's results. An importance of this problem increases in highperformance sports, and energy consumption sports. A complexity of solving of this problem is caused by the requirement of taking into account of the complex of the biomedical parameters and formation of an integral parameter. This parameter reflects functioning of various body systems which provide significant income to the sportsman’s result achievement. Objective. Development of the method and the system of PR assessing allowing complex investigation of the PR during the training process. Method and materials. For achievement of the aim the tasks were formulated and solved using methods of biomedical research and engineering, mathematical processing and analysis of the diagnostically valuable parameters. Results. The complex of the biomedical parameters reflecting sportsman’s body metabolism in condition of physical exercises is formed. They are the heart rate, the heart rate variability, the pulse frequency, the systolic and diastolic pressure, the respiratory rate, the blood saturation, and the stress index by Baevsky. It is important for PR assessing to assess parameters characterizing sportsman’s physiological reserves at the current moment and its dynamics. The circle diagram is proposed for taking into account of all mentioned parameters and its variation dynamics. The value of the integral PR parameter is an area of a polygon, which is obtained on the circle diagram using normalized values of the diagnostically significant parameters. The method of biomedical investigation of the sportsman and the method of PR assessing based on the complex of the body system parameters are developed. The scheme of assessing of sportsman's body physiological reserves before and after the training is proposed. The scheme allows to assess not only sportsman's body energy consumption during the training but also its recovery after the training. General structures of the biotechnical system and a structures of systems of picking up, registration, processing, and analysis of biomedical signals for assessing of sportsman's physiological reserves are developed. Special attention is given to the development of a wearable device for synchronous registration of the complex of biomedical parameters and algorithms of assessing of the diagnostically significant parameters of sportsman's body physiological reserves. Conclusion. The proposed method of sportsman's physiologic reserves investigation and the structure of the system with spatially distributed architecture allow sport medicine doctor and coach to assess an efficiency of sportsman's training process with respect to his potential capabilities, and efficiently control the training process.Введение. Оценка физиологического резерва (ФР) спортсмена и его динамики актуальна при планировании и проведении тренировок, прогнозировании результатов спортсмена. Актуальность данной проблемы усиливается в спорте высоких достижений, в частности в энергетически затратных видах спорта. Сложность решения этой проблемы обусловлена необходимостью учета комплекса медико-биологических показателей и формирования интегрального показателя, отражающего функционирование различных систем организма, которые обеспечивают значимый вклад в достижение результата спортсмена. Цель работы. Разработка метода и системы оценки ФР, позволяющих комплексно изучить ФР во время тренировочного процесса. Методы и материалы. Для достижения поставленной цели были сформулированы и решены задачи с использованием методов медико-биологических исследований, биомедицинской инженерии, математической обработки и анализа диагностически значимых показателей. Результаты. Сформирован комплекс медико-биологических показателей организма, отражающих метаболизм организма спортсмена в условиях физических нагрузок. Это частота сердечных сокращений, вариабельность сердечного ритма, частота пульса, систолическое и диастолическое давление, частота дыхания, сатурации крови, индекс напряженности Баевского. Для оценки ФР важно оценивать показатели, характеризующие физиологические резервы спортсмена в текущий момент времени и их динамику. Предложена круговая диаграмма для комплексного учета всех перечисленных показателей и динамики их изменения. Количественной мерой интегрального показателя ФР является площадь многогранника, полученного на круговой диаграмме по нормированным значениям диагностически значимых показателей. Разработан метод проведения медико-биологических исследований спортсмена и метод оценки ФР на основе комплекса показателей систем организма, предложена схема оценки физиологических резервов организма спортсмена до и после тренировок. Она позволяет оценить не только энергозатраты организма спортсмена во время тренировок, но и его восстановление после тренировок. Разработана обобщенная структура биотехнической системы и структуры системы съёма, регистрации, обработки и анализа биомедицинских сигналов для оценки физиологических резервов спортсмена. Особое внимание уделено разработке носимого устройства для синхронной регистрации комплекса биомедицинских сигналов и алгоритмам оценки диагностически значимых показателей физиологических резервов организма спортсмена. Заключение. Предложенный метод исследования физиологических резервов спортсмена и структура системы с пространственно-распределенной архитектурой позволяют тренеру и врачу спортивной медицины оценивать эффективность тренировочного процесса спортсмена с учетом его потенциальных возможностей, эффективно управлять тренировочным процессом

Heart Rate Dynamics Identification and Control in Cycle Ergometer Exercise: Comparison of First- and Second-Order Performance

Background: Accurate and robust feedback control of human heart rate is important for exercise testing and prescription. Feedback controllers can be designed using first-order, linear, time-invariant models of heart rate dynamics, but it remains to investigate whether second-order models lead to better identification and control performance. The distinguishing contribution of this research is the direct employment of established physiological principles to determine model structure, and to focus the feedbackdesign goals: cardiac physiology proposes a two-phase second-order response, delineated into fast and slow components; the natural phenomenon of broadspectrum heart-rate variability motivates a novel feedback design approach that appropriately shapes the input-sensitivity function. Aim: The aim of this work was to compare the fidelity of first- and second-order models of heart rate response during cycle-ergometer exercise, and to compare the accuracy and dynamics of feedback controllers that were designed using the two model structures. Methods: Twenty-seven participants each took part in two identification tests to generate separate estimation and validation data sets, where ergometer work rate was a pseudorandombinary sequence and in two feedback tests where controllers were designed using the first- or second-order models. Results: Second-order models gave substantially and significantly higher model fit (51.9 % vs. 47.9 %, p < 0.0001; second order vs. first order) and lower root-mean-square model error (2.93 bpm vs. 3.21 bpm, p < 0.0001). There was modest improvement in tracking accuracy with controllers based on second-order models, where mean root-mean-square tracking errors were 2.62 bpm (second order) and 2.77 bpm (first order), with p = 0.052. Controllers based on second-order models were found to be substantially and significantly more dynamic: mean values of average control signal power were 9.61 W^2 and 7.56 W^2, p < 0.0001. Conclusion: The results of this study confirm the hypotheses that second-order models of heart-rate dynamics give better fidelity than first-order models, and that feedback compensator designs that use the additional dynamic mode give more accurate and more dynamic closed-loop control performance

Robust control of heart rate for cycle ergometer exercise

The objective was to assess the performance and robustness of a novel strategy for automatic control of heart rate (HR) during cycle ergometry. Control design used a linear plant model and direct shaping of the closed-loop input-sensitivity function to achieve an appropriate response to disturbances attributable to broad-spectrum heart rate variability (HRV). The controller was evaluated in 73 feedback control experiments involving 49 participants. Performance and stability robustness were analysed using a separately identified family of 73 plant models. The controller gave highly accurate and stable HR tracking performance with mean root-mean-square tracking error between 2.5 beats/min (bpm) and 3.1 bpm, and with low average control signal power. Although plant parameters varied over a very wide range, key closed-loop transfer functions remained invariant to plant uncertainty in important frequency bands, while infinite gain margins and large phase margins (>62◦) were preserved across the whole plant model family. Highly accurate, stable and robust HR control can be achieved using LTI controllers of remarkably simple structure. The results highlight that HR control design must focus on disturbances caused by HRV. The input-sensitivity approach evaluated in this work provides a transparent method of addressing this challenge

Feedback control of heart rate during outdoor running: a smartphone implementation

AbstractThe aim was to develop and to investigate the technical feasibility of a novel smartphone-based mobile system for feedback control of heart rate during outdoor running. Accurate control is important because heart rate can be used for prescription of exercise intensity for development and maintenance of cardiorespiratory fitness.An Android smartphone was employed together with wearable, wireless sensors for heart rate and running speed. A simple feedback design algorithm appropriate for embedded mobile applications was developed. Controller synthesis uses a low-order, physiologically-validated plant model and requires a single bandwidth-related tuning parameter.Twenty real time controller tests demonstrated highly accurate tracking of target heart rate with a mean root-mean-square tracking error (RMSE) of less than 2 beats per minute (bpm); a sufficient level of robustness was demonstrated within the range of conditions tested. Adjustment of the tuning parameter towards lower closed-loop bandwidth gave markedly lower control signal power (0.0008 vs. 0.0030m2/s2, p<0.0001, low vs. high bandwidth), but at the cost of a significantly lower heart rate tracking accuracy (RMSE 1.99 vs. 1.67bpm, p<0.01).The precision achieved suggests that the system might be applicable for accurate achievement of prescribed exercise intensity for development and maintenance of cardiorespiratory fitness. High-accuracy feedback control of heart rate during outdoor running using smartphone technology is deemed feasible

A unified heart rate control approach for cycle ergometer and treadmill exercise

Objective: To develop a unified heart rate (HR) control approach for cycle ergometer (CE) and treadmill(TM) exercise, and to empirically compare the common controller’s performance between the CE andTM. Methods: The control method used frequency-domain shaping of the input-sensitivity function to addressrejection of disturbances arising from broad-spectrum heart rate variability (HRV). A single controllerwas calculated using an approximate, nominal linear plant model and an input-sensitivity bandwidthspecification. Fifty HR control tests were executed using the single controller: 25 healthy male participantseach did one test on the CE and one on the TM. Results: There was no significant difference in mean root-mean-square HR tracking error: 3.10 bpm ±0.68 bpm and 2.85 bpm ± 0.75 bpm (mean ± standard deviation, bpm = beats/min); CE vs. TM; p = 0.13.But mean normalised average control signal power was significantly different: 1.59 bpm2± 0.27 bpm2vs. 1.36 bpm2± 0.28 bpm2; CE vs. TM; p = 3.5 × 10−4. Conclusion and significance: The lower values for RMS tracking error and control signal power for the TMpoint to decreasing HRV intensity with increasing HR, because, in order to match perceived exertion forthe two modalities, mean HR for the TM was set 20 bpm higher than for the CE. These HR-intensity-dependent differences in HRV are consistent with previous observations in the literature. The unified HRcontrol approach for CE and TM exercise gave accurate, stable and robust performance in all tests, thuslending support to the concept that HRV disturbance rejection is the main issue in HR control design

Experimental heart rate regulation in cycle-ergometer exercises

The heart rate can be effectively used as a measure of the exercise intensity during long duration cycle-ergometer exercises: precisely controlling the heart rate (HR) becomes crucial especially for athletes or patients with cardiovascular/obesity problems. The aim of this letter is to experimentally show how the nonlocal and nonswitching nonlinear control that has been recently proposed in the literature for the HR regulation in treadmill exercises can be effectively applied to cycle-ergometer exercises at constant cycling speed. The structure of the involved nonlinear model for the HR dynamics in cycle-ergometer exercises is mathematically inspired by the structure of a recently identified and experimentally validated nonlinear model for the HR dynamics in treadmill exercises: the role played by the treadmill speed is played here by the work load while the zero speed case for the treadmill exercise is here translated into the cycling operation under zero work load. Experimental results not only validate the aforementioned nonlinear model but also demonstrate the effectiveness—in terms of precise HR regulation—of an approach which simply generalizes to the nonlinear framework the classical proportionalintegral control design. The possibility of online modifying the HR reference on the basis of the heart rate variability (HRV) is also suggested and experimentally motivated