Daily physical activity assessment with accelerometers: new insights and validation studies

Influence of Accelerometer Placement and/or Heart Rate on Energy Expenditure Prediction during Uphill Exercise

Studies using a triaxial accelerometer and heart rate (HR) simultaneously for estimating energy expenditure (EE) during uphill exercise are rare. Exploring the optimal location for placing the accelerometer for predicting EE during uphill exercise is essential. Sixteen healthy male participants (M ± SEM; age 25.00 ± 0.61 years; body weight 74.13 ± 2.51 kg; body height 1.74 ± 0.01 m; body mass index 24.30 ± 0.63 kg/m²) exercised on a treadmill under 12 conditions (4 speeds and 3 gradients) on 3 days. Triaxial accelerometers, an HR recorder, and a metabolic measurement system were simultaneously used. Accelerometer outputs from various anatomical locations (upper arm, chest, lower back, waist, thigh, and instep) showed significant positive correlations with EE (0.819, 0.846, 0.816, 0.820, 0.672, and 0.669, respectively; p < .05). The linear regression equation for changes in HR showed the highest coefficient of determination (r²) of .837 with 87.9% reliability. When the HR signal was included, the r² value (> .842) and reliability (87.9%) between the accelerometer outputs and EE improved. Accelerometer outputs from the waist position alone provide highly accurate EE values. Using both accelerometer outputs and HR for EE estimation during uphill exercise is feasible and improves the accuracy of EE prediction.

Assessment of lower arm movements using one inertial sensor

Reduction of the number of sensors needed to evaluate arm movements, makes a system for the assessment of human body movements more suitable for clinical practice and daily life assessments. In this study, we propose an algorithm to reconstruct lower arm orientation, velocity and position, based on a sensing system which consists of only one inertial measurement unit (IMU) to the forearm. Lower arm movements were reconstructed using a single IMU and assuming that within a measurement there are moments without arm movements. The proposed algorithm, together with a single IMU attached to the forearm, may be used to evaluate lower arm movements during clinical assessments or functional tasks. In this pilot study, reconstructed quantities were compared with an optical reference system. The limits of agreement in the magnitude of the orientation vector and the norm of the velocity vectors are respectively 4.2 deg (normalized, 5.2 percent) and 7.1 cm/s (normalized, 5.8 percent). The limit of agreement of the difference between the reconstructed positions of both sensing systems were relatively greater 7.7 cm (normalized, 16.8 percent).

The activPALTM Accurately Classifies Activity Intensity Categories in Healthy Adults

The activPAL (AP) monitor is well established for distinguishing sitting, standing, and stepping time. However, its validity in predicting time in physical activity intensity categories in a free-living environment has not been determined.

PURPOSE

This study aimed to determine the validity of the AP in estimating time spent in sedentary, light, and moderate-to-vigorous physical activity (MVPA) in a free-living environment.

METHODS

Thirteen participants (mean ± SD age = 24.8 ± 5.2 yr, BMI = 23.8 ± 1.9 kg·m) were directly observed for three 10-h periods wearing an AP. A custom R program was developed and used to summarize detailed active and sedentary behavior variables from the AP. AP estimates were compared with direct observation.

RESULTS

The AP accurately and precisely estimated time in activity intensity categories (bias [95% confidence interval]; sedentary = 0.8 min [-2.9 to 4.5], light = 1.7 min [2.2-5.7], and -2.6 min [-5.8 to 0.7]). The overall accuracy rate for time in intensity categories was 96.2%. The AP also accurately estimated guideline minutes, guideline bouts, prolonged sitting minutes, and prolonged sitting bouts.

CONCLUSION

The AP can be used to accurately capture individualized estimates of active and sedentary behavior variables in free-living settings.

Physical Activity in Pediatric Pulmonary Arterial Hypertension Measured by Accelerometry. A Candidate Clinical Endpoint

RATIONALE

The development of evidence-based treatment guidelines for pediatric pulmonary arterial hypertension (PAH) is hampered by lack of pediatric clinical trials. Trial design is hampered by lack of a feasible clinical endpoint in this population.

OBJECTIVES

To evaluate the use of accelerometry for measuring physical activity (PA) in pediatric PAH and to investigate its correlation with clinical disease severity markers.

METHODS

We included children from the Dutch National Network for Pediatric Pulmonary Hypertension. Control patients were recruited from the outpatient cardiology clinic of the Beatrix Children's Hospital. Children were asked to wear the accelerometer for 7 days. Vector magnitude counts per minute (VM CPM) and time per day spent in different PA intensity levels were defined as accelerometer outcomes.

MEASUREMENTS AND MAIN RESULTS

VM CPM was lower in children with PAH (n = 29) than in controls (n = 60; 647 vs. 921; P < 0.001). Children with PAH spent less time in moderate and vigorous PA (13 vs. 29 min/d and 2 vs. 13 min/d, respectively; P < 0.001). Time spent in moderate and vigorous PA correlated inversely with World Health Organization functional class. Time spent in moderate PA correlated positively with 6-minute-walk distance. In post hoc analyses, VM CPM and time spent in moderate/vigorous combined and vigorous PA were associated with outcome (P ≤ 0.044).

CONCLUSIONS

PA is markedly decreased in children with PAH. Accelerometer output correlated with clinical disease severity markers and may predict outcome. We showed an exciting potential of PA as a meaningful endpoint for clinical trials in pediatric PAH, although its clinical utility and prognostic value need to be further validated.

Wearable sensors: can they benefit patients with chronic kidney disease?

INTRODUCTION

This article ponders upon wearable medical measurement devices in relation to Chronic Kidney Disease (CKD) and its' associated comorbidities - and whether these might benefit CKD-patients. We aimed to map the intersection(s) of nephrology and wearable sensor technology to help technologists understand medical aspects, and clinicians to understand technological possibilities that are available (or soon will become so). Areas covered: A structured literature search on main comorbidities and complications CKD patients suffer from, was used to steer mini-reviews on wearable sensor technologies clustered around 3 themes being: Cardiovascular-related, diabetes-related and physical fitness/frailty. This review excludes wearable dialysis - although also strongly enabled by miniaturization - because that highly important theme deserves separate in-depth reviewing. Expert commentary: Continuous progress in integrated electronics miniaturization enormously lowered price, size, weight and energy consumption of electronic sensors, processing power, memory and wireless connectivity. These combined factors boost opportunities for wearable medical sensors. Such devices can be regarded as enablers for: Remote monitoring, influencing human behaviour (exercise, dietary), enhanced home care, remote consults, patient education and peer networks. However, to make wearable medical devices succeed, the challenge to fit them into health care structures will be dominant over the challenge to realize the bare technologies themselves.

Effect of an Internet-Based Program on Weight Loss for Low-Income Postpartum Women: A Randomized Clinical Trial

IMPORTANCE

Postpartum weight retention increases lifetime risk of obesity and related morbidity. Few effective interventions exist for multicultural, low-income women.

OBJECTIVE

To test whether an internet-based weight loss program in addition to the Special Supplemental Nutrition Program for Women, Infants, and Children (WIC program) for low-income postpartum women could produce greater weight loss than the WIC program alone over 12 months.

DESIGN, SETTING, AND PARTICIPANTS

A 12-month, cluster randomized, assessor-blind, clinical trial enrolling 371 adult postpartum women at 12 clinics in WIC programs from the California central coast between July 2011 and May 2015 with data collection completed in May 2016.

INTERVENTIONS

Clinics were randomized to the WIC program (standard care group) or the WIC program plus a 12-month primarily internet-based weight loss program (intervention group), including a website with weekly lessons, web diary, instructional videos, computerized feedback, text messages, and monthly face-to-face groups at the WIC clinics.

MAIN OUTCOMES AND MEASURES

The primary outcome was weight change over 12 months, based on measurements at baseline, 6 months, and 12 months. Secondary outcomes included proportion returning to preconception weight and changes in physical activity and diet.

RESULTS

Participants included 371 women (mean age, 28.1 years; Hispanic, 81.6%; mean weight above prepregnancy weight, 7.8 kg; mean months post partum, 5.2 months) randomized to the intervention group (n = 174) or standard care group (n = 197); 89.2% of participants completed the study. The intervention group produced greater mean 12-month weight loss compared with the standard care group (3.2 kg in the intervention group vs 0.9 kg in standard care group, P < .001; difference, 2.3 kg (95% CI, 1.1 to 3.5). More participants in the intervention group than the standard care group returned to preconception weight by 12 months (32.8% in the intervention group vs 18.6% in the standard care group, P < .001; difference, 14.2 percentage points [95% CI, 4.7 to 23.5]). The intervention group and standard care group did not significantly differ in 12-month changes in physical activity (mean [95% CI]: -7.8 min/d [-16.1 to 0.4] in the intervention group vs -7.2 min/d [-14.6 to 0.3] in the standard care group; difference, -0.7 min/d [95% CI, -42.0 to 10.6], P = .76), calorie intake (mean [95% CI]: -298 kcal/d [-423 to -174] in the intervention group vs -144 kcal/d [-257 to -32] in the standard care group; difference, -154 kcal/d [-325 to 17], P = .06), or incidences of injury (16 in the intervention group vs 16 in the standard care group) or low breastmilk supply from baseline to month 6 (21 of 61 participants in the intervention group vs 23 of 72 participants in the standard care group) and from month 6 to 12 (13 of 32 participants in the intervention group vs 14 of 37 participants in the standard care group).

CONCLUSIONS AND RELEVANCE

Among low-income postpartum women, an internet-based weight loss program in addition to the Special Supplemental Nutrition Program for Women, Infants, and Children (WIC program) compared with the WIC program alone resulted in a statistically significant greater weight loss over 12 months. Further research is needed to determine program and cost-effectiveness as part of the WIC program.

TRIAL REGISTRATION

clinicaltrials.gov Identifier: NCT01408147.

Physical inactivity and sedentary behavior: Overlooked risk factors in autoimmune rheumatic diseases?

This review aims to (1) summarize the estimates of physical inactivity and sedentary behavior in autoimmune rheumatic diseases; (2) describe the relationship between physical (in)activity levels and disease-related outcomes; (3) contextualize the estimates and impact of physical inactivity and sedentary behavior in autoimmune diseases compared to other rheumatic diseases and chronic conditions; and (4) discuss scientific perspectives around this theme and potential clinical interventions to attenuate these preventable risk factors. We compiled evidence to show that estimates of physical inactivity and sedentary behavior in autoimmune rheumatic diseases are generally comparable to other rheumatic diseases as well as to other chronic conditions (e.g., type 2 diabetes, cardiovascular diseases, and obesity), in which a lack of physical activity and excess of sedentary behavior are well-known predictors of morbimortality. In addition, we also showed evidence that both physical inactivity and sedentary behavior may be associated with poor health-related outcomes (e.g., worse disease symptoms and low functionality) in autoimmune rheumatic diseases. Thus, putting into practice interventions to make the patients "sit less and move more", particularly light-intensity activities and/or breaking-up sedentary time, is a simple and prudent therapeutic approach to minimize physical inactivity and sedentary behavior, which are overlooked yet modifiable risk factors in the field of autoimmune rheumatic diseases.

Clinical Evaluation of the Measurement Performance of the Philips Health Watch: A Within-Person Comparative Study

BACKGROUND

Physical inactivity is an important modifiable risk factor for chronic diseases. A new wrist-worn heart rate and activity monitor has been developed for unobtrusive data collection to aid prevention and management of lifestyle-related chronic diseases by means of behavioral change programs.

OBJECTIVE

The objective of the study was to evaluate the performance of total energy expenditure and resting heart rate measures of the Philips health watch. Secondary objectives included the assessment of accuracy of other output parameters of the monitor: heart rate, respiration rate at rest, step count, and activity type recognition.

METHODS

A within-person comparative study was performed to assess the performance of the health watch against (medical) reference measures. Participants executed a protocol including 15 minutes of rest and various activities of daily life. A two one-sided tests approach was adopted for testing equivalence. In addition, error metrics such as mean error and mean absolute percentage error (MAPE) were calculated.

RESULTS

A total of 29 participants (14 males; mean age 41.2, SD 14.4, years; mean weight 77.2, SD 10.2, kg; mean height 1.8, SD 0.1, m; mean body mass index 25.1, SD 3.1, kg/m2) completed the 81-minute protocol. Their mean resting heart rate in beats per minute (bpm) was 64 (SD 7.3). With a mean error of -10 (SD 38.9) kcal and a MAPE of 10% (SD 8.7%), total energy expenditure estimation of the health watch was found to be within the 15% predefined equivalence margin in reference to a portable indirect calorimeter. Resting heart rate determined during a 15-minute rest protocol was found to be within a 10% equivalence margin in reference to a wearable electrocardiogram (ECG) monitor, with a mean deviation of 0 bpm and a maximum deviation of 3 bpm. Heart rate was within 10 bpm and 10% of the ECG monitor reference for 93% of the duration of the protocol. Step count estimates were on average 21 counts lower than a waist-mounted step counter over all walking activities combined, with a MAPE of 3.5% (SD 2.4%). Resting respiration rate was on average 0.7 (SD 1.1) breaths per minute lower than the reference measurement by the spirometer embedded in the indirect calorimeter during the 15-minute rest, resulting in a MAPE of 8.3% (SD 7.0%). Activity type recognition of walking, running, cycling, or other was overall 90% accurate in reference to the activities performed.

CONCLUSIONS

The health watch can serve its medical purpose of measuring resting heart rate and total energy expenditure over time in an unobtrusive manner, thereby providing valuable data for the prevention and management of lifestyle-related chronic diseases.

TRIAL REGISTRATION

Netherlands trial register NTR5552; http://www.trialregister.nl/trialreg/admin/rctview.asp?TC=5552 (Archived by WebCite at http://www.webcitation.org/6neYJgysl).

Usefulness of motion sensors to estimate energy expenditure in children and adults: a narrative review of studies using DLW

It is well documented that meeting moderate-to-vigorous physical activity guidelines of 150 min per week is protective against chronic disease, and this is likely explained by higher energy expenditure (EE). In opposition, sedentary behavior (low EE) seems to impair health outcomes. There are gold standard methods to measure EE such as the doubly labeled water (DLW) or calorimetry. These methods are highly expensive and rely on complex techniques. Motion sensors present a good alternative to estimate EE and have been validated against these reference methods. This review summarizes findings from previous reviews and the most recently published studies on the validity of different motion sensors to estimate physical activity energy expenditure (PAEE) and total energy expenditure (TEE) against DLW, and whether adding other indicators may improve these estimations in children and adults. Regardless of the recognized validity of motion sensors to estimate PAEE and TEE at the group level, individual bias is very high even when combining biometric or physiological indicators. In children, accelerometers explained 13% of DLW's PAEE variance and 31% of TEE variance. In adults, DLW's explained variance was higher, 29 and 44% for PAEE and TEE, respectively. There is no ideal device, but identifying postures seems to be relevant for both children and adults' PAEE estimates. The variance associated with the number of methodological choices that these devices require invite investigators to work with the raw data in order to standardize all these procedures and potentiate the accelerometer signal-derived information. Models that consider biometric covariates seem only to improve TEE estimations, but adding heart rate enhances PAEE estimations in both children and adults.

Smart approaches for assessing free-living energy expenditure following identification of types of physical activity

Accurate assessment of physical activity and energy expenditure has been a research focus for many decades. A variety of wearable sensors have been developed to objectively capture physical activity patterns in daily life. These sensors have evolved from simple pedometers to tri-axial accelerometers, and multi sensor devices measuring different physiological constructs. The current review focuses on how activity recognition may help to improve daily life energy expenditure assessment. A brief overview is given about how different sensors have evolved over time to pave the way for recognition of different activity types. Once the activity is recognized together with the intensity of the activity, an energetic value can be attributed. This concept can then be tested in daily life using the independent reference technique doubly labeled water. So far, many studies have been performed to accurately identify activity types, and some of those studies have also successfully translated this into energy expenditure estimates. Most of these studies have been performed under standardized conditions, and the true applicability in daily life has rarely been addressed. The results so far however are highly promising, and technological advancements together with newly developed algorithms based on physiological constructs will further expand this field of research.

Physical Activity and Sleep Patterns in Hemodialysis Patients in a Suburban Environment

Background/Aims: Hemodialysis (HD) patients are less active than their healthy counterparts. They are often plagued with sleep disorders that affect the quality of their sleep. Our aim was to objectively quantify activity and sleep quality among HD patients in a suburban HD population. Methods: Activity and sleep parameters were measured using a commercially available activity tracker in 29 HD patients from Baton Rouge, LA, USA. Patients in the feedback group received their activity and sleep data at each dialysis treatment. In addition, questionnaires were administered at the beginning and end of the study period. Patients were stratified based on activity levels and sleep quality. Results: Patients walked an average of 5,281 steps/day and slept 370.5 min/night. Informing patients about their daily number of steps taken, did not increase activity. Only 3% of the population followed were active, defined as walking more than 10,000 steps per day. Patients walked significantly less on dialysis days compared to the other days of the week. Many of the patients experienced poor sleep quality, with patients in the first shift experiencing the greatest disturbance to their sleep/wake cycle. Conclusion: Patients in a suburban environment walked much less than those in a previously studied urban population. They rarely met the recommended goal of 10,000 steps/day, even on non-dialysis days. Interventions to increase physical activity may target any day of the week, particularly HD days. Prospective, long-term studies are needed to evaluate the use of activity trackers in dialysis patients and their impact on physical activity.

Measuring Physical Activity in Free-Living Conditions-Comparison of Three Accelerometry-Based Methods

We examined the agreement in time spent on different physical activity (PA) levels using (1) mean amplitude deviation (MAD) of raw acceleration from the hip, (2) wrist-worn Polar Active, and (3) hip-worn Actigraph counts using Freedson's cut-points among adults under free-living conditions. PA was measured in 41 volunteers (mean age 47.6 years) for 14 days. Two MET-based threshold sets were used for MAD and Polar Active for sedentary time (ST) and time spent in light (LPA), moderate (MPA), and vigorous (VPA) PA. Actigraph counts were divided into PA classes, ≤100 counts/min for ST and Freedson's cut-points for LPA, MPA, and VPA. Analysis criteria were simultaneous use of devices for at least 4 days of >500 min/d. The between-method differences were analyzed using a repeated measures analysis of variance test. Bland-Altman plots and ROC graphs were also employed. Valid data were available from 27 participants. Polar Active produced the highest amount of VPA with both thresholds (≥5 and ≥6 MET; mean difference 17.9-30.9 min/d, P < 0.001). With the threshold 3-6 MET for MPA, Polar Active indicated 19.2 min/d more than MAD (95% CI 5.8-32.6) and 51.0 min/d more than Actigraph (95% CI 36.7-65.2). The results did not differ with 3.5-5 MET for MPA [F_{(1.44, 37.43)} = 1.92, P = 0.170]. MAD and Actigraph were closest to each other for ST with the threshold < 1.5 MET (mean difference 22.2 min/d, 95% CI 7.1-37.3). With the threshold <2 MET, Polar Active and Actigraph provided similar results (mean difference 7.0 min/d, 95% CI -17.8-31.7). Moderate to high agreement (area under the ROC curve 0.806-0.963) was found between the methods for the fulfillment of the recommendation for daily moderate-to-vigorous PA of 60 min. In free-living conditions the agreement between MAD, Polar Active, and Actigraph for measuring time spent on different activity levels in adults was dependent on the activity thresholds used and PA intensity. ROC analyses showed moderate to high agreement for the fulfillment of the recommendation for daily MVPA. Without additional statistical adjustment, these methods cannot be used interchangeably when measuring daily PA, but any of the methods can be used to identify persons with insufficient daily amount of MVPA.

Impact of an 8-Month Trial Using Height-Adjustable Desks on Children's Classroom Sitting Patterns and Markers of Cardio-Metabolic and Musculoskeletal Health

During school hours, children can sit for prolonged and unbroken periods of time. This study investigated the impact of an 8-month classroom-based intervention focusing on reducing and breaking-up sitting time on children’s cardio-metabolic risk factors (i.e., body mass index, waist circumference, blood pressure) and perceptions of musculoskeletal discomfort. Two Year-6 classes (24 students per class) in one primary school were assigned to either an intervention or control classroom. The intervention classroom was equipped with height-adjustable desks and the teacher was instructed in the delivery of pedagogical strategies to reduce and break-up sitting in class. The control classroom followed standard practice using traditional furniture. At baseline, and after 8-months, time spent sitting, standing, stepping, and sitting-bouts (occasions of continuous sitting) as well as the frequency of sit-to-stand transitions were obtained from activPAL inclinometers and the time spent in light-intensity physical activity was obtained from ActiGraph accelerometers. Demographics and musculoskeletal characteristics were obtained from a self-report survey. Hierarchical linear mixed models found that during class-time, children’s overall time spent sitting in long bouts (>10 min) were lower and the number of sit-to-stand transitions were higher in the intervention group compared to the control group, while no changes were observed for musculoskeletal pain/discomfort. No significant intervention effects were found for the anthropometrics measures and blood pressure. Height-adjustable desks and pedagogical strategies to reduce/break-up sitting can positively modify classroom sitting patterns in children. Longer interventions, larger and varied sample size may be needed to show health impacts; however, these desks did not increase musculoskeletal pain/discomfort.

Diurnal Patterns of Physical Activity in Relation to Activity Induced Energy Expenditure in 52 to 83 Years-Old Adults

Background

Ageing is associated with a declining physical activity level (PAL) and changes in the diurnal activity pattern. Changes in the activity pattern might help explaining the age-associated reduction of physical activity.

Objective

The aims were to investigate diurnal activity patterns within groups of older adults classified by PAL, to investigate diurnal activity patterns within age-groups and to investigate the association between the drop in activity and aerobic fitness.

Methods

Thirty-one healthy subjects aged between 52 and 83y were recruited for the study. Subjects were divided in sedentary (PAL<1.75), moderately active (1.75<PAL<1.90), and active (1.90<PAL) older adults with energy expenditure measurements obtained with the doubly labelled water technique. Diurnal activity patterns were based on activity counts from an accelerometer during wake time and then divided in four quarters of equal time length. Additionally, aerobic fitness was measured as maximal oxygen uptake.

Results

Subjects had a PAL between 1.43 and 2.34 and an aerobic fitness between 18 and 49 ml/kg/min. Overall, activity patterns showed a peak in the first quarter of wake time (around 10AM) followed by a gradual decline of, on average, 5% per hour. Active subjects reached their peak in the first quarter and remained active until after the third quarter (11% drop each quarter on average). Moderately active and sedentary subjects reached their peak during the second quarter with a decrease during the third quarter (respectively 29% and 17% drop each quarter on average). The drop in physical activity between the first and the second half of the wake time was negatively associated with aerobic fitness (r = -0.39, p<0.05).

Conclusion

Active older adults maintained a larger amount of body movement for longer during their wake time. Diurnal physical activity declined more in adults ≥66 years old with lower aerobic fitness.

Obesity and energy balance: What is the role of physical activity?

Despite billions of dollars spent over decades of research, debate remains over the causes and solutions of the obesity epidemic. The specific role of physical activity in the prevention or treatment of obesity seems a particularly contentious issue, with opposing views put forth in both academic and popular media. In an attempt to provide context and clarity to the specific question of the role of physical activity in determination of body weight, we have attempted to identify evidence or lack thereof in the scientific literature and provide a summary of our findings. Areas covered: Topics included in this narrative review are an overview of energy balance, the relationship between physical activity and energy expenditure, compensatory responses in non-exercise energy expenditure and energy intake, and the relationship between physical activity and obesity. Expert commentary: Based on a review of the existing literature, daily physical activity and structured exercise has beneficial effects on an individual's body weight. In most instances, exercise occurring in adequate amounts will increase total daily energy expenditure and create an acute energy deficit, without compensatory decreases in non-exercise physical activity or energy expenditure nor compensatory increases in energy intake. Several gaps in the literature exist, both in terms of the number of adequately powered clinical trials with rigorous assessments of both energy intake and expenditure, and with a variety of study populations (by age, sex, race, etc.) and with varying exercise volumes and intensities.

Motivational Profiles for Physical Activity Practice in Adults with Type 2 Diabetes: A Self-Determination Theory Perspective

Drawing on Self-Determination Theory, this study explored the motivational profiles toward Physical Activity (PA) among adults with type 2 diabetes and the relationships between motivational profile, perceived competence and PA. Participants were 350 men and women (Mean age 62.77 years) who were interviewed on their motivations toward PA, perceived level of competence to practice, and PA practice. Cluster analyses reveal the existence of three distinct profiles: "High Combined" (ie, high scores on motivations ranging from intrinsic to external regulation, moderate level on amotivation), "Self-Determined" (ie, high scores on intrinsic, integrated, and identified regulations; low scores on other regulations), and "Moderate" (ie, moderate scores on all regulations). Participants with "High Combined" and "Self-Determined" profiles reported higher perceived competence and longer leisure-time PA practice in comparison to those with a "Moderate" profile. This study highlights the necessity of adopting a person-centered approach to better understand motivation toward PA among type 2 diabetics.

Validation study of Polar V800 accelerometer

BACKGROUND

The correct quantification of physical activity (PA) and energy expenditure (EE) in daily life is an important target for researchers and professionals. The objective of this paper is to study the validity of the Polar V800 for the quantification of PA and the estimation of EE against the ActiGraph (ActiTrainer) in healthy young adults.

METHODS

Eighteen Caucasian active people (50% women) aged between 19-23 years wore an ActiTrainer on the right hip and a Polar V800 on the preferred wrist during 7 days. Paired samples t-tests were used to analyze differences in outcomes between devices, and Pearson's correlation coefficients to examine the correlation between outcomes. The agreement was studied using the Bland-Altman method. Also, the association between the difference and the magnitude of the measurement (heteroscedasticity) was examined. Sensitivity, specificity and area under the receiver operating characteristic curve (ROC-AUC value) were calculated to evaluate the ability of the devices to accurately define a person who fulfills the recommendation of 10,000 daily steps.

RESULTS

The devices significantly differed from each other on all outcomes (P<0.05), except for Polar V800's alerts vs. ActiTrainer's 1 hour sedentary bouts (P=0.595) and Polar V800's walking time vs. ActiTrainer's lifestyle time (P=0.484). Heteroscedasticity analyses were significant for all outcomes, except for Kcal and sitting time. The ROC-AUC value was fair (0.781±0.048) and the sensitivity and specificity was 98% and 58%, respectively.

CONCLUSIONS

The Polar V800 accelerometer has a comparable validity to the accelerometer in free-living conditions, regarding "1 hour sedentary bouts" and "V800's walking time vs. ActiTrainer's lifestyle time" in young adults.

Using uncertain data from body-worn sensors to gain insight into type 1 diabetes

The amount of observational data available for research is growing rapidly with the rise of electronic health records and patient-generated data. However, these data bring new challenges, as data collected outside controlled environments and generated for purposes other than research may be error-prone, biased, or systematically missing. Analysis of these data requires methods that are robust to such challenges, yet methods for causal inference currently only handle uncertainty at the level of causal relationships – rather than variables or specific observations. In contrast, we develop a new approach for causal inference from time series data that allows uncertainty at the level of individual data points, so that inferences depend more strongly on variables and individual observations that are more certain. In the limit, a completely uncertain variable will be treated as if it were not measured. Using simulated data we demonstrate that the approach is more accurate than the state of the art, making substantially fewer false discoveries. Finally, we apply the method to a unique set of data collected from 17 individuals with type 1 diabetes mellitus (T1DM) in free-living conditions over 72 h where glucose levels, insulin dosing, physical activity and sleep are measured using body-worn sensors. These data often have high rates of error that vary across time, but we are able to uncover the relationships such as that between anaerobic activity and hyperglycemia. Ultimately, better modeling of uncertainty may enable better translation of methods to free-living conditions, as well as better use of noisy and uncertain EHR data.

Towards human exploration of space: The THESEUS review series on nutrition and metabolism research priorities

Nutrition has multiple roles during space flight from providing sufficient nutrients to meet the metabolic needs of the body and to maintain good health, to the beneficial psychosocial aspects related to the meals. Nutrition is central to the functioning of the body; poor nutrition compromises all the physiological systems. Nutrition is therefore likely to have a key role in counteracting the negative effects of space flight (e.g., radiation, immune deficits, oxidative stress, and bone and muscle loss). As missions increase in duration, any dietary/nutritional deficiencies will become progressively more detrimental. Moreover, it has been recognized that the human diet contains, in addition to essential macronutrients, a complex array of naturally occurring bioactive micronutrients that may confer significant long-term health benefits. It is therefore critical that astronauts be adequately nourished during missions. Problems of nutritional origin are often treatable by simply providing the appropriate nutrients and adequate recommendations. This review highlights six key issues that have been identified as space research priorities in nutrition field: in-flight energy balance; altered feeding behavior; development of metabolic stress; micronutrient deficiency; alteration of gut microflora; and altered fluid and electrolytes balance. For each of these topics, relevance for space exploration, knowledge gaps and proposed investigations are described. Finally, the nutritional questions related to bioastronautics research are very relevant to multiple ground-based-related health issues. The potential spin-offs are both interesting scientifically and potentially of great clinical importance.

Sedentary Behavior and Cardiovascular Morbidity and Mortality: A Science Advisory From the American Heart Association

Epidemiological evidence is accumulating that indicates greater time spent in sedentary behavior is associated with all-cause and cardiovascular morbidity and mortality in adults such that some countries have disseminated broad guidelines that recommend minimizing sedentary behaviors. Research examining the possible deleterious consequences of excess sedentary behavior is rapidly evolving, with the epidemiology-based literature ahead of potential biological mechanisms that might explain the observed associations. This American Heart Association science advisory reviews the current evidence on sedentary behavior in terms of assessment methods, population prevalence, determinants, associations with cardiovascular disease incidence and mortality, potential underlying mechanisms, and interventions. Recommendations for future research on this emerging cardiovascular health topic are included. Further evidence is required to better inform public health interventions and future quantitative guidelines on sedentary behavior and cardiovascular health outcomes.

Correlation between the level of physical activity as measured by accelerometer and the Harris Hip Score

BACKGROUND

The most widely used method to assess the outcome of total hip arthroplasty (THA) is the Harris Hip Score (HHS). Patients' expectations about the benefits of hip arthroplasty are increasing and are no longer limited to pain reduction. Patients believe they will be able to do recreational activity and sport after surgery. It is also essential to assess the level of physical activity after arthroplasty insofar as it is associated with early failure of the components. The purpose of this study is to explore correlation of the HHS with physical activity in patients with THA.

METHODS

This is a cross-sectional study on 47 patients with THA. Correlation of HHS with the results of physical activity obtained objectively using accelerometer worn for a week and subjectively using the IPAQ questionnaire and the UCLA scale.

FINDING

There was no correlation between the HHS and the activity measured using accelerometers, or with the IPAQ activity questionnaire. The HHS reported moderately significant correlations with the UCLA scale.

CONCLUSIONS

The HHS may not be as discriminatory as other instruments at assessing patient activity levels after THA.

Agreement between activPAL3c accelerometers placed at different thigh positions

ActivPAL3c triaxial accelerometers are increasingly used to assess physical activity and sedentary behaviours. However, little is known how attachment site (left vs. right or upper vs. lower thigh) affects activPAL3c accelerometer outcomes. Twenty-eight adults wore four activPAL3c accelerometers attached 2cm above and below the midpoint of the left and right thigh during five minutes of laboratory-based walking at a self-selected pace, treadmill walking at 0.89 and 1.56m/s, and treadmill running at 2.22m/s, and during approximately seven hours of free-living conditions. One-way ANOVA revealed no statistically significant differences in accelerometer output between ActivPAL3c accelerometers at these locations during both laboratory-based, and free-living conditions. Intraclass correlation coefficients showed a high level of agreement between activPAL3c accelerometers during laboratory and free living activities (ICC(2,1) 0.76-1.00). The attachment sites used in this study do not appear to significantly influence outcomes for step count, sitting or walking time, or number of postural transitions from triaxial activPAL3c accelerometers during laboratory-based walking or free-living conditions. Therefore if necessary, to enhance participant compliance during monitoring periods, these sites could be used interchangeably. Studies of longer duration incorporating additional laboratory and recreational activities are needed to confirm these findings.

Electronic Noses for Well-Being: Breath Analysis and Energy Expenditure

The wealth of information concealed in a single human breath has been of interest for many years, promising not only disease detection, but also the monitoring of our general well-being. Recent developments in the fields of nano-sensor arrays and MEMS have enabled once bulky artificial olfactory sensor systems, or so-called "electronic noses", to become smaller, lower power and portable devices. At the same time, wearable health monitoring devices are now available, although reliable breath sensing equipment is somewhat missing from the market of physical, rather than chemical sensor gadgets. In this article, we report on the unprecedented rise in healthcare problems caused by an increasingly overweight population. We first review recently-developed electronic noses for the detection of diseases by the analysis of basic volatile organic compounds (VOCs). Then, we discuss the primary cause of obesity from over eating and the high calorific content of food. We present the need to measure our individual energy expenditure from our exhaled breath. Finally, we consider the future for handheld or wearable devices to measure energy expenditure; and the potential of these devices to revolutionize healthcare, both at home and in hospitals.

Devices for Self-Monitoring Sedentary Time or Physical Activity: A Scoping Review

Background

It is well documented that meeting the guideline levels (150 minutes per week) of moderate-to-vigorous physical activity (PA) is protective against chronic disease. Conversely, emerging evidence indicates the deleterious effects of prolonged sitting. Therefore, there is a need to change both behaviors. Self-monitoring of behavior is one of the most robust behavior-change techniques available. The growing number of technologies in the consumer electronics sector provides a unique opportunity for individuals to self-monitor their behavior.

Objective

The aim of this study is to review the characteristics and measurement properties of currently available self-monitoring devices for sedentary time and/or PA.

Methods

To identify technologies, four scientific databases were systematically searched using key terms related to behavior, measurement, and population. Articles published through October 2015 were identified. To identify technologies from the consumer electronic sector, systematic searches of three Internet search engines were also performed through to October 1, 2015.

Results

The initial database searches identified 46 devices and the Internet search engines identified 100 devices yielding a total of 146 technologies. Of these, 64 were further removed because they were currently unavailable for purchase or there was no evidence that they were designed for, had been used in, or could readily be modified for self-monitoring purposes. The remaining 82 technologies were included in this review (73 devices self-monitored PA, 9 devices self-monitored sedentary time). Of the 82 devices included, this review identified no published articles in which these devices were used for the purpose of self-monitoring PA and/or sedentary behavior; however, a number of technologies were found via Internet searches that matched the criteria for self-monitoring and provided immediate feedback on PA (ActiGraph Link, Microsoft Band, and Garmin Vivofit) and sedentary time (activPAL VT, the Lumo Back, and Darma).

Conclusions

There are a large number of devices that self-monitor PA; however, there is a greater need for the development of tools to self-monitor sedentary time. The novelty of these devices means they have yet to be used in behavior change interventions, although the growing field of wearable technology may facilitate this to change.

Validity of two brief physical activity questionnaires with accelerometers among African-American women

AIM

To evaluate the validity of the Stanford Brief Activity Survey (SBAS) and Exercise Vital Sign (EVS) questionnaire against accelerometer-determined time in moderate-to-vigorous physical activity (MVPA) among African-American (AA) women.

BACKGROUND

Limited research has evaluated the validity of brief physical activity (PA) questionnaires among AA women. Since the validity of PA questionnaires may differ among members of varying racial/ethnic groups, research is needed to explore the validity of self-report PA measures among AA women.

METHODS

A total of 30 AA women [M age = 35.5 ± 5.3; M body mass index (BMI) = 31.1 ± 7.8] wore ActiGraph GT3X+ accelerometers (ActiGraph, LLC, Pensacola FL, USA) for seven days and completed both the SBAS and EVS at two different assessment periods (T1 and T2). Criterion validity was calculated using Spearman's rank order correlations between each questionnaire score and accelerometer-measured MVPA. Sensitivity, specificity, and positive and negative predictive values were calculated using accelerometer-measured MVPA as the criterion to determine the ability of each questionnaire to predict whether or not a participant was meeting the 2008 US PA Guidelines.

FINDINGS

Spearman correlation coefficients between questionnaire scores and minutes of accelerometer-measured MVPA were low (EVS, r = 0.27 at T1 and r = 0.26 at T2; SBAS, r = 0.10 at T1 and r = 0.28 at T2) and not statistically significant (P's > 0.05). The EVS had sensitivity, specificity, and negative and positive predictive values of 27, 89, 59, and 68% at T1 and 33, 74, 38, and 70% at T2, respectively. The SBAS had sensitivity, specificity, and negative and positive predictive values were 18, 79, 33, and 62% at T1 and 67, 58, 43, and 79% at T2. While both questionnaires may be useful in identifying AA women who do not meet the 2008 PA Guidelines, using the questionnaires to identify AA women meeting the PA Guidelines should be done with caution.

Changes in hunger and fullness in relation to gut peptides before and after 8 weeks of alternate day fasting

BACKGROUND & AIMS

Alternate day fasting (ADF; 25% energy intake "fast day", alternated with an ad libitum intake "feed day") is effective for weight loss. Whether or not ADF modulates hunger, fullness and gut peptides in a way that enhances dietary compliance and weight loss, remains unknown. Accordingly, this study examined the effect of ADF on postprandial appetite ratings and gut peptides.

METHODS

Obese subjects (n = 59) participated in an 8-week ADF protocol where food was provided on the fast day.

RESULTS

Body weight decreased (P < 0.0001) by 3.9 ± 0.6 kg after 8 weeks of diet. Reductions (P < 0.05) in fat mass (-2.2 ± 0.2 kg), fat free mass (-1.4 ± 0.2 kg), visceral fat mass (-0.1 ± 0.1 kg), and resting metabolic rate (RMR; -104 ± 28 kcal/day) were also observed. Fasting leptin and insulin decreased (P < 0.05), while AUC ghrelin levels increased (P < 0.05). Despite these metabolic changes, there was no increase in subjective hunger by the end of the study. Furthermore, fullness and PYY increased (P < 0.05). Fat free mass and RMR were not related to hunger or ghrelin at any time point.

CONCLUSION

These findings suggest that the absence of a compensatory increase in hunger in conjunction with an increase in sensations of fullness may contribute to the weight loss efficacy of an 8-week ADF regimen.

Objectively Measured Physical Activity in European Adults: Cross-Sectional Findings from the Food4Me Study

Background

Comparisons of objectively measured physical activity (PA) between residents of European countries measured concurrently with the same protocol are lacking. We aimed to compare PA between the seven European countries involved in the Food4Me Study, using accelerometer data collected remotely via the Internet.

Methods

Of the 1607 participants recruited, 1287 (539 men and 748 women) provided at least 3 weekdays and 2 weekend days of valid accelerometer data (TracmorD) at baseline and were included in the present analyses.

Results

Men were significantly more active than women (physical activity level = 1.74 vs. 1.70, p < 0.001). Time spent in light PA and moderate PA differed significantly between countries but only for women. Adherence to the World Health Organization recommendation to accumulate at least 150 min of moderate-equivalent PA weekly was similar between countries for men (range: 54–65%) but differed significantly between countries for women (range: 26–49%). Prevalence estimates decreased substantially for men and women in all seven countries when PA guidelines were defined as achieving 30 min of moderate and vigorous PA per day.

Conclusions

We were able to obtain valid accelerometer data in real time via the Internet from 80% of participants. Although our estimates are higher compared with data from Sweden, Norway, Portugal and the US, there is room for improvement in PA for all countries involved in the Food4Me Study.

Evaluation of the ability of three physical activity monitors to predict weight change and estimate energy expenditure

Activity monitors such as the Actical accelerometer, the Sensewear armband, and the Intelligent Device for Energy Expenditure and Activity (IDEEA) are commonly validated against gold standards (e.g., doubly labeled water, or DLW) to determine whether they accurately measure total daily energy expenditure (TEE) or activity energy expenditure (AEE). However, little research has assessed whether these parameters or others (e.g., posture allocation) predict body weight change over time. The aims of this study were to (i) test whether estimated energy expenditure or posture allocation from the devices was associated with weight change during and following a low-calorie diet (LCD) and (ii) compare free-living TEE and AEE predictions from the devices against DLW before weight change. Eighty-seven participants from 2 clinical trials wore 2 of the 3 devices simultaneously for 1 week of a 2-week DLW period. Participants then completed an 8-week LCD and were weighed at the start and end of the LCD and 6 and 12 months after the LCD. More time spent walking at baseline, measured by the IDEEA, significantly predicted greater weight loss during the 8-week LCD. Measures of posture allocation demonstrated medium effect sizes in their relationships with weight change. Bland-Altman analyses indicated that the Sensewear and the IDEEA accurately estimated TEE, and the IDEEA accurately measured AEE. The results suggest that the ability of energy expenditure and posture allocation to predict weight change is limited, and the accuracy of TEE and AEE measurements varies across activity monitoring devices, with multi-sensor monitors demonstrating stronger validity.

Should we reframe how we think about physical activity and sedentary behaviour measurement? Validity and reliability reconsidered

Background

The measurement of physical activity (PA) and sedentary behaviour (SB) is fundamental to health related research, policy, and practice but there are well known challenges to these measurements. Within the academic literature, the terms “validity” and “reliability” are frequently used when discussing PA and SB measurement to reassure the reader that they can trust the evidence.

Discussion

In this paper we argue that a lack of consensus about the best way to define, assess, or utilize the concepts of validity and reliability has led to inconsistencies and confusion within the PA and SB evidence base. Where possible we propose theoretical examples and solutions. Moreover we present an overarching framework (The Edinburgh Framework) which we believe will provide a process or pathway to help researchers and practitioners consider validity and reliability in a standardized way.

Conclusion

Further work is required to identify all necessary and available solutions and generate consensus in our field to develop the Edinburgh Framework into a useful practical resource. We envisage that ultimately the proposed framework will benefit research, practice, policy, and teaching. We welcome critique, rebuttal, comment, and discussion on all ideas presented.

Changes in Physical Activity Following a Genetic-Based Internet-Delivered Personalized Intervention: Randomized Controlled Trial (Food4Me)

Background

There is evidence that physical activity (PA) can attenuate the influence of the fat mass- and obesity-associated (FTO) genotype on the risk to develop obesity. However, whether providing personalized information on FTO genotype leads to changes in PA is unknown.

Objective

The purpose of this study was to determine if disclosing FTO risk had an impact on change in PA following a 6-month intervention.

Methods

The single nucleotide polymorphism (SNP) rs9939609 in the FTO gene was genotyped in 1279 participants of the Food4Me study, a four-arm, Web-based randomized controlled trial (RCT) in 7 European countries on the effects of personalized advice on nutrition and PA. PA was measured objectively using a TracmorD accelerometer and was self-reported using the Baecke questionnaire at baseline and 6 months. Differences in baseline PA variables between risk (AA and AT genotypes) and nonrisk (TT genotype) carriers were tested using multiple linear regression. Impact of FTO risk disclosure on PA change at 6 months was assessed among participants with inadequate PA, by including an interaction term in the model: disclosure (yes/no) × FTO risk (yes/no).

Results

At baseline, data on PA were available for 874 and 405 participants with the risk and nonrisk FTO genotypes, respectively. There were no significant differences in objectively measured or self-reported baseline PA between risk and nonrisk carriers. A total of 807 (72.05%) of the participants out of 1120 in the personalized groups were encouraged to increase PA at baseline. Knowledge of FTO risk had no impact on PA in either risk or nonrisk carriers after the 6-month intervention. Attrition was higher in nonrisk participants for whom genotype was disclosed (P=.01) compared with their at-risk counterparts.

Conclusions

No association between baseline PA and FTO risk genotype was observed. There was no added benefit of disclosing FTO risk on changes in PA in this personalized intervention. Further RCT studies are warranted to confirm whether disclosure of nonrisk genetic test results has adverse effects on engagement in behavior change.

Trial Registration

ClinicalTrials.gov NCT01530139; http://clinicaltrials.gov/show/NCT01530139 (Archived by WebCite at: http://www.webcitation.org/6XII1QwHz)

Prediction of activity-related energy expenditure using accelerometer-derived physical activity under free-living conditions: a systematic review

BACKGROUND/OBJECTIVES

Activity-related energy expenditure (AEE) might be an important factor in the etiology of chronic diseases. However, measurement of free-living AEE is usually not feasible in large-scale epidemiological studies but instead has traditionally been estimated based on self-reported physical activity. Recently, accelerometry has been proposed for objective assessment of physical activity, but it is unclear to what extent this methods explains the variance in AEE.

SUBJECTS/METHODS

We conducted a systematic review searching MEDLINE database (until 2014) on studies that estimated AEE based on accelerometry-assessed physical activity in adults under free-living conditions (using doubly labeled water method). Extracted study characteristics were sample size, accelerometer (type (uniaxial, triaxial), metrics (for example, activity counts, steps, acceleration), recording period, body position, wear time), explained variance of AEE (R(2)) and number of additional predictors. The relation of univariate and multivariate R(2) with study characteristics was analyzed using nonparametric tests.

RESULTS

Nineteen articles were identified. Examination of various accelerometers or subpopulations in one article was treated separately, resulting in 28 studies. Sample sizes ranged from 10 to 149. In most studies the accelerometer was triaxial, worn at the trunk, during waking hours and reported activity counts as output metric. Recording periods ranged from 5 to 15 days. The variance of AEE explained by accelerometer-assessed physical activity ranged from 4 to 80% (median crude R(2)=26%). Sample size was inversely related to the explained variance. Inclusion of 1 to 3 other predictors in addition to accelerometer output significantly increased the explained variance to a range of 12.5-86% (median total R(2)=41%). The increase did not depend on the number of added predictors.

CONCLUSIONS

We conclude that there is large heterogeneity across studies in the explained variance of AEE when estimated based on accelerometry. Thus, data on predicted AEE based on accelerometry-assessed physical activity need to be interpreted cautiously.

Constrained Total Energy Expenditure and Metabolic Adaptation to Physical Activity in Adult Humans

Current obesity prevention strategies recommend increasing daily physical activity, assuming that increased activity will lead to corresponding increases in total energy expenditure and prevent or reverse energy imbalance and weight gain [1-3]. Such Additive total energy expenditure models are supported by exercise intervention and accelerometry studies reporting positive correlations between physical activity and total energy expenditure [4] but are challenged by ecological studies in humans and other species showing that more active populations do not have higher total energy expenditure [5-8]. Here we tested a Constrained total energy expenditure model, in which total energy expenditure increases with physical activity at low activity levels but plateaus at higher activity levels as the body adapts to maintain total energy expenditure within a narrow range. We compared total energy expenditure, measured using doubly labeled water, against physical activity, measured using accelerometry, for a large (n = 332) sample of adults living in five populations [9]. After adjusting for body size and composition, total energy expenditure was positively correlated with physical activity, but the relationship was markedly stronger over the lower range of physical activity. For subjects in the upper range of physical activity, total energy expenditure plateaued, supporting a Constrained total energy expenditure model. Body fat percentage and activity intensity appear to modulate the metabolic response to physical activity. Models of energy balance employed in public health [1-3] should be revised to better reflect the constrained nature of total energy expenditure and the complex effects of physical activity on metabolic physiology.

Accelerometer Quantification of Physical Activity and Activity Patterns in Patients with Ankylosing Spondylitis and Population Controls

Objective.

To compare the total amount of physical activity (TPA) and time spent in various activity intensities of patients with ankylosing spondylitis (AS) and population controls, and to explore factors related to physical activity (PA).

Methods.

Subjects were asked to wear a triaxial accelerometer for 7 days and to complete a series of questionnaires. Multivariable regressions were used to assess generic determinants of TPA in patients and controls, and in patients to explore demographic and disease-specific determinants of various PA intensities.

Results.

One hundred and thirty-five patients [51 ± 13 yrs, 60% men, body mass index (BMI) 26.0 ± 4.3 kg/m2] and 99 controls (45 ± 12 yrs, 67% men, BMI 25.1 ± 4.3 kg/m2) were included. Patients did not differ from controls regarding TPA (589 vs 608 vector count/min, p = 0.98), minutes/day spent in sedentary (524 vs 541, p = 0.17), and light PA (290 vs 290 p = 0.95), but spent fewer minutes/day in moderate to vigorous PA (MVPA; 23 vs 30 min/day, p = 0.006). Perceived functional ability (physical component summary of the Medical Outcomes Study Short Form-36) and BMI were associated with TPA independent of having AS (p interaction = 0.21 and 0.94, respectively). Additional analyses in patients showed that time spent in MVPA was negatively influenced by BMI, physical function (Bath AS Functional Index), and disease duration. In patients ≥ 52 years old, a higher Bath AS Disease Activity Index was associated with less time spent in sedentary and more time spent in light activities.

Conclusion.

Compared with controls, patients with AS had similar TPA, but may avoid engagement in higher intensities of PA. Lower levels of functional ability and higher BMI were associated with lower TPA in both patients and controls.

Age group comparability of raw accelerometer output from wrist- and hip-worn monitors

PURPOSE

The study aims were to compare raw triaxial accelerometer output from ActiGraph GT3X+ (AG) and GENEActiv (GA) placed on the hip and the wrist and to develop regression equations for estimating energy expenditure.

METHODS

Thirty children (7-11 yr) and 30 adults (18-65 yr) completed eight activities (ranging from lying to running) while wearing one AG and one GA on the hip and the wrist. Oxygen consumption (V˙O2) was measured with indirect calorimetry. Analysis involved the use of ANOVA to examine the effect of activity, brand, and placement on the acceleration values, intraclass correlation coefficient to evaluate the agreement between the two brands and placements, and linear regression to establish intensity thresholds.

RESULTS

A significant difference in acceleration values between the hip and the wrist placement was found (P < 0.001). The output from the wrist placement was, in general, higher compared with that from the hip. There was no main effect of monitor brand in adults (P < 0.12) and children (P < 0.73), and the intraclass correlation coefficient showed a strong agreement (0.96-0.99). However, a three-way interaction and systematic error between the brands was found in children. Acceleration from both brands and placements showed a strong correlation with V˙O2. The intensity classification accuracy of the developed thresholds for both brands and placements was, in general, higher for adults compared with that for children and was greater for sedentary/light (93%-97%), and vigorous activities (68%-92%) than that for moderate activities (33%-59%).

CONCLUSIONS

Accelerometer outputs from AG and GA seem comparable when attached to the same body location in adults, whereas inconsistent differences are apparent between the two brands and placements in children, hence limiting the comparability between brands in this age group.

Effects of a Web-Based Personalized Intervention on Physical Activity in European Adults: A Randomized Controlled Trial

BACKGROUND

The high prevalence of physical inactivity worldwide calls for innovative and more effective ways to promote physical activity (PA). There are limited objective data on the effectiveness of Web-based personalized feedback on increasing PA in adults.

OBJECTIVE

It is hypothesized that providing personalized advice based on PA measured objectively alongside diet, phenotype, or genotype information would lead to larger and more sustained changes in PA, compared with nonpersonalized advice.

METHODS

A total of 1607 adults in seven European countries were randomized to either a control group (nonpersonalized advice, Level 0, L0) or to one of three personalized groups receiving personalized advice via the Internet based on current PA plus diet (Level 1, L1), PA plus diet and phenotype (Level 2, L2), or PA plus diet, phenotype, and genotype (Level 3, L3). PA was measured for 6 months using triaxial accelerometers, and self-reported using the Baecke questionnaire. Outcomes were objective and self-reported PA after 3 and 6 months.

RESULTS

While 1270 participants (85.81% of 1480 actual starters) completed the 6-month trial, 1233 (83.31%) self-reported PA at both baseline and month 6, but only 730 (49.32%) had sufficient objective PA data at both time points. For the total cohort after 6 months, a greater improvement in self-reported total PA (P=.02) and PA during leisure (nonsport) (P=.03) was observed in personalized groups compared with the control group. For individuals advised to increase PA, we also observed greater improvements in those two self-reported indices (P=.006 and P=.008, respectively) with increased personalization of the advice (L2 and L3 vs L1). However, there were no significant differences in accelerometer results between personalized and control groups, and no significant effect of adding phenotypic or genotypic information to the tailored feedback at month 3 or 6. After 6 months, there were small but significant improvements in the objectively measured physical activity level (P<.05), moderate PA (P<.01), and sedentary time (P<.001) for individuals advised to increase PA, but these changes were similar across all groups.

CONCLUSIONS

Different levels of personalization produced similar small changes in objective PA. We found no evidence that personalized advice is more effective than conventional "one size fits all" guidelines to promote changes in PA in our Web-based intervention when PA was measured objectively. Based on self-reports, PA increased to a greater extent with more personalized advice. Thus, it is crucial to measure PA objectively in any PA intervention study.

TRIAL REGISTRATION

ClinicalTrials.gov NCT01530139; http://clinicaltrials.gov/show/NCT01530139 (Archived by WebCite at: http://www.webcitation.org/6XII1QwHz).

Assessment of Energy Intake and Energy Expenditure of Male Adolescent Academy-Level Soccer Players during a Competitive Week

This study investigated the energy intake and expenditure of professional adolescent academy-level soccer players during a competitive week. Over a seven day period that included four training days, two rest days and a match day, energy intake (self-reported weighed food diary and 24-h recall) and expenditure (tri-axial accelerometry) were recorded in 10 male players from a professional English Premier League club. The mean macronutrient composition of the dietary intake was 318 ± 24 g·day⁻¹ (5.6 ± 0.4 g·kg⁻¹ BM) carbohydrate, 86 ± 10 g·day⁻¹ (1.5 ± 0.2 g·kg⁻¹ BM) protein and 70 ± 7 g·day⁻¹ (1.2 ± 0.1 g·kg⁻¹ BM) fats, representing 55% ± 3%, 16% ± 1%, and 29% ± 2% of mean daily energy intake respectively. A mean daily energy deficit of −1302 ± 1662 kJ (p = 0.035) was observed between energy intake (9395 ± 1344 kJ) and energy expenditure (10679 ± 1026 kJ). Match days (−2278 ± 2307 kJ, p = 0.012) and heavy training days (−2114 ± 2257 kJ, p = 0.016) elicited the greatest deficits between intake and expenditure. In conclusion, the mean daily energy intake of professional adolescent academy-level soccer players was lower than the energy expended during a competitive week. The magnitudes of these deficits were greatest on match and heavy training days. These findings may have both short and long term implications on the performance and physical development of adolescent soccer players.

Validation of Cut-Points for Evaluating the Intensity of Physical Activity with Accelerometry-Based Mean Amplitude Deviation (MAD)

Purpose

Our recent study of three accelerometer brands in various ambulatory activities showed that the mean amplitude deviation (MAD) of the resultant acceleration signal performed best in separating different intensity levels and provided excellent agreement between the three devices. The objective of this study was to derive a regression model that estimates oxygen consumption (VO2) from MAD values and validate the MAD-based cut-points for light, moderate and vigorous locomotion against VO₂ within a wide range of speeds.

Methods

29 participants performed a pace-conducted non-stop test on a 200 m long indoor track. The initial speed was 0.6 m/s and it was increased by 0.4 m/s every 2.5 minutes until volitional exhaustion. The participants could freely decide whether they preferred to walk or run. During the test they carried a hip-mounted tri-axial accelerometer and mobile metabolic analyzer. The MAD was calculated from the raw acceleration data and compared to directly measured incident VO₂. Cut-point between light and moderate activity was set to 3.0 metabolic equivalent (MET, 1 MET = 3.5 ml · kg^-1 · min^-1) and between moderate and vigorous activity to 6.0 MET as per standard use.

Results

The MAD and VO₂ showed a very strong association. Within individuals, the range of r values was from 0.927 to 0.991 providing the mean r = 0.969. The optimal MAD cut-point for 3.0 MET was 91 mg (milligravity) and 414 mg for 6.0 MET.

Conclusion

The present study showed that the MAD is a valid method in terms of the VO₂ within a wide range of ambulatory activities from slow walking to fast running. Being a device-independent trait, the MAD facilitates directly comparable, accurate results on the intensity of physical activity with all accelerometers providing tri-axial raw data.

Physical activity, depressed mood and pregnancy worries in European obese pregnant women: results from the DALI study

BACKGROUND

The purpose of this study was to examine the association between mental health status (i.e. depressed mood and pregnancy-related worries) and objectively measured physical activity levels in obese pregnant women from seven European countries.

METHODS

Baseline data from the vitamin D and lifestyle intervention for the prevention of gestational diabetes mellitus (DALI) study were used. Time spent in moderate-to-vigorous physical activity (MVPA) and sedentary behaviour was measured with accelerometers. Depressed mood was measured with the WHO well-being index (WHO-5) and pregnancy-related worries with the Cambridge Worry Scale (CWS). In addition, socio-demographic characteristics, lifestyle factors, and perceptions and attitude regarding weight management and physical activity were measured. Linear regression analyses were performed to assess the association of mental health status with MVPA and sedentary behaviour.

RESULTS

A total of 98 obese pregnant women from Austria, Belgium, Ireland, Italy, Poland, Spain and the Netherlands were included. Women had a mean age of 31.6 ± 5.8 years, a pre-pregnancy BMI of 34.1 ± 4.3 kg/m(2), and were on average 15.4 ± 2.8 weeks pregnant. WHO-5 scores indicative of depressed mood (<50) were reported by 27.1 % of the women and most frequently endorsed pregnancy-related worries pertained to own and the baby's health. Women with good well-being spent 85% more time in MVPA compared to women with a depressed mood (P = 0.03). No differences in MVPA levels were found for women with no, some, or many pregnancy worries. Depressed mood and pregnancy-related worries were not associated with sedentary behaviour.

CONCLUSIONS

These findings suggest that in pregnant women who are obese, a depressed mood, but not pregnancy-related worries, may be associated with less physical activity. The combined risk of poor mental health and low physical activity levels makes women vulnerable for pregnancy complications. Whether a depressed mood may be a barrier for improving physical activity warrants further study.

Sensitivity of the accelerometer as a measurement tool for upper extremity movement by stroke patients: a comparison with the action research arm test

[Purpose] This study investigated the sensitivity of an accelerometer in a comparison with the Action Research Arm Test (ARAT). [Subjects] Fifteen stroke patients participated in this study. [Methods] Subjects wore accelerometers on both wrists and performed the ARAT items. We then compared the data measured by the accelerometer with that of the ARAT. [Results] ARAT scores were higher on the non-affected side than the affected side, while the amount of upper extremity movement was higher on the affected side. The correlation coefficients for the two tools were not significantly different. [Conclusion] Our findings indicate that an accelerometer is a useful and sensitive instrument for clinically measuring the upper extremity activity of patients with stroke.

Physical education: the effect of epoch lengths on children's physical activity in a structured context

Background

Despite a consensus emerging that affirms that shorter epochs should be used in youth to correctly register physical activity levels in free-living conditions, little is known about its effect on children’s physical activity conducted in structured periods of time. This study analyzed the effect that epoch length (1, 2, 3, 5, 10, 15, 30 and 60s) may have on different physical activity intensities in physical education lessons.

Methods

A sample of 1912 individual measures of physical education lessons were measured with a GT3X accelerometer. Data were collected from 1227 Swiss Elementary school students recruited in 17 elementary schools. PE lessons lasted from 45 minutes to one and a half hours. Data, originally collected in 1-s epoch, were then reintegrated into 2s, – 3s – 5s – 10s – 15s – 30s –60s epochs.

Results

Longer epochs were associated with higher levels of light (F = 8197.6, p < .001), moderate (F = 2708.17, p < .001), and moderate-to-vigorous physical activity (F = 888.08, p < .001). However, longer epochs showed lower levels of sedentary activity (F = 31714.33, p < .001) and vigorous physical activity (F = 1910.97, p < .001). Bias increased in all PA intensities when shorter epochs were compared with longer epochs. There were statistically significant differences in compliance with physical education guidelines (χ2 = 989.27, p<.001), showing higher levels with longer epochs.

Conclusion

PA context may have some influence on the effects that epoch length have on PA estimates, more specifically on MVPA. Nevertheless, the use of a high-frequency sampling interval should be used to more accurately assess children’s PA.

Validation of five minimally obstructive methods to estimate physical activity energy expenditure in young adults in semi-standardized settings

We compared the accuracy of five objective methods, including two newly developed methods combining accelerometry and activity type recognition (Acti4), against indirect calorimetry, to estimate total energy expenditure (EE) of different activities in semi-standardized settings. Fourteen participants performed a standardized and semi-standardized protocol including seven daily life activity types, while having their EE measured by indirect calorimetry. Simultaneously, physical activity was quantified by an ActivPAL³, two ActiGraph GT3X+’s and an Actiheart. EE was estimated by the standard ActivPAL³ software (ActivPAL), ActiGraph GT3X+ (ActiGraph) and Actiheart (Actiheart), and by a combination of activity type recognition via Acti4 software and activity counts per minute (CPM) of either a hip- or thigh-worn ActiGraph GT3X+ (AGhip + Acti4 and AGthigh + Acti4). At group level, estimated physical activities EE by Actiheart (MSE = 2.05) and AGthigh + Acti4 (MSE = 0.25) were not significantly different from measured EE by indirect calorimetry, while significantly underestimated by ActiGraph, ActivPAL and AGhip + Acti4. AGthigh + Acti4 and Actiheart explained 77% and 45%, of the individual variations in measured physical activity EE by indirect calorimetry, respectively. This study concludes that combining accelerometer data from a thigh-worn ActiGraph GT3X+ with activity type recognition improved the accuracy of activity specific EE estimation against indirect calorimetry in semi-standardized settings compared to previously validated methods using CPM only.

Fuzzy logic for characterizing the moderate intensity of physical activity in children

OBJECTIVES

The aim of this study was to better characterize the moderate intensity of PA among children by applying fuzzy logic as the most appropriate analytical approach. In this perspective, the 6-MWT was selected as a pertinent exercise modality, which covers as a whole, this intensity level.

DESIGN

Methodological study.

METHODS

Fuzzy logic was applied to accelerometer output obtained on 46 children aged 9-11 years. A fuzzy subset A was defined from the reference set E using a membership function (degree of truth). To adequately tap the moderate PA, a core of X¯±σ and a support of X¯±2σ (with X¯ the mean, and σ the standard deviation of the distribution) were selected.

RESULTS

The walking speed during the exercise averaged 6.1±0.6kmh(-1) and the mean HR was 135±14bpm. The movement count (419±127 to 433±148 counts) exhibited no significant changes during the test. A value of 260 counts per 5-s (i.e., 3120cpm) had equally 50% of degree of truth to encompass both "light" and "moderate" intensities of PA. Results suggest that the cut-point of >2296cpm covers a low PA at 100% and a moderate PA at 0%.

CONCLUSIONS

Fuzzy logic provides a robust basis to processing accelerometer data, and brings a reliable solution to the concern about the in-between of PA intensities. Its application to calibration studies should not support the use of a cut-point of about 2000cpm in children, and linguistic variables should now be preferred to numbered data in defining PA intensities.

Validation of two accelerometers to determine mechanical loading of physical activities in children

The purpose of this study was to assess the validity of accelerometers using force plates (i.e., ground reaction force (GRF)) during the performance of different tasks of daily physical activity in children. Thirteen children (10.1 (range 5.4-15.7) years, 3 girls) wore two accelerometers (ActiGraph GT3X+ (ACT), GENEA (GEN)) at the hip that provide raw acceleration signals at 100 Hz. Participants completed different tasks (walking, jogging, running, landings from boxes of different height, rope skipping, dancing) on a force plate. GRF was collected for one step per trial (10 trials) for ambulatory movements and for all landings (10 trials), rope skips and dance procedures. Accelerometer outputs as peak loading (g) per activity were averaged. ANOVA, correlation analyses and Bland-Altman plots were computed to determine validity of accelerometers using GRF. There was a main effect of task with increasing acceleration values in tasks with increasing locomotion speed and landing height (P < 0.001). Data from ACT and GEN correlated with GRF (r = 0.90 and 0.89, respectively) and between each other (r = 0.98), but both accelerometers consistently overestimated GRF. The new generation of accelerometer models that allow raw signal detection are reasonably accurate to measure impact loading of bone in children, although they systematically overestimate GRF.

The association between daily physical activity and plasma B-type natriuretic peptide in patients with glucose intolerance: a cross-sectional study

OBJECTIVES

In spite of accumulating evidences suggesting an inverse association between insulin resistance and plasma B-type natriuretic peptide (BNP) levels, the effect of daily physical activity on plasma BNP in individuals with glucose intolerance remains unknown. We investigated the association of physical activity level (PAL) with plasma BNP in patients with impaired fasting glucose, impaired glucose tolerance and type 2 diabetes.

DESIGN

Cross-sectional study.

SETTING

Outpatients visiting the National Center for Global Health and Medicine Kohnodai Hospital.

PARTICIPANTS

A total of 60 patients with glucose intolerance who did not take any hypoglycaemic agents, cholesterol-lowering agents and antihypertensive agents were recruited. Patients who were diagnosed as having heart failure and renal impairment, engaged in sports-like exercise and resistance training were excluded.

PRIMARY OUTCOME MEASURES

PAL was objectively measured by a triaxial accelerometer. The association between PAL and plasma BNP levels was assessed by multiple regression analysis.

RESULTS

PAL was positively correlated with plasma BNP levels (r=0.296, p=0.021). PAL was still significantly correlated with plasma BNP levels after adjustment for age (β=0.290, p=0.014), and adjustment for age and body mass index (β=0.282, p=0.018). Plasma BNP levels were inversely correlated with serum insulin levels (r=-0.350, p=0.006) and homeostasis model assessment-estimated insulin resistance (HOMA-IR; r=-0.363, p=0.004). Serum insulin levels (mean±SD, 8.1±6.4 μU/mL) and HOMA-IR (2.4±1.9) in the high-BNP group were significantly lower than those (11.2±7.4 μU/mL and 3.7±3.0, respectively) in the low-BNP group.

CONCLUSIONS

Our findings propose the possibility that plasma BNP may be increased by daily physical activity and BNP is associated with insulin resistance.

Daily Physical Activity Assessed by a Triaxial Accelerometer Is Beneficially Associated with Waist Circumference, Serum Triglycerides, and Insulin Resistance in Japanese Patients with Prediabetes or Untreated Early Type 2 Diabetes

AIM

To investigate the association between daily physical activity and metabolic risk factors in Japanese adults with prediabetes or untreated early type 2 diabetes (T2D).

METHODS

Daily physical activity level was measured using a triaxial accelerometer. We assessed correlations between physical activity level and waist circumference, blood pressure, fasting levels of plasma glucose, serum triglycerides, and insulin and homeostasis model assessment-insulin resistance (HOMA-IR).

RESULTS

A total of 80 patients were studied. After adjustment for age and body mass index, in all subjects, physical activity level was negatively associated with waist circumference (β = -0.124, P = 0.018) and fasting serum triglycerides (β = -0.239, P = 0.035), insulin (β = -0.224, P = 0.022). In men, physical activity level was negatively associated with systolic blood pressure (β = -0.351, P = 0.044), fasting plasma glucose (β = -0.369, P = 0.025) and insulin (β = -0.362, P = 0.012), and HOMA-IR (β = -0.371, P = 0.011). No significant associations were found between physical activity level and metabolic risk factors in women.

CONCLUSION

Objectively measured daily physical activity is beneficially associated with waist circumference, serum triglycerides, and insulin resistance in individuals with prediabetes or untreated early T2D. (This trial is registered with UMIN000015774.).