Estimation of maximal oxygen uptake via submaximal exercise testing in sports, clinical, and home settings

Estimation of aerobic fitness of underground coal mine workers and development of a predictive equation to determine their VO2max

This study aims to evaluate the aerobic fitness of miners and develop a predictive equation to assess their maximum oxygen uptake (VO2max), which is crucial for ensuring their safety and health in harsh working conditions. Measurement of VO2max via indirect calorimetry is costly and requires skilled personnel; developing a predictive equation is a viable alternative. Existing predictive equations, e.g., Hunt, Kline and Dolgener equations, were tested using the Pearson correlation coefficient, constant error, standard error of estimate and total error. The aerobic fitness of shearer operators, bolters miners, jackhammer drillers and road header operators was very low. Bland-Altman analysis revealed that predicted VO2max measurements of all three equations had a total error of >10%, which is unacceptable for usage. Therefore, a new predictive equation was developed with a total error of 9.78%. The developed predictive equation is useful to evaluate miners' functional capacity with higher precision and assist in allocating work.

Validity and between-days reliability of two different metabolic systems for measuring gas exchange during walking

BACKGROUND

Portable metabolic systems for assessing gas exchange outside the laboratory and clinical settings are increasing their popularity. We aimed to determine the validity and the reliability of the K5 portable system (Cosmed, Rome, Italy) and the Omnical (Maastricht Instruments, Maastricht, The Netherlands) metabolic cart.

METHODS

Gas exchange was measured, using the K5 and the Omnical in a randomised and counterbalanced order, in 35 participants (19 women; age: 26 ± 3 yrs.) using a walking protocol on 2 non-consecutive (48 h apart) days. The protocol consisted of a 5 min walk and 2.5 min rest cycle starting at 3.5 km/h and increasing in 1 km/h to 6.5 km/h. The protocol was repeated twice after a 10-15 min resting. To determine validity and reliability, we conducted two-factor repeated measures analysis of variance (ANOVA), intraclass correlation coefficients (ICC), coefficients of variation (CV) and Bland-Altman analyses.

RESULTS

Repeated measures ANOVA showed that mean oxygen consumption, carbon dioxide production and energy expenditure were higher for the K5 compared to the Omnical on both visits (all P < 0.001). Respiratory exchange ratio (RER) was similar among systems at faster (≥4.5 km/h) walking speeds. ICC, CV and Bland-Altman showed a better reliability of the Omnical (ICCs ranged from 0.71 to 0.86, and CVs from 3.1 % to 7.1 %) compared to the K5 (ICCs ranged from 0.40 to 0.98, and CVs from 2.6 % to 6.3 %).

CONCLUSIONS

The K5 portable system provides similar RER values to the Omnical metabolic cart, although the Omnical reliability was better for most outcomes.

Assessment and repeatability of aerobic capacity using the Chester Step Test among current, former, and never smokers

Cigarette smoking contributes to reduced cardiorespiratory performance, which may improve upon cessation. Consequently, former smokers' cardiorespiratory fitness should not be significantly different from that of never-smokers. This study aims to compare V̇O2max values among current, former, and never smokers and assess the repeatability of measurements using the Chester Step Test (CST). V̇O2max measurements were available from a total of 70 subjects (23 current, 23 former, and 24 never-smokers) and showed significant repeatability. Current smokers had the worst aerobic capacity, with a mean VO2max ± SD of 38.8 ± 4.5, which was significantly lower than the VO2max of 41.62 ± 3.8 in never-smokers (p < 0.0001) and 41.43 ± 4.6 in former smokers (p < 0.0001). No significant differences were observed between never-smokers and former smokers. V̇O2max estimates by CST were reproducible and showed that the aerobic capacity of individuals who smoke is substantially inferior compared to never and former smokers. Improvement in cardiorespiratory performance following smoking cessation may have important implications for smoking cessation, especially for those smokers who perceive enhanced physical performance as a tangible benefit.

Criterion validity of a newly developed Apple Watch app ('MVPA') compared to the native Apple Watch 'activity' app for measuring criterion moderate intensity physical activity

Introduction

Many people fail to meet physical activity guidelines. One possible solution is wearable technology. Yet it is unclear if popular devices such as the Apple Watch can accurately measure intensity, which is a cornerstone of physical activity guidelines. We developed a bespoke Apple Watch app based on the use of relative intensity (%HRR), with the aim to determine if the bespoke app measures 'moderate' intensity more accurately compared to the native Apple Watch Activity app, using % oxygen consumption reserve (%VO2R) as the criterion.

Methods

Seventy-four participants (18-65 years) attended the laboratory twice. During Visit 1, they completed medical screening, and measurements of resting heart rate, maximal oxygen consumption, and maximal heart rate on a motorised treadmill. During Visit 2, participants completed 5-minute treadmill bouts starting at 3.5 km.h-1, increasing by 0.5 km.h-1 until the bespoke app recorded 3 minutes at ≥40%HRR, and the native app recorded 5 minutes of 'exercise'. Oxygen consumption and heart rate were recorded. Bayesian posterior distributions were used to compare the two apps.

Results

At the walking speed that the native app recorded exercise, the mean (95% HDI) %VO2R was 33 (31-36)%, which is below moderate relative intensity (40%HRR). This is compared to a mean (95% HDI) of 43 (40-44)% for our bespoke app.

Conclusion

The bespoke app measured relative moderate intensity more accurately compared to the native app when compared to the %VO2R criterion. Exercise guidelines and wearable devices should incorporate relative measures of physical activity to better individualise monitoring and prescription.

Commentary on "A systematic review and meta-analysis comparing objectively measured and estimated fitness to predict all-cause and cardiovascular disease mortality in adults"

•Higher cardiorespiratory fitness (CRF) reduces all-cause and cardiovascular disease (CVD) mortality risks. •CRF measured from cardiopulmonary exercise testing and estimated from maximal treadmill duration, submaximal exercise tests, and non-exercise algorithms show similar associations between CRF and all-cause and CVD mortality. •Protective associations between higher CRF and all-cause and CVD mortality were consistent when stratified by measurement year, global region, age, gender, follow-up duration, number of mortality events, and exercise test modality. •Populations with low CRF are encouraged to engage in moderate-intensity physical activity to reduce their risks for all-cause and CVD mortality.

Comparison of objectively measured and estimated cardiorespiratory fitness to predict all-cause and cardiovascular disease mortality in adults: A systematic review and meta-analysis of 42 studies representing 35 cohorts and 3.8 million observations

BACKGROUND

Cardiorespiratory fitness (CRF) is a powerful health marker recommended by the American Heart Association as a clinical vital sign. Comparing the predictive validity of objectively measured CRF (the "gold standard") and estimated CRF is clinically relevant because estimated CRF is more feasible. Our objective was to meta-analyze cohort studies to compare the associations of objectively measured, exercise-estimated, and non-exercise-estimated CRF with all-cause and cardiovascular disease (CVD) mortality in adults.

METHODS

Systematic searches were conducted in 9 databases (MEDLINE, SPORTDiscus, Embase, Scopus, PsycINFO, Web of Science, PubMed, CINAHL, and the Cochrane Library) up to April 11, 2024. We included full-text refereed cohort studies published in English that quantified the association (using risk estimates with 95% confidence intervals (95%CIs)) of objectively measured, exercise-estimated, and non-exercise-estimated CRF with all-cause and CVD mortality in adults. CRF was expressed as metabolic equivalents (METs) of task. Pooled relative risks (RR) for all-cause and CVD mortality per 1-MET (3.5 mL/kg/min) higher level of CRF were quantified using random-effects models.

RESULTS

Forty-two studies representing 35 cohorts and 3,813,484 observations (81% male) (362,771 all-cause and 56,471 CVD deaths) were included. The pooled RRs for all-cause and CVD mortality per higher MET were 0.86 (95%CI: 0.83-0.88) and 0.84 (95%CI: 0.80-0.87), respectively. For both all-cause and CVD mortality, there were no statistically significant differences in RR per higher MET between objectively measured (RR range: 0.86-0.90) and maximal exercise-estimated (RR range: 0.85-0.86), submaximal exercise-estimated (RR range: 0.91-0.94), and non-exercise-estimated CRF (RR range: 0.81-0.85).

CONCLUSION

Objectively measured and estimated CRF showed similar dose-response associations for all-cause and CVD mortality in adults. Estimated CRF could provide a practical and robust alternative to objectively measured CRF for assessing mortality risk across diverse populations. Our findings underscore the health-related benefits of higher CRF and advocate for its integration into clinical practice to enhance risk stratification.

Assessing the Accuracy of Smartwatch-Based Estimation of Maximum Oxygen Uptake Using the Apple Watch Series 7: Validation Study

BACKGROUND

Determining maximum oxygen uptake (VO2max) is essential for evaluating cardiorespiratory fitness. While laboratory-based testing is considered the gold standard, sports watches or fitness trackers offer a convenient alternative. However, despite the high number of wrist-worn devices, there is a lack of scientific validation for VO2max estimation outside the laboratory setting.

OBJECTIVE

This study aims to compare the Apple Watch Series 7's performance against the gold standard in VO2max estimation and Apple's validation findings.

METHODS

A total of 19 participants (7 female and 12 male), aged 18 to 63 (mean 28.42, SD 11.43) years were included in the validation study. VO2max for all participants was determined in a controlled laboratory environment using a metabolic gas analyzer. Thereby, they completed a graded exercise test on a cycle ergometer until reaching subjective exhaustion. This value was then compared with the estimated VO2max value from the Apple Watch, which was calculated after wearing the watch for at least 2 consecutive days and measured directly after an outdoor running test.

RESULTS

The measured VO2max (mean 45.88, SD 9.42 mL/kg/minute) in the laboratory setting was significantly higher than the predicted VO2max (mean 41.37, SD 6.5 mL/kg/minute) from the Apple Watch (t18=2.51; P=.01) with a medium effect size (Hedges g=0.53). The Bland-Altman analysis revealed a good overall agreement between both measurements. However, the intraclass correlation coefficient ICC(2,1)=0.47 (95% CI 0.06-0.75) indicated poor reliability. The mean absolute percentage error between the predicted and the actual VO2max was 15.79%, while the root mean square error was 8.85 mL/kg/minute. The analysis further revealed higher accuracy when focusing on participants with good fitness levels (mean absolute percentage error=14.59%; root-mean-square error=7.22 ml/kg/minute; ICC(2,1)=0.60 95% CI 0.09-0.87).

CONCLUSIONS

Similar to other smartwatches, the Apple Watch also overestimates or underestimates the VO2max in individuals with poor or excellent fitness levels, respectively. Assessing the accuracy and reliability of the Apple Watch's VO2max estimation is crucial for determining its suitability as an alternative to laboratory testing. The findings of this study will apprise researchers, physical training professionals, and end users of wearable technology, thereby enhancing the knowledge base and practical application of such devices in assessing cardiorespiratory fitness parameters.

Reliability, validity, usefulness, and sensitivity of a submaximal test of performing burpees in 3 minutes, in assessing and detecting changes in aerobic fitness of athletes during future prolonged self-isolation in a confined environment

BACKGROUND

During a prolonged quarantine, there is a need to monitor aerobic fitness levels of trained individuals who are isolated with a simple fitness test that can be performed in confined space of their own homes. This study examined the reliability, validity, usefulness and sensitivity of a novel 3-min submaximal heart rate burpees test (or SubHR3-MBT) to assess and monitor changes in aerobic fitness, of trained athletes. In the SubHR3-MBT, male and female athletes performed 48 and 39 burpees respectively, within 3 min by following a constant beeping pace. The performance criterion of the SubHR3-MBT is the highest heart rate attained (or exercise HRpeak) at the end of 3-min (wherein a lower exercise HRpeak indicates a higher level of aerobic fitness).

METHODS

A total of 40 male and female national athletes from various sports volunteered for the study.

RESULTS

For reliability (Part 1), the SubHR3-MBT showed good relative and excellent reliability, with intraclass correlation coefficient 0.90 and coefficient of variation 2.6%, respectively. For validity (Part II), there was significant negative correlation between relative exercise HRpeak with respiratory gas-measured VO2max (r=-0.51, large; P<0.001). The test's technical error of measurement of 2.3 is slightly greater than its smallest worthwhile change of 1.5. For sensitivity (Part III), the athletes were tested twice for their SubHR3-MBT and VO2max, once at baseline and another at a followed-up test after >10 weeks. There was a significant correlation between the % change in relative exercise HRpeak with the % change in VO2max (r=-0.66, large; P<0.001).

CONCLUSIONS

The SubHR3-MBT is a reliable, valid, marginally useful test and may be able to track changes in aerobic fitness in trained athletes with moderate levels of sensitivity, in case of future isolation due to pandemic occurrence.

NIRS-Derived Muscle-Deoxygenation and Microvascular Reactivity During Occlusion-Reperfusion at Rest Are Associated With Whole-Body Aerobic Fitness

Purpose: Near-infrared spectroscopy (NIRS) indices during arterial occlusion-reperfusion maneuver have been used to examine the muscle's oxidative metabolism and microvascular function-important determinants of whole-body aerobic-fitness. The association of NIRS-derived parameters with whole-body VO2max was previously examined using a method requiring exercise (or electrical stimulation) followed by multiple arterial occlusions. We examined whether NIRS-derived indices of muscle deoxygenation and microvascular reactivity assessed during a single occlusion-reperfusion at rest are (a) associated with maximal/submaximal indices of whole-body aerobic-fitness and (b) could discriminate individuals with different VO2max. We, also, investigated which NIRS-parameter during occlusion-reperfusion correlates best with whole-body aerobic-fitness. Methods: Twenty-five young individuals performed an arterial occlusion-reperfusion at rest. Changes in oxygenated- and deoxygenated-hemoglobin (O2Hb and HHb, respectively) in vastus-lateralis were monitored; adipose tissue thickness (ATT) at NIRS-application was assessed. Participants also underwent a maximal incremental exercise test for VO2max, maximal aerobic velocity (MAV), and ventilatory-thresholds (VTs) assessments. Results: The HHbslope and HHbmagnitude of increase (occlusion-phase) and O2Hbmagnitude of increase (reperfusion-phase) were strongly correlated with VO2max (r = .695-.763, p < .001) and moderately with MAV (r = .468-.530; p < .05). O2Hbmagnitude was moderately correlated with VTs (r = .399-.414; p < .05). After controlling for ATT, the correlations remained significant for VO2max (r = .672-.704; p < .001) and MAV (r = .407; p < .05). Individuals in the high percentiles after median and tritile splits for HHbslope and O2Hbmagnitude had significantly greater VO2max vs. those in low percentiles (p < .01-.05). The HHbslope during occlusion was the best predictor of VO2max. Conclusion: NIRS-derived muscle deoxygenation/reoxygenation indices during a single arterial occlusion-reperfusion maneuver are strongly associated with whole-body maximal indices of aerobic-fitness (VO2max, MAV) and may discriminate individuals with different VO2max.

Enhancing performance: unveiling the physiological impact of submaximal and supramaximal tests on mixed martial arts athletes in the -61 kg and -66 kg weight divisions

This study delves into the intricate details of Mixed Martial Arts (MMA) by examining key variables such as maximal oxygen uptake (VO2 peak), aerobic energy (EAER), anaerobic energy (EAN), and accumulated O2 deficit (DOA). By investigating associations and comparing athletes in the -61 kg bantamweight and -66 kg featherweight weight divisions, we aim to shed light on their physiological characteristics. The sample consisted of 20 male volunteers separated into two paired groups: ten athletes in the category up to 61 kg (age: 27.7 ± 5.9 years old, height: 170.9 ± 3.4 cm, body mass: 72.8 ± 1.4 kg, fat percentage: 9.5% ± 3.0%, professional experience: 7.5 ± 7.1 years) and ten athletes up to 66 kg (age: 27.6 ± 2.9 years old, height: 176.0 ± 5.5 cm, body mass: 77.0 ± 1.5 kg, fat percentage: 7.85% ± 0.3%, professional experience: 5.5 ± 1.5 years). Remarkably, our findings revealed striking similarities between the two weight divisions. Furthermore, we discovered a negative correlation between VO2 peak and the number of MMA fights, indicating a potential impact of professional experience on aerobic capacity (r = -0.65, p < 0.01). Additionally, the number of fights exhibited negative correlations with anaerobic energy (r = -0.53, p < 0.05) and total energy cost (r = -0.54, p < 0.05). These results provide valuable insights for designing training programs in the context of MMA. While training both weight divisions together can be beneficial, it is equally crucial to incorporate specific weight-class-focused training to address each division's unique physical demands and requirements.

Prediction of peak oxygen consumption using cardiorespiratory parameters from warmup and submaximal stage of treadmill cardiopulmonary exercise test

This study investigates the quality of peak oxygen consumption (VO2peak) prediction based on cardiac and respiratory parameters calculated from warmup and submaximal stages of treadmill cardiopulmonary exercise test (CPET) using machine learning (ML) techniques and assesses the importance of respiratory parameters for the prediction outcome. The database consists of the following parameters: heart rate (HR), respiratory rate (RespRate), pulmonary ventilation (VE), oxygen consumption (VO2) and carbon dioxide production (VCO2) obtained from 369 treadmill CPETs. Combinations of features calculated based on the HR, VE and RespRate time-series from different stages of CPET were used to create 11 datasets for VO2peak prediction. Thirteen ML algorithms were employed, and model performances were evaluated using cross-validation with mean absolute percentage error (MAPE), R2 score, mean absolute error (MAE), and root mean squared error (RMSE) calculated after each iteration of the validation. The results demonstrated that incorporating respiratory-based features improves the prediction of VO2peak. The best results in terms of R2 score (0.47) and RMSE (5.78) were obtained for the dataset which included both cardiac- and respiratory-based features from CPET up to 85% of age-predicted HRmax, while the best results in terms of MAPE (10.5%) and MAE (4.63) were obtained for the dataset containing cardiorespiratory features from the last 30 seconds of warmup. The study showed the potential of using ML models based on cardiorespiratory features from submaximal tests for prediction of VO2peak and highlights the importance of the monitoring of respiratory signals, enabling to include respiratory parameters into the analysis. Presented approach offers a feasible alternative to direct VO2peak measurement, especially when specialized equipment is limited or unavailable.

Feasibility of predicting maximal oxygen uptake by using the efficiency factor in healthy men

Conventionally, efficiency is indirectly estimated through a respiratory gas analyser (oxygen, carbon dioxide), which is a complex and rather costly calculation method that is difficult to perform in many situations. Therefore, the present study proposed a modified definition of efficiency, called the efficiency factor (EF) (i.e., the ratio of work to the corresponding exercise intensity), and evaluated the relation between the EF and maximal oxygen uptake ([Formula: see text]), as well as compared the prediction models established based on the EF. The heart rate (maximal heart rate: 186 ± 6 beats min-1), rating of perceived exertion (19 ± 1), and [Formula: see text] (39.0 ± 7.1 mL kg-1 min-1) of 150 healthy men (age: 20 ± 2 years; height: 175.0 ± 6.0 cm; weight: 73.6 ± 10.7 kg; body mass index [BMI]: 24.0 ± 3.0 kg m-2; percent body fat [PBF]: 17.0 ± 5.7%) were measured during the cardiopulmonary exercise test (CPET). Through multiple linear regression analysis, we established the BMI model using age and BMI as parameters. Additionally, we created the PBF modelHRR utilizing weight, PBF, and heart rate reserve (HRR) and developed PBF modelEF6 and PBF modelEF7 by incorporating EF6 from the exercise stage 6 and EF7 from the exercise stage 7 during the CPET, respectively. EF6 (r = 0.32, p = 0.001) and EF7 (r = 0.31, p = 0.002) were significantly related to [Formula: see text]. Among the models, the PBF modelEF6 showed the highest accuracy, which could explain 62.6% of the variance in the [Formula: see text] at with a standard error of estimate (SEE) of 4.39 mL kg-1 min-1 (%SEE = 11.25%, p < 0.001). These results indicated that the EF is a significant predictor of [Formula: see text], and compared to the other models, the PBF modelEF6 is the best model for estimating [Formula: see text].

Estimation of cardiorespiratory fitness using heart rate and step count data

Predicting cardiorespiratory fitness levels can be useful for measuring progress in an exercise program as well as for stratifying cardiovascular risk in asymptomatic adults. This study proposes a model to predict fitness level in terms of maximal oxygen uptake using anthropometric, heart rate, and step count data. The model was trained on a diverse cohort of 3115 healthy subjects (1035 women and 2080 men) aged 42 ± 10.6 years and tested on a cohort of 779 healthy subjects (260 women and 519 men) aged 42 ± 10.18 years. The developed model is capable of making accurate and reliable predictions with the average test set error of 3.946 ml/kg/min. The maximal oxygen uptake labels were obtained using wearable devices (Apple Watch and Garmin) during recorded workout sessions. Additionally, the model was validated on a sample of 10 subjects with maximal oxygen uptake determined directly using a treadmill protocol in a laboratory setting and showed an error of 4.982 ml/kg/min. Unlike most other models, which use accelerometer readings as additional input data, the proposed model relies solely on heart rate and step counts-data readily available on the majority of fitness trackers. The proposed model provides a point estimation and a probabilistic prediction of cardiorespiratory fitness level, thus it can estimate the prediction's uncertainty and construct confidence intervals.

Impact of an online guided physical activity training on cognition and gut-brain axis interactions in older adults: protocol of a randomized controlled trial

Introduction

By 2050, the worldwide percentage of people 65 years and older is assumed to have doubled compared to current numbers. Therefore, finding ways of promoting healthy (cognitive) aging is crucial. Physical activity is considered an effective approach to counteract not only physical but also cognitive decline. However, the underlying mechanisms that drive the benefits of regular physical activity on cognitive function are not fully understood. This randomized controlled trial aims to analyze the effect of an eight-week standardized physical activity training program in older humans on cognitive, brain, and gut-barrier function as well as the relationship between the resulting changes.

Methods and analysis

One-hundred healthy participants aged 60 to 75 years will be recruited. First, participants will undergo an extensive baseline assessment consisting of neurocognitive tests, functional and structural brain imaging, physical fitness tests, and gut-microbiome profiling. Next, participants will be randomized into either a multi-component physical activity group (experimental condition) or a relaxation group (active control condition), with each training lasting 8 weeks and including an equal number and duration of exercises. The whole intervention will be online-based, i.e., participants will find their intervention schedule and all materials needed on the study website. After the intervention phase, participants will have their post-intervention assessment, which consists of the same measures and tests as the baseline assessment. The primary outcome of this study is the change in the cognitive parameter of visual processing speed from baseline to post-measurement, which will on average take place 10 weeks after the randomization. Secondary outcomes related to cognitive, brain, and microbiome data will be analyzed exploratory. Clinical trial registration: https://drks.de/search/de/trial/DRKS00028022.

Maximal oxygen uptake prediction from submaximal bicycle ergometry using a differential model

The maximal oxygen uptake (VO₂max) estimation has been a subject of research for many years. Cardiorespiratory measurements during incremental tests until exhaustion are considered the golden yard stick to assess VO₂max. However, precise VO₂max determination based on submaximal tests is attractive for athlete as well for clinical populations. Here, we propose and verify such a method based on experimental data. Using a recently developed model of heart rate (HR) and VO₂ kinetics in graded exercise tests, we applied a protocol, which is terminated at 80% of the estimated maximal HR during ergometer cycling. In our approach, initially, formula for maximal HR is selected by retrospective study of a reference population (17 males, 23.5 ± 2.0 years, BMI: 23.9 ± 3.2 kg/m²). Next, the subjects for experimental group were invited (nine subjects of both sexes: 25.1 ± 2.1 years, BMI 23.2 ± 2.2 kg/m²). After calculation of maximal HR using cardiorespiratory recordings from the submaximal test, VO₂max is predicted. Finally, we compared the prediction with the values from the maximal exercise test. The differences were quantified by relative errors, which vary from 1.2% up to 13.4%. Some future improvements for the procedure of VO₂max prediction are discussed. The experimental protocol may be useful for application in rehabilitation assessment and in certain training monitoring settings, since physical exertion is not a prerequisite and the approach provides an acceptable VO₂max estimation accuracy.

Modified Isoinertial-Based Ruffier Test in Healthy Individuals: A Feasibility Study

Cardiorespiratory fitness is an essential indicator in sports science and sports medicine that can be assessed with several tests. The Ruffier test is a submaximal test valid to estimate maximum oxygen uptake; it consists of 30 squats in 45 s, which may be challenging for inexperienced individuals. This study aims to verify the feasibility of a modified inertial-based version of the Ruffier test to assess cardiorespiratory fitness with 10 squats in 15 s. Both classic and isoinertial Ruffier tests were administered to thirty-five healthy young adults (20 men and 15 women), age 22.06 ± 2.13 years, BMI 23.87 ± 2.74. The two one-sided test confirmed the comparability of the isoinertial Ruffier test with its classic version within equivalence bounds of ±3.726. Furthermore, gender, age, body weight, the difference between peak heart rate after isoinertial squatting and resting heart rate, and the isoinertial Ruffier index are the coefficients of our best VO₂max prediction model with an adjusted R² of 0.937, sensitivity of 0.89, and specificity of 0.81. The study evidenced the feasibility of the isoinertial Ruffier test to measure cardiorespiratory fitness through a quick, safe, and short squat test easy to perform in fitness centers and primary care clinics.

Predicting Maximum Oxygen Uptake from Non-Exercise and Submaximal Exercise Tests in Paraplegic Men with Spinal Cord Injury

This study aimed to develop prediction equations for maximum oxygen uptake (VO₂max) based on non-exercise (anthropometric) and submaximal exercise (anthropometric and physiological) variables in paraplegic men with a spinal cord injury. All participants were tested on an arm ergometer using a maximal graded exercise test. Anthropometric variables such as age, height, weight, body fat, body mass index, body fat percentage, and arm muscle mass and physiological variables such as VO₂, VCO₂, and heart rate at 3 and 6 min of graded exercise tests were included in the multiple linear regression analysis. The prediction equations revealed the following. Regarding non-exercise variables, VO₂max was correlated with age and weight (equation R = 0.771, R² = 0.595, SEE= 3.187). Regarding submaximal variables, VO₂max was correlated with weight and VO₂ and VCO₂ at 6 min (equation R = 0.892, R² = 0.796, SEE = 2.309). In conclusion, our prediction equations can be used as a cardiopulmonary function evaluation tool to estimate VO₂max simply and conveniently using the anthropometric and physiological characteristics of paraplegic men with spinal cord injuries.

Predicting VO2max in competitive cyclists: Is the FRIEND equation the optimal choice?

Predicting VO_2max in athletes is vital for determining endurance capacity, for performance monitoring, in clinical diagnostic procedures, and for disease management. This study aimed to assess the most suitable equation for predicting VO_2max in competitive cyclists. Competitive cyclists (496 males, 84 females, Caucasian, 580 total) were included in the study from 1 January 2014 to 31 December 2019. Only subjects who were actively participating in national or international competitions and who were registered competitive cyclists and part of cycling teams at the time of the measurements were included. Subjects performed an incremental test on a cycle ergometer, and VO_2max was measured as indicated by a plateau in VO₂. In addition, four prediction equations (the FRIEND, Storer, Fairbarn, and Jones) were used to estimate VO_2max. The predicted VO_2max using the FRIEND equation was in good agreement with the measured VO_2max in male and female athletes. This was reflected by a high correlation with r = 0.684 for men and r = 0.897 for women (p = 0.000), with ICC = 0.568 (95% CI 0.184, 0.752) for men and ICC = 0.881 (95% CI 0.813, 0.923) for women. Total error was 1.56 and 1.48 ml/min/kg and a minimal bias of-3.6 and -1.1 ml/min/kg (men and women, respectively). Using other equations resulted in a slight decline in agreement with the measured standard. The FRIEND equation predicted VO_2max accurately with small total error, small prediction errors, and with the smallest constant error in our study cohort, indicating the potential value of using FRIEND equation also in competitive cyclists. This equation proved to have the highest accuracy both in male and female cyclists.

Benefits of Cycling Wheelchair Training for Elderly with Physical Disability: A Prospective Cohort Study

AIM

In order to investigate the effect of cycling wheelchair training as an exercise for aged 65+ disabled patients on cognitive function, quality of life, aerobic capacity and physiological parameters.

METHODS

Participants in nursing home performed cycling wheelchair training for 30 min a day, 5 days a week, for a total of 4 weeks. The main outcome measure was the short form 12 survey (SF-12). Other outcome measures included the Mini-Mental State Examination (MMSE), aero bike work rate test, resting blood pressure, and heart rate.

RESULTS

In this study, 41 volunteers were recruited and no participants dropped out of the study voluntarily during training, and no serious adverse effect was identified. Physical and mental component summary total scores of SF-12 were significantly higher after training with statistical significance (p = 0.001). 8 subscales also showed significant improvements after training (p = 0.025 ~ <0.001). Total MMSE score has no difference before and after training. Attention/calculation (p = 0.018), short term memory (p = 0.041), and aerobic capacity (p < 0.001) as measured by subscales of MMSE and aero bike test showed marked improvements, while resting systolic blood pressure (p = 0.931) and heart rate (p = 0.793) did not change.

CONCLUSIONS

Cycling wheelchair is practical for the disabled elderly to exercise, and a 4-week exercise program enhanced their quality of life and aerobic capacity.

Validity and reproducibility of a method to estimate cardiorespiratory fitness in college adults

Introduction: Cardiorespiratory fitness is a predictor of cardiovascular and all-cause mortality. Its assessment in different groups has clinical and public health usefulness. Objective: To evaluate the validity and reproducibility of a no-exercise method [National Aeronautics and Space Administration (NASA) method] to estimate the maximum oxygen consumption (VO2máx) in college adults. Materials and methods: This study included 94 healthy individuals of both sexes (18-55 years). The gold standard was ergospirometry. The validity and reproducibility were evaluated with the intraclass correlation coefficient (ICC) and the Bland-Altman method. Results: Among the participants, we found a mean age of 30.54 ± 9.33 years and a VO2máx of 41.29 ± 9.54 ml O2.kg-1.min-1; 48.9 % were women. A mean difference of VO2máx between ergospirometry and that estimated by the NASA method of 3.41 ± 5.64 ml O2.kg-1.min-1 was found. The concordance between the two methods was good, with an ICC of 0.858 (CI95% 0.672-0.926). The percentage of error was 29.70 %. The reproducibility of the two estimates by the NASA method was excellent, with an ICC of 0.986 (CI95% 0.927-0.995). Conclusions: The NASA method is valid and reproducible to estimate VO2máx in college adults. In addition, it is safe and easy to apply. Estimating cardiorespiratory fitness is recommended to improve screening in cardiometabolic risk programs and to implement timely interventions.

Cardiorespiratory Fitness Estimation Based on Heart Rate and Body Acceleration in Adults With Cardiovascular Risk Factors: Validation Study

Background

Cardiorespiratory fitness (CRF) is an independent risk factor for cardiovascular morbidity and mortality. Adding CRF to conventional risk factors (eg, smoking, hypertension, impaired glucose metabolism, and dyslipidemia) improves the prediction of an individual’s risk for adverse health outcomes such as those related to cardiovascular disease. Consequently, it is recommended to determine CRF as part of individualized risk prediction. However, CRF is not determined routinely in everyday clinical practice. Wearable technologies provide a potential strategy to estimate CRF on a daily basis, and such technologies, which provide CRF estimates based on heart rate and body acceleration, have been developed. However, the validity of such technologies in estimating individual CRF in clinically relevant populations is poorly known.

Objective

The objective of this study is to evaluate the validity of a wearable technology, which provides estimated CRF based on heart rate and body acceleration, in working-aged adults with cardiovascular risk factors.

Methods

In total, 74 adults (age range 35-64 years; n=56, 76% were women; mean BMI 28.7, SD 4.6 kg/m²) with frequent cardiovascular risk factors (eg, n=64, 86% hypertension; n=18, 24% prediabetes; n=14, 19% type 2 diabetes; and n=51, 69% metabolic syndrome) performed a 30-minute self-paced walk on an indoor track and a cardiopulmonary exercise test on a treadmill. CRF, quantified as peak O₂ uptake, was both estimated (self-paced walk: a wearable single-lead electrocardiogram device worn to record continuous beat-to-beat R-R intervals and triaxial body acceleration) and measured (cardiopulmonary exercise test: ventilatory gas analysis). The accuracy of the estimated CRF was evaluated against that of the measured CRF.

Results

Measured CRF averaged 30.6 (SD 6.3; range 20.1-49.6) mL/kg/min. In all participants (74/74, 100%), mean difference between estimated and measured CRF was −0.1 mL/kg/min (P=.90), mean absolute error was 3.1 mL/kg/min (95% CI 2.6-3.7), mean absolute percentage error was 10.4% (95% CI 8.5-12.5), and intraclass correlation coefficient was 0.88 (95% CI 0.80-0.92). Similar accuracy was observed in various subgroups (sexes, age, BMI categories, hypertension, prediabetes, and metabolic syndrome). However, mean absolute error was 4.2 mL/kg/min (95% CI 2.6-6.1) and mean absolute percentage error was 16.5% (95% CI 8.6-24.4) in the subgroup of patients with type 2 diabetes (14/74, 19%).

Conclusions

The error of the CRF estimate, provided by the wearable technology, was likely below or at least very close to the clinically significant level of 3.5 mL/kg/min in working-aged adults with cardiovascular risk factors, but not in the relatively small subgroup of patients with type 2 diabetes. From a large-scale clinical perspective, the findings suggest that wearable technologies have the potential to estimate individual CRF with acceptable accuracy in clinically relevant populations.

Prediction of peak oxygen uptake from 6-minute walk test in pulmonary hypertension

Maximal oxygen uptake (V′_O2max), assessed by cardiopulmonary exercise testing (CPET), is an important parameter for risk assessment in patients with pulmonary hypertension (PH). However, CPET may not be available for all PH patients. Thus, we aimed to test previously published predictive models of V′_O2max from the 6-min walk distance (6MWD) for their accuracy and to create a new model.

We tested four models (two by Ross et al. (2010), one by Miyamoto et al. (2000) and one by Zapico et al. (2019)). To derive a new model, data were split into a training and testing dataset (70:30) and step-wise linear regression was performed. To compare the different models, the standard error of the estimate (SEE) was calculated and the models graphically compared by Bland–Altman plots. Sensitivity and specificity for correct prediction into low-risk classification (V′_O2max >15 mL/min/kg) was calculated for all models.

A total of 276 observations were included in the analysis (194/82 training/testing dataset); 6MWD and V′_O2max were significantly correlated (r=0.65, p<0.001). Linear regression showed significant correlation of 6MWD, weight and heart rate response (HRR) with V′_O2max and the best fitting prediction equation was: V′_O2max = 1.83 + 0.031 × 6MWD (m) – 0.023 × weight (kg) – 0.015 × HRR (bpm). SEEs for the different models were 3.03, 3.22, 4.36 and 3.08 mL/min/kg for the Ross et al., Miyamoto et al., Zapico et al. models and the new model, respectively. Predicted mean V′_O2max was 16.5 mL/min/kg (versus observed 16.1 mL/min/kg).

6MWD and V′_O2max reveal good correlation in all models. However, the accuracy of all models is inadequate for clinical use. Thus, CPET and 6MWD both remain valuable risk assessment tools in the management of PH.

Although maximal oxygen uptake and the 6-min walk distance show good correlation in pulmonary hypertension, all predictive models are of inadequate accuracy for clinical use and cardiopulmonary exercise testing remains an irreplaceable toolhttps://bit.ly/33HBQFk

The Determination of Step Frequency in 3-min Incremental Step-in-Place Tests for Predicting Maximal Oxygen Uptake from Heart Rate Response in Taiwanese Adults

The maximal oxygen uptake (VO_2max) prediction models established by step tests are often used for evaluating cardiorespiratory fitness (CRF). However, it is unclear which type of stepping frequency sequence is more suitable for the public to assess the CRF. Therefore, the main purpose of this study was to test the effectiveness of two 3-min incremental step-in-place (3MISP) tests (i.e., 3MISP_30s and 3MISP_60s) with the same total number of steps but different step-frequency sequences in predicting VO_2max. In this cross-sectional study, a total of 200 healthy adults in Taiwan completed 3MISP_30s and 3MISP_60s tests, as well as cardiopulmonary exercise testing. The 3MISP_30s and 3MISP_60s models were established through multiple stepwise regression analysis by gender, age, percent body fat, and 3MISP-heart rate. The statistical analysis included Pearson's correlations, the standard errors of estimate, the predicted residual error sum of squares, and the Bland-Altman plot to compare the measured VO_2max values and those estimated. The results of the study showed that the exercise intensity of the 3MISP_30s test was higher than that of the 3MISP_60s test (% heart rate reserve (HRR) during 3MISP_30s vs. %HRR during 3MISP_60s = 81.00% vs. 76.81%, p < 0.001). Both the 3MISP_30s model and the 3MISP_60s model explained 64.4% of VO_2max, and the standard errors of the estimates were 4.2043 and 4.2090 mL·kg^-1·min^-1, respectively. The cross-validation results also indicated that the measured VO_2max values and those predicted by the 3MISP_30s and 3MISP_60s models were highly correlated (3MISP_30s model: r = 0.804, 3MISP_60s model: r = 0.807, both p < 0.001). There was no significant difference between the measured VO_2max values and those predicted by the 3MISP_30s and 3MISP_60s models in the testing group (p > 0.05). The results of the study showed that when the 3MISP_60s test was used, the exercise intensity was significantly reduced, but the predictive effectiveness of VO_2max did not change. We concluded that the 3MISP_60s test was physiologically less stressful than the 3MISP_30s test, and it could be a better choice for CRF evaluation.

Test-Retest Reliability of Physiological Variables During Submaximal Seated Upper-Body Poling in Able-Bodied Participants

Purpose: To investigate the test–retest reliability of physiological variables across four different test days and four different submaximal exercise intensities during seated upper-body poling (UBP).

Methods: Thirteen abled-bodied, upper-body trained men (age 29±3years; body mass 84±12kg; height 183±5cm) performed four submaximal 4-min stages of seated UBP on four separate test days. The four submaximal stages were set at individual power outputs corresponding to a rating of perceived exertion of 9, 11, 13, and 15. The absolute reliability for pairwise test-day comparisons of the physiological variables was investigated with the smallest detectable change percentage (%SDC) and the relative reliability with the interclass correlation coefficient (ICC).

Results: Absolute and relative reliability across test-day comparisons and submaximal stages were moderate to excellent for all variables investigated (V̇O₂ – %SDC range: 5–13%, ICC range: 0.93–0.99; HR – %SDC range: 6–9%, ICC range: 0.91–0.97) other than blood lactate, for which absolute reliability was poor and relative reliability highly variable (%SDC range: 26–69%, ICC range: 0.44–0.92). Furthermore, absolute and relative reliability were consistent across the low-to-moderate exercise intensity spectrum and across test days.

Conclusion: Absolute and relative test–retest reliability were acceptable for all investigated physiological variables but blood lactate. The consistent test–retest reliability across the exercise intensity spectrum and across test days indicates that a familiarization period to the specific exercise modality may not be necessary. For generalizability, these findings need to be confirmed in athletes with a disability by future large-scale studies.

Temporal trends in step test performance for Chinese adults between 2000 and 2014

BACKGROUD/OBJECTIVE

Cardiorespiratory endurance is an excellent marker of functional endurance and health among adults. The aim of this study was to estimate temporal trends in step test performance for Chinese adults between 2000 and 2014.

METHODS

Apparently healthy adults aged 20-59 years were included. Nationally representative step test data (n = 603,977) from 2000, 2005, 2010, and 2014 were reported descriptively by the China Physical Fitness Surveillance Center. Temporal trends in means were estimated at the sex-age level for all adults and separate location/occupation groups using sample-weighted linear regression, with trends in distributional characteristics described visually and estimated as the ratio of coefficients of variation (CVs).

RESULTS

Collectively, there was a negligible improvement in mean step test performance of 0.12 standardized effect sizes (95% confidence interval (95%CI): 0.11-0.13). Negligible to small improvements were observed for all age, sex, location, and occupation groups. Variability declined substantially over time (ratio of CVs (95%CI): 0.86 (0.86-0.86)), with negligible to large improvements in those below the 10th percentile, and negligible to moderate declines in those above the 90th percentile.

CONCLUSION

There have been negligible to large improvements in step test performance for low to average performing Chinese adults since 2000, which may be meaningful to public health because low endurance is an important risk factor for all-cause mortality.

A New Fitness Test of Estimating VO2max in Well-Trained Rowing Athletes

Background

This study was designed to investigate the validity of maximal oxygen consumption (VO_2max) estimation through the Firstbeat fitness test (FFT) method when using submaximal rowing and running programs for well-trained athletes.

Methods

Well-trained flatwater rowers (n = 45, 19.8 ± 3.0 years, 184 ± 8.7 cm, 76 ± 12.9 kg, and 58.7 ± 6.0 mL⋅kg^–1⋅min^–1) and paddlers (n = 45, 19.0 ± 2.5 years, 180 ± 7.7 cm, 74 ± 9.4 kg, and 59.9 ± 4.8 mL⋅kg^–1⋅min^–1) completed the FFT and maximal graded exercise test (GXT) programs of rowing and running, respectively. The estimated VO_2max was calculated using the FFT system, and the measured VO_2max was obtained from the GXT programs. Differences between the estimated and measured VO_2max values were analyzed to assess the accuracy and agreement of the predictions. Equations from the previous study were also used to predict the VO_2max in the submaximal programs to compare the accuracy of prediction with the FFT method.

Results

The FFT method was in good agreement with the measured VO_2max in both groups based on the intraclass correlation coefficients (>0.8). Additionally, the FFT method had considerable accuracy in VO_2max estimation as the mean absolute percentage error (≤5.0%) and mean absolute error (<3.0 mL⋅kg^–1⋅min^–1) were fairly low. Furthermore, the FFT method seemed more accurate in the estimation of VO_2max than previously reported equations, especially in the rowing test program.

Conclusion

This study revealed that the FFT method provides a considerably accurate estimation of VO_2max in well-trained athletes.

Measures of Left Ventricular Diastolic Function and Cardiorespiratory Fitness According to Glucose Metabolism Status: The Maastricht Study

Background

This cross‐sectional study evaluated associations between structural and functional measures of left ventricular diastolic function and cardiorespiratory fitness (CRF) in a well‐characterized population‐based cohort stratified according to glucose metabolism status.

Methods and Results

Six hundred seventy‐two participants from The Maastricht Study (mean±SD age, 61±9 years; 17.4% prediabetes and 25.4% type 2 diabetes mellitus) underwent both echocardiography to determine left atrial volume index, left ventricular mass index, maximum tricuspid flow regurgitation, average e′ and E/e′ ratio; and submaximal cycle ergometer test to determine CRF as maximum power output per kilogram body mass. Associations were examined with linear regression adjusted for cardiovascular risk and lifestyle factors, and interaction terms. After adjustment, in normal glucose metabolism but not (pre)diabetes, higher left atrial volume index (per 1 mL/m²), left ventricular mass index (per 1 g/m^2.7), maximum tricuspid regurgitation flow (per 1 m/s) were associated with higher CRF (maximum power output per kilogram body mass; β in normal glucose metabolism 0.015 [0.008–0.023], P_interaction (pre)diabetes <0.10; 0.007 [−0.001 to 0.015], P_interaction type 2 diabetes mellitus <0.10; 0.129 [0.011–0.246], P_interaction >0.10; for left atrial volume index, left ventricular mass index, maximum tricuspid regurgitation flow, respectively). Furthermore, after adjustment, in all individuals, higher average E/e′ ratio (per unit), but not average e′, was associated with lower CRF (normal glucose metabolism −0.044 [−0.071 to −0.016]), P_interaction >0.10).

Conclusions

In this population‐based study, structural and functional measures of left ventricular diastolic function were independently differentially associated with CRF over the strata of glucose metabolism status. This suggests that deteriorating left ventricular diastolic function, although of small effect, may contribute to the pathophysiological process of impaired CRF in the general population. Moreover, the differential effects in these structural measures may be the consequence of cardiac structural adaptation to effectively increase CRF in normal glucose metabolism, which is absent in (pre)diabetes.

Validation of a Modified Submaximal Balke Protocol to Assess Cardiorespiratory Fitness in Individuals at High Risk of or With Chronic Health Conditions-A Pilot Study

Objectives: This study aims to validate a submaximal treadmill walking test for estimation of maximal oxygen consumption (VO_2max) in individuals at high risk of or with chronic health conditions. Method: Eighteen participants (age 62 ± 16 years; VO_2max 31.2 ± 5.9 ml kg^-1 min^-1) at high risk of getting or with established chronic diseases performed two valid modified Balke treadmill walking protocols, one submaximal protocol, and one maximal protocol. Test duration, heart rate (HR), and rate of perceived exertion (RPE) were measured during both tests. VO_2max was measured during the maximal test. VO_2max was estimated from the submaximal test by multiple regression using time to RPE ≥ 17, gender, age, and body mass as independent variables. Model fit was reported as explained variance (R ²) and standard error of the estimate (SEE). Results: The model fit for estimation of VO_2max from time to RPE ≥ 17 at the submaximal test, body mass, age, and gender was R ² = 0.78 (SEE = 3.1 ml kg^-1 min^-1, p ≤ 0.001). Including heart rate measurement did not improve the model fit. Conclusions: The submaximal walking test is feasible and valid for assessing cardiorespiratory fitness in individuals with high risk of or chronic health conditions.

Estimation of maximal oxygen uptake from the 3,000 m run in adult men and women

The 3,000 m run is a frequently used field test for evaluating aerobic fitness. The test has previously been validated using smaller sample sizes and with focus restricted to the correlation between run performance and maximal oxygen uptake (V̇O_2max). The aim of the present study was to generate equations for converting 3,000 m performance into predicted V̇O_2max , and present corresponding validity statistics. In total 259 (30 female) military cadets and recruits (18-39 years) participated in the study. The subjects carried out a 3,000 m run and a direct treadmill V̇O_2max test. The Pearson r between V̇O_2max and average 3,000 m run speed were 0.74 and 0.79 in men and women, respectively. Two V̇O_2max prediction equations were generated: (1) Men: Ŷ = 17.5 + 2.57X and (2) Women: Ŷ = 14.6 + 2.48X (X = 3,000 m average run speed in km·h^-1). The equations produced a standard error of estimate of 3.3 and 2.6 mL·kg^-1·min^-1, and limits of agreement of 6.4 and 5.0 mL·kg^-1·min^-1 in men and women, respectively. The validity of the 3,000 m test is comparable to other indirect maximal running tests and is a time-effective alternative aerobic fitness test in healthy and motivated subjects.

Predicting Maximal Oxygen Uptake Using the 3-Minute All-Out Test in High-Intensity Functional Training Athletes

Maximal oxygen uptake (VO2max) and critical speed (CS) are key fatigue-related measurements that demonstrate a relationship to one another and are indicative of athletic endurance performance. This is especially true for those that participate in competitive fitness events. However, the accessibility to a metabolic analyzer to accurately measure VO2max is expensive and time intensive, whereas CS may be measured in the field using a 3 min all-out test (3MT). Therefore, the purpose of this study was to examine the relationship between VO2max and CS in high-intensity functional training (HIFT) athletes. Twenty-five male and female (age: 27.6 ± 4.5 years; height: 174.5 ± 18.3 cm; weight: 77.4 ± 14.8 kg; body fat: 15.7 ± 6.5%) HIFT athletes performed a 3MT as well as a graded exercise test with 48 h between measurements. True VO2max was determined using a square-wave supramaximal verification phase and CS was measured as the average speed of the last 30 s of the 3MT. A statistically significant and positive correlation was observed between relative VO2max and CS values (r = 0.819, p < 0.001). Based on the significant correlation, a linear regression analysis was completed, including sex, in order to develop a VO2max prediction equation (VO2max (mL/kg/min) = 8.449(CS) + 4.387(F = 0, M = 1) + 14.683; standard error of the estimate = 3.34 mL/kg/min). Observed (47.71 ± 6.54 mL/kg/min) and predicted (47.71 ± 5.7 mL/kg/min) VO2max values were compared using a dependent t-test and no significant difference was displayed between the observed and predicted values (p = 1.000). The typical error, coefficient of variation, and intraclass correlation coefficient were 2.26 mL/kg/min, 4.90%, and 0.864, respectively. The positive and significant relationship between VO2max and CS suggests that the 3MT may be a practical alternative to predicting maximal oxygen uptake when time and access to a metabolic analyzer is limited.

Prediction of VO2max based on a 3-kilometer running test for water sports athletes

BACKGROUND

No studies have reported the 3-kilometer running test (3KRT) intending to predict VO2max for water sports athletes. Therefore, the purpose of this study was to develop a new model to predict the maximal aerobic capacity (VO2max) for water sports athletes based on 3KRT.

METHODS

One hundred and two water sports athletes completed two sessions of experiments consisting of a maximal graded exercise test (GXT) and a 3KRT. Multiple linear regression was applied to predict VO2max value based on the performance and physiological responses of 3KRT, along with participants' anthropometric and demographic variables. The predicted residual error sum of square (PRESS) and error terms (constant error and total error) were calculated to further evaluate the predictive accuracy.

RESULTS

Two significant prediction models based on elapsed exercise time (T3KRT), post-exercise heart rate (PHR3KRT), body mass, and gender were proposed. One model including PHR3KRT was identified (VO2max=120.77-0.028×T3KRT [second]-0.11×PHR3KRT [bpm]-0.334×body mass [kg]+8.70×gender [1: male, 0: female]), with an adjusted R2 of 0.723. Another model excluding PHR3KRT was also identified (VO2max=103.65-0.034×T3KRT [second]-0.317×Body mass [kg] + 7.89×gender [1: male, 0: female]), with an adjusted R2 of 0.713. Both models were further validated by the result of PRESS statistics.

CONCLUSIONS

This endurance 3-kilometer running test accurately predicted VO2max value for water sports athletes (rowers, canoeists, and kayakers), and the model excluding PHR3KRT would be easier to use.

Validation of the 6-minute race test as a predictor of maximal aerobic speed in university endurance athletes

BACKGROUND: The maintenance of maximal aerobic speed (MAS) until exhaustion is an important parameter for the evaluation of sports performance and prescription and planning of training. OBJECTIVE: To validate a 6-minute race test (6MRT) as a predictor of MAS in university endurance athletes. METHODS: Twenty two university endurance athletes (12 males and 10 females) were part of the study. The design was pre-experimental. The primary variables were the time of maintenance of the MAS on the field through a Time Limit Test (Tlim test), and the VO2 max (laboratory and field). The statistical analysis of the time and ventilatory variables was carried out using descriptive statistics; the comparison between males and females for all variables was carried out through a t-Student test for independent samples (p< 0.05). RESULTS: The performance in the Tlim test was 356.4 ± 52.9 and 327.0 ± 120.2 s in males and females, respectively. CONCLUSION: Based on the time of maintenance of the MAS (Tlim test), the 6MRT is a valid test to determine the MAS in university endurance male athletes. However, the MAS in university endurance female athletes must be evaluated with a shorter test (between 5 and 5.30 minutes long).

Cardiorespiratory Fitness as a Correlate of Cardiovascular, Anthropometric, and Physical Risk Factors: Using the Ruffier Test as a Template

Background

Assessment of cardiorespiratory fitness (CRF) is a standard procedure in routine clinical practices. Early identification of risk factors through screening is vital in the fight against chronic diseases. Evaluation of CRF can impose cost implications in the clinical setting; thus, a simple and easy-to-use test is to be advocated. The Ruffier test is a simple test that can assess CRF, and it is necessary to find whether the test reflects the effects of compounding factors in CRF.

Objective

This study aims to determine the association between CRF (estimated VO2max) with cardiovascular, anthropometric, and physical risk factors using the Ruffier test.

Methods

A cross-sectional study with a sample of 52 male participants was conducted. Before the Ruffier test, each participant's body weight, height, waist circumference, skinfold thickness, thigh length, lower-limb length, thigh circumference, physical activity, blood pressure, smoking, diabetes, and pulmonary functions were recorded, and these factors correlated with CRF.

Results

There was a significant inverse relationship found between the estimated VO2max and age, height, body weight, body mass index, waist circumference, a sum of skinfold, fat percentage, thigh length, lower-limb length, thigh circumference, smoking, blood pressure, heart rates, and diabetes (p < 0.05). A significant positive correlation was found between the estimated VO2max with physical activity and respiratory functions (p < 0.05). In the multivariable model, body weight and resting heart rate were significantly inversely associated with the estimated VO2max(p < 0.05).

Conclusion

Using the Ruffier test, various risk factors of CRF are correlated with the estimated VO2max. This test reflects the effects of different compounding factors on CRF; therefore, it can be used in routine clinical practices to identify the risk factors early.

Factors Influencing Walking and Exercise Adherence in Healthy Older Adults Using Monitoring and Interfacing Technology: Preliminary Evidence

BACKGROUND

Monitoring and interfacing technologies may increase physical activity (PA) program adherence in older adults, but they should account for aspects influencing older adults' PA behavior. This study aimed at gathering preliminary wrist-based PA adherence data in free-living and relate these to the influencing factors.

METHODS

Ten healthy older adults (4 females, aged 70-78 years) provided health, fatigue, activity levels, attitude towards pacing, and self-efficacy information and performed a 6 min-walk test to assess their fitness. After a baseline week they followed a two-week walking and exercise intervention. Participants saw their progress via a purposely designed mobile application.

RESULTS

Walking and exercise adherence did not increase during the intervention (p = 0.38, p = 0.65). Self-efficacy decreased (p = 0.024). The baseline physical component of the Short Form Health Survey was the most predictive variable of walking adherence. Baseline perceived risk of over-activity and resting heart rate (HRrest) were the most predictive variables of exercise adherence. When the latter two were used to cluster participants according to their exercise adherence, the fitness gap between exercise-adherent and non-adherent increased after the intervention (p = 0.004).

CONCLUSIONS

Risk of over-activity and HRrest profiled short-term exercise adherence in older adults. If confirmed in a larger and longer study, these could personalize interventions aimed at increasing adherence.

Association of Blood Pressure Responses to Submaximal Exercise in Midlife With the Incidence of Cardiovascular Outcomes and All-Cause Mortality: The Framingham Heart Study

Background

Few studies examined the associations of midlife blood pressure (BP) responses to submaximal exercise with the risk of cardiovascular outcomes and mortality in later life.

Methods and Results

We evaluated 1993 Framingham Offspring Study participants (mean age, 58 years; 53.2% women) attending examination cycle 7. We related BP responses to submaximal exercise with prevalent subclinical cardiovascular disease (CVD) using multivariable linear regression models. We also related BP responses to submaximal exercise to the incidence of hypertension, CVD, and all‐cause mortality using Cox proportional hazards regression models. Each SD increment of exercise BP was associated with higher log‐transformed left ventricular mass (systolic blood pressure [SBP], β=0.02, P=<0.001; diastolic blood pressure [DBP], β=0.01, P=0.004) and carotid intima‐media thickness (SBP, β=0.08, P=<0.001). Rapid BP recovery (per 1 SD increment) was associated with lower log left ventricular mass (SBP_recovery; β=−0.03, P=<0.001) and carotid intima‐media thickness (SBP_recovery, β=−0.07, P=0.003; DBP_recovery, β=−0.09, P=0.003). Additionally, Each SD increment of exercise BP was associated with a higher risk of incident hypertension (SBP, hazard ratio [HR], 1.40; 95% CI, 1.20–1.62; DBP, HR, 1.24; 95% CI, 1.11–1.40) and CVD (DBP, HR, 1.15; 95% CI, 1.02–1.30). Finally, the multivariable‐adjusted HR for each 1‐SD increment of BP recovery was 0.46 (SBP_recovery, 95% CI, 0.38–0.54) and 0.55 (DBP_recovery, 95% CI, 0.45–0.67) for hypertension; 0.80 (SBP_recovery, 95% CI, 0.69–0.93) for CVD; and 0.76 (SBP_recovery, 95% CI, 0.65–0.88) for all‐cause mortality.

Conclusions

Higher submaximal exercise BP and impaired BP recovery after submaximal exercise in midlife may be markers of subclinical and clinical CVD and mortality in later life.

[Measuring physical fitness in the German National Cohort-methods, quality assurance, and first descriptive results]

Physical fitness is defined as an individual's ability to be physically active. The main components are cardiorespiratory fitness (CRF), muscle strength, and flexibility. Regardless of physical activity level, physical fitness is an important determinant of morbidity and mortality.The aim of the current study was to describe the physical fitness assessment methodology in the German National Cohort (NAKO) and to present initial descriptive results in a subsample of the cohort.In the NAKO, hand grip strength (GS) and CRF as physical fitness components were assessed at baseline using a hand dynamometer and a submaximal bicycle ergometer test, respectively. Maximum oxygen uptake (VO_2max) was estimated as a result of the bicycle ergometer test. The results of a total of 99,068 GS measurements and 3094 CRF measurements are based on a data set at halftime of the NAKO baseline survey (age 20-73 years, 47% men).Males showed higher values of physical fitness compared to women (males: GS = 47.8 kg, VO_2max = 36.4 ml·min^-1 · kg^-1; females: GS = 29.9 kg, VO_2max = 32.3 ml · min^-1 · kg^-1). GS declined from the age of 50 onwards, whereas VO_2max levels decreased continuously between the age groups of 20-29 and ≥60 years. GS and VO_2max showed a linear positive association after adjustment for body weight (males β = 0.21; females β = 0.35).These results indicate that the physical fitness measured in the NAKO are comparable to other population-based studies. Future analyses in this study will focus on examining the independent relations of GS and CRF with risk of morbidity and mortality.

The Validity of the YMCA 3-Minute Step Test for Estimating Maximal Oxygen Uptake in Healthy Korean and Vietnamese Adults

Background

Cardiorespiratory fitness (CRF) is a fundamental component of physical fitness. While maximal oxygen uptake (VO₂max) is the gold standard for quantifying CRF, standard maximal exercise tests using direct measurements VO₂max are dependent on the availability of laboratory equipment, and thereby expensive and time consuming. Recently, an equation was formulated to indirectly estimate VO₂max using the YMCA 3-minute step test.

Methods

The study included 15 Korean (KR) and 15 Vietnamese (VN) healthy adults aged 19-35 years. All subjects completed a YMCA 3-minute step test (YMCA 3MST) and a maximal exercise treadmill test to predict VO₂max and VO₂max measures, respectively.

Results

There was a significant relationship between VO₂max predicted from the YMCA 3MST and actual VO₂max measurements from the treadmill test (r = 0.80, p < 0.0001; KR group: r = 0.81, p < 0.0001; VN group: r = 0.93, p < 0.0001). Bland-Altman analysis revealed statistical agreement between tests, although there was a systematic overestimation of 3.36 mL/kg/min for the KR group.

Conclusion

The equation for predicting VO₂max from the YMCA 3MST was validated among the study subjects. However, future research should explore the validity and reliability of the YMCA 3MST equation for estimating VO₂max in other populations.

Cardiorespiratory fitness estimation from heart rate and body movement in daily life

Low cardiorespiratory fitness (CRF) increases risk of all-cause mortality and cardiovascular events. Periodic CRF assessment can have an important preventive function. The objective of this study was to develop a protocol-free method to estimate CRF in daily life based on heart rate (HR) and body acceleration measurements. Acceleration and HR data were collected from 37 subjects (men = 49%) while they performed a standardized laboratory activity protocol (sitting, walking, running, cycling) and during a 5-day free-living monitoring period. CRF was determined by oxygen uptake (V̇o_2max) during maximal exercise testing. A doubly labeled water-validated equation was used to predict total energy expenditure (TEE) from acceleration data. A fitness index was defined as the ratio between TEE and HR (TEE-pulse). Activity recognition techniques were used to process acceleration features and classify sedentary, ambulatory, and other activity types. Regression equations based on TEE-pulse data from each activity type were developed to predict V̇o_2max. TEE-pulse measured within each activity type of the laboratory protocol was highly correlated with V̇o_2max (r from 0.74-0.91). Averaging the outcome of each activity-type specific equation based on TEE-pulse from the laboratory data led to accurate estimates of V̇o_2max [root mean square error (RMSE): 300 mL O₂/min, or 10%]. The difference between laboratory and free-living determined TEE-pulse was 3.7 ± 11% (r = 0.85). The prediction method preserved the prediction accuracy when applied to free-living data (RMSE: 367 mL O₂/min, or 12%). Measurements of body acceleration and HR can be used to predict V̇o_2max in daily life. Activity-specific prediction equations are needed to achieve highly accurate estimates of CRF.NEW & NOTEWORTHY This is among the very few studies validating, in free-living conditions, a method to estimate cardiorespiratory fitness using heart rate and body acceleration data. A novel parameter called TEE-pulse, which was defined as the ratio between accelerometer-determined energy expenditure and heart rate, was highly correlated with maximal oxygen uptake (V̇o_2max). Activity classification and the use of activity-selective prediction equations outperformed previously published methods for estimating V̇o_2max from heart rate and acceleration data.

Identifying poor cardiorespiratory fitness in overweight and obese children and adolescents by using heart rate variability analysis under resting conditions

Background: Childhood obesity, including overweight, continues increasing worldwide affecting health expectancy, quality of life and healthcare expenditure. These subjects have higher probability of suffering or developing cardio metabolic risk factors. Recent studies have revealed cardiorespiratory fitness (CRF) as a valuable clinical parameter to identify these subjects and have even suggested cut-off values. However, evaluating CRF in overweight and obese youth can be difficult to implement, unfriendly and expensive.Objective: Develop a screening tool to identify high-risk subjects in a representative population of those attending overweight/obesity assessment programmes without prior intervention. It will be based on heart rate variability parameters, which has strong association with CRF and cardio metabolic risk factors.Methods: Sixty-three subjects, overweight and obese, between 9 and 17 years of age, and of both sexes were enrolled. None of them had secondary obesity syndromes and/or suffered from acute or chronic disease. Anthropometric parameters, electrocardiogram signal recording under resting conditions and cardiorespiratory fitness - evaluated by oxygen consumption and time elapsed of cardiopulmonary exercise test - were measured.Results: Significant differences in the sympathetic nervous system activity - assessed by heart rate variability analysis - are observed when grouping by overweight and obesity degree as well as by CRF (poor/normal). Body mass index, puberty and sympathetic nervous system activity are the significant variables of a logistic regression model develop to identify poor CRF individuals. Its accuracy reaches 92%.Conclusions: A screening tool based on heart rate variability and anthropometric parameters was developed to identify subjects with higher probability of suffering or developing cardio metabolic risk factors.

Effect of 8-weeks intensive lifestyle intervention on LDL and HDL subfractions

OBJECTIVE

Atherogenic dyslipidemia is a cardinal feature of obesity and the metabolic syndrome, which increases the risk of cardiovascular diseases. Many interventional studies, describing the influence of weight loss on cardiometabolic risks, are bariatric surgery studies. The aim of our study was to analyze the effect of intensive lifestyle changes on LDL- and HDL-cholesterol subfractions and cardiometabolic risk factors in obese subjects.

METHODS

A group of 41 patients with obesity (11M/30F; 44.1±12.4 years; BMI 30.2±6.3kg/m²) participated in an 8-week weight loss interventional program (NCT02325804), consisting of caloric intake reduced by 30% and physical activity (150min/week). Insulin sensitivity was evaluated according to the homeostasis model assessment of insulin resistance (HOMA-IR) and physical fitness was measured using bicycle ergometry. Lipid subfractions were measured using the Lipoprint system (Quantimetrix Corp., CA, USA).

RESULTS

After the intervention, body weight was reduced by 5.4±4.5kg, as well as body fat mass and waist circumference. Physical fitness improved, systolic and diastolic blood pressure as well as heart rate decreased after the intervention. Insulin sensitivity improved after the intervention. Total, LDL, HDL cholesterol, as well as triglycerides decreased after the intervention. Regarding the lipoprotein subfractions, LDL2 and small HDL subfractions decreased, while others have not changed.

CONCLUSION

Eight weeks of diet and physical activity intervention led to weight and fat mass loss and induced improvement of insulin sensitivity, as well as atheroprotective changes of lipid profile. However, the weight loss associated changes in cholesterol subfractions as cardiovascular risk biomarkers deserve further studies.

Validity and Reliability of the New Portable Metabolic Analyzer PNOE

Assessment of the oxygen and carbon dioxide content of expired air during exercise is critical for determining cardiorespiratory status. The purpose of this study was to compare the new portable metabolic analyzer PNOE with COSMED – Quark CPET, a previously validated stationary metabolic cart.

Methods: A total of 22 subjects (17 male and 5 female) aged 32.3 ± 11.1 years took part in the study. Breath by breath gas exchange was measured by both devices during a four-stage incremental protocol on a cycle ergometer. On a separate day, 10 participants repeated the trial to assess the reliability of the PNOE metabolic cart.

Results: Strong correlations were obtained in VO₂ (r = 0.98, p < 0.001), VCO₂ (r = 0.98, p < 0.001), VE (r = 0.98, p < 0.001), and RQ (r = 0.91, p < 0.001), between the two devices. Bland-Altman plots revealed a mean difference of 34.0 ± 118 ml/min and 36.4 ± 110 ml/min in VO₂ and VCO₂ analysis, respectively. There were no significant differences in VO₂, VCO₂, VE, or RQ between the two devices. Intraclass correlation coefficient was high between the two trials for VO₂ (r = 0.98, p < 0.001), VCO₂ (r = 0.98, p < 0.001), VE (r = 0.99, p < 0.001), and RQ (r = 0.93, p < 0.001).

Conclusions: Our data indicate that the portable metabolic cart PNOE can accurately determine respiratory gases over a wide range of exercise intensities, in healthy individuals, in a controlled laboratory setting.

A Combined EEG-fNIRS Study Investigating Mechanisms Underlying the Association between Aerobic Fitness and Inhibitory Control in Young Adults

The current evidence suggests that aerobic fitness is associated with inhibitory control of executive functioning in children and older adults. However, the relative contributions of different neurophysiological mechanisms to this relation remain unclear and have not yet been examined in young adults. The present study aimed to compare inhibitory control between high and low-fit young adult men, and to investigate a possible mediation of fitness effects by conflict monitoring (N450 component of event-related potentials) and lateralized oxygenation difference (LOD) in the DLPFC. For the present cross-sectional study, participants with different physical activity levels were recruited and divided into low-fit and high-fit participants based on relative power on the PWC170. A Stroop Color-Word task was administered and combined EEG-fNIRS was simultaneously utilized to assess the N450 and LOD, because these parameters are linked with behavioral performance. The results of the statistical analysis showed that high-fitcompared to low-fit participants showed less Stroop interference and lower negativity of the N450, whereas no difference was found for LOD. Path-analyses further revealed that the relation between aerobic fitness levels and Stroop interference was indirect and mediated by N450. In contrast, LOD was inversely correlated with Stroop interference, but did not explain the relation of aerobic fitness with behavioral performance. The present findings indicate that greater inhibitory control in high- compared to low-fit young men can be explained by more effective conflict monitoring. Moreover, young adults with left-lateralizedDLPFC oxygenation also show higher inhibitory control, but this oxygenation pattern is not influenced by aerobic fitness.

Quarter-mile walk test sensitive to training-induced fitness changes

BACKGROUND

Cardiorespiratory fitness (CRF) is an important aspect of the overall health of an individual and its monitoring must be promoted in the general population. Thus, the aim of the study was to cross-validate and improve CRF estimation based on quarter-mile Rockport Fitness Walking Test.

METHODS

Thirty participants (31.4±7.99 years) were randomized in either a four-week aerobic training group (10 men and 10 women) or a control group (eight men and two women). CRF was assessed via VO2max test and estimated via quarter-mile Rockport Fitness and Ebbeling treadmill tests, before and after the training intervention. The original quarter-mile Rockport VO2max estimation was found to greatly overestimate CRF by 22 mL/kg/min. When its coefficient was updated according to our data, it largely improved (by 6.8 mL/kg/min). Furthermore, a new algorithm for predicting VO2max was designed using multi-linear regression analysis.

RESULTS

The original quarter-mile Rockport Fitness Walking Test was not sensitive to CRF changes. It showed changes in VO2max, which were significantly different from the actual observed changes (-1.1±4.08 vs. 1.61±2.84, P=0.02, respectively). The Ebbeling treadmill test appeared to systematically overestimate CRF changes. Our new algorithm showed improved sensitivity for detecting CRF changes and stability.

CONCLUSIONS

The original quarter-mile Rockport Fitness Walking Test equation for predicting VO2max was neither accurate nor sensitive to changes in CRF, most likely due to cardiovascular drift. Our new algorithm, based on the same brisk walking test, can provide a more accurate estimate of CRF, which is also sensitive to VO2max changes, in a broad age range (18 to 50 years).

Estimating Maximal Oxygen Uptake From Daily Activity Data Measured by a Watch-Type Fitness Tracker: Cross-Sectional Study

BACKGROUND

Cardiorespiratory fitness (CRF), an important index of physical fitness, is the ability to inhale and provide oxygen to the exercising muscle. However, despite its importance, the current gold standard for measuring CRF is impractical, requiring maximal exercise from the participants.

OBJECTIVE

This study aimed to develop a convenient and practical estimation model for CRF using data collected from daily life with a wristwatch-type device.

METHODS

A total of 191 subjects, aged 20 to 65 years, participated in this study. Maximal oxygen uptake (VO2 max), a standard measure of CRF, was measured with a maximal exercise test. Heart rate (HR) and physical activity data were collected using a commercial wristwatch-type fitness tracker (Fitbit; Fitbit Charge; Fitbit) for 3 consecutive days. Maximal activity energy expenditure (aEEmax) and slope between HR and physical activity were calculated using a linear regression. A VO2 max estimation model was built using multiple linear regression with data on age, sex, height, percent body fat, aEEmax, and the slope. The result was validated with 2 different cross-validation methods.

RESULTS

aEEmax showed a moderate correlation with VO2 max (r=0.50). The correlation coefficient for the multiple linear regression model was 0.81, and the SE of estimate (SEE) was 3.518 mL/kg/min. The regression model was cross-validated through the predicted residual error sum of square (PRESS). The PRESS correlation coefficient was 0.79, and the PRESS SEE was 3.667 mL/kg/min. The model was further validated by dividing it into different subgroups and calculating the constant error (CE) where a low CE showed that the model does not significantly overestimate or underestimate VO2 max.

CONCLUSIONS

This study proposes a CRF estimation method using data collected by a wristwatch-type fitness tracker without any specific protocol for a wide range of the population.

Dose-response effects of high-intensity interval neuromuscular exercise training on weight loss, performance, health and quality of life in inactive obese adults: Study rationale, design and methods of the DoIT trial

Obesity is associated with high mortality and morbidity rates and low levels of quality of life among adults globally. It is critical to examine evidence-based practices for developing lifestyle behavioral changes such as physical movement and structured exercise training. The DoIT protocol, a high-intensity interval exercise training (HIIT) program, effectively reduces body mass, alters energy balance, and improves performance of obese adults with a high adherence rate. This study aims to determine the dose-response effects of the DoIT protocol on body composition, health, performance and quality of life in sedentary obese adults. This study will recruit 88 sedentary, obese males and females (BMI 25.0–34.9; 30–50 years) who will be randomly assigned to one of four groups: (i) control (n = 22), (ii) one session/week (n = 22), (iii) two sessions/week (n = 22) or (iv) three sessions/week (n = 22). DoIT will use a supervised, circuit-type (1–3 rounds), functional/neuromotor and progressive exercise program for 12 months. DoIT incorporates 8–12 multi-planar, fundamental and complex, whole body movements and uses bodyweight and alternative exercise modes as a resistance. DoIT utilizes prescribed work-to-rest ratios which will be varied every four weeks. Each session will last less than 30 min. DoIT will be implemented for a year and its effects on body mass and body composition, physical fitness, functional capacity, bone health, leptin, adiponectin, blood lipids, glycemic control, inflammation, oxidative stress and quality of life will be assessed. The outcomes of the proposed study will provide insight on optimal exercise prescription guidelines for such HIIT-type exercise protocols for overweight or obese individuals.

High-Intensity Interval Training in the Real World: Outcomes from a 12-Month Intervention in Overweight Adults

PURPOSE

Although high-intensity interval training (HIIT) and moderate-intensity continuous exercise have comparable health outcomes in the laboratory setting, effectiveness studies in real-world environments are lacking. The aim of this study was to determine the effectiveness of an unsupervised HIIT program in overweight/obese adults over 12 months.

METHODS

Two hundred and fifty overweight/obese adults could choose HIIT or current exercise guidelines of 30 min·d moderate-intensity exercise. HIIT participants received a single training session and were advised to independently perform HIIT three times per week using a variety of protocols. Mixed models, with a random effect for participant, compared differences in weight, body composition, blood pressure, aerobic fitness, physical activity, and blood indices at 12 months, adjusting for relevant baseline variables.

RESULTS

Forty-two percent (n = 104) of eligible participants chose HIIT in preference to current guidelines. At 12 months, there were no differences between exercise groups in weight (adjusted difference HIIT vs conventional = -0.44 kg; 95% confidence interval [CI] = -2.5 to 1.6) or visceral fat (-103 cm; -256 to 49), although HIIT participants reported greater enjoyment of physical activity (P = 0.01). Evidence of adherence to ≥2 sessions per week of unsupervised HIIT (from HR monitoring) declined from 60.8% at baseline to 19.6% by 12 months. Participants remaining adherent to HIIT over 12 months (23%) were more likely to be male (67% vs 36%, P = 0.03), with greater reductions in weight (-2.7 kg; -5.2 to 0.2) and visceral fat (-292 cm; -483 to -101) than nonadherent participants.

CONCLUSIONS

HIIT was well accepted by overweight adults, and opting for HIIT as an alternative to standard exercise recommendations led to no difference in health outcomes after 12 months. Although regular participation in unsupervised HIIT declined rapidly, those apparently adherent to regular HIIT demonstrated beneficial weight loss and visceral fat reduction.

TRIAL REGISTRATION

Australian New Zealand Clinical Trials Registry (ACTRN12615000010594), retrospectively registered.

Prediction of maximal oxygen consumption using the Young Men's Christian Association-step test in Korean adults

PURPOSE

To develop accurate and practical prediction models of maximal oxygen consumption (VO₂max) using the Young Men's Christian Association (YMCA)-step test in South Korean adults.

METHODS

In total, 568 adults (20-66 years) were included in this study. To develop and cross-validate prediction models of VO₂max, the total sample was divided into 80% training and 20% testing using a simple random sampling method. VO₂max was measured using the maximal-graded exercise treadmill test. Sex, age, 1-min recovery heart rate, body weight, and height were measured as potential predictors. Each test was conducted within a 2- to 3-day interval, ensuring sufficient rest. Preliminary prediction models were developed from training datasets, which were cross-validated using regression analyses and/or repeated-measures analysis of variance. The accuracy of prediction models was evaluated using R², standard error of estimate (SEE), and mean difference (MD) against a criterion-measured VO₂max.

RESULTS

The average age and VO₂max were 43.5 ± 12.9 years and 39.1 ± 7.5 ml/kg/min, respectively. For model development, three practical models with acceptable accuracy were developed (R² = 0.56-0.61; SEE = 4.74-5.01). For model cross-validation, significant relationships between the criterion-measured and predicted VO₂max were observed in all three models (R² = 0.56-0.61; SEE = 4.62-4.88). The difference between criterion-measured and predicted VO₂max was not significant in the models (MD =- 0.03 to - 0.14).

CONCLUSIONS

The prediction models included 3-5 variables as significant predictors of VO₂max and had acceptable accuracy in a large sample of South Korean adults. The selected models provide a simple and practical method to estimate VO₂max using the YMCA-step test for South Korean adults.