Effect of sampling rate on acceleration and counts of hip- and wrist-worn ActiGraph accelerometers in children

Sampling rate (Hz) of ActiGraph accelerometers may affect processing of acceleration to activity counts when using a hip-worn monitor, but research is needed to quantify if sampling rate affects actual acceleration (mg's), when using wrist-worn accelerometers and during non-locomotive activities. Objective: To assess the effect of ActiGraph sampling rate on total counts/15-sec and mean acceleration and to compare differences due to sampling rate between accelerometer wear locations and across different types of activities. Approach: Children (n=29) wore a hip- and wrist-worn accelerometer (sampled at 100 Hz, downsampled in MATLAB to 30 Hz) during rest/transition periods, active video games, and a treadmill test to volitional exhaustion. Mean acceleration and counts/15-sec were computed for each axis and as vector magnitude. Main Results: There were mostly no significant differences in mean acceleration. However, 100 Hz data resulted in significantly more total counts/15-sec (mean bias 4-43 counts/15-sec across axes) for both the hip- and wrist-worn monitor when compared to 30 Hz data. Absolute differences increased with activity intensity (hip: r=0.46-0.63; wrist: r=0.26-0.55) and were greater for hip- versus wrist-worn monitors. Percent agreement between 100 and 30 Hz data was high (97.4-99.7%) when cut-points or machine learning algorithms were used to classify activity intensity. Significance: Our findings support that sampling rate affects the generation of counts but adds that differences increase with intensity and when using hip-worn monitors. We recommend researchers be consistent and vigilantly report the sampling rate used, but note that classifying data into activity intensities resulted in agreement despite differences in sampling rate

Physical activity assessment by accelerometry in people with heart failure

Background: International guidelines for physical activity recommend at least 150 min per week of moderate-to-vigorous physical activity (MVPA) for adults, including those with cardiac disease. There is yet to be consensus on the most appropriate way to categorise raw accelerometer data into behaviourally relevant metrics such as intensity, especially in chronic disease populations. Therefore the aim of this study was to estimate acceleration values corresponding to inactivity and MVPA during daily living activities of patients with heart failure (HF), via calibration with oxygen consumption (VO2) and to compare these values to previously published, commonly applied PA intensity thresholds which are based on healthy adults. Methods: Twenty-two adults with HF (mean age 71 ± 14 years) undertook a range of daily living activities (including laying down, sitting, standing and walking) whilst measuring PA via wrist- and hip-worn accelerometers and VO2 via indirect calorimetry. Raw accelerometer output was used to compute PA in units of milligravity (mg). Energy expenditure across each of the activities was converted into measured METs (VO2/resting metabolic rate) and standard METs (VO2/3.5 ml/kg/min). PA energy costs were also compared with predicted METs in the compendium of physical activities. Location specific activity intensity thresholds were established via multilevel mixed effects linear regression and receiver operator characteristic curve analysis. A leave-one-out method was used to cross-validate the thresholds. Results: Accelerometer values corresponding with intensity thresholds for inactivity ( 50% lower than previously published intensity thresholds for both wrists and waist accelerometers (inactivity: 16.7 to 18.6 mg versus 45.8 mg; MVPA: 43.1 to 49.0 mg versus 93.2 to 100 mg). Measured METs were higher than both standard METs (34-35%) and predicted METs (45-105%) across all standing and walking activities. Conclusion: HF specific accelerometer intensity thresholds for inactivity and MVPA are lower than previously published thresholds based on healthy adults, due to lower resting metabolic rate and greater energy expenditure during daily living activities for HF patients. Trial registration: Clinical trials.gov NCT03659877, retrospectively registered on September 6th 2018.This article is freely available via Open Access. Click on the Publisher URL to access it via the publisher's site.This study was undertaken as part of a PhD, which was funded by a University of Exeter Postgraduate Studentship Grant. The funders were not involved in design of the study, data collection, analysis, and interpretation of data, and in writing the manuscript.published version, accepted versio

Accelerometer Validation of Questionnaires Used in Clinical Settings to Assess MVPA

Introduction The exercise vital sign (EVS) and General Practice Physical Activity Questionnaire (GPPAQ) are questionnaires designed for clinical settings to identify individuals who are not meeting physical activity (PA) guidelines in the United States and United Kingdom, respectively. To date, neither has been objectively validated. Methods Subjects (N = 76) from the United States (n = 38; age, 49 ± 20 yr) and United Kingdom (n = 38; age, 43 ± 21 yr) completed a health history questionnaire, wore an accelerometer for 7 d, and then completed the EVS and GPPAQ. Accelerometry, EVS, and GPPAQ data were scored to dichotomize subjects into groups of meeting (≥150 min of moderate-to-vigorous PA (MVPA) per week) or not meeting (<150 min of MVPA per week) the PA guidelines, and accelerometry was used as a criterion measure for comparing both questionnaires. The sensitivity and specificity of the EVS and GPPAQ were calculated to represent the ability of the questionnaires to identify subjects who did not and did meet the PA guidelines. Total MVPA accumulated in ≥10-min bouts were compared between accelerometry and the EVS using a 2 × 2 × 2 repeated measures ANOVA with one within-subjects effect (PA assessment method) and two between-subjects effects (gender and country). The alpha level was P = 0.05 for all analyses. Results The EVS had marginally better sensitivity (59% vs 46%) and specificity (77% vs 50%) than the GPPAQ. The EVS grossly overestimated the minutes of MVPA when compared to accelerometry (P < 0.05) for all subjects, except UK women. Conclusion In practice, the EVS and GPPAQ may not identify ∼50% of patients who should be advised to increase their PA. Therefore, physicians should advocate that all of their patients adopt an active lifestyle, including the achievement of ≥150 min of MVPA per week

Cardiopulmonary exercise testing : what is its value?

Compared with traditional exercise tests, cardiopulmonary exercise testing (CPET) provides a thorough assessment of exercise integrative physiology involving the pulmonary, cardiovascular, muscular, and cellular oxidative systems. Due to the prognostic ability of key variables, CPET applications in cardiology have grown impressively to include all forms of exercise intolerance, with a predominant focus on heart failure with reduced or with preserved ejection fraction. As impaired cardiac output and peripheral oxygen diffusion are the main determinants of the abnormal functional response in cardiac patients, invasive CPET has gained new popularity, especially for diagnosing early heart failure with preserved ejection fraction and exercise-induced pulmonary hypertension. The most impactful advance has recently come from the introduction of CPET combined with echocardiography or CPET imaging, which provides basic information regarding cardiac and valve morphology and function. This review highlights modern CPET use as a single or combined test that allows the pathophysiological bases of exercise limitation to be translated, quite easily, into clinical practice

Cross-country skiing and running’s association with cardiovascular events and all-cause mortality:A review of the evidence

Abstract A large body of evidence demonstrates positive, graded effects of PA on cardiovascular disease (CVD) morbidity and mortality with increasing intensity compared with lower PA intensity. Running is often designated as a high-intensity PA with substantial evidence supporting its health benefits. Cross-country skiing is among the most demanding aerobic endurance exercises and requires engaging the upper- and lower-body. Cross-country skiing is often regarded as high-intensity PA, which has been associated with significant health benefits. However, a robust body of evidence identifying the dose-response relation between cross-country skiing volume and health outcomes is sparse. Therefore, this review aims to summarize the available evidence linking cross-country skiing with CVD morbidity and all-cause mortality; postulated pathways that may elucidate the relation between these associations; outline areas of ongoing uncertainty; and the implications for primary and secondary CVD prevention. To put the findings into perspective, we also summarized the evidence linking running with CVD morbidity and all-cause mortality. Though a head-to-head comparison is not available, the evidence indicates that performing PA as cross-country skiing associates with lower mortality risk when compared with that observed in those undertaking their PA as running. Potential adverse effects of extreme high weekly doses of cross-country skiing over decades may be cardiac arrhythmias, such as atrial fibrillation. Evidence suggests that cross-country skiing may reduce the risk of CVD events and all-cause mortality via anti-inflammatory pathways, improvements in endothelial function and reduced levels of CVD risk factors, such as lipids, glucose, and blood pressure; and enhancement of cardiorespiratory fitness