Reliability of the assessment of the oxygen/heart rate relationship during a workday

Constructing energy expenditure regression model using heart rate with reduced training time

Accurate estimation of energy expenditure (EE) is a key enabler for many applications of healthcare and wellness. Heart rate (HR) based EE estimation methods typically require extensive training time to establish a relationship between HR and EE. In this work, we propose a method where just the few most representative EE-HR data pairs are used to train the estimation model. Furthermore, we present a systematical methodology based on the ranking of the correlation coefficients between EE and HR to find the least amount of EE-HR data pairs required for training while satisfying the constraint of estimation accuracy. During the experimental evaluation, while the study participants walk and run on a treadmill, our method is compared to three different training paradigms: training the EE-HR model 1) using all available data collected during the experiment, 2) using the EE-HR data only during speed changes (or during monotonic HR changes) and 3) using the EE-HR data pairs collected during constant speed. The results show that our method could maintain a comparable EE estimation performance as shown by only 2~4% changes on the coefficient of variation of root-mean-squared error (CV(RMSE)) for the testing dataset while saving nearly 91-97% training time for each individual.

An equivalent circuit model for onset and offset exercise response

Background

The switching exercise (e.g., Interval Training) has been a commonly used exercise protocol nowadays for the enhancement of exerciser’s cardiovascular fitness. The current difficulty for simulating human onset and offset exercise responses regarding the switching exercise is to ensure the continuity of the outputs during onset-offset switching, as well as to accommodate the exercise intensities at both onset and offset of exercise.

Methods

Twenty-one untrained healthy subjects performed treadmill trials following both single switching exercise (e.g., single-cycle square wave protocol) and repetitive switching exercise (e.g., interval training protocol). During exercise, heart rate (HR) and oxygen uptake (VO ₂) were monitored and recorded by a portable gas analyzer (K4b ², Cosmed). An equivalent single-supply switching resistance-capacitor (RC) circuit model was proposed to accommodate the observed variations of the onset and offset dynamics. The single-cycle square wave protocol was utilized to investigate the respective dynamics at onset and offset of exercise with the aerobic zone of approximate 70% - 77% of HR _max, and verify the adaption feature for the accommodation of different exercise strengths. The design of the interval training protocol was to verify the transient properties during onset-offset switching. A verification method including Root-mean-square-error (RMSE) and correlation coefficient, was introduced for comparisons between the measured data and model outputs.

Results

The experimental results from single-cycle square wave exercises clearly confirm that the onset and offset characteristics for both HR and VO ₂ are distinctly different. Based on the experimental data for both single and repetitive square wave exercise protocols, the proposed model was then presented to simulate the onset and offset exercise responses, which were well correlated indicating good agreement with observations.

Conclusions

Compared with existing works, this model can accommodate the different exercise strengths at both onset and offset of exercise, while also depicting human onset and offset exercise responses, and guarantee the continuity of outputs during onset-offset switching. A unique adaption feature by allowing the time constant

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and steady state gain to re-shift back to their original states, more closely mimics the different exercise strengths during normal daily exercise activities.

Relationships of Borg's RPE 6-20 scale and heart rate in dynamic and static exercises among a sample of young Taiwanese men

The objective of this study was to assess the relationship between the scores collected from Borg's rating of perceived exertion (RPE) scale and the heart rates (HR) of young Taiwanese men. Three exercises types (dynamic, partially dynamic, and static) were performed by 12 participants (six were familiar with Borg's scale and 6 were unfamiliar) under nine test conditions of three load levels for each exercise. The effect of familiarity on the relationship between RPE and HR was also examined. The results showed that the familiarity of the participants regarding the Borg's scale did not affect the scores. The relationship between Borg's RPE 6-20 scale and the HR values during dynamic exercise was described by the regression equation HR = 8.88 x RPE + 38.2 (beats/min). The HR had lower correlations with RPE values when the participants performed both partially dynamic and static exercises. The findings may serve as a reference when using Borg's RPE scale to evaluate the physical exertion of young Taiwanese men.

Modelling and regulating of cardio-respiratory response for the enhancement of interval training

BACKGROUND

The interval training method has been a well known exercise protocol which helps strengthen and improve one's cardiovascular fitness.

PURPOSE

To develop an effective training protocol to improve cardiovascular fitness based on modelling and analysis of Heart Rate (HR) and Oxygen Uptake (VO2) dynamics.

METHODS

In order to model the cardiorespiratory response to the onset and offset exercises, the (K4b2, Cosmed) gas analyzer was used to monitor and record the heart rate and oxygen uptake for ten healthy male subjects. An interval training protocol was developed for young health users and was simulated using a proposed RC switching model which was presented to accommodate the variations of the cardiorespiratory dynamics to running exercises. A hybrid system model was presented to describe the adaptation process and a multi-loop PI control scheme was designed for the tuning of interval training regime.

RESULTS

By observing the original data for each subject, we can clearly identify that all subjects have similar HR and VO2 profiles. The proposed model is capable to simulate the exercise responses during onset and offset exercises; it ensures the continuity of the outputs within the interval training protocol. Under some mild assumptions, a hybrid system model can describe the adaption process and accordingly a multi-loop PI controller can be designed for the tuning of interval training protocol. The self-adaption feature of the proposed controller gives the exerciser the opportunity to reach his desired setpoints after a certain number of training sessions.

CONCLUSIONS

The established interval training protocol targets a range of 70-80% of HRmax which is mainly a training zone for the purpose of cardiovascular system development and improvement. Furthermore, the proposed multi-loop feedback controller has the potential to tune the interval training protocol according to the feedback from an individual exerciser.

Evaluation of three methodologies to estimate the VO2max in people of different ages

Aging and gender are factors that affect the variation of physical work capacity. The present paper highlights the importance of the metabolism used by ergonomics to establish the appropriate limits of loads at work. This study compares the aerobic capacity of people from 20 to 71 years old split in 5 different groups. The laboratory experiment tested 33 volunteers (19 women and 14 men). A submaximal step test was used to measure the VO(2) using a portable breath by breath metabolic system and a telemetric heart rate monitor. Three methods to estimate the VO(2max) were compared: 1) a direct measurement of VO(2), 2) estimation by heart rate, and 3) a step test method using predetermined charts. Significant difference was encountered among the estimation methods as well as among the age ranges (F(2,92)=6.43, p<0.05 y F(4,92)=7.18, p<0.05 respectively). The method of direct measurement and the method of predetermined charts were different for the estimation of the VO(2max) with a confidence level of 95%. The method of predetermined charts is better adapted for males and people younger than 30 years. The estimation through non invasive heart rate apparatus was a good appraiser of the maximal oxygen consumption considering both genders and all the age groups.

Metabolic rate and clothing insulation data of children and adolescents during various school activities

Data on metabolic rates (n = 81) and clothing insulation (n = 96) of school children and adolescents (A, primary school: age 9-10; B, primary school: age 10-11 year; C, junior vocational (technical) education: age 13-16 (lower level); D, same as C but at advanced level; and E, senior vocational (technical) education, advanced level: age 16-18) were collected (Diaferometer, Oxylog, Heart Rate derivation) during theory-, practical- and physical education- lessons. Clothing insulation was calculated from clothing weight, covered body surface area, and the number of clothing layers worn. Clothing insulation was found to be similar to that expected for adults in the same (winter) season, with minimal variation with age or school type (0.9 to 1.0 clo; 1.38 clo where coverall was worn), but more variation within groups (coefficient of variation 6-12%). Metabolic rate values (W.m(-2)) were lower than expected from adult data for similar activities, but are supported by other child data. The results of this study can be used to establish design criteria for school climate control systems or as general data on energy expenditure for children and adolescents. The results emphasize the need for specific child data and show the limited value of size-corrected adult data for use in children.