The heart rate method for estimating oxygen uptake: analyses of reproducibility using a range of heart rates from commuter walking

SMART System in the Assessment of Exercise Tolerance in Adults

Health-oriented physical activity should meet two key criteria: safety and an optimal level of exercise. The system of monitoring and rationalization of training (SMART) was designed to meet them. SMART integrates a custom-configured inertial measurement unit (IMU) and a sensor with real-time heart rate measurement (HR) using a proprietary computer application. SMART was used to evaluate the safety and exercise load with 115 study participants: 51 women (44.35%) and 64 men (55.65%) aged 19 to 65 years. The exercise test was the 6MWT test. In 35% of the participants, the mean HR exceeded the recognized safe limit of HR 75% max. Ongoing monitoring of HR allows for optimal exercise and its safety. Step count data were collected from the SMART system. The average step length was calculated by dividing the distance by the number of steps. The aim of the present study was to assess the risk of excessive cardiovascular stress during the 6MWT test using the SMART system.

Reliability of the 3-Component Model of Aerobic, Anaerobic Lactic, and Anaerobic Alactic Energy Distribution (PCr-LA-O2) for Energetic Profiling of Continuous and Intermittent Exercise

Purpose: To assess the test–retest reliability of the continuous (PCr-LA-O2) and intermittent (PCr-LA-O2int) version of the 3-component model of energy distribution in an applied setting. Methods: Sixteen male handball players (age 23 [3] y, height 185 [7] cm, weight 85 [14] kg) completed the 30–15 Intermittent Fitness Test (30–15IFT) twice. Performance was assessed by peak speed (speed of the last successfully completed stage of the 30–15IFT [VIFT], in kilometers per hour) and time to exhaustion (in seconds). Oxygen uptake (in milliliters per kilogram per minute) and blood lactate concentrations (in millimoles per liter) were obtained before, during, and until 15 minutes after exercise. Total metabolic energy (in joules per kilogram), total metabolic power (in watts per kilogram), and energy shares (in joules per kilogram and percentage) of the aerobic (energy contribution of the aerobic system [WAERint]), anaerobic lactic, and anaerobic alactic (anaerobic alactic energy [WPCrint]) systems were calculated using both model versions, respectively. Results: Test–retest reliability was very good for VIFT (limits of agreement [LoA]: −1.13 to 0.63 km·h−1, coefficient of variation [CV%] 1.68), time to exhaustion (LoA: −101 to 38 s, CV% 2.92), peak oxygen uptake (LoA: −2.68 to 4.04 mL·min−1·kg−1, CV% 1.48), and peak heart rate (−6.9 to 7.7 beats·min−1, CV% 1.1), but moderate for change in blood lactate concentration (LoA: −3.84 to 4.07 mmol·L−1, CV% 11.43). Reliability of the modeled total energy and its fractions were high for total metabolic energy (LoA: −1489 to 1177 J·kg−1, CV% 2.88), total metabolic power (LoA: −2.0 to 1.9 W·kg−1, CV% 3.58), contribution of aerobic (LoA: −1673 to 1283 J·kg−1, CV% 3.62), WAERint (LoA: −1760 to 2160 J·kg−1, CV% 6.04), and moderate for anaerobic alactic (LoA: −368 to 439 J·kg−1, CV% 14.85), WPCrint (LoA: −1707 to 988 J·kg−1, CV% 9.98), and energy share of anaerobic lactic concentration (LoA: −229 to 235 J·kg−1, CV% 11.43). Conclusion: Considering the inherent fluctuations of the underlying energetics, the reliabilities of both versions of the 3-component model of energy distribution are acceptable for applied settings.

Perspectives on exercise intensity, volume, step characteristics and health outcomes in walking for transport

Background

Quantification of movement intensity and energy utilization, together with frequency of trips, duration, distance, step counts and cadence, is essential for interpreting the character of habitual walking for transport, and its potential support of health. The purpose of the study is to illuminate this with valid methods and novel perspectives, and to thereby provide a new basis for characterizing and interpreting walking in relation to health outcomes.

Methods

Habitual middle-aged commuting pedestrians (males = 10, females = 10) were investigated in the laboratory at rest and with maximal treadmill and cycle ergometer tests. Thereafter, levels of oxygen uptake, energy expenditure, ventilation, heart rate, blood lactate, rated perceived exertion, cadence, number of steps, duration, distance, and speed were recorded during the normal walking commute of each participant in Greater Stockholm, Sweden. The number of commutes per week over the year was self-reported.

Results

Walking in the field demanded about 30% more energy per km compared to level treadmill walking. For both sexes, the walking intensity in field was about 46% of maximal oxygen uptake, and energy expenditure amounted to 0.96 kcal · kg^{- 1} · km^{- 1}. The MET values (males: 6.2; females: 6.5) mirrored similar levels of walking speed (males: 5.7; females: 5.9 km · h^{- 1}) and levels of oxygen uptake (males: 18.6; females: 19.5 mL · kg^{- 1} · min^{- 1}). The average number of MET-hours per week in a typical month was 22 for males and 20 for females. This resulted in a total weekly energy expenditure of ~1,570 and 1,040 kcal for males and females, respectively. Over the year, the number of walking commutes and their accumulated distance was ~385 trips and 800 km for both sexes.

Conclusion

Walking in naturalistic field settings demands its own studies. When males and females walk to work, their relative aerobic intensities and absolute energy demands for a given distance are similar. It is equivalent to the lower part of the moderate relative intensity domain. The combination of oxygen uptake, trip duration and frequency leads to high and sustained levels of MET-hours as well as energy expenditure per week over the year, with a clear health enhancing potential. Based on this study we recommend 6000 transport steps per day, or equivalent, during five weekdays, over the year, in order to reach optimal health gains.

An Experimental Feasibility Study Evaluating the Adequacy of a Sportswear-Type Wearable for Recording Exercise Intensity

Sportswear-type wearables with integrated inertial sensors and electrocardiogram (ECG) electrodes have been commercially developed. We evaluated the feasibility of using a sportswear-type wearable with integrated inertial sensors and electrocardiogram (ECG) electrodes for evaluating exercise intensity within a controlled laboratory setting. Six male college athletes were asked to wear a sportswear-type wearable while performing a treadmill test that reached up to 20 km/h. The magnitude of the filtered tri-axial acceleration signal, recorded by the inertial sensor, was used to calculate the acceleration index. The R-R intervals of the ECG were used to determine heart rate; the external validity of the heart rate was then evaluated according to oxygen uptake, which is the gold standard for physiological exercise intensity. Single regression analysis between treadmill speed and the acceleration index in each participant showed that the slope of the regression line was significantly greater than zero with a high coefficient of determination (walking, 0.95; jogging, 0.96; running, 0.90). Another single regression analysis between heart rate and oxygen uptake showed that the slope of the regression line was significantly greater than zero, with a high coefficient of determination (0.96). Together, these results indicate that the sportswear-type wearable evaluated in this study is a feasible technology for evaluating physical and physiological exercise intensity across a wide range of physical activities and sport performances.

Monitoring of Maximum Oxygen Intake of Breathing and Heart Rate in Exercise Training Based on Regression Equations

In order to provide a new reference method and basis for the physical testing study in healthy adults aged 40∼and 49, this paper proposes a regression equation-based monitoring study of exercise training breathing and heart rate. Sixty four subjects (30 males and 34 females), aged 40∼and 49 years, were selected. First, the subjects were screened by relevant health test and medical questionnaire to exclude the subjects with exercise contraindications and high-intensity exercise; then, the incremental load test was directly measured by gas analysis, and then, the subjects who completed the maximum oxygen intake test were tested twice, the corresponding heart rate value was recorded, and walking time were averaged for calculation. We show that the regression analysis of each index yielded regression equations and cross-validation regression equations show correlation statistics for measured and inferred maximum oxygen intake of RLOOCV = 0.826 and SEELOOCV = 0.378 (L/min). The equation can effectively speculate on the maximum oxygen intake of 40∼in healthy adults aged 49, with the advantages of efficient, low cost, fast, and convenient.

Construction of the Maximum Oxygen Intake Regression Equations for Exercise Training on Respiration and Heart Rate

To explore the correlation between the maximum percentage heart rate and the maximum percentage oxygen intake, provide an evaluation basis for heart rate for the assessment of exercise load intensity. Four boys and 4 girls were randomly selected, aged 26.25 ± 2.12 years old with good health, good cardiopulmonary function, no other medical history, and irregular physical training history. The subject measured the first 30 min of rest at 25°C at room temperature, kept awake and static, and the heart rate was measured as the quiet heart rate in the state. Prepredicted maximum heart rate and health index were determined according to the Polar s810 heart rate table instructions. Prepredicted maximum heart rate and health index were measured three consecutive times and reliability analysis was performed on three measurements. The regression equations were established by a stepwise method with data represented that all metrics were tested for normality for fitness index and maximum oxygen intake compared using a paired t test with a significance level of $P<0.05$ . The results showed that the highest value of VO2max motor cardiopulmonary test was 47.83 ml/(kg·min), the lowest was 35.06 ml/(kg·min), the two-step test was 44.50 ml/(kg·min), and the lowest was 32.89 ml/(kg min).With a positive correlation between the postexercise heart rate and the maximum oxygen intake, the maximum oxygen intake value can be indirectly inferred using the heart rate after the exercise and the work completed by the exercise. The results measured by two-step test have some accuracy and can be used to speculate the maximum oxygen intake in the ordinary young population. The polar heart rate meter allows subjects to indirectly measure the maximum oxygen intake in silence, requiring less equipment and being easy to operate. The indirect measurement of the maximum oxygen intake can be used for the monitoring of competitive sports and national fitness.

Interchangeability and optimization of heart rate methods for estimating oxygen uptake in ergometer cycling, level treadmill walking and running

Background

The heart rate (HR) method enables estimating oxygen uptake (V̇O₂) in physical activities. However, there is a paucity in knowledge about the interchangeability of this method when applied to cycling, walking and running. Furthermore, with the aim of optimization, there is a need to compare different models for establishing HR-V̇O₂ relationships.

Methods

Twenty-four physically active individuals (12 males and 12 females) participated. For each participant, two models of HR-V̇O₂ relationships were individually established in ergometer cycling, level treadmill walking and running. Model 1 consisted of five submaximal workloads, whereas model 2 included also a maximal workload. Linear regression equations were used to estimate V̇O₂ at seven intensity levels ranging between 25 and 85% of heart rate reserve (HRR). The estimated V̇O₂ levels were compared between the exercise modalities and models, as well as with data from a previous study.

Results

A high level of resemblance in estimated V̇O₂ was noted between running and cycling as well as between running and walking, with both model 1 and model 2. When comparing walking and cycling, the V̇O₂ levels for given intensities of %HRR were frequently slightly higher in walking with both models (range of significant differences: 5–12%). The variations of the estimated individual V̇O₂ values were reduced when using model 2 compared to model 1, both between and within the exercise modalities.

Conclusion

The HR method is optimized by more workloads and wider ranges. This leads to overall high levels of interchangeability when HR methods are applied in ergometer cycling, level treadmill walking and running.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12874-022-01524-w.

Effects of chronic intermittent hypobaric hypoxia on prostate-specific antigen (PSA) in Chilean miners

OBJECTIVE

The aim was to determine the effects of chronic intermittent hypobaric hypoxia (CIHH) on prostate-specific antigen (PSA) levels in Chilean miners who work at different altitudes.

METHODS

A cross-sectional study was conducted between April and July 2019. Miners from five mines (N=338) at different altitudes were evaluated. We recorded sociodemographic, working and altitude information. Haemoglobin oxygen saturation (SaO2) and haemoglobin (Hb) were measured in situ, while PSA and testosterone were analysed at a low level. Linear mixed-effect models were used to evaluate the association between PSA level and two CIHH exposures: composite CIHH (with four descriptors) and ChileStd-CIHH (CIHH Chilean standard; based on the Chilean technical guide for occupational exposure to CIHH). All models were adjusted by age, body mass index and day of the work the samples were taken.

RESULTS

Highest and lowest PSA levels were found in mines ≥3000 m above sea level (mine 3: median=0.75, IQR=-0.45; mine 4: median=0.46, IQR=-0.35). In the multilevel models, the wider altitude difference between mining operation and camp showed lower PSA levels (model D: βPSA=-0.93 ng/mL, βlogPSA=-0.07, p<0001), adjusted for other CIHH descriptors, SaO2, Hb and testosterone. The descriptors of composite CIHH explained better PSA variations than ChileStd-CIHH (model D: marginal R2=0.090 vs model A: marginal R2=0.016).

CONCLUSIONS

Occupational health regulations and high altitude medicine should consider these results as initial evidence on the inclusion of new descriptors for CIHH and the possible effect of this exposure on PSA levels in this male-dominated occupational sector.

Heart Rate Methods Can Be Valid for Estimating Intensity Spectrums of Oxygen Uptake in Field Exercise

Purpose

Quantifying intensities of physical activities through measuring oxygen uptake (V̇O₂) is of importance for understanding the relation between human movement, health and performance. This can in principle be estimated by the heart rate (HR) method, based on the linear relationship between HR and V̇O₂ established in the laboratory. It needs, however, to be explored whether HR methods, based on HR-V̇O₂ relationships determined in the laboratory, are valid for estimating spectrums of V̇O₂ in field exercise. We hereby initiate such studies, and use cycle commuting as the form of exercise.

Methods

Ten male and ten female commuter cyclists underwent measurements of HR and V̇O₂ while performing ergometer cycling in a laboratory and a normal cycle commute in the metropolitan area of Stockholm County, Sweden. Two models of individual HR-V̇O₂ relationships were established in the laboratory through linear regression equations. Model 1 included three submaximal work rates, whereas model 2 also involved a maximal work rate. The HR-V̇O₂ regression equations of the two models were then used to estimate V̇O₂ at six positions of field HR: five means of quintiles and the mean of the whole commute. The estimations obtained were for both models compared with the measured V̇O₂.

Results

The measured quintile range during commuting cycling was about 45–80% of V̇O₂max. Overall, there was a high resemblance between the estimated and measured V̇O₂, without any significant absolute differences in either males or females (range of all differences: −0.03–0.20 L⋅min^–1). Simultaneously, rather large individual differences were noted.

Conclusion

The present HR methods are valid at group level for estimating V̇O₂ of cycle commuting characterized by relatively wide spectrums of exercise intensities. To further the understanding of the external validity of the HR method, there is a need for studying other forms of field exercises.

Are heart rate methods based on ergometer cycling and level treadmill walking interchangeable?

Introduction

The heart rate (HR) method is a promising approach for evaluating oxygen uptake (V˙O2), energy demands and exercise intensities in different forms of physical activities. It would be valuable if the HR method, established on ergometer cycling, is interchangeable with other regular activities, such as level walking. This study therefore aimed to examine the interchangeability of the HR method when estimating V˙O2 for ergometer cycling and level treadmill walking in submaximal conditions.

Methods

Two models of HR‐V˙O2 regression equations for cycle ergometer exercise (CEE) and treadmill exercise (TE) were established with 34 active commuters. Model 1 consisted of three submaximal intensities of ergometer cycling or level walking, model 2 included also one additional workload of maximal ergometer cycling or running. The regression equations were used for estimating V˙O2 with seven individual HR values based on 25–85% of HR reserve (HRR). The V˙O2 estimations were compared between CEE and TE, within and between each model.

Results

Only minor, and in most cases non-significant, average differences were observed when comparing the estimated V˙O2 levels between CEE and TE. Model 1 ranged from -0.4 to 4.8% (n.s.) between 25–85%HRR. In model 2, the differences between 25–65%HRR ranged from 1.3 to -2.7% (n.s.). At the two highest intensities, 75 and 85%HRR, V˙O2 was slightly lower (3.7%, 4.4%; P < 0.05), for CEE than TE. The inclusion of maximal exercise in the HR‐V˙O2 relationships reduced the individual V˙O2 variations between the two exercise modalities.

Conclusion

The HR methods, based on submaximal ergometer cycling and level walking, are interchangeable for estimating mean V˙O2 levels between 25–85% of HRR. Essentially, the same applies when adding maximal exercise in the HR‐V˙O2 relationships. The inter-individual V˙O2 variation between ergometer cycling and treadmill exercise is reduced when using the HR method based on both submaximal and maximal workloads.