Assessing cardiorespiratory fitness in clinical and community settings: Lessons and advancements in the 100th year anniversary of VO2max

Cardiorespiratory fitness (CRF) is a well-established biomarker that has applications to all adults across the health and disease spectrum. Despite overwhelming evidence supporting the prognostic utility of CRF, it remains vastly underutilized. CRF is optimally measured via cardiopulmonary exercise testing which may not be feasible to implement on a large scale. Therefore, it is prudent to develop ways to accurately estimate CRF that can be applied in clinical and community settings. As such, several prediction equations incorporating non-exercise information that is readily available from routine clinical encounters have been developed that provide an adequate reflection of CRF that could be implemented to raise awareness of the importance of CRF. Further, technological advances in smartphone apps and consumer-grade wearables have demonstrated promise to provide reasonable estimates of CRF that are widely available, which could enhance the utilization of CRF in both clinical and community settings.

Non-exercise estimated cardiorespiratory fitness and cancer incidence: The NIH-AARP diet and health study

BACKGROUND

Non-exercise estimated cardiorespiratory fitness (NEE-CRF) has been shown to be associated with mortality, although its association with cancer incidence is unknown. The study aimed to assess the prospective association between NEE-CRF and cancer incidence in a large cohort of men and women.

METHODS

The National Institutes of Health-American Association of Retired Persons diet and health study is a prospective cohort that included 402,548 participants aged 50-71 years who were free from cancer at baseline (1995-1996) (men (n = 238,835) and women (n = 163,713)) and were followed until December 31, 2015. The exposure variable was NEE-CRF expressed in metabolic equivalents. NEE-CRF was estimated using a validated equation of self-reported predictors on demographics and lifestyle behaviors derived from baseline questionnaires. Primary outcomes were total cancer incidence and incidence of prostate, breast, lung, and colorectal cancers. Cox proportional hazards models were analyzed for the association between NEE-CRF and cancer incidence outcomes adjusted for established cancer risk factors.

RESULTS

During 13.7 ± 3.2 years of follow-up (mean ± SD), 64,344 men and 31,315 women developed a new cancer. For every 1-metabolic equivalent higher NEE-CRF, the hazard ratios and 95% confidence intervals (95%CIs) were 0.96 (95%CI: 0.94-0.97) and 0.88 (95%CI: 0.84-0.92) of total and colorectal cancer incidence among men, and 0.95 (95%CI: 0.93-0.97) and 0.94 (95%CI: 0.91-0.97) of total and breast cancer incidence among women, respectively (all p < 0.001). NEE-CRF was not associated with incidence of prostate and lung cancers in men or colorectal and lung cancers in women.

CONCLUSION

These results suggest that higher CRF levels, as assessed by the applied non-exercise estimated method, may provide preventive benefits against the development of cancer, while low CRF could potentially serve as a modifiable cancer risk factor. Integrating NEE-CRF into screening paradigms and referring low-fit individuals to improve CRF could complement the public health prevention strategy against cancer.

Pilates-mat training and detraining: Effects on body composition and physical fitness in pilates-trained women

INTRODUCTION

Pilates-mat is an effective training method to enhance several physiological and fitness parameters, although the effects of pilates-mat detraining on body composition and physical fitness remains largely unknown. The purpose of the study was to investigate the effect of pilates-mat training and detraining on body composition and physical fitness in pilates-trained females.

METHODS

Twenty females (age: 45.1 ± 8.7 years) followed an 8-week pilates-mat training program followed by a 3-week detraining period. Measurements performed at the beginning of the training intervention, at the end of the 8-week training program and at the end of the 3-week detraining period and included: anthropometric characteristics, body composition analysis, thigh, hip and waist circumferences, blood pressure, heart rate at rest (HRr), maximum handgrip strength, abdominal curls, lower body flexibility and aerobic capacity.

RESULTS

Pilates-mat training significantly decreased body fat percentage (BF%), visceral fat and HRr (p < 0.05) but these variables returned to baseline after detraining. Trunk fat, thigh and waist circumferences decreased significantly after training and remained significantly low following detraining (p < 0.05). Abdominal curls, lower body flexibility and aerobic capacity increased significantly following pilates-mat training and remained unchanged after detraining (p < 0.05).

CONCLUSIONS

These results suggest that 8 weeks of pilates-mat training enhanced body composition and physical fitness and these physiological and physical fitness benefits were remained unaltered during the 3-week of pilates-mat detraining period. However, BF% and visceral fat returned to baseline levels following the detraining period suggesting that for maintaining the reduction in BF% and visceral fat a long-period of pilates-mat detraining should be avoided.

Physiological, Anatomical and Metabolic Correlates of Aerobic Fitness in Human Primary Motor Cortex: A Multimodal Study

Physical activity (PA) has been shown to benefit various cognitive functions and promote neuroplasticity. Whereas the effects of PA on brain anatomy and function have been well documented in older individuals, data are scarce in young adults. Whether high levels of cardiorespiratory fitness (CRF) achieved through regular PA are associated with significant structural and functional changes in this age group remains largely unknown. In the present study, twenty young adults that engaged in at least 8 hours per week of aerobic exercise during the last 5 years were compared to twenty sedentary controls on measures of cortical excitability, white matter microstructure, cortical thickness and metabolite concentration. All measures were taken in the left primary motor cortex and CRF was assessed with VO_2max. Transcranial magnetic stimulation (TMS) revealed higher corticospinal excitability in high- compared to low-fit individuals reflected by greater input/output curve amplitude and slope. No group differences were found for other TMS (short-interval intracortical inhibition and intracortical facilitation), diffusion MRI (fractional anisotropy and apparent fiber density), structural MRI (cortical thickness) and magnetic resonance spectroscopy (NAA, GABA, Glx) measures. Taken together, the present data suggest that brain changes associated with increased CRF are relatively limited, at least in primary motor cortex, in contrast to what has been observed in older adults.

Elaboration of a French version of the Duke Activity Status Index questionnaire and performance to predict functional capacity

BACKGROUND

Guidelines recommend detecting poor functional capacity (VO_2max < 14 ml.kg^-1.min^-1) to assess preoperative cardiac risk. This screening is performed via a cardiopulmonary exercise test (CPET), the self-reported inability to climb two flights of stairs, or the use of the Duke Activity Status Index (DASI) questionnaire, which has shown a significant correlation with VO_2max and postoperative outcomes. The objectives of the present study were: 1) to create a French version of the DASI questionnaire (FDASI); 2) to assess its diagnostic performance in predicting functional capacity.

METHODS

Consecutive adult patients undergoing CPET for medical or preoperative evaluation were prospectively included between May 2020 and March 2021. All patients were asked to complete FDASI as a self-questionnaire and report their inability to climb two flights of stairs.

RESULTS

122 patients were included. Test-retest reliability was 0.88 and 23 (19%) patients experienced a VO_2max < 14 ml.kg^-1.min^-1. There was a significant positive relationship between FDASI and VO_2max: r² = 0.32; p <  0.001. ROC_AUC was 0.81 [95%CI: 0.73-0.89]. The best FDASI score threshold was 36 points, leading to sensitivity and specificity values of 87% [74-100] and 68% [56-79], respectively. Besides, sensitivity and specificity were 35% [17-56] and 92% [86-97] for the self-reported inability to climb two flights of stairs.

CONCLUSION

A FDASI score of 36 represents a reliable threshold the clinicians could routinely use to identify patients with a VO_2max < 14 ml.kg^-1.min^-1. FDASI could advantageously replace the self-reported inability to climb two flights of stairs.

Altitude acclimatization, hemoglobin-oxygen affinity, and circulatory oxygen transport in hypoxia

In mammals and other air-breathing vertebrates that live at high altitude, adjustments in convective O₂ transport via changes in blood hemoglobin (Hb) content and/or Hb-O₂ affinity can potentially mitigate the effects of arterial hypoxemia. However, there are conflicting views about the optimal values of such traits in hypoxia, partly due to the intriguing observation that hypoxia-induced acclimatization responses in humans and other predominantly lowland mammals are frequently not aligned in the same direction as evolved phenotypic changes in high-altitude natives. Here we review relevant theoretical and empirical results and we highlight experimental studies of rodents and humans that provide insights into the combination of hematological changes that help attenuate the decline in aerobic performance in hypoxia. For a given severity of hypoxia, experimental results suggest that optimal values for hematological traits are conditional on the states of other interrelated phenotypes that govern different steps in the O₂-transport pathway.

Cardiorespiratory strain during stroke rehabilitation: Are patients trained enough? A systematic review

BACKGROUND

Rehabilitation is a mandatory component of stroke management, aiming to recover functional capacity and independence. To that end, physical therapy sessions must involve adequate intensity in terms of cardiopulmonary stress to meet the physiological demands of independent living.

OBJECTIVE

The aim of this systematic review was to determine the current level of cardiopulmonary strain during rehabilitation sessions in stroke patients.

METHODS

Three electronic databases (PubMed, CINAHL and Embase. com) were searched to identify observational studies that documented cardiopulmonary strain during rehabilitation sessions in post-stroke patients (last search performed in February 2019). A manual cross-referencing search was also performed. To be included, articles needed to report data related to both cardiopulmonary strain (heart rate, oxygen consumption or energy expenditure) and active therapy time. The methodological quality of each study was assessed with the Evidence-Based Librarianship Critical Appraisal Tool. Data related to both cardiorespiratory strain and active therapy time were extracted from selected articles.

RESULTS

Four of 43 full-text articles assessed for eligibility met the inclusion criteria. Results extracted from these articles suggested that the intensity of rehabilitation sessions was insufficient to induce a cardiopulmonary training effect in a post-stroke context as measured by metabolic stress. Patients were inactive from 21% to 80% of the therapy time. The Evidence-Based Librarianship tool scores ranged from 65% (15/23) to 91% (21/23), which indicates questionable to good quality.

CONCLUSION

The current literature on cardiopulmonary solicitation during stroke rehabilitation sessions is poor in terms of both the number of studies available and their methodological quality. Summarized results tend to support previous claims that rehabilitation sessions offered to stroke patients are of suboptimal cardiopulmonary strain, which can interfere with their capacity to regain functional independence.

Sigmoidal VO2 on-kinetics: A new pattern in VO2 responses at the lower district of extreme exercise domain

The aim of the study was to analyse the VO₂ on-kinetics belonging to the work rates within the lower district of extreme exercise domain. Maximal O₂ utilisation and peak power outputs of eight well-trained cyclists were revealed by multisession trails. Critical threshold (CT) as the lower boundary of severe domain and aerobic limit power (ALP) as the upper boundary of severe domain were determined by multisession constant-load exercises. VO₂ on-kinetics over time were best fitted by multicomponent exponential models described by an initial concave-up response known as cardio-dynamic phase (τ = 18.2 ± 2.88 s; a = 1.56 ± 0.39 L·min^-1) before a primary concave-up phase (τ = 35.4 ± 12.4 s; a = 1.53 ± 0.36 L·min^-1), and then a slow component in two of the participants (τ = 80.8 ± 37 s; a = 0.47 ± 0.05 L·min^-1) or without a slow component in six of the participants during exercises performed at 50 W above the CT (R²≥0.96; SEE ≤ 0.24; p < 0.001). However, VO₂ on-kinetics over time belonging to exercises performed at 50 W above the ALP were best fitted by sigmoidal model (R²≥0.98; SEE ≤ 0.14; p < 0.001) in comparison with linear (R² = 0.37-0.66; SEE = 0.46-0.64; p < 0.01), or exponential functions (p> 0.05). Indeed, during those exercises, a short period of convex-up response (τ = 16.8 ± 3.1 s; a = 1.72 ± 0.39 L·min^-1) was determined just before a concave-up primary phase in VO₂ over time (τ = 24.6 ± 5.86 s; a = 1.31 ± 0.20 L·min^-1). It was shown that multicomponent exponential trend in VO₂ transformed into a sigmoidal shape, once the work rate exceeded the upper boundary of severe exercise domain.

Selection for high aerobic capacity has no protective effect against obesity in laboratory mice

Aerobic capacity (VO_2max measured during intensive physical exercise) both trained and intrinsic (i.e. genetically determined) has recently been deemed a good predictor of cardiometabolic risks. However, the underlying mechanisms linking VO_2max and health risk factors are not entirely clear, as it seems that not VO_2max per se, but rather some correlated traits, like spontaneous physical activity (SPA) are responsible for sustaining the lean phenotype. Here we investigated the link between genetically determined aerobic capacity, SPA and resistance to diet-induced health risks using replicated lines of mice selected for high aerobic capacity during swimming in mid-cold water (25°C) and Randomly Bred control mice. After four months of consumption of the western type HFat and HCarb diets and no forced nor voluntary training, we found no evidence of protective effects of intrinsic high VO_2max. The Selected mice displayed similar levels of blood glucose, cholesterol, triglycerides and body fat as the Random Bred control animals. Most notably we found no correlation between VO_2max and SPA levels. Our results therefore call into question the ubiquity of VO_2max as a predictor of metabolic health and leanness, at least in animal models.

Physical activity versus cardiorespiratory fitness: two (partly) distinct components of cardiovascular health?

Physical activity (PA) and cardiorespiratory fitness (CRF) both have inverse relationships to cardiovascular (CV) morbidity and mortality. Recent position papers and guidelines have identified the important role of both of these factors in CV health. The benefits of PA and CRF in the prevention of CV disease and risk factors are reviewed. In addition, assessment methodology and utilization in the research and clinical arenas are discussed. Finally, the benefits, methodology, and utilization are compared and contrasted to better understand the two (partly) distinct components and their impact on CV health.

Supporting public health priorities: recommendations for physical education and physical activity promotion in schools

Physical activity (PA) provides numerous physiological and psychosocial benefits. However, lifestyle changes, including reduced PA opportunities in multiple settings, have resulted in an escalation of overweight and obesity and related health problems. Poor physical and mental health, including metabolic and cardiovascular problems is seen in progressively younger ages, and the systematic decline in school PA has contributed to this trend. Of note, the crowded school curriculum with an intense focus on academic achievement, lack of school leadership support, funding and resources, plus poor quality teaching are barriers to PA promotion in schools. The school setting and physical educators in particular, must embrace their role in public health by adopting a comprehensive school PA program. We provide an overview of key issues and challenges in the area plus best bets and recommendations for physical education and PA promotion in the school system moving forward.

An alternative method for predicting the risk of postoperative complications in lung resection

OBJECTIVES

The aims of this study were to design a best fit linear regression model to estimate VO2max (estimated VO2) and to compare the ability of VO2 values (measured and estimated) predicting cardiorespiratory complications in a series of patients undergoing lung resection for lung cancer.

METHOD

This was a prospective, observational study performed in 83 patients. Variables analyzed were: demographic characteristics, comorbidity, body mass index (BMI), FEV1%, FVC%, diffusion capacity (DLCO%), mean daily distance walked in kilometers, VO2max measured by cardio-pulmonary exercise test (CPET) and postoperative complications. Descriptive and comparative statistical analysis of the variables was performed using the Mann-Whitney test for categorical variables and the Student's t-test for continuous variables. A new linear regression model was designed, where the dependent variable (measured VO2max) was estimated by the distance, DLCO% and age, resulting in the estimated VO2. The predictive power of the measured and estimated consumption was analyzed using the Student's t-test, grouping by the occurrence or absence of cardiorespiratory complications.

RESULTS

Both groups were homogeneous for age, sex, BMI, FEV1%, DLCO%, comorbidity, type of resection performed and mean distance walked per day. Estimated VO2 and measured VO2 were normally distributed (K-Smirnov test, P>.32). VO2 means estimated by the model (age, DLCO% and mean distance walked per day) were significantly different between patients with and without complications (Student's t test, P=.037) compared with measured VO2 values, which did not differentiate groups (Student's t test, P=.42).

CONCLUSION

The VO2max estimated by the model is more predictive in this case series than the VO2max measured during a standard exercise test.

Obese but not lean adolescents spontaneously decrease energy intake after intensive exercise

BACKGROUND

Acute intensive exercise has been shown to induce a decreased subsequent daily energy intake in obese adolescents without altering the subjective appetite feelings. It is however unclear whether or not those nutritional adaptations to acute exercise are affected by the adolescents' weight status. The aim of this study was to compare the energy intake and macronutrient preferences, appetite feeling and energy expenditure response to acute exercise between lean and obese adolescents.

METHODS

Ten obese and nine normal weight 12-15year old adolescents randomly completed a session with a 30minute cycling exercise at 75% VO2max and a sedentary session. During both sessions energy expenditure was assessed using Armband, ad libitum energy intake measured by weighing at both lunch and dinner time and appetite feelings assessed using visual analog scales.

RESULTS

Daily, morning and afternoon energy expenditure were significantly higher in obese than in normal weight adolescents (p<0.001). Total energy expenditure was significantly higher during EX (1086±157kcal) compared to SED (853±154kcal) in lean (p<0.05) but not significantly different in obese (respectively 1865±222 and 1803±232kcal). Afternoon energy expenditure was significantly lower during EX compare to SED in obese (p<0.05) but not in normal weight adolescents. Lunch, dinner and total daily energy intake were significantly reduced after the exercise session in obese (p>0.05) but not in lean adolescents. No group or condition effects were observed on subjective appetite feelings.

DISCUSSION

Post exercise spontaneous energy intake and energy expenditure are reduced in obese but not in normal weight adolescents, without appetite feeling changes. Acute exercise may have a greater impact on energy balance through the induced decreased energy intake in the absence of significant change in energy expenditure in obese youth.

Body composition and reproductive function exert unique influences on indices of bone health in exercising women

Reproductive function, metabolic hormones, and lean mass have been observed to influence bone metabolism and bone mass. It is unclear, however, if reproductive, metabolic and body composition factors play unique roles in the clinical measures of areal bone mineral density (aBMD) and bone geometry in exercising women. This study compares lumbar spine bone mineral apparent density (BMAD) and estimates of femoral neck cross-sectional moment of inertia (CSMI) and cross-sectional area (CSA) between exercising ovulatory (Ov) and amenorrheic (Amen) women. It also explores the respective roles of reproductive function, metabolic status, and body composition on aBMD, lumbar spine BMAD and femoral neck CSMI and CSA, which are surrogate measures of bone strength. Among exercising women aged 18-30 years, body composition, aBMD, and estimates of femoral neck CSMI and CSA were assessed by dual-energy x-ray absorptiometry. Lumbar spine BMAD was calculated from bone mineral content and area. Estrone-1-glucuronide (E1G) and pregnanediol glucuronide were measured in daily urine samples collected for one cycle or monitoring period. Fasting blood samples were collected for measurement of leptin and total triiodothyronine. Ov (n = 37) and Amen (n = 45) women aged 22.3 ± 0.5 years did not differ in body mass, body mass index, and lean mass; however, Ov women had significantly higher percent body fat than Amen women. Lumbar spine aBMD and BMAD were significantly lower in Amen women compared to Ov women (p < 0.001); however, femoral neck CSA and CSMI were not different between groups. E1G cycle mean and age of menarche were the strongest predictors of lumbar spine aBMD and BMAD, together explaining 25.5% and 22.7% of the variance, respectively. Lean mass was the strongest predictor of total hip and femoral neck aBMD as well as femoral neck CSMI and CSA, explaining 8.5-34.8% of the variance. Upon consideration of several potential osteogenic stimuli, reproductive function appears to play a key role in bone mass at a site composed of primarily trabecular bone. However, lean mass is one of the most influential predictors of bone mass and bone geometry at weight-bearing sites, such as the hip.