Accuracy of Exercise-based Equations for Estimating Cardiorespiratory Fitness

Measuring Cardiorespiratory Fitness without Exercise Testing: The Development and Validation of a New Tool for Spanish Adults

Background: Cardiorespiratory fitness (CRF) is an important component of overall physical fitness and is associated with numerous health benefits, including a reduced risk of heart disease, diabetes, and obesity. However, direct measurement of CRF is time-consuming and therefore not feasible for screening purposes. Methods: A maximal treadmill exercise test with the Bruce protocol was performed to estimate VO2max in 1047 Spanish men and women aged 17 to 62 years. Weight, height, and heart rate were measured. Leisure-time physical activity (LTPA) was recorded using the Minnesota Leisure Time Physical Activity Questionnaire. A multiple linear regression model was developed to predict exercise-based VO2max. The validity of the model was examined by correlation, concordance, Bland-Altman analysis, cross-validation, and construct validity analysis. Results: There was no significant difference between VO2max obtained by the Bruce protocol (43.56 mL/kg/min) or predicted by the equation (43.59 mL/kg/min), with R2 of 0.57, and a standard error of the estimate of 7.59 mL/kg/min. Pearson's product-moment correlation and Lin's concordance correlation between measured and predicted CRF values were 0.75 and 0.72, respectively. Bland-Altman analysis revealed a significant proportional bias of non-exercise eCRF, overestimating unfit and underestimating highly fit individuals. However, 64.3% of participants were correctly classified into CRF tertile categories, with an important 69.9% in the unfit category. Conclusions: The eCRF equation was associated with several cardiovascular risk factors in the anticipated directions, indicating good construct validity. In conclusion, the non-exercise eCRF showed a reasonable validity to estimate true VO2max, and it may be a useful tool for screening CRF.

Change in Peak Oxygen Uptake Predicted by the Moderate 1-km Treadmill Walking Test After Walking Training in Outpatients With Cardiovascular Disease

PURPOSE

The purpose of this study was to determine the ability of the moderate 1-km treadmill walking test (1km-TWT) to predict changes in peak oxygen uptake (V˙O 2peak ) in patients with stable cardiovascular disease (CVD) during an exercise-based secondary prevention program.

METHODS

Sixty-four male outpatients with stable CVD (age 64 [41-85] yr) performed the 1km-TWT before and after an 8-wk walking training program. Patient V˙O 2peak was estimated using a sex-specific equation including age, body mass index, 1km-TWT performance time, and heart rate (V˙O 2peakEST ). Forty-one patients completed a maximal cardiopulmonary treadmill test (CPX) for direct V˙O 2peak determination (V˙O 2peakMEAS ). The training prescription consisted of moderate-to-high intensity supervised walking for 30-40 min/session, and an additional 2-4 times/wk of unsupervised home moderate walking sessions between 20-60 min at the end of the program. The walking intensity was based on the results of the 1km-TWT.

RESULTS

Patients participated in an average of 14 of the 16 supervised sessions. An overall significant improvement in V˙O 2peakMEAS and weekly recreational physical activity levels were observed. No differences were observed between V˙O 2peakMEAS and V˙O 2peakEST . Compared with CPX results, the 1km-TWT underestimated the V˙O 2peak increase after the exercise intervention (mean difference -0.3 mL/kg/min, P > .05).

CONCLUSIONS

The 1km-TWT provides a reasonably accurate and simple tool to predict changes in V˙O 2peak due to moderate walking training in male outpatients with CVD. These findings contribute to the growing body of evidence supporting the use of the 1km-TWT for exercise testing and training purposes in the context of cardiac rehabilitation/secondary prevention programs.

Association between the triglyceride-glucose index and impaired cardiovascular fitness in non-diabetic young population

BACKGROUND

The triglyceride-glucose (TyG) index has been linked to the onset, progression, and prognosis of cardiovascular disease (CVD) in middle-aged and elderly individuals. Nevertheless, the relationship between the TyG index and impaired cardiovascular fitness (CVF) remains unexplored in non-diabetic young population.

METHODS

We used data from the National Health and Nutrition Examination Survey (NHANES) study (1999-2004) to conduct a cross-sectional study of 3364 participants who completed an examination of CVF. Impaired CVF was defined as low and moderate CVF levels determined by estimated maximal oxygen consumption (Vo2max), based on sex- and age-specific criteria. The TyG index was calculated by [Formula: see text].

RESULTS

The age (median with interquartile range) of the study population was 28 (19-37) years, and the TyG index (median ± standard deviation) was 8.36 ± 0.52. A significant association between the TyG index and impaired CVF was found in multivariable logistical regression analysis (per 1-unit increase in the TyG index: OR, 1.46; 95% Cl 1.13-1.90). A dose‒response relationship between the TyG index and impaired CVF was presented by restricted cubic splines (RCS). A significant interaction (p = 0.027) between sex and the TyG index for impaired CVF was found in the population aged < 20 years.

CONCLUSIONS

In non-diabetic young population, individuals with higher TyG index values are at an increased likelihood of encountering impaired CVF. Furthermore, sex may exert an impact on CVF, as males tend to be more susceptible to impaired CVF under comparable TyG index conditions.

Reference Values for Cardiorespiratory Fitness in Patients Aged 6 to 18 Years

OBJECTIVE

To develop reference values for cardiorespiratory fitness, as quantified by peak oxygen uptake (VO2peak) and treadmill time, in patients aged 6 through 18 years referred for cardiopulmonary exercise testing (CPET).

STUDY DESIGN

We reviewed a clinical pediatric CPET database for fitness data in children aged 6-18 years with no underlying heart disease. CPET was obtained via the Bruce protocol utilizing objectively confirmed maximal effort via respiratory exchange ratio. Fitness data (VO2peak and treadmill test duration) were analyzed to determine age- and sex-specific reference values for this pediatric cohort.

RESULTS

Data from 2025 pediatric CPETs (53.2% female) were included in the analyses. VO2peak increased with age in males, but not females. Treadmill test duration increased with age in both males and females. Fitness was generally higher in males when compared with females in the same age groups.

CONCLUSIONS

Our study provides extensive reference values for both VO2peak and total treadmill test time via the Bruce protocol for a pediatric population without known cardiac disease. Furthermore, the inclusion of objectively confirmed maximal exercise effort increases confidence in these findings compared with prior studies in this area. Clinicians performing CPET in pediatric populations can utilize these reference values to characterize test results according to representative peer data.

Cardiorespiratory fitness as a vital sign of CVD risk in the COVID-19 era

The severe health consequences of the corona virus disease 2019 (COVID-19) pandemic have been exacerbated by the prevalence of cardiovascular disease (CVD) risk factors, such as physical inactivity, obesity, hypertension, and diabetes. Further, policy decisions during the pandemic augmented unhealthy lifestyle behaviors and health inequalities, likely increasing the global disease burden. Cardiorespiratory fitness (CRF) is a well-established biomarker associated with CVD risk. Emerging data demonstrate that high CRF offers some protection against severe outcomes from COVID-19 infection, highlighting the importance of CRF for population health and the potential for limiting the severity of future pandemics. CRF is best assessed by cardiopulmonary exercise testing (CPET), which will be an important tool for understanding the prolonged pathophysiology of COVID-19, the emergence of long-COVID, and the lasting effects of COVID-19 on CVD risk. Utilization of CRF and CPET within clinical settings should become commonplace because of lessons learned from the COVID-19 pandemic.

Cardiorespiratory Optimal Point Is a Submaximal Exercise Test Variable and a Predictor of Mortality Risk: THE BALL STATE ADULT FITNESS LONGITUDINAL LIFESTYLE STUDY (BALL ST)

PURPOSE

The cardiorespiratory optimal point (COP) is the minimum ventilatory equivalent for oxygen. The COP can be determined during a submaximal incremental exercise test. Reflecting the optimal interaction between the respiratory and cardiovascular systems, COP may have prognostic utility. The aim of this investigation was to determine the relationship between COP and all-cause mortality in a cohort of apparently healthy adults.

METHODS

The sample included 3160 apparently healthy adults (46% females) with a mean age of 44.0 ± 12.5 yr who performed a cardiopulmonary exercise test. Cox proportional hazards models were performed to assess the relationship between COP and mortality risk. Prognostic peak oxygen uptake (V˙ o2peak ) and COP models were compared using the concordance index.

RESULTS

There were 558 deaths (31% females) over a follow-up period of 23.0 ± 11.9 yr. For males, all Cox proportional hazards models, including the model adjusted for traditional risk factors and V˙ o2peak , had a positive association with risk for mortality ( P < .05). For females, only the unadjusted COP model was associated with risk for mortality ( P < .05). The concordance index values indicated that unadjusted COP models had lower discrimination compared with unadjusted V˙ o2peak models ( P < .05) and V˙ o2peak did not complement COP models ( P ≥ .13).

CONCLUSIONS

Cardiorespiratory optimal point is related to all-cause mortality in males but not females. These findings suggest that a determination of COP can have prognostic utility in apparently healthy males aged 18-85 yr, which may be relevant when a maximal exercise test is not feasible or desirable.

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.

Cardiorespiratory fitness estimations and their ability to predict all-cause mortality in patients with cardiovascular disease

Background

In cardiac rehabilitation programs, cardiorespiratory fitness is commonly estimated (eCRF) from the maximum workload achieved on a graded exercise test. This study compared four well-established eCRF equations in their ability to predict mortality in patients with cardiovascular disease (CVD).

Methods

A total of 7269 individuals with CVD were studied (81% male; age 59.4 ± 10.3yr). eCRF was calculated using equations from the American College of Sports Medicine, Bruce et al., the Fitness Registry and the Importance of Exercise International Database, and McConnell and Clark. The eCRF from each equation was compared with a RMANOVA. Cox proportional hazard models assessed the relationship between the eCRF equations and mortality risk. The predictive ability of the models was compared using the concordance index.

Results

There were 284 deaths (85% male) over a follow-up period of 5.8 ± 2.8yr. Although differences in eCRF were observed between each equation (P < 0.05), the eCRF from each of the four equations was predictive of mortality (P < 0.05). The concordance index values for each of the models were the same (0.77) indicating similar predictive performance.

Conclusions

The four well-established eCRF equations did not differ in their ability to predict mortality in patients with CVD, indicating any could be used for this purpose. However, the differences in eCRF from each of the equations suggest potential differences in their ability to guide clinical care and should be the focus of future research.

Updating Framingham CVD risk score using waist circumference and estimated cardiopulmonary function: a cohort study based on a southern Xinjiang population

Purpose

To explore the association between waist circumference (WC), estimated cardiopulmonary function (eCRF), and cardiovascular disease (CVD) risk in southern Xinjiang. Update the Framingham model to make it more suitable for the southern Xinjiang population.

Methods

Data were collected from 7705 subjects aged 30–74 years old in Tumushuke City, the 51st Regiment of Xinjiang Production and Construction Corps. CVD was defined as an individual's first diagnosis of non-fatal acute myocardial infarction, death from coronary heart disease, and fatal or non-fatal stroke. The Cox proportional hazards regression analysis was used to analyze the association between WC, eCRF and CVD risk. Restricted cubic spline plots were drawn to describe the association of the two indicators with CVD risk. We update the model by incorporating the new variables into the Framingham model and re-estimating the coefficients. The discrimination of the model is evaluated using AUC, NRI, and IDI metrics. Model calibration is evaluated using pseudo R² values.

Results

WC was an independent risk factor for CVD (multivariate HR: 1.603 (1.323, 1.942)), eCRF was an independent protective factor for CVD (multivariate HR: 0.499 (0.369, 0.674)). There was a nonlinear relationship between WC and CVD risk (nonlinear χ2 = 12.43, P = 0.002). There was a linear association between eCRF and CVD risk (non-linear χ2 = 0.27, P = 0.6027). In the male, the best risk prediction effect was obtained when WC and eCRF were added to the model (AUC = 0.763((0.734,0.792)); pseudo R² = 0.069). In the female, the best risk prediction effect was obtained by adding eCRF to the model (AUC = 0.757 (0.734,0.779); pseudo R² = 0.107).

Conclusion

In southern Xinjiang, WC is an independent risk factor for CVD. eCRF is an independent protective factor for CVD. We recommended adding WC and eCRF in the male model and only eCRF in the female model for better risk prediction.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12889-022-14110-y.

Submaximal Testing to Estimate Aerobic Capacity Using a Matrix C5x Stepmill

The primary purpose of this study was to determine if the Matrix C5x stepmill’s preprogrammed submaximal test is able to accurately predict maximal oxygen uptake. Sixteen participants completed a maximal treadmill test and a preprogrammed submaximal test on a Matrix C5x stepmill. Oxygen uptake was measured using a Cosmed K5 during both tests. Maximal oxygen uptake (VO_2max) was calculated from submaximal data using a multi-stage calculation and compared against measured VO_2max from the maximal test and estimated VO_2max from the submaximal stepmill test. METs were also measured during the submaximal test and compared to the METs estimated by the stepmill and METs calculated using submaximal stepping equations. Measured VO_2max (39.18 α 6.6 ml^.kg^-1.min^-1) was significantly higher (p < 0.001) than estimated VO_2max (28.06 α 3.2 ml^.kg^-1.min^-1) and calculated VO_2max (35.58 α 8.0 ml^.kg^-1.min^-1). Measured METs were significantly (p = 0.04) higher than estimated METs in all stages, and higher than calculated METs in stage 1 of the submaximal test. The C5x did not provide accurate estimations of METs or maximal oxygen uptake. Calculating maximal oxygen uptake from submaximal stepmill data may provide an alternative, although development of a new equation may be warranted.

Estimating Cardiorespiratory Fitness Without Exercise Testing or Physical Activity Status in Healthy Adults: Regression Model Development and Validation

Background

Low cardiorespiratory fitness (CRF) is an independent predictor of morbidity and mortality. Most health care settings use some type of electronic health record (EHR) system. However, many EHRs do not have CRF or physical activity data collected, thereby limiting the types of investigations and analyses that can be done.

Objective

This study aims to develop a nonexercise equation to estimate and classify CRF (in metabolic equivalent tasks) using variables commonly available in EHRs.

Methods

Participants were 42,676 healthy adults (female participants: n=9146, 21.4%) from the Aerobics Center Longitudinal Study examined from 1974 to 2005. The nonexercise estimated CRF was based on sex, age, measured BMI, measured resting heart rate, measured resting blood pressure, and smoking status. A maximal treadmill test measured CRF.

Results

After conducting nonlinear feature augmentation, separate linear regression models were used for male and female participants to calculate correlation and regression coefficients. Cross-classification of actual and estimated CRF was performed using low CRF categories (lowest quintile, lowest quartile, and lowest tertile). The multiple correlation coefficient (R) was 0.70 (mean deviation 1.33) for male participants and 0.65 (mean deviation 1.23) for female participants. The models explained 48.4% (SE estimate 1.70) and 41.9% (SE estimate 1.56) of the variance in CRF for male and female participants, respectively. Correct category classification for low CRF (lowest tertile) was found in 77.2% (n=25,885) of male participants and 74.9% (n=6,850) of female participants.

Conclusions

The regression models developed in this study provided useful estimation and classification of CRF in a large population of male and female participants. The models may provide a practical method for estimating CRF derived from EHRs for population health research.

Cardiac Rehabilitation and Risk of Incident Atrial Fibrillation in Patients with Coronary Artery Disease

BACKGROUND

Patients with coronary artery disease (CAD) are at risk for developing atrial fibrillation (AF). Whether attending a cardiac rehabilitation (CR) program can attenuate this risk is unclear.

METHODS

This retrospective cohort study included patients who were free of pre-existing AF and referred to CR after coronary revascularization between April 2004 and March 2015 in Calgary, Canada. Patients with incident AF were identified using administrative data and the local electrocardiogram repository. Exposure variables and covariates were extracted from electronic medical records of a CR program and a clinical registry.

RESULTS

The study included 11,662 patients [mean age (standard deviation), 60.9 (10.9) years; male, 80.6%]. In a median follow-up of 4.8 years, the cumulative incidence rate of AF was 1.04 per 100 person-years. There was no association between CR completion and the risk of incident AF after adjusting for baseline characteristics [Hazard ratio (HR): 0.97; 95% confidence interval (CI): 0.83-1.15]. However, each higher metabolic equivalent (MET) of baseline cardiorespiratory fitness (CRF) and each MET gain in CRF following CR were independently associated with a 12% (95% CI: 6%-18%) and 18% (95% CI: 6%-28%) lower relative risk of incident AF, respectively. The risk of incident AF declined progressively with the baseline CRF increasing up to 9.0 peak METs, and with the 12-week CRF increasing up to 10.3 peak METs; beyond these peak MET levels, benefits plateaued.

CONCLUSIONS

CR completion alone was not associated with a lower risk of incident AF. However, higher baseline CRF and greater CRF improvement had dose-dependent protective effects.

Current state of unhealthy living characteristics in White, African American and Latinx populations

The United States (US) is similar to most industrialized countries in that it falls short on many of the basic metrics related to cardiovascular and overall health. These metrics include nutritional patterns, levels of physical activity (PA), cardiorespiratory fitness (CRF), and prevalence of overweight and obesity. These issues are even more apparent in underserved communities, among whom unhealthy living characteristics cluster and contribute to a disproportionate chronic disease burden. The reasons for these inequities are complex and include social and economic factors as well as reduced access to health care. CRF has been demonstrated to be a critically important risk factor that tends to be lower in disadvantaged groups. In this article we discuss the current state of health & lifestyle characteristics in the US, the impact of social inequality on health, and the particular role that CRF and PA patterns play in the current state of unhealthy living characteristics as they relate to underserved populations.

Updated Reference Standards for Cardiorespiratory Fitness Measured with Cardiopulmonary Exercise Testing: Data from the Fitness Registry and the Importance of Exercise National Database (FRIEND)

OBJECTIVE

To provide updated reference standards for cardiorespiratory fitness (CRF) for the United States derived from cardiopulmonary exercise (CPX) testing when using a treadmill or cycle ergometer.

PATIENTS AND METHODS

Thirty-four laboratories in the United States contributed data to the Fitness Registry and the Importance of Exercise National Database. Analysis included 22,379 tests (16,278 treadmill and 6101 cycle ergometer) conducted between January 1, 1968, through March 31, 2021, from apparently healthy adults (aged 20 to 89 years). Percentiles of peak oxygen consumption for men and women were determined for each decade from 20 through 89 years of age for treadmill and cycle exercise modes, as well as when defining maximal effort as respiratory exchange ratio (RER) greater than or equal to 1.0 or RER greater than or equal to 1.1.

RESULTS

For both men and women, the 50^th percentile scores for each exercise mode decreased with age and were higher in men across all age groups and higher for treadmill compared with cycle CPX. The average rate of decline per decade over a 6-decade period was 13.5%, 4.0 mLO₂·kg^-1·min^-1 for treadmill CPX and 16.4%, 4.3 mLO₂·kg^-1·min^-1 for cycle CPX. Observationally, the mean peak oxygen consumption was similar whether using an RER criterion of greater than or equal to 1.0 or greater than or equal to 1.1 across the different test modes, ages, and for both sexes. The updated reference standards for treadmill CPX were 1.5 - 4.6 mLO₂·kg^-1·min^-1 lower compared with the previous 2015 standards whereas the updated cycling standards were generally comparable to the original 2017 standards.

CONCLUSION

These updated cardiorespiratory fitness reference standards improve the representativeness of the US population compared with the original standards.

Accuracy of exercise-based tests for estimating cardiorespiratory fitness and muscle strength in early-stage breast cancer survivors in Japan

PURPOSE

We aimed to examine whether cardiorespiratory fitness and leg strength can be estimated based on their relationship with physical performance tests in Japanese breast cancer survivors.

METHODS

Participants were 50 sedentary women aged 20 to 59 years who have received breast surgery in the past 2 to 13 months after diagnosis of invasive breast cancer (stage I-IIa). Cardiorespiratory fitness and leg strength were measured by peak oxygen consumption (VO₂peak), and one-repetition maximum for leg press (leg press 1RM). Physical performance tests were performed 6-min walk test, chair stand test, and grip strength. Using multiple regression analysis, we developed prediction equations for VO₂peak and leg strength based on their associations with the physical performance tests. The validity of the estimation equations was assessed using Bland-Altman plots.

RESULTS

Mean age, VO₂peak, and leg press 1RM were 48 ± 6 years, 25.0 ± 3.6 mL/kg/min, and 95 ± 32 kg, respectively. Multiple regression analysis yielded 6-min walk test distance, age, height, and body weight as predictors of VO₂peak. Measured VO₂peak and predicted VO₂peak showed a moderate positive correlation (r = 0.463, p < 0.001). Chair stand test, grip strength, age, height, and body weight were selected as predictors of leg press 1RM. There was a strong positive correlation between predicted and measured leg press 1RM (r = 0.754, p < 0.001).

CONCLUSION

The results suggest that leg strength can be predicted using physical performance tests. However, further examination may be needed to determine whether cardiorespiratory fitness can be predicted based on 6-min walk test.

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.

The importance of healthy lifestyle behaviors in the prevention of cardiovascular disease

Cardiovascular disease (CVD) is the leading cause of death globally. Advancements in the treatment of CVD have reduced mortality rates, yet the global burden of CVD remains high. Considering that CVD is still largely a preventable disease, prioritizing preventative measures through healthy lifestyle (HL) behaviors is necessary to lessen the burden of CVD. HL behaviors, such as regular exercise, healthy eating habits, adequate sleep, and smoking cessation, can influence a number of traditional CVD risk factors as well as a less commonly measured risk factor, cardiorespiratory fitness (CRF). It is important to note that cardiac rehabilitation programs, which traditionally have focused on secondary prevention, also emphasize the importance of making comprehensive HL behavior changes. This review discusses preventative measures to reduce the burden of CVD through an increased uptake and assessment of HL behaviors. An overview of the importance of CRF as a risk factor is discussed along with how to improve CRF and other risk factors through HL behavior interventions. The role of the clinician for promoting HL behaviors to prevent CVD is also reviewed.

Evaluation of Latent Models Assessing Physical Fitness and the Healthy Eating Index in Community Studies: Time-, Sex-, and Diabetes-Status Invariance

Accurate measurement requires assessment of measurement equivalence/invariance (ME/I) to demonstrate that the tests/measurements perform equally well and measure the same underlying constructs across groups and over time. Using structural equation modeling, the measurement properties (stability and responsiveness) of intervention measures used in a study of metabolic syndrome (MetS) treatment in primary care offices, were assessed. The primary study (N = 293; mean age = 59 years) had achieved 19% reversal of MetS overall; yet neither diet quality nor aerobic capacity were correlated with declines in cardiovascular disease risk. Factor analytic methods were used to develop measurement models and factorial invariance were tested across three time points (baseline, 3-month, 12-month), sex (male/female), and diabetes status for the Canadian Healthy Eating Index (2005 HEI-C) and several fitness measures combined (percentile VO₂ max from submaximal exercise, treadmill speed, curl-ups, push-ups). The model fit for the original HEI-C was poor and could account for the lack of associations in the primary study. A reduced HEI-C and a 4-item fitness model demonstrated excellent model fit and measurement equivalence across time, sex, and diabetes status. Increased use of factor analytic methods increases measurement precision, controls error, and improves ability to link interventions to expected clinical outcomes.

Accuracy of Non-Exercise Estimated Cardiorespiratory Fitness in Japanese Adults

Cardiorespiratory fitness (CRF) is an independent predictor of morbidity and mortality. In Japan, annual physical exams are mandatory in workplace settings, and most healthcare settings have electronic medical records (EMRs). However, in both settings, CRF is not usually determined, thereby limiting the potential for epidemiological investigations using EMR data. PURPOSE: To estimate CRF (mL/kg/min) using variables commonly recorded in EMRs. METHODS: Participants were 5293 Japanese adults (11.7% women) who completed an annual physical exam at a large gas company in Tokyo, Japan, in 2004. The mean age was 48.3 ± 8.0 years. Estimated CRF (eCRF) was based on age, measured body mass index, resting heart rate, systolic and diastolic blood pressure, and smoking. Measured CRF was determined by a submaximal cycle ergometer graded exercise test. RESULTS: Regression models were used for males and females to calculate Pearson’s correlation and regression coefficients. Cross-classification of measured CRF and eCRF was conducted using the lowest quintile, quartile, and tertile as the unfit categories. R’s for eCRF were 0.61 (MD 4.41) for men and 0.64 (MD 4.22) for women. The overall accuracy level was reasonable and consistent across models, yet the unfit lower tertile model provided the best overall model when considering the positive predictive value and sensitivity. CONCLUSION: eCRF may provide a useful method for conducting investigations using data derived from EMRs or datasets devoid of CRF or physical activity measures.

Effects of Individualized Low-Intensity Exercise and Its Duration on Recovery Ability in Adults

Exercise is recommended to increase physical health and performance. However, it is unclear how low-intensity exercise (LIE) of different durations may affect or improve recovery ability. This study aimed to investigate how LIE-duration with the same volume affects recovery ability in adults. Twenty healthy male adults participated in this study. Participants were randomly assigned to the 30-min (n = 10) or the 1-h LIE group (n = 10). The intervention included sixteen exercise sessions/four weeks with a 30-min LIE group, and eight exercise sessions/four weeks with a 1-h LIE group. Heart rate (HR) corresponding to <2 mmol∙L^-1 blood lactate (La^-) was controlled for LIE. Pre- and post-testing was conducted before and after 4-week LIE and tests included jogging/running speed (S), HR, and differences (delta; ∆) in HR and S between pre- and post-testing at 1.5, 2.0, and 4.0 mmol∙L^-1 La^-. Only the HR at 2.0 mmol∙L^-1 La^- of the 30-min LIE group was decreased in the post-test compared to the pre-test (p = 0.043). The jogging/running speed of the 1-h LIE group was improved in the post-test compared to the pre-test (p < 0.001, p = 0.006, p = 0.002, respectively). ∆HR at 2.0 and ∆S between the 30-min and 1-h LIE group at 1.5, 2.0, and 4.0 mmol∙L^-1 La^- were significantly different (p = 0.023, p < 0.001, p = 0.002, and p = 0.019, respectively). Furthermore, moderate to high positive correlations between ∆HR and ∆S of all subjects at 1.5 (r = 0.77), 2.0 (r = 0.77), and 4.0 (r = 0.64) mmol∙L^-1 La^- were observed. The 1-h LIE group showed improved endurance not only in the low-intensity exercise domain, but also in the beginning of the moderate to high-intensity exercise domain while the 30-min LIE group was not affected by the 4-week LIE intervention. Therefore, LIE (<2.0 mmol∙L^-1) for at least 1-h, twice a week, for 4 weeks is suggested to improve recovery ability in adults.

Trends in cardiorespiratory fitness among apparently healthy adults from the Ball State Adult Fitness Longitudinal Lifestyle STudy (BALL ST) cohort from 1970-2019

Introduction

Cardiorespiratory fitness (CRF) is a strong independent predictor of cardiovascular disease (CVD) and CVD mortality. However, little is known in regards to how CRF has trended in apparently healthy adults over the past several decades.

Purpose

To analyze trends in CRF and CVD risk factors over the last 50 years in a population of apparently healthy adult men and women.

Methods

Participants were 4,214 apparently healthy adults (2,390 men and 1,824 women) from the Ball State Adult Fitness Longitudinal Lifestyle STudy (BALL ST) that performed maximal cardiopulmonary exercise testing between 1970–2019 for the assessment of CRF defined as VO_2max (ml/kg/min). Participants were self-referred either to a community-based exercise program, fitness testing, or were research subjects in exercise related studies and were placed into groups by decade based on testing date.

Results

CRF showed a general trend to decline (P<0.05) from the 1970s to the 2000s with an increase (P<0.05) from the 2000s to the 2010s for both men and women. This pattern persisted for age and sex-adjusted CRF level, determined by Fitness Registry and the Importance of Exercise: A National Data Base (FRIEND). For both women and men, CRF across the decades was associated (P<0.05) with the prevalence of physical inactivity, smoking, obesity, dyslipidemia and hypertension, and with diabetes in men only.

Conclusion

CRF declined from 1970 through the 2000s in a cohort of apparently healthy men and women which was associated with worsening CVD risk profiles. However, the decline in CRF was attenuated over the past decade which may have a positive impact on future CVD in the population. Promoting physical activity to increase CRF should be a primary aspect of CVD prevention programs.