Determining Cardiorespiratory Fitness With Precision: Compendium of Findings From the FRIEND Registry

Physical activity, quality of life, and physical fitness of police officers: An exploratory study

BackgroundA high level of physical activity (PAL) is necessary for the safety performance of police officers.ObjectiveTo evaluate the PAL, quality of life (QoL), and cardiorespiratory fitness (CRF) of Civil Police Officers (PO) of Brazil, in association with gender and career time.MethodsWe evaluated 55 PO (50.9% male), with a median age of 40 and a BMI of 25.7 kg/m2. Descriptive analysis and associations with gender and career time (G1: longer/G2: shorter) were carried out. PAL was evaluated by the IPAQ-short version. QoL and CRF were estimated using the WHOQOL and Jackson questionnaires. The chi-square test was used for associations; the odds ratio was calculated with a 95% confidence interval (95%CI) to express the strength of the association.ResultsThere was a proportion of 72.7% (95% CI:69.0-91.0%) of active PO, with a trend for a higher proportion among women and G2 (p = 0.07/0.08), respectively. Only 36.4% of PO (95% CI:24.0-49.0) achieved the minimum CRF required for career entry, with G1 showing a lower proportion than G2 (p < 0.01) and a lower chance of achieving the recommended CRF (OR: 0.03 / 95% CI:0.01-0.17). The median QoL was >70 points in three of the four evaluated domains, with G2 showing higher scores than G1 in the physical domain (p = 0.02).ConclusionMore than two-thirds of the PO assessed achieved the PA recommendations for health, but the majority had a CRF below the recommended. The median QoL was good in 3 of the four WHOQOL domains. Women and those with less carrier time had higher QoL, PAL, and CRF.

A reference equation for peak oxygen uptake for cycle ergometry in Chinese adult participants

Accurately quantifying cardiorespiratory fitness (CRF) through cardiopulmonary exercise testing (CPET) is increasingly important for improving risk assessment and guiding clinical decisions. However, research on V̇O2peak reference values and predictive equations for the Chinese population remains limited. This study aimed to establish a V̇O2peak predictive equation for Chinese adults. This study analyzed healthy participants who underwent CPET at Peking University Third Hospital (PUTH) from September 1, 2017, to September 1, 2023. Data from September 1, 2017, and August 31, 2021 were used as the derivation cohort, and September 1, 2021, to September 1, 2023 were utilized as an external validation cohort for temporal validation. The derivation cohort underwent backward multivariate regression analysis to generate the V̇O2peak prediction equation, which was compared with the widely-used Wasserman, FRIEND and Xiangya equations. The PUTH derivation cohort (N = 4531, mean age: 50.7 years, 18-88 years) and validation cohort (N = 4624, mean age: 46.1 years, 18-89 years) included 48.8 and 48.5% men, respectively. With increasing age, both men and women V̇O2peak exhibited a general decline. The predictive equation for V̇O2peak was established based on the derivation cohort: V̇O2peak (mL·min-1) =  -24364.9 - 621.3 × Sex (Women = 1, Men = 2) -10.7 × Age + 0.2 × Height2 (cm) + 6464.7 × Log(BMI) -24997.2 × Log(BSA) +12388.6 × Log(LBM) (adjusted R2 = 0.624, p < 0.001). It demonstrated higher consistency between measured and predicted results compared to Xiangya, Wasserman, and FRIEND equations. This study presents the PUTH equation, a new V̇O2peak prediction equation for Chinese adults. Compared to existing equations, the PUTH equation shows reduced bias and improved accuracy, providing a more reliable tool for assessing CRF and guiding clinical interventions in the Chinese population.

Transferability of Exercise Intensity Based on Muscle Oxygenation from Normoxia to Hypoxia in Ski-Mountaineering Athletes-Exploratory Study

Frequent changes in altitude and oxygen levels limit the practical application of traditionally derived exercise thresholds or training zones based on heart rate (HR) or blood lactate concentration (bLa). We investigated the transferability of a muscle oxygenation (SmO2)-based intensity prescription between different hypoxic conditions to assess the suitability of real-time SmO2 measurements for ski-mountaineering (SKIMO) athletes during submaximal endurance exercise. A group of 15 well-trained male SKIMO athletes performed a graded-intensity run test in normoxia (87 m ASL, FiO2 = 20.8%) to determine the anaerobic threshold (AnT) with the mod-Dmax method, and maximal lactate steady state (MLSS) assessments in acute normobaric hypoxia (3000 m ASL, FiO2 = 14.4%) with the intensity aligned to 90-105% of SmO2 at the normoxia-determined AnT. SmO2, HR, and bLa were monitored during both tests. The number of MLSS assessments without a bLa increase over 1 mmol·L-1 was reported. Paired t-tests with Cohen's d effect sizes and intraclass correlation coefficient (ICC) were computed to compare the bLa and HR at the AnT in normoxia and MLSS averages in hypoxia, as both corresponded to equivalent SmO2. Out of the 15 MLSS assessments, 11 (73.3%) were performed without a bLa increase over 1 mmol·L-1. Significant differences at equivalent SmO2 in normoxia and hypoxia were found for HR (175 ± 11.7 vs. 160 ± 14.2 bpm, p = 0.005, d = 1.02), but not for bLa (4.9 ± 1.2 vs. 5.1 ± 2.4 mmol·L-1, p = 0.845, d = -0.05). ICC(2,k) for HR and bLa were 0.56 (95% CI: -0.24, 0.85) and 0.40 (95% CI: -0.75, 0.80), respectively. The results indicate a fair transferability of a SmO2-based intensity prescription between different hypoxic conditions in well-trained SKIMO athletes during submaximal endurance exercise. The practical significance of the observations depends on the required accuracy of the exercise intensity determination.

A generalized equation for predicting peak oxygen consumption during treadmill exercise testing: mitigating the bias from total body mass scaling

Background

Indexing peak oxygen uptake (VO2peak) to total body mass can underestimate cardiorespiratory fitness (CRF) in women, older adults, and individuals with obesity. The primary objective of this multicenter study was to derive and validate a body size-independent scaling metric for VO2peak. This metric was termed exercise body mass (EBM).

Method

In a cohort of apparently healthy individuals from the Fitness Registry and the Importance of Exercise National Database, we derived EBM using multivariable log-normal regression analysis. Subsequently, we developed a novel workload (WL) equation based on speed (Sp), fractional grade (fGr), and heart rate reserve (HRR). The generalized equation for VO2peak can be expressed as VO2peak = Cst × EBM × WL, where Cst is a constant representing the VO2peak equivalent of one metabolic equivalent of task. This generalized equation was externally validated using the Stanford exercise testing (SET) dataset.

Results

A total of 5,618 apparently healthy individuals with a respiratory exchange ratio >1.0 (57% men, mean age 44 ± 13 years) were included. The EBM was expressed as Mass (kg)0.63 × Height (m)0.53 × 1.16 (if a man) × exp (-0.39 × 10-4 × age2), which was also approximated using simple sex-specific additive equations. Unlike total body mass, EBM provided body size-independent scaling across both sexes and WL categories. The generalized VO2peak equation was expressed as 11 × EBM × [2 + Sp (in mph) × (1.06 + 5.22 × fGr) + 0.019 × HRR] and had an R 2 of 0.83, p < 0.001. This generalized equation mitigated bias in VO2peak estimations across age, sex, and body mass index subgroups and was validated in the SET registry, achieving an R 2 of 0.84 (p < 0.001).

Conclusions

We derived a generalized equation for measuring VO2peak during treadmill exercise testing using a novel body size-independent scaling metric. This approach significantly reduced biases in CRF estimates across age, sex, and body composition.

Leisure-time physical activity, cardiorespiratory fitness, and cognitive decline in middle-aged and older adults - The ELSA-Brasil study

OBJECTIVES

Dementia is a fast-growing public health problem. This study examined the association of physical activity and estimated cardiorespiratory fitness (eCRF) with the risk of cognitive impairment.

STUDY DESIGN

Multicentric, prospective cohort study.

METHODS

We analyzed 10,121 participants of the ELSA-Brasil study. We assessed leisure-time physical activity using the long version of the IPAQ questionnaire and defined moderate-to-vigorous physical activity (MVPA) per week. We applied a non-exercise prediction equation to estimate eCRF and classified participants as unfit (lowest tertile) and fit. Leisure-time MVPA and eCRF were measured at baseline and follow-up. Incident cognitive impairment was based on memory, language, and executive function assessed at baseline and follow-up.

RESULTS

During a median of 8.1 (7.8-8.5) years of follow-up, we identified 396 (3.9 %) incident cases of cognitive impairment. There was an inverse, non-linear association between the incidence of cognitive impairment and both leisure time MVPA and eCRF. Low eCRF (IRR: 1.29; 95%CI: 1.02, 1.64) and low MVPA (IRR: 1.40; 1.09, 1.82) were independently associated with an increased incidence. Increasing 1 MET in eCRF from baseline to follow-up visit was associated with a lower incidence of cognitive impairment (IRR: 0.80; 95%CI: 0.71, 0.91), while a decrease of 13.7 min per day in leisure time MVPA is associated with an increased incidence (IRR: 1.16; 95%CI: 1.01, 1.33) of cognitive impairment. These associations remained statistically significant in adults under 65 but not in older adults.

CONCLUSION

Low eCRF and leisure time MVPA are strong and independent predictors of incident cognitive impairment especially in middle-aged adults.

Exercise intolerance in patients with chronic coronary syndrome: insights from exercise stress echocardiography

Aims

This study applied exercise stress echocardiography (ESE) to identify risk factors associated with exercise intolerance in patients with chronic coronary syndrome (CCS).

Methods and results

90 CCS patients underwent a cardiopulmonary exercise test and ESE, assessing exercise capacity, left ventricular systolic and diastolic function, and systolic reserve. The patients were divided into two groups according to the percentage of predicted oxygen consumption (VO2) at peak (≥85%, normal exercise tolerance group; <85%, exercise intolerant group). The left ventricular ejection fraction, average mitral valve S', and left ventricular global longitudinal strain were lower in the exercise intolerant group than in the normal group, but no significant differences were observed in myocardial work parameters at rest. The average mitral valve E/e', EDVi/E/e', and proportion of abnormal diastolic function at the peak were higher in the exercise intolerant group than in the normal group. Moreover, the ΔSVi and flow reserve were lower, but the Δaverage mitral valve E/e' was higher in the exercise-intolerant group. From univariate and multivariate logistic regression analysis, only peak EDVi/E/e' and ΔSVi correlated independently with exercise intolerance in CCS patients. With cutoff values of 8.64 ml/m2 for peak EDVi/E/e' and 12.17 ml/m2 for ΔSVi, the combination of these factors had an area under the receiver operating characteristic curve of 0.906 (95% confidence interval, 0.820-0.960) for the prediction of exercise intolerance in CCS patients.

Conclusion

Hemodynamic changes during exercise in CCS patients were effectively evaluated using ESE. An elevated peak EDVi/E/e' and a decreased ΔSVi are independent risk factors for exercise intolerance in patients with CCS.

Cardiorespiratory Fitness Assessment for Exercise Research in Mild Cognitive Impairment Due to Alzheimer's Disease

PURPOSE

To analyze cardiorespiratory fitness (CRF) levels using the gold-standard, laboratory-based cardiopulmonary exercise test (CPET) in community-dwelling older adults (N = 145) with amnestic mild cognitive impairment (aMCI), specifically CPET feasibility, CRF prediction, and CRF status in comparison to published sedentary, cognitively normal, age- and sex-adjusted normative data.

METHOD

Peak oxygen consumption (VO2Peak [mL/kg/min]) was assessed by CPET, which was categorized as submaximal, near-maximal, or maximal tests. VO2Max predicted was compared to VO2Max measured to assess its utility. Data were analyzed with t tests.

RESULTS

Participants' mean age was 73.77 years (SD = 5.74 years), with 51.7% males, 91.7% Caucasian, 68.3% married, and 16.9 years (SD = 2.88 years) of education. Mean VO2Peak measured was 17.07 (SD = 4.92) for the total sample (18.29 [SD = 4.64] for males, 15.78 [SD = 4.91] for females). Sixteen (11.03%) CPETs were submaximal, 53 (36.55%) were near-maximal, and 76 (52.41%) were maximal. Mean VO2Max predicted was 28.59 (SD = 21.94) for the total sample (29.36 [SD = 22.3] for males, 27.76 [SD = 21.68] for females) and was significantly higher than VO2Max measured (p < 0.0001). Among participants with maximal CPETs, VO2Peak measured was significantly lower than sedentary normative data (p < 0.0001).

CONCLUSION

CPET was feasible for older adults with aMCI. VO2Max predicted overly inflates CRF estimates. Low levels of CRF in older adults with aMCI suggest aerobic exercise as an important intervention. [Journal of Gerontological Nursing, 50(9), 31-36.].

Relations Between Cardiorespiratory Fitness and Cognition in Older Adults With Amnestic Mild Cognitive Impairment From the Aerobic Exercise and Cognitive Training (ACT) Trial: Sex Differences

Objective

To examine the associations of cardiorespiratory fitness with executive function, episodic memory, and global cognition and sex differences in these associations in community-dwelling older adults with amnestic mild cognitive impairment.

Design

A cross-sectional study using baseline data from the aerobic exercise and cognitive training (ACT) trial.

Setting

The ACT trial conducted exercise testing in an exercise laboratory and data collections in a research facility.

Participants

ACT trial participants were recruited through referrals, registries, exhibits, flyers, media, and advertisements and screened for eligibility. To be eligible for this study, ACT enrollees needed complete data on all study variables. Among 146 ACT enrollees, 142 met eligibility for this study (N=142).

Interventions

None.

Main Outcome Measures

Cardiorespiratory fitness was measured as peak oxygen consumption (Vo2peak) with a peak cycle-ergometer test, executive function with the EXAMINER, episodic memory with the Brief Visuospatial Memory Test-Revised, and global cognition with Montreal Cognitive Assessment.

Results

The average age of the sample was 73.8±5.8 years with 16.9±2.9 years of education, with 87.3% White, 51.4% men, and 69.7% married. After controlling for covariates, Vo2peak was significantly related to executive function (b=.037, standard error [SE]=0.015, P=.0154, semipartial [sr] correlation coefficient=.239) and episodic memory (b=.590, SE=0.226, P=.0102, sr=.216), but not global cognition (b=.074, SE=0.055, P=.1837, sr=.125). For men, Vo2peak was significantly associated with executive function (b=.063, SE=0.024, P=.0099, r=.430) and episodic memory (b=1.088, SE=0.312, P=.0009, r=.382).

Conclusions

Our findings show that Vo2peak was associated with executive function and episodic memory in the overall sample and in men. Future studies can examine the longitudinal relations between cardiorespiratory fitness and cognition.

Global status of cardiorespiratory fitness and physical activity - Are we improving or getting worse?

Despite heightened recognition of the importance of cardiorespiratory fitness (CRF) to cardiovascular (CV) health, along with updated international consensus guidelines for physical activity (PA) and sedentary behavior (SB), significant proportions of the global adult population are physically inactive, and do not meet the threshold for CRF. Physical inactivity is considered a surrogate for low CRF given that the former is defined as not reaching the recommended minimum level of PA per week to derive a health benefit. Physical inactivity remains a major global public health problem despite decades of work by various United Nations agencies, and members of the international community to improve PA levels. Given the common coupling between physical inactivity and poor health status, it is reasonable to suggest that for a significant proportion of the global population, CRF is compromised by physical inactivity. This poses a longer-term risk to morbidity and mortality. Here we provide an indicative summary of the global status of CRF and PA and reference the implications for global health. We briefly reference opportunities moving forward, including reinforcement of the importance of engaging in movement from an early age, discouraging SB, and taking a life course approach to optimise healthy living for all.

2023 update: The importance of cardiorespiratory fitness in the United States

The American Heart Association issued a Policy Statement in 2013 that characterized the importance of cardiorespiratory fitness (CRF) as an essential marker of health outcomes and specifically the need for increased assessment of CRF. This statement summarized the evidence demonstrating that CRF is "one of the most important correlates of overall health status and a potent predictor of an individual's future risk of cardiovascular disease." Subsequently, this Policy Statement led to the development of a National Registry for CRF (Fitness Registry and the Importance of Exercise: A National Data Base [FRIEND]) which established normative reference values for CRF for adults in the United States (US). This review provides an overview of the progress made in the past decade to further our understanding of the importance of CRF, specifically related to prevention and for clinical populations. Additionally, this review overviews the evolvement and additional uses of FRIEND and summarizes a hierarchy of assessment methods for CRF. In summary, continued efforts are needed to expand the representation of data from across the US, and to include data from pediatric populations, to further develop the CRF Reference Standards for the US as well as further develop Global CRF Reference Standards.

Does COVID-19 impair V̇o2peak in patients with cardiorespiratory disease? Insight from cardiopulmonary responses to maximal exercise pre- and post-illness

Reduced exercise capacity has been suggested as a cardinal sequela of COVID-19. However, only cross-sectional approaches that either do not consider individuals with concomitant cardiorespiratory disease or account for exercise capacity before infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) support this assumption. Is reduced exercise capacity a sequela of SARS-CoV-2 infection in patients with concomitant cardiorespiratory disease? We retrospectively reviewed cardiopulmonary exercise testing (CPET) data collected across three hospitals between October 2018 and March 2022. Forty-two patients who completed a CPET before and after COVID-19 and 25 patients who performed two separate CPETs but did not contract COVID-19 (CTL) were included. Within each patient, the same test protocol was performed at the first and second CPETs. The time between CPETs was similar between the groups (COVID-19 489 ± 534 vs. CTL 534 ± 257 days, P = 0.662). The COVID-19 group performed the CPETs 312 ± 232 days before and 176 ± 110 days after infection. Exercise time, peak heart rate, peak systolic pressure, oxygen uptake (V̇o2) at anaerobic threshold, peak ventilation, and ventilatory efficiency were not different between the CPETs in both groups. Peak V̇o2 was reduced from before to after SARS-CoV-2 infection. However, the change in V̇o2peak from the first to the second CPET was not different between COVID-19 vs. CTL. Accounting for V̇o2peak before COVID-19 and including a group of control patients, we find limited evidence for reduced exercise capacity as a sequela of SARS-CoV-2 infection in patients with concomitant cardiorespiratory disease.NEW & NOTEWORTHY There is accumulating evidence that reduced exercise capacity is, or can be, an outcome following COVID-19. However, evidence to date relies upon cross-sectional approaches that either do not consider patients with concomitant cardiorespiratory disease or account for pre-infection exercise capacity data. Accounting for V̇o2peak before COVID-19 and including a group of control patients, we find limited evidence for reduced exercise capacity as a sequela of SARS-CoV-2 infection in patients with concomitant cardiorespiratory disease.

Estimated standard values of aerobic capacity according to sex and age in a Japanese population: A scoping review

Aerobic capacity is a fitness measure reflecting the ability to sustain whole-body physical activity as fast and long as possible. Identifying the distribution of aerobic capacity in a population may help estimate their health status. This study aimed to estimate standard values of aerobic capacity (peak oxygen uptake [Formula: see text] and anaerobic threshold [AT]/kg) for the Japanese population stratified by sex and age using a meta-analysis. Moreover, the comparison of the estimated standard values of the Japanese with those of other populations was performed as a supplementary analysis. We systematically searched original articles on aerobic capacity in the Japanese population using PubMed, Ichushi-Web, and Google Scholar. We meta-analysed [Formula: see text] (total: 78,714, men: 54,614, women: 24,100) and AT (total: 4,042, men: 1,961, women: 2,081) data of healthy Japanese from 21 articles by sex and age. We also searched, collected and meta-analysed data from other populations. Means and 95% confidence intervals were calculated. The estimated standard values of [Formula: see text] (mL/kg/min) for Japanese men and women aged 4-9, 10-19, 20-29, 30-39, 40-49, 50-59, 60-69, and 70-79 years were 47.6, 51.2, 43.2, 37.2, 34.5, 31.7, 28.6, and 26.3, and 42.0, 43.2, 33.6, 30.6, 27.4, 25.6, 23.4, and 23.1, respectively. The AT/kg (mL/kg/min) for Japanese men and women aged 20-29, 30-39, 40-49, 50-59, 60-69, and 70-79 years were 21.1, 18.3, 16.8, 15.9, 15.8, and 15.2, and 17.4, 17.0, 15.7, 15.0, 14.5, and 14.2, respectively. Herein, we presented the estimated standard values of aerobic capacity according to sex and age in a Japanese population. In conclusion, aerobic capacity declines with ageing after 20-29 years of age. Additionally, aerobic capacity is lower in the Japanese population than in other populations across a wide range of age groups. Standard value estimation by meta-analysis can be conducted in any country or region and for public health purposes.

Associations between cardiovascular risk factors, disease activity and cardiorespiratory fitness in patients with inflammatory joint disease: a cross-sectional analysis

BACKGROUND

Inflammatory joint diseases (IJD) are accompanied by an increased risk of cardiovascular disease (CVD). Cardiorespiratory fitness (CRF) is a modifiable CVD risk factor and low levels of CRF associate with an elevated CVD risk. This study aimed to investigate the associations between CVD risk factors, disease activity and CRF in patients with IJD and to explore differences between patients with normal versus low levels of CRF.

METHODS

CRF was measured as peak oxygen uptake (VO_2peak) with a cardiopulmonary exercise test. Participants were also evaluated for: Body composition, blood pressure, blood lipids, inflammatory markers and disease activity. Patient-reported use of cigarettes/snuff, medication, disease duration, pain, fatigue, CVD history, habitual physical activity and exercise beliefs and self-efficacy were collected by questionnaire. Cross-sectional associations between CVD risk factors, disease-related factors and CRF were analyzed by multiple linear regression. CRF was categorized to normal CRF (VO_2peak ≥ 80%) or low CRF (VO_2peak < 80%) according to age- and gender-stratified reference data. Differences in demographic, CVD and disease-related factors between patients with normal versus low CRF were explored.

RESULTS

In 60 Norwegian patients with IJD [34 females, age 59 years (IQR: 52-63)], mean VO_2peak was 30.2 (± 6.9) mL/kg/min, corresponding to 83% (± 18) of normative reference values. Age (coefficient: - 0.18 years, p = 0.01) and fat mass (coefficient: - 0.67 %, p < 0.001) were inversely associated with CRF, while physical activity index (coefficient: 0.13 points, p = 0.05) was positively associated with CRF (R² = 0.66). There were no significant associations between CRF, classical CVD risk factors and disease-related variables. Compared to patients with low CRF (n = 30), patients with normal CRF (n = 30) had higher peak oxygen uptake (+ 9.4 mL/kg/min, p < 0.001), high-density lipoprotein cholesterol (+ 0.5 mmol L^-1, p < 0.001), and exercise self-efficacy (+ 6.9, p < 0.01) as well as lower fat mass (- 8.7%, p < 0.001), resting heart rate (- 8.0 beats/min, p < 0.01) and triglycerides (- 0.5 mmol L^-1, p < 0.01).

CONCLUSIONS

In this sample of IJD-patients, age, fatmass and physical activity level were associated with CRF. CRF was lower than reference values and patients with normal CRF presented with a more favorable health profile. There is a continued need for exercise interventions to improve CRF in patients with IJD.

TRIAL REGISTRATION

NCT04922840.

Epidemiological, mechanistic, and practical bases for assessment of cardiorespiratory fitness and muscle status in adults in healthcare settings

Given their importance in predicting clinical outcomes, cardiorespiratory fitness (CRF) and muscle status can be considered new vital signs. However, they are not routinely evaluated in healthcare settings. Here, we present a comprehensive review of the epidemiological, mechanistic, and practical bases of the evaluation of CRF and muscle status in adults in primary healthcare settings. We highlight the importance of CRF and muscle status as predictors of morbidity and mortality, focusing on their association with cardiovascular and metabolic outcomes. Notably, adults in the best quartile of CRF and muscle status have as low as one-fourth the risk of developing some of the most common chronic metabolic and cardiovascular diseases than those in the poorest quartile. The physiological mechanisms that underlie these epidemiological associations are addressed. These mechanisms include the fact that both CRF and muscle status reflect an integrative response to the body function. Indeed, muscle plays an active role in the development of many diseases by regulating the body's metabolic rate and releasing myokines, which modulate metabolic and cardiovascular functions. We also go over the most relevant techniques for assessing peak oxygen uptake as a surrogate of CRF and muscle strength, mass, and quality as surrogates of muscle status in adults. Finally, a clinical case of a middle-aged adult is discussed to integrate and summarize the practical aspects of the information presented throughout. Their clinical importance, the ease with which we can assess CRF and muscle status using affordable techniques, and the availability of reference values, justify their routine evaluation in adults across primary healthcare settings.

Longitudinal changes in cardiorespiratory fitness among firefighters based on a fixed 12.0 MET standard and an age-adjusted fitness standard

BACKGROUND

Firefighting is a physically demanding profession. Firefighters (FFs) need adequate physical fitness (PF) to perform duty tasks efficiently. While FFs' work demands are constant throughout their career, there is an expected age-related decline in PF.

OBJECTIVE

To describe longitudinal changes in cardiorespiratory fitness (CRF) based on a fixed (12.0 METs) and an age-adjusted standard and compare the prevalence of fit/unfit firefighters (FFs) over eight years.

METHODS

297 Brazilian male firefighters were randomly selected. CRF was assessed by the 12-minute Cooper test. To compare the prevalence's of fit/unfit FFs depending on the standard (12 METs vs. age-adjusted), the McNemar test was used.

RESULTS

The reduction in the prevalence of fit firefighters was 4.4-fold higher when the analysis did not consider age.

CONCLUSION

After eight years, the prevalence of fit FFs decreased by 30.5% based on the fixed standard, while this reduction was only 7% when using an age-adjusted standard.

A Nonexercise Estimate of Cardiorespiratory Fitness Using a Symptom Questionnaire and Clinical Variables

PURPOSE

Cardiorespiratory fitness (CRF) has recently been recognized as a risk factor for mortality, but it is not routinely measured in clinical settings. The purpose of this study was to assess a nonexercise method to estimate CRF (eCRF) and its association with mortality in a clinically referred population.

METHODS

A symptom tool, termed the Veterans Specific Activity Questionnaire (VSAQ), and nonexercise clinical variables were obtained from 1545 clinically referred subjects (60 ± 13 yr), and followed for a mean of 5.6 ± 4.2 yr. The VSAQ along with nonexercise clinical and historical variables was used to develop a multivariate model to predict achieved CRF from maximal exercise testing. Proportional hazards analysis was used to assess the association between measured and eCRF and all-cause mortality.

RESULTS

The eCRF model was significantly associated with achieved CRF (multiple R= 0.67, P< .001). Mean achieved CRF from maximal treadmill testing and eCRF were similar (8.6 ± 5.0 metabolic equivalents [METs] vs 8.7 ± 4.7 METs respectively, P= .27). Achieved CRF and eCRF performed similarly for predicting mortality. After full adjustment, each 1 MET higher increment in achieved CRF and eCRF was associated with 19% and 26% reductions in mortality risk, respectively. Compared with the lowest fit group (<5 METs), the highest CRF groups (>11 METs) had 88% and 87% lower risks for mortality for achieved CRF and eCRF, respectively.

CONCLUSIONS

A multivariable nonexercise model featuring a symptom questionnaire combined with clinical variables that are readily available during a typical clinical encounter had a reasonably strong association with achieved CRF and exhibited prognostic characteristics that were similar to achieved CRF.

An Evolving Approach to Assessing Cardiorespiratory Fitness, Muscle Function and Bone and Joint Health in the COVID-19 Era

Cardiorespiratory fitness (CRF) is now an established vital sign. CRF, along with muscle function and bone and joint health is related to functional independence and a higher quality of life. Wasserman and colleagues proposed a gear model illustrating the integrated role of the respiratory, cardiovascular, and skeletal muscle systems during aerobic exercise; in 2015, a revision to the original model was proposed. Our understanding of the effects and challenges associated with the coronavirus disease 2019 (COVID-19) are rapidly evolving. Initial evidence indicates higher levels of CRF, and muscle function protect individuals infected with COVID-19 from a complicated medical course. Moreover, for those individuals infected with COVID-19, there are initial signs of a reduction in CRF following the initial phase of recovery. We are also gaining an understanding of long COVID syndrome, where individuals who have recovered from the acute phase of viral infection present with lasting symptoms, which include but are not limited to reduced CRF, shortness of breath, and fatigue. Clearly, these individuals will require rehabilitation to restore and/or improve CRF, muscle function, bone and joint health, functional capacity (ie, the ability to perform activities of daily living), and quality of life. The importance of assessing the synergistic function of systems essential to performing activities that require physical exertion is a health care imperative. This graphical narrative provides an update to the gear model initially proposed by Wasserman and updated to a gear and circuit in 2015. External CRF, muscle function, and bone and joint health influencers and an approach to clinical assessment are also introduced.

Reference Standards for Cardiorespiratory Fitness by Cardiovascular Disease Category and Testing Modality: Data From FRIEND

Background

The importance of cardiorespiratory fitness for stratifying risk and guiding clinical decisions in patients with cardiovascular disease is well‐established. To optimize the clinical value of cardiorespiratory fitness, normative reference standards are essential. The purpose of this report is to extend previous cardiorespiratory fitness normative standards by providing updated cardiorespiratory fitness reference standards according to cardiovascular disease category and testing modality.

Methods and Results

The analysis included 15 045 tests (8079 treadmill, 6966 cycle) from FRIEND (Fitness Registry and the Importance of Exercise National Database). Using data from tests conducted January 1, 1974, through March 1, 2021, percentiles of directly measured peak oxygen consumption (VO_2peak) were determined for each decade from 30 through 89 years of age for men and women with a diagnosis of coronary artery bypass surgery, myocardial infarction, percutaneous coronary intervention, or heart failure. There were significant differences between sex and age groups for VO_2peak (P<0.001). The mean VO_2peak was 23% higher for men compared with women and VO_2peak decreased by a mean of 7% per decade for both sexes. Among each decade, the mean VO_2peak from treadmill tests was 21% higher than the VO_2peak from cycle tests. Differences in VO_2peak were observed among the age groups in both sexes according to cardiovascular disease category.

Conclusions

This report provides normative reference standards by cardiovascular disease category for both men and women performing cardiopulmonary exercise testing on a treadmill or cycle ergometer. These updated and enhanced reference standards can assist with patient risk stratification and guide clinical care.

Cross-Validation of Predictive Equation for Cardiorespiratory Fitness by Modified Shuttle Walk Test in Adults with Schizophrenia: A Secondary Analysis of the CORTEX-SP Study

Cardiorespiratory fitness (CRF) can be direct or estimated from different field tests. The Modified Shuttle Walk Test (MSWT) is suitable for all levels of function, allowing a peak response to be elicited. Therefore, we aimed (1) to validate the equation presented in the original study by Singh et al. for evaluating the relationship between MSWT with peak oxygen uptake (VO_2peak) in adults with schizophrenia (SZ), (2) to develop a new equation for the MSWT to predict VO_2peak, and (3) to validate the new equation. Participants (N = 144, 41.3 ± 10.2 years old) with SZ performed a direct measurement of VO_2peak through a cardiopulmonary exercise test and the MSWT. A new equation incorporating resting heart rate, body mass index, and distance from MSWT (R² = 0.617; adjusted R² = 0.60; p < 0.001) performs better than the Singh et al. equation (R² = 0.57; adjusted R² = 0.57; p < 0.001) to estimate VO_2peak for the studied population. The posteriori cross-validation method confirmed the model’s stability (R² = 0.617 vs. 0.626). The findings of the current study support the validity of the new regression equation incorporating resting heart rate, body mass index, and distance from MSWT to predict VO_2peak for assessment of CRF in people with SZ.

Systematic Review and Regression Modeling of the Effects of Age, Body Size, and Exercise on Cardiovascular Parameters in Healthy Adults

PURPOSE

Blood pressure, cardiac output, and ventricular volumes correlate to various subject features such as age, body size, and exercise intensity. The purpose of this study is to quantify this correlation through regression modeling.

METHODS

We conducted a systematic review to compile reference data of healthy subjects for several cardiovascular parameters and subject features. Regression algorithms used these aggregate data to formulate predictive models for the outputs-systolic and diastolic blood pressure, ventricular volumes, cardiac output, and heart rate-against the features-age, height, weight, and exercise intensity. A simulation-based procedure generated data of virtual subjects to test whether these regression models built using aggregate data can perform well for subject-level predictions and to provide an estimate for the expected error. The blood pressure and heart rate models were also validated using real-world subject-level data.

RESULTS

The direction of trends between model outputs and the input subject features in our study agree with those in current literature.

CONCLUSION

Although other studies observe exponential predictor-output relations, the linear regression algorithms performed the best for the data in this study. The use of subject-level data and more predictors may provide regression models with higher fidelity.

SIGNIFICANCE

Models developed in this study can be useful to clinicians for personalized patient assessment and to researchers for tuning computational models.

Combined use of stress echocardiography and cardiopulmonary exercise testing to assess exercise intolerance in patients treated for acute myocardial infarction

Exercise intolerance after acute myocardial infarction (AMI) is a predictor of worse prognosis, but its causes are complex and poorly studied. This study assessed the determinants of exercise intolerance using combined stress echocardiography and cardiopulmonary exercise testing (CPET-SE) in patients treated for AMI. We prospectively enrolled patients with left ventricular ejection fraction (LV EF) ≥40% for more than 4 weeks after the first AMI. Stroke volume, heart rate, and arteriovenous oxygen difference (A-VO2Diff) were assessed during symptom-limited CPET-SE. Patients were divided into four groups according to the percentage of predicted oxygen uptake (VO2) (Group 1, <50%; Group 2, 50-74%; Group 3, 75-99%; and Group 4, ≥100%). Among 81 patients (70% male, mean age 58 ± 11 years, 47% ST-segment elevation AMI) mean peak VO2 was 19.5 ± 5.4 mL/kg/min. A better exercise capacity was related to a higher percent predicted heart rate (Group 2 vs. Group 4, p <0.01), higher peak A-VO2Diff (Group 1 vs. Group 3, p <0.01) but without differences in stroke volume. Peak VO2 and percent predicted VO2 had a significant positive correlation with percent predicted heart rate at peak exercise (r = 0.28, p = 0.01 and r = 0.46, p < 0.001) and peak A-VO2Diff (r = 0.68, p <0.001 and r = 0.36, p = 0.001) but not with peak stroke volume. Exercise capacity in patients treated for AMI with LV EF ≥40% is related to heart rate response during exercise and peak peripheral oxygen extraction. CPET-SE enables non-invasive assessment of the mechanisms of exercise intolerance.

Two-minute exercise testing is sufficient to estimate maximal cardiorespiratory fitness in people with epilepsy

We aimed to examine the agreement between submaximal cardiopulmonary exercise testing (CPET) measures and peak oxygen consumption (VO_2peak) in adults with epilepsy. Data from a randomized controlled trial with adults with epilepsy (N = 21) were analyzed. VO_2peak was assessed using indirect calorimetry during a treadmill graded maximal CPET. Oxygen uptake efficiency slope (OUES) was calculated from the relationship between oxygen uptake and minute ventilation during the entire test (OUES_peak) and the first 2 (OUES_2min), 3 (OUES_3min), and 4 (OUES_4min) minutes of the CPET. The strength of the association between measures was tested by Pearson correlation. Linear regression models were used to predict VO_2peak based on OUES from the different testing durations. Agreement between measured and predicted maximal values was tested using intraclass correlation coefficient (ICC) and Bland-Altman plots. OUES_2min, OUES_3min, and OUES_4min were highly associated with absolute (r = 0.84, r = 0.76, r = 0.75, respectively) and relative (r = 0.84, r = 0.78, r = 0.78, respectively) VO_2peak. Agreement (ICC = 0.83) between CPET-measured and OUES-predicted VO_2peak values was stronger with OUES_2min than the other time-based OUES markers. Bland-Altman plot showed satisfactory agreement between predicted and measured CPET measures with the narrowest limits of agreement observed with the OUES_2min. No potential bias was identified between these two measurements (p = 0.33). Changes in absolute (r = 0.77) and relative (r = 0.88) VO₂peak were highly associated with the change in OUES_2min. OUES_2min can be used as a surrogate for maximal cardiorespiratory fitness in adults with epilepsy. Studies with larger samples size are encouraged to confirm our findings in a more heterogeneous population.

Peak oxygen pulse and mortality risk in healthy women and men: The Ball State Adult Fitness Longitudinal Lifestyle Study (BALL ST)

Peak oxygen pulse (O₂ pulse_peak) may have predictive utility for health outcomes yet, presently, has only been examined in men and only using a single baseline measure.

PURPOSE

The primary aim of this investigation was to evaluate the relationship between O₂ pulse_peak and all-cause mortality in apparently healthy women and men. A secondary aim was to explore the relationship between longitudinal changes to O₂ pulse_peak and mortality.

METHODS

The sample included 3877 participants (43% women) for the primary aim and 759 participants (32% women) who performed two cardiopulmonary exercise tests ≥1 year apart for the secondary aim. Cox proportional hazard models were performed to determine the relationship between O₂ pulse_peak and mortality. Prognostic peak oxygen consumption (VO_2peak) and O₂ pulse_peak models were compared using the concordance index and Akaike information criterion (AIC).

RESULTS

In the assessment from baseline, there were 730 deaths over a 24.7 ± 11.8 year follow-up period. For men, a single measure of O₂ pulse_peak was inversely associated with risk for mortality (P < 0.05). However, the concordance index and AIC indicated lower discrimination compared to VO_2peak models and O₂ pulse_peak did not provide complementary benefit to VO_2peak models. For women, O₂ pulse_peak was not associated with mortality risk. In the longitudinal analysis, there were 168 deaths over a follow-up of 20.1 ± 11.4 years. Changes to O₂ pulse_peak were not significantly related to mortality in either sex.

CONCLUSIONS

Within an apparently healthy cohort, a single assessment of O₂ pulse_peak is related to all-cause mortality in men but not women. Further, longitudinal changes to O₂ pulse_peak are not predictive of mortality in either sex. These findings suggest O₂ pulse_peak may have limited prognostic utility in healthy individuals, particularly within healthy women.

The V˙E/V˙co2 Slope During Maximal Treadmill Cardiopulmonary Exercise Testing: REFERENCE STANDARDS FROM FRIEND (FITNESS REGISTRY AND THE IMPORTANCE OF EXERCISE: A NATIONAL DATABASE)

PURPOSE

Cardiopulmonary exercise testing (CPX) is the gold standard approach for the assessment of cardiorespiratory fitness (CRF). The primary aim of the current study was to determine reference standards for the minute ventilation/carbon dioxide production (V˙E/V˙co2) slope in a cohort from the "Fitness Registry and the Importance of Exercise: A National Database" (FRIEND) Registry.

METHODS

The current analysis included 2512 tests from 10 CPX laboratories in the United States. Inclusion criteria included CPX data on apparently healthy men and women: (1) age ≥20 yr; and (2) with a symptom-limited exercise test performed on a treadmill. Ventilation and V˙co2 data, from the initiation of exercise to peak, were used to calculate the V˙E/V˙co2 slope via least-squares linear regression. Reference values were determined for men and women by decade of life.

RESULTS

On average, V˙E/V˙co2 slope values were lower in men and increased with age independent of sex. Fiftieth percentile values increased from 27.1 in the second decade to 33.9 in the eighth decade in men and from 28.5 in the second decade to 33.7 in the eighth decade in women. In the overall group, correlations with baseline characteristics and the V˙E/V˙co2 slope were statistically significant (P < .05) although generally weak, particularly for age and body mass index.

CONCLUSION

The results of the current study establish reference values for the V˙E/V˙co2 slope when treadmill testing is performed, and all exercise data are used for the slope calculation. These results may prove useful in enhancing the interpretation of CPX results when assessing CRF.

Peak Oxygen Consumption Achieved at the End of Cardiac Rehabilitation Predicts Long-Term Survival in Patients with Coronary Heart Disease

BACKGROUND

Cardiac rehabilitation (CR) improves survival in patients with coronary heart disease (CHD), which is largely mediated by the improvements in cardiorespiratory fitness (CRF) defined as peak oxygen consumption (VO2). Therefore, measuring CRF is essential to predict long-term outcomes in this population. It is unclear, however, whether peak VO2 achieved at the end of CR (END-peak VO2) predicts survival or whether the changes of CRF achieved during CR provide a greater prognostic value.

OBJECTIVES

To determine whether END-peak VO2 independently predicts long-term survival in patients with CHD undergoing CR. We also aimed at identifying cut-offs for END-peak VO2 that could be used in clinical practice.

METHODS

Retrospective analysis of 853 patients with CHD referred to CR who completed a maximal cardiopulmonary exercise test. Survival analysis was performed to examine the risk of all-cause mortality (average follow-up years: 6.65) based on peak VO2. The Contal and O'Quigley's method was used to determine the optimal cutoff of END-peak VO2 based on the log-rank statistic.

RESULTS

END-peak VO2 was inversely associated with mortality risk (hazard ratio [HR]=0.84; 95% CI = 0.78-0.90), independent of changes in peak VO2 adjusted for the baseline peak VO2. The estimated cutoff of end-peak VO2 at ≥ 17.6 mL/kg/min best predicted the survival with high predictive accuracy and patients with END-peak VO2 under the cutoff had a greater risk of mortality (HR = 2.93; 95% CI = 1.81-4.74).

CONCLUSIONS

In patient with CHD undergoing CR, END-peak VO2 is an independent predictor for long-term survival. Studies utilizing higher intensity CR programs, with and without pharmacologic strategies, to increase peak VO2 to a greater degree in those achieving a suboptimal END-peak VO2, are urgently needed.

Novel CPET Reference Values in Healthy Adults: Associations with Physical Activity

PURPOSE

Cardiopulmonary exercise testing (CPET) is an important measurement in clinical practice, and its primary outcome, maximal oxygen uptake (V˙O2peak), is inversely associated with morbidity and mortality. The purposes of this study are to provide CPET reference values for maximal and submaximal parameters across the adult age spectrum of a healthy European cohort, to compare V˙O2peak values with other reference data sets, and to analyze the associations between physical activity (PA) levels and CPET parameters.

METHODS

In this cross-sectional study, we prospectively recruited 502 participants (47% female) from 20 to 90 yr old. The subjects performed a CPET on a cycle ergometer using a ramp protocol. PA was objectively and continuously measured over 14 d using a triaxial accelerometer. Quantile curves were calculated for CPET parameters. To investigate the associations between CPET parameters and PA levels, linear regression analysis was performed.

RESULTS

V˙O2peak values observed in the group of 20-29 yr were 46.6 ± 7.9 and 39.3 ± 6.5 mL·kg⋅min for males and females, respectively. On average, each age category (10-yr increments) showed a 10% lower V˙O2peak relative to the next younger age category. V˙O2peak values of previous studies were on average 7.5 mL·kg⋅min (20%) lower for males and 6.5 mL·kg⋅min (21%) lower for females. There was strong evidence supporting a positive association between the V˙O2peak (mL·kg⋅min) and the level of habitual PA performed at vigorous PA (estimate, 0.26; P < 0.001].

CONCLUSION

Maximal and submaximal CPET reference values over a large age range are novel, and differences to other studies are clinically highly relevant. Objectively measured vigorous-intensity PA showed a strong positive association with higher V˙O2peak and other performance-related CPET parameters, supporting the implementation of higher-intensity aerobic exercise in health promotion.

Healthy Vascular Aging Is Associated With Higher Cardiorespiratory Fitness

BACKGROUND

Healthy vascular aging (HVA) and cardiorespiratory fitness (CRF) are each independently associated with lower cardiovascular disease-related mortality. It is unknown, however, whether the CRF-related reductions in cardiovascular disease risk are related to HVA. We hypothesized that HVA would be associated with higher CRF in men and women from the Ball State Adult Fitness Longitudinal Lifestyle STudy (BALL ST).

METHODS

Apparently healthy men and women ≥50 yr of age from the BALL ST cohort (n = 101) who underwent a maximal cardiopulmonary exercise test to assess CRF (V˙O2peak) were included in the study. Participants were divided into either HVA, defined as brachial systolic blood pressure <140/90 mm Hg without taking medications and carotid-femoral pulse wave velocity <7.6 m/sec, or no HVA for subjects with SBP >140/90 mm Hg and/or PWV >7.6 m/sec.

RESULTS

Participants with HVA had a higher age- and sex-adjusted CRF percentile (62 ± 5 vs 47 ± 3, P < .05), with women having a greater prevalence of HVA than men (36% vs 15%, P < .05). Both carotid-femoral pulse wave velocity (r =-0.27, P < .05) and brachial systolic blood pressure (r =-0.23, P < .05) were independently and inversely associated with CRF for the entire cohort. Men and women with HVA were younger having a lower body fat percentage and higher low-density lipoprotein cholesterol (P < .05, all).

CONCLUSIONS

These data demonstrate that HVA is associated with higher CRF, which may partially explain the preventative cardioprotective effects of CRF.

VO2max-Based Physical Fitness Categories in a Brazilian Population with Supposed High Socioeconomic Status and without Structural Heart Disease

Fundamento

Os dados mais utilizados como referência de aptidão cardiorrespiratória (ACR) são os de Cooper, que utiliza valores calculados de captação máxima de oxigênio (VO₂máx).

Objetivo

Desenvolver valores de ACR a partir do teste cardiopulmonar de exercício (TCPE) em uma população brasileira com alto nível socioeconômico e livre de cardiopatia estrutural. Os resultados dos testes de VO₂max foram comparados aos dados de Cooper e do FRIEND Registry.

Métodos

Foram utilizados neste estudo dados de TCPE de indivíduos consecutivos entre 1º de janeiro de 2000 e 31 de maio de 2016. Os critérios de inclusão foram: VO₂máx pré-definido. Foi construído um gráfico de ACR de acordo com os percentuais do VO₂máx: muito ruim (≤20%), ruim (20-40%), regular (40-60%), boa (60-80%), excelente (80-90%), e superior (≥90%). A correlação Kappa foi usada para analisar nossos dados em comparação aos dados dos outros dois bancos de dados. Os testes estatísticos com p<0,005 foram considerados significativos.

Resultados

A coorte final incluiu 18.186 testes: 12.552 homens, 5.634 mulheres (7 a 84 anos). A resposta mais recorrente foi “boa” (20,2%). Houve diferença média de peso, altura, índice de massa corporal (IMC) e idade no gráfico da ACR. Houve correlação inversa entre VO₂máx e idade, peso e IMC. Usando uma regressão linear e essas variáveis, uma equação preditiva foi desenvolvida para o VO₂máx. Nossas descobertas diferiram das dos outros bancos de dados.

Conclusão

Desenvolvemos uma classificação para a ACR e encontramos valores mais altos em todas as faixas de classificação de capacidade funcional, em contraste com os dados de Cooper e do FRIEND Registry. Nossos achados oferecem uma interpretação mais precisa da ACR nessa grande amostra populacional brasileira, quando comparados aos padrões anteriores, com base no VO₂máx estimado. (Arq Bras Cardiol. 2020; 115(3):468-477)

Validation of FRIEND and ACSM Equations for Cardiorespiratory Fitness: Comparison to Direct Measurement in CAD Patients

The regression equation of the American College of Sports Medicine (ACSM) was a preferred method for estimating maximal oxygen consumption (VO2max). Recently, a more precise equation from the fitness registry and the importance of exercise national database (FRIEND) for healthy people was developed. This study compared VO2max estimated by the ACSM and FRIEND equations to VO2max directly measured in coronary artery disease (CAD) patients. Overall, 293 CAD patients who participated in cardiac rehabilitation between June 2015 and December 2018 were analyzed. Directly measured VO2max values were compared to the ACSM and FRIEND equations. The directly measured VO2max was significantly different from the estimated VO2max by ACSM equation (24.16 vs. 28.7 mL/kg/min, p < 0.001), which was overestimated by 20% in men and 16% in women. However, there was no statistically significant difference between the directly measured VO2max and the estimated VO2max by the FRIEND equation. (24.16 vs. 24.15 mL/kg/min, p = 0.986). In CAD patients, the estimated VO2max from the ACSM equation was significantly higher than the directly measured VO2max. In addition, estimated cardiorespiratory fitness (CRF) by the FRIEND equation showed similar results with directly measured CRF. As a result, the FRIEND equation can predict CRF more accurately than the ACSM.

Cardiorespiratory Fitness, Physical Activity, Sedentary Time and Its Association with the Atherogenic Index of Plasma in Chilean Adults: Influence of the Waist Circumference to Height Ratio

Atherogenic index of plasma (AIP) is a novel biomarker related to cardiovascular disease (CVD). Cardiorespiratory fitness (CRF) and physical activity (PA) have an inverse relationship with the AIP, while sedentary time (ST) and fatness present a positive association. This study aimed to determine the combined and independent association of CRF, PA, and ST with the AIP, and additionally to establish the waist-to-height ratio (WHtR) mediation role. Data from the Chilean national health survey were used (4671 adults). A PACS (Physical Activity Cardiorespiratory Sedentary) score was created ranging from 0 to 3, indicating the number of positive recommendations met (PA, ST, and CRF). AIP was calculated (Log10 triglycerides/high-density lipoprotein-cholesterol). The combined analysis showed that compared to those with a PACS score of 0, those with a score of 1 or 2 did not present significantly reduced AIP values (adjusted by the WHtR); however, those with a score of 3 did (OR (odds ratio) = 0.50; 95% CI, 0.32 to 0.77; p < 0.001). Independent analysis showed that CRF seems to be the only variable that supports the combined result (β = -0.212; p < 0.001). Finally, the mediation analysis indicated that the WHtR mediated the association between CRF and the AIP in 34.2% of cases. Overall, only CRF had a significant and inverse association with the AIP. Nonetheless, around one-third of this beneficial relationship is affected by an elevated WHtR.

Changes in cardiorespiratory fitness through adolescence predict metabolic syndrome in young adults

BACKGROUND AND AIMS

Higher cardiorespiratory fitness (CRF) has been suggested to reduce the risk of metabolic syndrome (MetS). We aimed to longitudinally examine the changes of CRF on MetS and its risk factors from adolescence to adulthood.

METHODS AND RESULTS

At the age of 15 years, 1076 subjects were recruited from 2 cohorts. CRF was measured on a cycle ergometer. MetS was classified as having at least 3 of the following parameters above the threshold of risk factors: waist circumference, triglycerides, high-density lipoprotein cholesterol (HDL), high blood pressure (BP) and fasting glucose. In addition, insulin, total cholesterol and low-density lipoprotein cholesterol were measured and homeostasis model assessment of insulin resistance (HOMA-IR) was calculated. Persistently high, increasing, decreasing and persistently low CRF groups were formed according to change in CRF from adolescence to adulthood. Longitudinal increase in CRF was positively associated with change in HDL and negatively associated with change in insulin, HOMA-IR, triglycerides, BP and prevalence of MetS after adjustment for potential confounders. Subjects with persistently low CRF had 11.5- to 34.4-times higher risk of MetS at the age of 25 and 33 years compared to subjects with persistently high CRF and 14.6- to 15.9-times higher risk compared to the increasing CRF group.

CONCLUSION

Higher CRF is strongly related to lower values of MetS risk factors. Increasing CRF from adolescence to adulthood reduces the risk to have MetS later in adulthood. High CRF in adolescence that decreases during adulthood has similar risks to MetS compared to individuals with persistently low CRF.

[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.

Reference values for aerobic capacity estimated by cardiopulmonary exercise test on a cycle ergometer in a healthy Greek population

OBJECTIVE

Aerobic capacity (AC) is inversely associated with a high risk of cardiovascular morbidity and mortality as well as all-cause mortality. Cardiopulmonary exercise testing (CPET) represents the gold standard for assessing exercise capacity based on maximum oxygen uptake (VO₂max). The purpose of our study was to provide for the first time CPET-derived normative reference values in a Greek cohort of apparently healthy men and women on a cycle ergometer to evaluate their AC, and to compare our results with similar studies from other countries.

METHODS

A cohort of 194 apparently healthy subjects (118 males and 76 females, age range, 15-69 years) was submitted to CPET using a cycle ergometer. Mean ± SD values for several exercise parameters, VO₂max included, were determined. We compared our results with existing data derived from USA and North Europe cohorts.

RESULTS

Male subjects achieved significantly higher levels of relative and absolute VO₂max (p < 0.001) across all ages compared to female subjects. A decline in relative and absolute VO₂max among older participants was observed in both sexes. Greek subjects had lower AC than the North Europe cohort and almost similar to the USA cohort.

CONCLUSION

We provide the first reference data for AC in apparently healthy Greek subjects based on CPET using cycle ergometer. Our findings will allow for more accurate interpretation of CPET in several groups of healthy subjects or patients with CV diseases. The differences found between our reference values and those reported from the USA and northern European countries, underscore the need for individual countries to develop their own AC reference values.

[Reference Values for Cardiorespiratory Fitness of the General Population: The German National Health Interview and Examination Survey for Adults (DEGS1) 2008-2011]

AIM OF STUDY

This study aims to provide population-based reference values for heart rate-based indicators of cardiorespiratory fitness for adults with physical activity readiness aged 18 to 64 years living in Germany.

METHODS

Based on data on 2,826 individuals who participated in a submaximal cycle ergometer exercise test as part of the German National Health Interview and Examination Survey for Adults (DEGS1) between 2008 and 2011, we calculated the following indicators: physical working capacity at 150 and 130 beats/min and at 75% of estimated maximum heart rate (PWC150, PWC130 and PWC75%) as well as heart rate-based estimated maximum oxygen uptake (VO₂max). We used the LMS method by Cole & Green 1992 to calculate reference values.

RESULTS

25^th, 50^th and 75^th percentiles of PWC150 were 1.5, 1.77 and 2.08 watts/kg among men and 1.18, 1.44 and 1.69 among women. 25^th, 50^th and 75^th percentiles of PWC130 were 1.16, 1.41 and 1.68 watts/kg among men and 0.81, 1.05 and 1.29 among women. Age-dependent median PWC75% values among men and women were 1.87 - age in years× 0.01 and 1.31 - (age in years/100)²× 0.98, respectively, and VO₂max among men is 41.7 - age× 0.15.

CONCLUSIONS

The references values presented can be used for individual rating of cardiorespiratory fitness among adults living in Germany. Furthermore, they can serve as a basis for regular monitoring purposes.

Hemodynamic Changes During Physiological and Pharmacological Stress Testing in Healthy Subjects, Aortic Stenosis and Aortic Coarctation Patients-A Systematic Review and Meta-Analysis

Introduction: Exercise testing has become a diagnostic standard in the evaluation and management of heart disease. While different methods of exercise and pharmacological stress testing exist, only little is known about their comparability. We aimed to assess hemodynamic changes during dynamic exercise, isometric exercise, and dobutamine stress testing at different stress intensities in healthy subjects and patients with aortic stenosis (AS) and aortic coarctation (CoA).

Methods: A systematic literature search (PROSPERO 2017:CRD42017078608) in MEDLINE of interventional trials was conducted to identify eligible studies providing evidence of changes in hemodynamic parameters under different stress conditions acquired by MRI or echocardiography. A random effects model was used to estimate pooled mean changes in hemodynamics.

Results: One hundred and twenty-eight study arms with a total of 3,139 stress-examinations were included. In healthy subjects/(where available) in AS, pooled mean changes (95% CIs) during light dynamic stress were 31.78 (27.82–35.74) bpm in heart rate (HR) and 6.59 (2.58–10.61) ml in stroke volume (SV). Changes during light pharmacological stress were 13.71 (7.87–19.56)/14.0 (9.82–18.18) bpm in HR, and 5.47 (0.3–10.63)/8.0 (3.82–12.18) ml in SV. Changes during light isometric stress were 18.44 (10.74–26.14)/5.0 (−1.17–11.17) bpm in HR and −4.17 (−14.37–6.03)/−4.0 (−16.43–8.43) ml in SV. Changes during moderate dynamic stress were 49.57 (40.03–59.1)/46.45 (42.63–50.27) bpm in HR and 11.64 (5.87–17.42) ml in SV. During moderate pharmacological stress, changes in HR were 42.83 (36.94–48.72)/18.66 (2.38–34.93) bpm and in SV 6.29 (−2.0–14.58)/13.11 (7.99–18.23) ml. During high intensity dynamic stress changes in HR were 89.31 (81.46–97.17)/55.32 (47.31–63.33) bpm and in SV 21.31 (13.42–29.21)/−0.96 (−5.27–3.35) ml. During high pharmacological stress, changes in HR were 53.58 (36.53–70.64)/42.52 (32.77–52.28) bpm, and in SV 0.98 (−9.32–11.27)/14.06 (−1.62–29.74) ml. HR increase and age were inversely correlated at high stress intensities. In CoA, evidence was limited to single studies.

Conclusion: This systematic review and meta-analysis presents pooled hemodynamic changes under light, moderate and high intensity exercise and pharmacological stress, while considering the potential influence of age. Despite limited availability of comparative studies, the reference values presented in this review allow estimation of the expected individual range of a circulatory response in healthy individuals and patients with AS and may contribute to future study planning and patient-specific models even when stress testing is contraindicated.

Personal Activity Intelligence (PAI): A new standard in activity tracking for obtaining a healthy cardiorespiratory fitness level and low cardiovascular risk

Despite all the evidence of health benefits related to physical activity (PA) and cardiorespiratory fitness (CRF), low levels of PA have reached pandemic proportions, and inactivity is the fourth leading cause of death worldwide. Lack of time, and inability to self-manage are often cited as main barriers to getting adequate PA. Recently, a new personalized metric for PA tracking named Personal Activity Intelligence (PAI) was developed with the aim to make it easier to quantify how much PA per week is needed to reduce the risk of premature mortality from non-communicable diseases. PAI can be integrated in self-assessment heart rate devices and defines a weekly beneficial heart rate pattern during PA by considering the individual's sex, age, and resting and maximal heart rates. Among individuals ranging from the general population to subgroups of patients with cardiovascular disease (CVD), a PAI score ≥100 per week at baseline, an increase in PAI score, and a sustained high PAI score over time were found to delay premature death from CVD and all causes, regardless of whether or not the current PA recommendations were met. Importantly, a PAI score ≥100 at baseline, maintaining ≥100 PAIs and an increasing PAI score over time was associated with multiple years of life gained. Moreover, obtaining a weekly PAI ≥100 attenuated the deleterious association between CVD risk factor clustering and prolonged sitting time. PAI and objectively measured CRF (as indicated by VO_2peak) were positively associated in a graded fashion, and individuals with a PAI score between 100 and 150 had expected age and sex specific average VO_2peak values. A PAI score ≥100 was associated with higher VO_2peak in both men (4.1 mL·kg^-1·min^-1; 95% CI, 3.5 to 4.6) and women (2.9 mL·kg^-1·min^-1; 95% CI, 2.4 to 3.3), compared to the reference group of <100 PAI. The combined analysis of PAI, PA and VO_2peak demonstrated that a PAI score ≥100 was associated with high VO_2peak values regardless of meeting or not meeting the current PA recommendations. Collectively, these findings suggest that PAI has the potential to be a useful tool to motivate people to become and stay physically active by quantifying the amount of PA needed to produce significant health benefits.

Cardiorespiratory fitness and cardiovascular disease - The past, present, and future

The importance of cardiorespiratory fitness (CRF) is now well established and it is increasingly being recognized as an essential variable which should be assessed in health screenings. The key findings that have established the clinical significance of CRF are reviewed in this report, along with an overview of the current relevance of exercise as a form of medicine that can provide a number of positive health outcomes, including increasing CRF. Current assessment options for assessing CRF are also reviewed, including the direct measurement via cardiopulmonary exercise testing which now can be interpreted with age and sex-specific reference values. Future directions for the use of CRF and related measures are presented.