Metabolic equivalents of task are confounded by adiposity, which disturbs objective measurement of physical activity

Defining air quality standards for pesticides through population exposure modeling

Atmospheric pesticide pollution is a global problem that poses risks to human health. However, controlling air pollution remains challenging, as few countries have established air quality standards (AQS) for pesticides. Here, we proposed a modeling framework based on human exposure assessment, comprising scenarios: screening, advanced, and aggregated. In addition, the AQSs of 13 selected pesticides in China were simulated using this framework as practice. In the screening scenario, the inhalation rates by age were included in the exposure assessment. The results showed that the adjusted exposure coefficients (θscreening) were below 1 in young age groups, indicating that the derived AQSscreening should be stricter than the reference concentration (RfC) to ensure sufficient protection across all age groups. For the advanced scenario, outdoor and indoor conditions, as well as physical activity levels were incorporated into the exposure assessment. The results revealed that adjusted coefficients (θadv) exceeded 1 at all age groups, suggesting that a more lenient AQS could be appropriated for a pesticide in this scenario. For the aggregated scenario, exposure source allocation within the human body was considered in the exposure assessment to ensure a sufficient safety margin. The result found that the simulated adjusted coefficients (θadv) were generally two to four orders of magnitude below 1. This scenario could provide the most conservative simulated AQSs. In conclusion, the proposed framework can assist environmental agencies in comprehensively assessing human exposure and provide the potential adjusted coefficients for AQS derivation. Future research is recommended to refine the framework with more factors related to human exposure.

Preoperative Echocardiographic Unknown Valvopathy Evaluation in Elderly Patients Undergoing Neuraxial Anesthesia during Major Orthopedic Surgery: A Mono-Centric Retrospective Study

Background: The assessment of cardiac risk is challenging for elderly patients undergoing major orthopedic surgery with preoperative functional limitations. Currently, no specific cardiac risk scores are available for these critical patients. Echocardiography may be a reliable and safe instrument for assessing cardiac risks in this population. This study aims to evaluate the potential benefits of echocardiography in elderly orthopedic patients, its impact on anesthesiologic management, and postoperative Major Adverse Cardiac Events (MACEs). Methods: This is a retrospective, one-arm, monocentric study conducted at ''Federico II'' Hospital-University of Naples-from January to December 2023, where 59 patients undergoing hip or knee revision surgery under neuraxial anesthesia were selected. The demographic data, the clinical history, and the results of preoperative Echocardiography screening (pEco-s) were collected. After extensive descriptive statistics, the χ2 test was used to compare the valvopathies and impaired Left Ventricular Function (iLVEF) prevalence before and after echocardiography screening and the incidence of postoperative MACE; a p-value < 0.05 was considered statistically significant. Results: The mean age was 72.5 ± 6.9, and the prevalence of cardiac risk factors was about 90%. The cumulative prevalence of iLVEF and valvopathy was higher after the screening (p < 0.001). The pEco-s diagnosed 25 new valvopathies: three of them were moderate-severe. No patients had MACE. Conclusions: pEco-s evaluation could discover unknown heart valve pathology; more studies are needed to understand if pEco-s could affect the anesthetic management of patients with functional limitations, preventing the incidence of MACE, and assessing its cost-effectiveness.

Reduced exercise capacity for muscle mass in adolescents living with obesity

BACKGROUND

Adolescents living with obesity (AlwO) can have limited exercise capacity. Exercise capacity can be predicted by a 2-factor model comprising lung function and leg muscle function, but no study has looked at cycling leg muscle function and its contribution to cycling exercise capacity in AlwO.

METHODS

Twenty-two nonobese adolescents and 22 AlwO (BMI > 95 percentile) were studied. Anthropometry, body composition (dual-energy X-ray absorptiometry), spirometry, 30-s isokinetic work capacity, and maximal exercise (cycle ergometry) were measured.

RESULTS

AlwO had greater total body mass, lean body mass, and lean leg mass (LLM). Lung function trended higher in AlwO. Leg 30-s work did not differ in absolute terms or per allometrically scaled LLM. Peak oxygen consumption did not differ between the groups in absolute terms or as percent predicted values (79.59 ± 14.6 vs. 82.3 ± 11.2% predicted control versus ALwO) but was lower in AlwO when expressed per kg body mass, kg lean body mass, scaled lean body mass, and LLM. Peak oxygen consumption related to both lung function and 30-s work, with no observed group effect. 30-s leg work related to the scaled LLM, with a small group effect. There was some correlation between leg work and time spent in moderate to vigorous physical activity in AlwO (rs = 0.39, p = .07).

CONCLUSION

AlwO have larger LLM and preserved exercise capacity, when expressed as percentage of predicted, but not per allometrically scaled LLM. Increasing time spent in moderate to vigorous activity may benefit AlwO.

Designing Mobile Health Applications to Support Walking for Older Adults

Physical activity is extremely important at an older age and has major benefits. There is a range of applications that help maintain physical activity. However, their adoption among older adults is still limited. The purpose of the study is to explore the key aspects of the design of mobile applications that support walking for older adults. We conducted a field study with older adults, aged 69-79 years, using a technology probe (a mobile application developed as an early prototype) with the purpose of eliciting requirements for mobile health applications. We interviewed the participants during and after the study period, asking them about their motivation for walking, usage of the application, and overall preferences when using such technologies. The findings suggest that mobile applications that support walking should address a range of walking variables, support a long-term learning process, and enable the user to take control and responsibility for the walk. In addition, we provide design guidelines concerning the motivation for walking and the data visualization that would make technology adoption easier. The findings from this study can be used to inform the design of more usable products for older users.

Beyond steps per day: other measures of real-world walking after stroke related to cardiovascular risk

Background

Significant variability exists in how real-world walking has been measured in prior studies in individuals with stroke and it is unknown which measures are most important for cardiovascular risk. It is also unknown whether real-world monitoring is more informative than laboratory-based measures of walking capacity in the context of cardiovascular risk. The purpose of this study was to determine a subset of real-world walking activity measures most strongly associated with systolic blood pressure (SBP), a measure of cardiovascular risk, in people with stroke and if these measures are associated with SBP after accounting for laboratory-based measures of walking capacity.

Methods

This was a cross-sectional analysis of 276 individuals with chronic (≥ 6 months) stroke. Participants wore an activity monitor for ≥ 3 days. Measures of activity volume, activity frequency, activity intensity, and sedentary behavior were calculated. Best subset selection and lasso regression were used to determine which activity measures were most strongly associated with systolic blood pressure. Sequential linear regression was used to determine if these activity measures were associated with systolic blood pressure after accounting for walking capacity (6-Minute Walk Test).

Results

Average bout cadence (i.e., the average steps/minute across all bouts of walking) and the number of long (≥ 30 min) sedentary bouts were most strongly associated with systolic blood pressure. After accounting for covariates (ΔR² = 0.089, p < 0.001) and walking capacity (ΔR² = 0.002, p = 0.48), these activity measures were significantly associated with systolic blood pressure (ΔR² = 0.027, p = 0.02). Higher systolic blood pressure was associated with older age (β = 0.219, p < 0.001), male gender (β = − 0.121, p = 0.046), black race (β = 0.165, p = 0.008), and a slower average bout cadence (β = − 0.159, p = 0.022).

Conclusions

Measures of activity intensity and sedentary behavior may be superior to commonly used measures, such as steps/day, when the outcome of interest is cardiovascular risk. The relationship between walking activity and cardiovascular risk cannot be inferred through laboratory-based assessments of walking capacity.

The Effect of ω3 Fatty Acids Supplementation on Levels of PPARγ and UCP2 Genes Expression, Serum Level of UCP2 Protein, Metabolic Status, and Appetite in Elite male Athletes: Protocol for a Randomized Control Trial

Some genetic factors may influence body composition, such as PPARγ and UCP2. PPARγ plays an important role in body fat distribution. The objective of the present study is to determine the effects of omega3 fatty acids on the gene expression of PPARγ and UCP2, levels of blood lipid profile, fat mass, and fat-free mass, and appetite.

Elite male athlete volunteers of up to 36 subjects were invited to participate in this RCT. Following a public announcement, volunteers were recruited from gyms, teams, and sports medicine boards in Tabriz, Iran. Gene’s expression of PPARγ and UCP2, serum levels of blood lipid profile, fat mass, and fat-free mass was collected. Data collection time points include baseline in addition to 3 weeks follow up. The study was approved by the Ethics Committee of the Tabriz University Medical of Sciences (IR.TBZMED.REC.1398.782) in October 2019 and was registered with the Iranian Registry of Clinical Trials: 20190625044008N1 on December 19, 2019.

Recruitment began in July and concluded in December 2019. As of August 19, 2019, we have screened 373 volunteers. 36 were enrolled. Baseline measurements of participants were collected. After three-week of intervention, end study measurements of participants were collected. The results are expected to be released in 2021. Participants have a median age of 21.86 (±3.15). The finding of this study showed Results showed PPARγ mRNA levels, and UCP2 mRNA and protein levels increased in the omega3 group (p < 0.05), as did REE (p < 0.05). Also, differences in the sensation of hunger or satiety were significant (p < 0.05).

This study could result in the effects of omega-3 fatty acids on PPARγ, and UCP2 expressions, blood lipid profiles and body composition. In addition, the results of this trial can be used as baseline information for conducting further clinical and sport nutrition studies.

Associations of age, body size, and maturation with physical activity intensity in different laboratory tasks in children

We investigated the associations of age, sex, body size, body composition, and maturity with measures of physical activity (PA) intensity in children. PA intensity was assessed using VO₂ as % of VO_2reserve or VO₂ at ventilatory threshold (VT), muscle activity measured by textile electromyography, mean amplitude deviation (MAD) measured by accelerometry, and metabolic equivalent of task (MET) during laboratory activities.Age, stature, and muscle mass were inversely associated with VO2 as % of VO_2reserve and % of VT, during walking or running on a treadmill for 4, 6, and 8 km/h (Spearman r = -0.645 to -0.358). Age was inversely associated with MAD during walking on treadmill for 4 km/h (r = -0.541) and positively associated with MAD during running on a treadmill for 8 km/h, playing hopscotch, and during self-paced running (r = 0.368 to 0.478). Fat mass was positively associated with VO2 as % of VO_2reserve and VO2 as % of VO2 at VT and waist circumference was positively associated with VO2 as a % of VO_2reserve and muscle activity during stair climbing (r = 0.416 to 0.519).Fixed accelerometry cut-offs used to define PA intensities should be adjusted for age, sex, body size, and body composition.

Balancing time use for children's fitness and adiposity: Evidence to inform 24-hour guidelines for sleep, sedentary time and physical activity

PURPOSE

Daily time spent on one activity cannot change without compensatory changes in others, which themselves may impact on health outcomes. Optimal daily activity combinations may differ across outcomes. We estimated optimal daily activity durations for the highest fitness and lowest adiposity.

METHODS

Cross-sectional Child Health CheckPoint data (1182 11-12-year-olds; 51% boys) from the population-based Longitudinal Study of Australian Children were used. Daily activity composition (sleep, sedentary time, light physical activity [LPA], moderate-to-vigorous physical activity [MVPA]) was from 8-day, 24-hour accelerometry. We created composite outcomes for fitness (VO2max; standing long jump) and adiposity (waist-to-height ratio; body mass index; fat-to-fat-free log-ratio). Adjusted compositional models regressed activity log-ratios against each outcome. Best activity compositions (optimal time-use zones) were plotted in quaternary tetrahedrons; the overall optimal time-use composition was the center of the overlapping area.

RESULTS

Time-use composition was associated with fitness and adiposity (all measures p<0.001). Optimal time use differed for fitness and adiposity. While both maximized MVPA and minimized sedentary time, optimal fitness days had higher LPA (3.4 h) and shorter sleep (8.25 h), but optimal adiposity days had lower LPA (1.0 h) and longer sleep (10.9 h). Balancing both outcomes, the overall optimal time-use composition was (mean [range]): 10.2 [9.5; 10.5] h sleep, 9.9 [8.8; 11.2] h sedentary time, 2.4 [1.8; 3.2] h LPA and 1.5 [1.5; 1.5] h MVPA.

CONCLUSION

Optimal time use for children's fitness and adiposity involves trade-offs. To best balance both outcomes, estimated activity durations for sleep and LPA align with, but for MVPA exceed, 24-h guidelines.

Validity of traditional physical activity intensity calibration methods and the feasibility of self-paced walking and running on individualised calibration of physical activity intensity in children

There are no practical and valid methods for the assessment of individualised physical activity (PA) intensity in observational studies. Therefore, we investigated the validity of commonly used metabolic equivalent of tasks (METs) and pre-determined PA intensity classification methods against individualised PA intensity classification in 35 children 7–11-years-of-age. Then, we studied validity of mean amplitude deviation (MAD) measured by accelerometry during self-paced walking and running in assessment of individualised PA intensity. Individualised moderate PA (MPA) was defined as V̇O₂ ≥ 40% of V̇O_2reserve and V̇O₂ < ventilatory threshold (VT) and vigorous PA (VPA) as V̇O₂ ≥ VT. We classified > 3–6 (or alternatively > 4–7) METs as MPA and > 6 (> 7) METs as VPA. Task intensities were classified according to previous calibration studies. MET-categories correctly identified 25.9–83.3% of light PA, 85.9–90.3% of MPA, and 56.7–82.2% of VPA. Task-specific categories correctly classified 53.7% of light PA, 90.6% of MPA, and 57.8% of VPA. MAD during self-paced walking discriminated MVPA from light PA (sensitivity = 67.4, specificity = 88.0) and MAD during self-paced running discriminated VPA from MPA (sensitivity = 78.8, specificity = 79.3). In conclusion, commonly used methods may misclassify PA intensity in children. MAD during self-paced running may provide a novel and practical method for determining individualised VPA intensity in children.

Sedentary Thresholds for Accelerometry-Based Mean Amplitude Deviation and Electromyography Amplitude in 7-11 Years Old Children

We investigated the ability of energy expenditure, movement sensing, and muscle activity to discriminate sedentary and non-sedentary activities in children. Thirty-five 7–11-year-old children participated in the study. Simultaneous assessment of oxygen uptake (V̇O₂), triaxial accelerometry, and thigh muscle electromyography (EMG) were performed during eight different sedentary and non-sedentary activities including lying down, sitting-, standing-, and walking-related activities, which were performed in a random order. Mean values of V̇O₂, accelerometry, and EMG from the concurrent 2 min epochs during each activity were computed. Resting energy expenditure (REE) was measured during 30 min supine rest. Directly measured metabolic equivalent of tasks (METs, V̇O₂ in activities/V̇O₂ in REE) were calculated for each activity. Mean amplitude deviation (MAD) was computed for accelerometry. EMG was normalized for mean muscle activity during self-paced walking. The classification accuracy of METs, MAD, and EMG to discriminate sedentary activities from physical activities was investigated by receiver operating characteristic curves and optimal cut-offs based on maximal sensitivity and specificity. Mean (SD) REE was 5.0 ± 0.8 ml/kg/min. MET, MAD, and EMG values ranged from 1.0 to 4.9, 0.0020 to 0.4146 g, and 4.3 to 133.9% during lying down and walking at 6 km/h, respectively. Optimal cut-offs to discriminate sedentary activities from non-sedentary activities were 1.3 for METs (sensitivity = 82%, specificity = 88%), 0.0033 g for MAD (sensitivity = 80%, specificity = 91%), and 11.9% for EMG (sensitivity = 79%, specificity = 92%). In conclusion, this study provides applicable thresholds to differentiate sitting and standing and sedentary and non-sedentary activities based on METs, MAD, and EMG in young children.

High sedentary time in children is not only due to screen media use: a cross-sectional study

Background

Sedentary behaviour has become a growing public health concern. Currently, it is a common belief that screen time (SCT) is a key factor in high overall sedentary time (ST) and is often used as a primary outcome. However, the evidence is lacking. Therefore, this study investigated the association of objectively assessed total ST with SCT among children. Further, SCT was investigated separately for sedentary level, weight status, gender, and migration background.

Methods

For 198 primary school children (7.1 ± 0.7 years, boys: 43.9%) ST was assessed objectively using a multi-sensor device (Actiheart®; CamNtech, Cambridge, UK). The sample was split into three groups (tertiles) to investigate SCT of children with low, medium and high ST. SCT and socio-demographic parameters, such as migration background, were assessed using a parental questionnaire; anthropometric data was collected at schools.

Results

Absolut SCT did not differ significantly among the three sedentary groups: Daily average of SCT was 83.8 ± 55.0 min (27.4% of ST) for children with high ST, 82.8 ± 50.5 min (39.8% of ST) for children with medium ST, and 77.2 ± 59.4 min (71.3% of ST) for those with low ST. However, relatively the SCT percentage of total ST was significantly higher among children with low ST (p < 0.01). Significantly higher SCT was found in children with migration background (p < 0.01), while underweight children had significantly less SCT (p < 0.05). An association of total SCT and overall ST was found for the whole sample (B = 17.11, [2.75; 31.48], p = 0.02), but did not remain when analysis were separated for the groups, except for normal weight children (B = 15.97, [0.13; 31.81], p = 0.05).

Conclusions

The amount of SCT is the same among high, low and medium sedentary children, and high ST is largely independent of SCT. Therefore, SCT cannot be the key contributor to high ST and should not solely be used for predicting or changing children’s sedentary behaviour. Moreover, children’s weight status to classify activity levels and the role of possible compensation mechanisms should be considered in future research and when trying to intervene on ST.

Trial registration

German Clinical Trials Register (DRKS), DRKS-ID: DRKS00000494 DATE: 25/08/2010.

Exercise stress test in apparently healthy individuals - where to place the finish line? The Ferrari corporate wellness programme experience

AIMS

The aim of our study was to assess the clinical significance of the exercise stress testing endpoints, namely 85% of maximal theoretical heart rate (MTHR), metabolic equivalent of task, and rating of perceived exertion (RPE), and their relation to electrocardiographic (ECG) changes in a healthy adult population.

METHODS

A cross-sectional study was conducted on 408 males and 52 females (mean age 39.4 ± 8.6 years) who performed the maximal cycle ergometer exercise stress test until volitional exhaustion, reporting the RPE score at 85% of MTHR and at peak exercise. Metabolic equivalents of task were indirectly calculated from the maximum workload and compared with the predicted values. Sitting torso-lead ECG and blood pressure were recorded at rest, during exercise and during recovery.

RESULTS

Of 460 participants, 73% exceeded 85% of MTHR. The RPE score represented the overall most significant endpoint of exercise stress testing, with the median value of 17 at peak exercise. ECG events were detected in 23/124 (18.5%) who reached ≤ 85% of MTHR and in 61/336 (18.2%) who achieved >85% of MTHR ( p = 0.92). In the latter group, 54% of ECG changes occurred at < 85% of MTHR and 46% at > 85% of MTHR ( p = 0.51). If the exercise stress testing had been interrupted at ≤ 85% of MTHR, almost half of the ECG events would have remained undetected and 35% of the cardiovascular abnormalities observed at the diagnostic follow-up would have remained undiagnosed.

CONCLUSION

Terminating exercise stress testing before volitional exhaustion and an RPE score of 17 limits the test accuracy and reduces the possibility to detect cardiovascular abnormalities in apparently healthy adult populations.

Cardiopulmonary fitness is strongly associated with body cell mass and fat-free mass: The Study of Health in Pomerania (SHIP)

Peak oxygen uptake (VO2peak) is commonly indexed by total body weight (TBW) to determine cardiopulmonary fitness (CPF). This approach may lead to misinterpretation, particularly in obese subjects. We investigated the normalization of VO2peak by different body composition markers. We analyzed combined data of 3848 subjects (1914 women; 49.7%), aged 20-90, from two independent cohorts of the population-based Study of Health in Pomerania (SHIP-2 and SHIP-TREND). VO2peak was assessed by cardiopulmonary exercise testing. Body cell mass (BCM), fat-free mass (FFM), and fat mass (FM) were determined by bioelectrical impedance analysis. The suitability of the different markers as a normalization variable was evaluated by taking into account correlation coefficients (r) and intercept (α-coefficient) values from linear regression models. A combination of high r and low α values was considered as preferable for normalization purposes. BCM was the best normalization variable for VO2peak (r = .72; P ≤ .001; α-coefficient = 63.3 mL/min; 95% confidence interval [CI]: 3.48-123) followed by FFM (r = .63; P ≤ .001; α-coefficient = 19.6 mL/min; 95% CI: -57.9-97.0). On the other hand, a much weaker correlation and a markedly higher intercept were found for TBW (r = .42; P ≤ .001; α-coefficient = 579 mL/min; 95% CI: 483 to 675). Likewise, FM was also identified as a poor normalization variable (r = .10; P ≤ .001; α-coefficient = 2133; 95% CI: 2074-2191). Sex-stratified analyses confirmed the above order for the different normalization variables. Our results suggest that BCM, followed by FFM, might be the most appropriate marker for the normalization of VO2peak when comparing CPF between subjects with different body shape.

Sedentary time among primary school children in south-west Germany: amounts and correlates

BACKGROUND

Sedentary behaviour in children is related to different health consequences such as overweight and cardio-metabolic diseases that can track into adulthood. Previous studies have shown that children spend hours being sedentary, but no data of sedentary time (ST) among German children has been available, yet. Therefore, this study investigated objectively measured amounts and correlates of ST in a sample of German primary school children.

METHODS

Children's physical activity (PA) was objectively assessed for 6 days using a multi-sensor device (Actiheart®; CamNtech, Cambridge, UK). Activity levels were categorized on the basis of energy expenditure (MET) into sedentary, light PA (LPA), and moderate to vigorous PA (MVPA). ST excluding sleeping hours was assessed for 231 children (7.1 ± 0.6 years, male: 45.9%) and analysed for independent groups. Examined factors (parental education, household income, and migration background) were assessed by parental questionnaire. Children's weight, height and gender were collected in schools. Weight status was calculated on the basis of BMI percentiles.

RESULTS

On average, children spent 3.5 ± 1.5 h daily being sedentary, excluding sleeping hours. Significantly higher ST was found in girls (t = -4.6; p < 0.01), in children with migration background (t = -6.9; p < 0.01), at the weekend (t = -2.8; p < 0.01), and among inactive children (t = 6.8; p < 0.01). Additionally, significant correlations with ST in this sample were identified for MVPA (B = -0.99; [-1.09;-0.88], p < 0.01), LPA (B = -0.89; [-0.97;-0.82], p < 0.01), migration background (B = -17.64; [5.24;30.04], p < 0.01), gender (B = -13.48; [-25.94;-1.01], p < 0.05) and household income (B = -4.80; [-9.07; -0.53], p < 0.05).

CONCLUSION

Girls, children with migration background, and inactive children were identified as potential risk groups. A higher income was associated with less ST. In general, ST was higher at the weekend. Furthermore, as PA was found to be negatively correlated to ST, these activities may replace each other. Therefore, these findings should be considered in future health interventions.

TRIAL REGISTRATION

German Clinical Trials Register (DRKS), DRKS-ID: DRKS00000494 DATE: 25/08/2010.

Relation of oxygen uptake to work rate in prepubertal healthy children - reference for VO2 /W-slope and effect on cardiorespiratory fitness assessment

PURPOSE

Exercise testing by cycle ergometer allows to observe the interaction between oxygen uptake (VO₂ ) and workload (W), and VO₂ /W-slope can be used as a diagnostic tool. Respectively, peak oxygen uptake (VO_2PEAK ) can be estimated by maximal workload. We aim to determine reference for VO₂ /W-slope among prepubertal children and define agreement between estimated and measured VO_2PEAK .

METHODS

A total of 38 prepubertal children (20 girls) performed a maximal cycle ergometer test with respiratory gas analysis. VO₂ /W-slopes were computed using linear regression. Agreement analysis by Bland and Altman for estimated and measured VO_2PEAK was carried out including limits of agreement (LA). Determinants for VO₂ /W-slopes and estimation bias were defined.

RESULTS

VO2/W-slope was in both girls and boys ≥9·4 and did not change with exercise level, but the oxygen cost of exercise was higher among physically more active children. Estimated VO_2PEAK had 6·4% coefficient of variation, and LA varied from 13% underestimation to 13% overestimation. Bias had a trend towards underestimation along lean mass proportional VO_2PEAK . The primary determinant for estimation bias was VO2/W-slope (β = -0·65; P<0·001).

CONCLUSION

The reference values for VO₂ /W-slope among healthy prepubertal children were similar to those published for adults and among adolescents. Estimated and measured VO_2PEAK should not be considered to be interchangeable because of the variation in the relationship between VO₂ and W. On other hand, variation in the relationship between VO₂ and W enables that VO₂ /W-slope can be used as a diagnostic tool.

How is rating of perceived capacity related to VO2max and what is VO2max at onset of training?

Objective

To evaluate how rating of perceived capacity (RPC) is related to maximal oxygen uptake (VO_2max) and examine VO_2max at onset of training in healthy adults.

Methods

In total, 125 newly registered fitness centre members, equally men and women, answered the RPC scale and performed a treadmill test for measurement of VO_2max. Eligible criteria were <4 weeks of fitness centre membership, physically inactive, ≥18 years and not pregnant. The RPC is a one-page scale (1–20) based on metabolic equivalent tasks, where the individual chooses the most strenuous activity that can be sustained for at least 30 min.

Results

The Bland-Altman plot demonstrated a tendency of overestimation, meaning that the participants ranked their own aerobic capacity 17.5% higher than objectively measured values of VO_2max. The mean difference between the two methods were +4.92±1.96 and +6.35±1.96 mL/min/kg VO₂ in men and women, respectively. The Pearson correlation coefficient was moderate, with r=0.426 (p<0.01). A linear regression analysis showed that both age and VO_2max were significant predictors of RPC (p<0.01). Measured VO_2max at onset of fitness centre membership was in men aged 38.7±11.7 and women aged 34.7±9.9, 40.5±7.2 and 35.0±6.0 mL/min/kg, respectively. Estimated VO_2max from the RPC scale was 45.7±9.8 and 41.4±10.1 mL/min/kg in men and women, respectively.

Conclusions

The RPC seems less accurate at the individual level and may overestimate VO_2max. Still, it may be considered useful in large-scale studies.

Appropriateness of the metabolic equivalent (MET) as an estimate of exercise intensity for post-myocardial infarction patients

AIMS

To explore: (1) whether during exercise metabolic equivalents (METs) appropriately indicate the intensity and/or metabolic cost for post-myocardial infarction (MI) males and (2) whether post-exercise VO2 parameters provide insight into the intensity and/or metabolic cost of the prior exercise.

METHODS

15 male phase-IV post-MIs (64.4±6.5 years) and 16 apparently healthy males (63.0±6.4 years) participated. Participants performed a graded cycle ergometer test (CET) of 50, 75 and 100 W, followed by 10 min active recovery (at 50 W) and 22 min seated recovery. Participants' heart rate (HR, bpm), expired air parameters and ratings of perceived exertion (exercise only) were measured.

RESULTS

General linear model analysis showed throughout significantly lower HR values in post-MI participants that were related to β-blocker medication (F(2,5)=18.47, p<0.01), with significantly higher VCO2/VO2 (F(2,5)=11.25, p<0.001) and gross kcals/LO2/min (F(2,5)=11.25, p<0.001). Analysis comparing lines of regression showed, during the CET: post-MI participants worked at higher percentage of their anaerobic threshold (%AT)/MET than controls (F(2,90)=18.98, p<0.001), as well as during active recovery (100-50 W) (F(2,56)=20.81, p<0.001); during seated recovery: GLM analysis showed significantly higher values of VCO2/VO2 for post-MI participants compared with controls (F(2,3)=21.48, p=0.001) as well as gross kcals/LO2/min (F(2,3)=21.48, p=0.001).

CONCLUSION

Since METs take no consideration of any anaerobic component, they failed to reflect the significantly greater anaerobic contribution during exercise per MET for phase-IV post-MI patients. Given the anaerobic component will be greater for those with more severe forms of cardiac disease, current METs should be used with caution when determining exercise intensity in any patient with cardiac disease.

Metabolic Equivalent in Adolescents, Active Adults and Pregnant Women

“Metabolic Equivalent” (MET) represents a standard amount of oxygen consumed by the body under resting conditions, and is defined as 3.5 mL O₂/kg × min or ~1 kcal/kg × h. It is used to express the energy cost of physical activity in multiples of MET. However, universal application of the 1-MET standard was questioned in previous studies, because it does not apply well to all individuals. Height, weight and resting metabolic rate (RMR, measured by indirect calorimetry) were measured in adolescent males (n = 50) and females (n = 50), women during pregnancy (gestation week 35–41, n = 46), women 24–53 weeks postpartum (n = 27), and active men (n = 30), and were compared to values predicted by the 1-MET standard. The RMR of adolescent males (1.28 kcal/kg × h) was significantly higher than that of adolescent females (1.11 kcal/kg × h), with or without the effects of puberty stage and physical activity levels. The RMR of the pregnant and post-pregnant subjects were not significantly different. The RMR of the active normal weight (0.92 kcal/kg × h) and overweight (0.89 kcal/kg × h) adult males were significantly lower than the 1-MET value. It follows that the 1-MET standard is inadequate for use not only in adult men and women, but also in adolescents and physically active men. It is therefore recommended that practitioners estimate RMR with equations taking into account individual characteristics, such as sex, age and Body Mass Index, and not rely on the 1-MET standard.

Heterogeneity of muscle activity during sedentary behavior

Replacing sitting by standing has been hypothesized to reduce the health risks of sitting, based on the assumption that muscles are passive during sitting and active during standing. Interventions have been more effective in overweight (OW) than in normal weight (NW) individuals, but subjects' muscle activities have not been quantified. This study compared quadriceps and hamstring muscle electromyographic (EMG) activity between 57 NW (body mass index (BMI) 22.5 ± 1.5 kg/m², female n = 36) and 27 OW (BMI 28.4 ± 2.9 kg/m², female n = 8) subjects during non-fatiguing standing (15 s, EMG_standing) and sitting (30 min). EMG amplitude was normalized to EMG measured during maximal isometric knee extension and flexion (% EMG_MVC), and sitting muscle inactivity and bursts were determined using 4 thresholds (60% or 90% EMG_standing and 1% or 2% EMG_MVC). Comparisons were adjusted for sex, age, knee extension strength, and the individual threshold. Standing EMG amplitude was 36% higher in OW (1.9% ± 1.5% EMG_MVC) than in NW (1.4% ± 1.4% EMG_MVC, P < 0.05) subjects. During sitting, muscles were inactive 89.8% ± 12.7% of the measurement time with 12.7 ± 14.2 bursts/min across all thresholds. On average, 6% more activity was recorded in NW than in OW individuals for 3 of the 4 thresholds (P < 0.05 for 60% or 90% EMG_standing and 1% EMG_MVC). In conclusion, the OW group had higher muscle activity amplitude during standing but more muscle inactivity during sitting for 3/4 of the thresholds tested. Interventions should test whether the observed heterogeneity in muscle activity affects the potential to gain cardiometabolic benefits from replacing sitting with standing.