Objective assessment of sedentary time and physical activity throughout the week in adolescents with Down syndrome. The UP&DOWN study

This study aimed to examine the patterns of sedentary time and physical activity (PA) throughout the week in adolescents with Down syndrome (DS). The study comprised 109 adolescents with DS (68 males and 41 females) aged 11-20 years, participating in the UP&DOWN study, but only a total of 100 adolescents provided valid data. Sedentary time and total, light, moderate, vigorous, and moderate-to-vigorous PA (MVPA) were measured by accelerometers. There were no significant differences in the time spent in sedentary time and PA levels between weekdays vs. weekend days, as well as between school time vs. after school-time periods (all p>0.05). Adolescent males engaged in more total PA, moderate PA, vigorous PA and MVPA than females on weekend days (all p<0.05). Differences between age groups showed that sedentary time increases and PA decreases with advancing age in all analyses, so that the oldest groups were more sedentary and less active (all p<0.05). Only 43% of adolescents with DS met the PA recommendations of ≥60min/day of MVPA. Our findings show valuable information to be considered in future interventions aiming to decrease sedentary time and increase PA levels in adolescents with DS.

Patterns of optimization in single- and inter-leg gait dynamics

INTRODUCTION

We examined the influence of walking speed on the fluctuation and synchronization dynamics of stride intervals and ground reaction force (GRF) profiles. Our aim was to identify patterns of optimization in the single-leg and inter-leg dynamics at preferred walking speed (PWS). PWS is thought to bring about the most stable walking pattern in terms of the attractor dynamics of the locomotion system.

METHODS

Twenty healthy subjects (29.1 ± 1.8 years; 10 women) walked on a treadmill for 5-min periods at their PWS and at 20, 40, 70, and 80% of maximal walking speed. The coefficient of variation (CV) and long-range correlations α of GRF profile and stride time fluctuations as well as the phase synchronization ρ of inter-leg stride timing were analyzed.

RESULTS

GRF profile α increased with increasing walking speed (p < 0.001). In contrast, stride time CV and α showed a U-shaped speed-dependency with lowest values at PWS (p < 0.05). The speed-dependency of single-leg stride time fluctuations was mirror-inverted in the speed-dependency of inter-leg stride timing ρ; its highest values occurred at PWS (p < 0.001).

CONCLUSIONS

Fluctuations in GRF profiles become more consistent with increasing walking speed. In contrast, the dynamics of single-leg and inter-leg timing show a collective pattern of optimization at PWS. Less correlated noise in single-leg timing at PWS, imposed on the two coupled oscillating legs, increases the phase synchronization of bilateral timing, thereby enhancing gait stability at the attractor of self-paced walking. Thus, the attractor dynamics of locomotion appear to rely on the interaction of single- and inter-leg timing.

Increasing objectively measured sedentary time increases clustered cardiometabolic risk: a 6 year analysis of the ProActive study

AIMS/HYPOTHESIS

We aimed to quantify the associations between change in objectively measured sedentary and moderate-to-vigorous physical activity (MVPA) times and self-reported television viewing over 6 years and change in a clustered cardiometabolic risk score (CCMR), including and excluding waist circumference (CCMR without adiposity component, CCMR no adip ), and its individual components, among the adult children of people with type 2 diabetes.

METHODS

In 171 adults (mean ± SD age 42.52 ± 6.30 years; 46% men) with a parental history of diabetes (ProActive UK), physical activity accelerometer measures and self-reported television viewing were assessed at baseline and a mean ± SD of 6.27 ± 0.46 years later. Associations between change in sedentary time, MVPA time and television viewing and cardiometabolic risk and mediation by adiposity change were examined by multiple linear regression and the product of coefficients method, respectively.

RESULTS

Greater increases in sedentary time (h/day) were associated with larger increases in clustered cardiometabolic risk (CCMR: 0.08 [95% CI 0.01, 0.15]; CCMR no adip : 0.08 [0.01, 0.16]) and triacylglycerol (0.15 [0.01, 0.29]), independent of baseline sedentary and MVPA times, change in MVPA time and other confounders. No evidence was found for mediation by change in waist circumference and BMI for the associations with CCMR no adip and triacylglycerol. Greater increases in MVPA time (h/day) were associated with larger decreases in waist circumference (-3.86 [-7.58, -0.14]), independently of baseline MVPA and sedentary times, change in sedentary time and other confounders. Television viewing was not independently associated with any of the cardiometabolic outcomes.

CONCLUSIONS/INTERPRETATION

Increasing sedentary time is independently related to increasing clustered cardiometabolic risk and triacylglycerol in adults at high risk of developing diabetes. Strategies to prevent diabetes might target reducing sedentary time. Trial registration ISRCTN61323766.

Accelerometer-determined physical activity and its comparison with the International Physical Activity Questionnaire in a sample of Nigerian adults

INTRODUCTION

Accurate assessment of physical activity to identify current levels and changes within the population is dependent on the precision of the measurement tools. The aim of this study was to compare components of physical activity measured with an adapted version of the International Physical Activity Questionnaire (Hausa IPAQ-SF) and the accelerometer in a sample of Nigeria adults.

METHODS

One hundred and forty-four participants (Mean age = 32.6 ± 9.9 years, 40.3% women) in a cross-sectional study wore an accelerometer for seven consecutive days and completed the Hausa IPAQ-SF questionnaire on the eighth day. Total physical activity, time spent in moderate-to-vigorous activity (MVPA) and sedentary time assessed by Hausa IPAQ-SF and accelerometer were compared. The absolute and criterion- related validity of the Hausa IPAQ-SF was assessed by Bland-Altman analysis and Spearman Correlation Coefficients, respectively. Specificity and sensitivity were calculated to classify individuals according to the global standard guideline for sufficient physical activity.

RESULTS

Compared with the accelerometer, higher time in MVPA and total physical activity were reported on the Hausa IPAQ-SF (p<0.001), while low to moderate correlations (Rs = 0.03-0.38) were found between the two methods. The 95% limits of agreement were wide between methods for total physical activity (-23019 to 20375 METmin.d(-1)) and sedentary time (-510 to 150 min.d(-1)). The sensitivity (76.2%) of Hausa IPAQ-SF to identify insufficiently active people was good, but its specificity (33.3%) to correctly classify sufficiently active people was low.

CONCLUSIONS

The Hausa IPAQ-SF overestimated components of physical activity among Nigerian adults, and demonstrated poor to moderate evidence of absolute and criterion validity. Further evaluation of IPAQ and other self-report physical activity instruments in other Africa populations could enhance accurate evaluation of physical activity data in the region countries.

Rotational acceleration during head impact resulting from different judo throwing techniques

Most severe head injuries in judo are reported as acute subdural hematoma. It is thus necessary to examine the rotational acceleration of the head to clarify the mechanism of head injuries. We determined the rotational acceleration of the head when the subject is thrown by judo techniques. One Japanese male judo expert threw an anthropomorphic test device using two throwing techniques, Osoto-gari and Ouchi-gari. Rotational and translational head accelerations were measured with and without an under-mat. For Osoto-gari, peak resultant rotational acceleration ranged from 4,284.2 rad/s(2) to 5,525.9 rad/s(2) and peak resultant translational acceleration ranged from 64.3 g to 87.2 g; for Ouchi-gari, the accelerations respectively ranged from 1,708.0 rad/s(2) to 2,104.1 rad/s(2) and from 120.2 g to 149.4 g. The resultant rotational acceleration did not decrease with installation of an under-mat for both Ouchi-gari and Osoto-gari. We found that head contact with the tatami could result in the peak values of translational and rotational accelerations, respectively. In general, because kinematics of the body strongly affects translational and rotational accelerations of the head, both accelerations should be measured to analyze the underlying mechanism of head injury. As a primary preventative measure, throwing techniques should be restricted to participants demonstrating ability in ukemi techniques to avoid head contact with the tatami.

Factors associated with physical inactivity among female and male rural adolescents in Borneo - a cross-sectional study

Rural communities have shown marked increase in metabolic syndrome among young people, with physical inactivity as one of the main contributing factors. This study aimed to determine factors associated with physical inactivity among male and female rural adolescents in a sample of schools in Malaysia. A cross-sectional study was conducted among 145 students aged 13-15 years. Data on socio-demographic, health-related, and psychosocial factors (perceived barriers, self-efficacy, social influences) were collected using a self-administered questionnaire. Anthropometric measurement was taken to generate body mass index (BMI)-for-age, while physical activity (PA) level was assessed using pedometers. The mean steps per day was 6251.37 (SD=3085.31) with males reported as being more active. About 27% of the respondents were either overweight or obese, with more females in this group. There was no significant difference in steps among males and females (p=0.212), and nutritional status (BMI-for-age) (p=0.439). Females consistently scored higher in most items under perceived barriers, but had significantly lower scores in self-efficacy's items. Males were more influenced by peers in terms of PA (p<0.001) and were more satisfied with their body parts (p=0.047). A significantly higher body size discrepancy score was found among females (p=0.034, CI -0.639, -0.026). PA level was low and almost one-third of the respondents were overweight and obese. Female students faced more barriers and had lower self-efficacy with regards PA. Based on the findings, it is recommended that interventions focus on reducing barriers while increasing support for PA. This is particularly important in improving the health status of the youth, especially among the females.

Impact of physical activity on depression after cardiac surgery

BACKGROUND

Physical activity is associated with a lower prevalence of depressive symptoms in cardiac patients. However, the benefits of physical activity on depression perioperatively are unknown. We sought to identify independent parameters associated with depression in patients undergoing cardiac surgery.

METHODS

Patients awaiting nonemergent cardiac surgery (n = 436) completed the Patient Health Questionnaire-9 (PHQ-9) to quantify depression (PHQ-9 score > 9). Physical activity was assessed with the International Physical Activity Questionnaire (IPAQ-short) and accelerometry. Data collection occurred preoperatively (Q1, n = 436), at hospital discharge (Q2, n = 374), at 3 months (Q3, n = 318), and at 6 months (Q4, n = 342) postoperatively. Patients were categorized as "depression naive", "at risk" or "depressed" preoperatively. Physical inactivity was defined as < 600 metabolic equivalent min/wk. Independent perioperative variables associated with depression were identified with univariate and multivariate logistic regression.

RESULTS

Depression prevalence from Q1-Q4 was 23%, 37%, 21%, and 23%, respectively. Independent associations with depression were preoperative left ventricular ejection fraction < 50% (Q1, P < 0.05), physical inactivity (Q1, P < 0.05), baseline "at-risk" (Q2, P < 0.05), and baseline "depressed" groups (Q2-Q4, P < 0.05), hospital stay > 7 days (Q2, P < 0.05), postoperative stressful event (Q3 and Q4, P < 0.05), and cardiopulmonary bypass time > 120 minutes (Q4, P = 0.05). Newly depressed patients 6 months postoperatively reported lower IPAQ-short physical activity than depression-free patients (median change, -40 min/wk (interquartile range [IQR], -495 to +255) vs +213 min/wk (IQR, +150 to +830; P < 0.05).

CONCLUSIONS

Up to 40% of patients are depressed after cardiac surgery. Preoperative depression and postoperative stressful events were the strongest independent associations postoperatively. Physical inactivity was associated with preoperative depression and new depression 6 months postoperatively.

Validity and reliability of two brief physical activity questionnaires among Spanish-speaking individuals of Mexican descent

BACKGROUND

Mexican Americans are the largest minority group in the US and suffer disproportionate rates of diseases related to the lack of physical activity (PA). Since many of these Mexican Americans are Spanish-speaking, it is important to validate a Spanish language physical activity assessment tool that can be used in epidemiology as well as clinical practice. This study explored the utility of two Spanish translated physical activity questionnaires, the Stanford Brief Activity Survey (SBAS) and the Rapid Assessment of Physical Activity (RAPA), for use among Spanish-speaking Mexican Americans.

METHODS

Thirty-four participants (13 M, 21 F; 37.6 ± 9.5 y) completed each of the two PA surveys twice, one week apart. During that week 31 participants also wore an ActiGraph GT1M accelerometer for 7 days to objectively measure PA. Minutes of moderate and vigorous PA (MVPA) were determined from the accelerometer data using Freedson and Matthews cut points.

RESULTS

Validity, determined by Spearman correlation coefficients between questionnaire scores and minutes of ActiGraph measured MVPA were 0.38 and 0.45 for the SBAS and RAPA, respectively. Test-retest reliability was 0.61 for the SBAS and 0.65 for the RAPA. Sensitivity and specificity were 0.60 and 0.47 for the SBAS, and 0.73 and 0.75 for the RAPA. Participants who were classified as meeting the 2008 National Physical Activity Guidelines by the RAPA engaged in significantly (p < 0.05) more minutes of MVPA than those who were not, while there were no significant differences in minutes of MVPA classified by the SBAS.

CONCLUSIONS

The SBAS and the RAPA are both reasonably valid measures for quickly assessing PA and determining compliance to the PA guidelines in Spanish-speaking Mexican Americans. Although the two questionnaires had comparable reliability, the RAPA was better able to distinguish between those who met and did not meet National PA Guidelines.

Objectively measured physical activity in four-year-old British children: a cross-sectional analysis of activity patterns segmented across the day

BACKGROUND

Little is known about preschool-aged children's levels of physical activity (PA) over the course of the day. Using time-stamped data, we describe the levels and patterns of PA in a population-based sample of four-year-old British children.

METHODS

Within the Southampton Women's Survey the PA levels of 593 4-year-old children (51% female) were measured using (Actiheart) accelerometry for up to 7 days. Three outcome measures: minutes spent sedentary (<20 cpm); in light (LPA: ≥20-399 cpm) and in moderate-to-vigorous activity (MVPA: ≥400 cpm) were derived. Average daily activity levels were calculated and then segmented across the day (morning, afternoon and evening). MVPA was log-transformed. Two-level random intercept models were used to analyse associations between activity level and temporal and demographic factors.

RESULTS

Children were active for 67% (mean 568.5 SD 79.5 minutes) of their daily registered time on average, with 88% of active time spent in LPA. All children met current UK guidelines of 180 minutes of daily activity. There were no differences in children's average daily levels of sedentary activity and LPA by temporal and demographic factors: differences did emerge when activity was segmented across the day. Sex differences were largest in the morning, with girls being more sedentary, spending fewer minutes in LPA and 18% less time in MVPA than boys. Children were more sedentary and less active (LPA and MVPA) in the morning if they attended childcare full-time compared to part-time, and on weekend mornings compared to weekdays. The reverse was true for weekend afternoons and evenings. Children with more educated mothers were less active in the evenings. Children were less sedentary and did more MVPA on summer evenings compared to winter evenings.

CONCLUSIONS

Preschool-aged children meet current physical activity guidelines, but with the majority of their active time spent in LPA, investigation of the importance of activity intensity in younger children is needed. Activity levels over the day differed by demographic and temporal factors, highlighting the need to consider temporality in future interventions. Increasing girls' morning activity and providing opportunities for daytime activity in winter months may be worthwhile.

Objective indicators of physical activity and sedentary time and associations with subjective well-being in adults aged 70 and over

This study explored the associations of the volume and intensity of physical activity and the volume of sedentary time with subjective well-being in a diverse group of 228 older adults in the UK (111 female, mean age 78.2 years (SD 5.8)). Physical activity (PA) and sedentary behaviour were assessed by accelerometry deriving mean steps per day, mean moderate/vigorous PA minutes per hour (MVPA min · h(-1)) and minutes of sedentary time per hour (ST min · h(-1)). Lower limb function was assessed by the Short Physical Performance Battery. Subjective well-being was assessed using the SF-12 health status scale, the Ageing Well Profile and the Satisfaction with Life Scale. Linear regressions were used to investigate associations between the independent variables which included physical activity (steps and MVPA), sedentary time, participant characteristics (gender, age, BMI, education, number of medical conditions), and lower limb function and dependent variables which included mental and physical well-being. Steps, MVPA and lower limb function were independently and moderately positively associated with perceived physical well-being but relationships with mental well-being variables were weak. No significant associations between sedentary behaviours and well-being were observed. The association between objectively evaluated physical activity and function and subjective evaluations of physical well-being suggest that improving perceptions of physical health and function may provide an important target for physical activity programmes. This in turn may drive further activity participation.

A single vs. multi-sensor approach to enhanced detection of smartphone placement

In this paper, the authors evaluate the ability to detect on-body device placement of smartphones. A feasibility study is undertaken with N=5 participants to identify nine key locations, including in the hand, thigh and backpack, using a multitude of commonly available smartphone sensors. Sensors examined include the accelerometer, magnetometer, gyroscope, pressure and light sensors. Each sensor is examined independently, to identify the potential contributions it can offer, before a fused approach, using all sensors is adopted. A total of 139 features are generated from these sensors, and used to train five machine learning algorithms, i.e. C4.5, CART, Naïve Bayes, Multilayer Perceptrons, and Support Vector Machines. Ten-fold cross validation is used to validate these models, achieving classification results as high as 99%.

Time-frequency visualization of alcohol withdrawal tremors

In this paper, we propose a signal processing method of assessing the severity tremors caused by alcohol withdrawal (AW) syndrome. We have developed an iOS application to calculate the Clinical Institute Withdrawal Assessment (CIWA) score which captures iPod movements using the built-in accelerometer in order to reliably estimate the tremor severity component of the score. We report on the characteristics of AW tremor, the accuracy of electronic assessment of tremor compared to expert clinician assessment, and the potential for using signal processing assessment to differentiate factitious from real tremor in patients seen in the emergency department, as well as in nurses mimicking a tremor. Our preliminary results are based on 84 recordings from 61 subjects (49 patients, 12 nurses). In general we found a linear relationship between energy measured by the accelerometer (in the 4.4-10 Hz range) and the expert rating of tremor severity. Additionally, we demonstrate that 75% of the recordings from patients with actual AW syndrome had a mean peak frequency higher than 7 Hz whereas only 17% of the nurses' factitious tremors were above 7 Hz, suggesting that tremor above 7 Hz could be a potential discriminator of real versus factitious tremors.

Accelerometer-measured versus self-reported physical activity in college students: implications for research and practice

OBJECTIVE

To determine the level of moderate-vigorous-intensity physical activity (MVPA) assessed via self-report and accelerometer in the college population, and to examine intrapersonal and contextual variables associated with physical activity (PA).

PARTICIPANTS

Participants were 77 college students at a university in the northwest sampled between January 2011 and December 2011.

METHODS

Participants completed a validated self-report measure of PA and measures of athletic identity and benefits and barriers to exercise. Participants' PA levels were assessed for 2 weeks via accelerometry.

RESULTS

Participants' estimations of their time spent engaged in MVPA were significantly higher when measured via self-report versus accelerometry. Stronger athletic identity, perceived social benefits and barriers, and time-effort barriers were related to PA levels.

CONCLUSIONS

Estimation of college students' level of PA may require interpretation of data from different measurement methods, as self-report and accelerometry generate different estimations of PA in college students who may be even less active than previously believed.

Effectiveness of three different walking prescription durations on total physical activity in normal- and overweight women

OBJECTIVE

While there is a dose-response relationship between physical activity (PA) and health benefit, little is known about the effectiveness of different PA prescriptions on total daily PA.

AIM

To test, under real-life conditions and using an objective, non-invasive measurement technique (accelerometry), the effect of prescribing additional physical activity (walking only) of different durations (30, 60 and 90 min/day) on compliance (to the activity prescribed) and compensation (to total daily PA). Participants in each group were prescribed 5 sessions of walking per week over 4 weeks.

METHODS

55 normal-weight and overweight women (mean BMI 25 ± 5 kg/m(2), height 165 ± 1 cm, weight 68 ± 2 kg and mean age 27 ± 1 years) were randomly assigned to 3 prescription groups: 30, 60 or 90 min/day PA.

RESULTS

Walking duration resulted in an almost linear increase in the number of steps per day during the prescription period from an average of about 10,000 steps per day for the 30-min prescription to about 14,000 for the 90-min prescription. Compliance was excellent for the 30-min prescription but decreased significantly with 60-min and 90-min prescriptions. In parallel, degree of compensation subsequent to exercise increased progressively as length of prescription increased.

CONCLUSION

A 30-min prescription of extra walking 5 times per week was well tolerated. However, in order to increase total PA further, much more than 60 min of walking may need to be prescribed in the majority of individuals. While total exercise 'volume' increased with prescriptions longer than 30 min, compliance to the prescription decreased and greater compensation was evident.

Diurnal changes of the postural control in young women without and with hormonal contraceptive treatment

OBJECTIVES

The aim of this study was to investigate diurnal changes of the postural control in young women without and with hormonal contraceptive treatment.

METHODS

The postural activity was assessed during stance from two accelerometers positioned at the level of the lumbar (L5) and thoracic (Th4) vertebra in twenty healthy young women non-using (13) and using (7) hormonal contraception.

RESULTS

We observed a significant increase of trunk tilts in the morning in the group of women with hormonal contraception compared to control. Women with hormonal contraception showed the significant decrease of trunk tilts and their velocity in the evening in relation to increased morning data at the L5 in anterior-posterior direction during stance on foam. Measurements at Th4 showed higher variability of lateral trunk tilts in conditions with altered somatosensory inputs. Distinct reduction of velocity of lateral trunk tilts in the evening related to morning measurements were present in the control group at the L5 in conditions with altered somatosensory inputs and at the Th4 in all experimental conditions in both groups.

CONCLUSION

We demonstrated diurnal changes of the postural control in young women. Women using hormonal contraceptives showed a weakened postural stability compared with the control group in the morning and the normalization of postural stability in the evening to the values of the control group. These findings suggest that the time of day and the use of hormonal contraception affect postural stability of women.

Effects of dual-tasking on control of trunk movement during gait: respective effect of manual- and cognitive-task

Trunk control during gait provides a stable platform for vision and head control. However, in dual-task gait, cognitive tasks result in increased trunk movements, reduced gait speed, and increased gait variability. Manual tasks have been associated with reduced gait speed, but their effects on trunk movement have not been fully investigated. Furthermore, the fear of falling (FoF) during dual-task gait remains relatively unstudied. We aimed to assess trunk movements during cognitive-task gait (CG) and manual-task gait (MG), and examine the effects of CG and MG on individuals with and without FoF. The participants were 117 healthy older adults. We used two triaxial accelerometers: one to record trunk movements at the L3 spinous process and one at the heel to measure initial contact. Participants counted backward by one (CG) or carried a ball on a tray (MG), and we calculated stride time variability and standardized root-mean-square trunk accelerations in the mediolateral (ML) and anteroposterior (AP) directions. CG significantly increased lower trunk oscillations in the ML (t=4.9, p<0.001) and AP directions (t=6.1, p<0.001). Conversely, MG significantly decreased trunk oscillations in the ML (t=-5.9, p<0.001) and AP directions (t=-8.3, p<0.001). The difference in trunk oscillations during CG in the ML direction was significantly larger in subjects with FoF than without FoF (t=2.6, p<0.01). We conclude that for the tasks we studied, CG and MG have different effects on trunk movement. Finally, FoF was associated with changes in trunk movement in the ML direction during CG but not MG.

Physical activity in different preschool settings: an exploratory study

INTRODUCTION

Physical activity (PA) in preschoolers is vital to protect against obesity but is influenced by different early-life factors. The present study investigated the impact of different preschool programs and selected family factors on preschoolers' PA in different countries in an explorative way.

METHODS

The PA of 114 children (age = 5.3 ± 0.65 years) attending different preschool settings in four cities of the trinational Upper Rhine region (Freiburg, Landau/Germany, Basel/Switzerland, and Strasbourg/France) was measured by direct accelerometry. Anthropometrical and family-related data were obtained. Timetables of preschools were analyzed.

RESULTS

Comparing the preschool settings, children from Strasbourg and Landau were significantly more passive than children from Basel and Freiburg (P < .01). With regard to the family context as an important early-life factor, a higher number of children in a family along with the mother's and child's anthropometrical status are predictors of engagement in PA.

CONCLUSION

More open preschool systems such as those in Basel, Freiburg, and Landau do not lead to more PA "per se" compared to the highly regimented desk-based system in France. Preliminaries such as special training and the number of caregivers might be necessary elements to enhance PA. In family contexts, targeted PA interventions for special groups should be more focused in the future.

An implantable instrument for studying the long-term flight biology of migratory birds

The design of an instrument deployed in a project studying the high altitude Himalayan migrations of bar-headed geese (Anser indicus) is described. The electronics of this archival datalogger measured 22 × 14 × 6.5 mm, weighed 3 g, was powered by a ½AA-sized battery weighing 10 g and housed in a transparent biocompatible tube sealed with titanium electrodes for electrocardiography (ECG). The combined weight of 32 g represented less than 2% of the typical bodyweight of the geese. The primary tasks of the instrument were to continuously record a digitised ECG signal for heart-rate determination and store 12-bit triaxial accelerations sampled at 100 Hz with 15% coverage over each 2 min period. Measurement of atmospheric pressure provided an indication of altitude and rate of ascent or descent during flight. Geomagnetic field readings allowed for latitude estimation. These parameters were logged twice per minute along with body temperature. Data were stored to a memory card of 8 GB capacity. Instruments were implanted in geese captured on Mongolian lakes during the breeding season when the birds are temporarily flightless due to moulting. The goal was to collect data over a ten month period, covering both southward and northward migrations. This imposed extreme constraints on the design's power consumption. Raw ECG can be post-processed to obtain heart-rate, allowing improved rejection of signal interference due to strenuous activity of locomotory muscles during flight. Accelerometry can be used to monitor wing-beat frequency and body kinematics, and since the geese continued to flap their wings continuously even during rather steep descents, act as a proxy for biomechanical power. The instrument enables detailed investigation of the challenges faced by the geese during these arduous migrations which typically involve flying at extreme altitudes through cold, low density air where oxygen availability is significantly reduced compared to sea level.

Impact of accelerometer epoch length on physical activity and sedentary behaviour outcomes for preschool-aged children

BACKGROUND

The Canadian Health Measures Survey uses accelerometry to collect physical activity and sedentary behaviour data. Between cycles 2 and 3, a transition was made from 60-second to 15-second epochs in accelerometry data for children aged 3 to 5. This study examines the impact of epoch length on physical activity and sedentary behaviour outcomes.

DATA AND METHODS

Twenty-nine children aged 3 to 5 wore two accelerometers at the same time, one initialized to collect data in 60-second epochs, and the other, in 15-second epochs. Comparisons between epoch settings were made for several physical activity variables.

RESULTS

Compared with the 60-second epoch setting, the 15-second setting captured more moderate-to-vigorous physical activity (MVPA) and sedentary time, but fewer steps and less light and total physical activity. The correlation between epoch settings was high for all variables except steps.

INTERPRETATION

The epoch length used in accelerometer data collection affects physical activity and sedentary behaviour data for preschool-aged children.

Research of cyclist's spine dynamical model

The purpose of the paper is to present a dynamic model of bicyclist's lumbar spine for the evaluation of linear and angular variation of intervertebral distance in sagittal plane. Ten degrees of freedom biomechanical model of the spine was solved numerically. Larger loads acting on a cyclist spine occur mostly while sitting in a sport position in comparison with recreation or middle sitting. The load on lumbar spine region is influenced by cycle's tire pressure, road bumps and wheeling speed. The biggest linear and angular displacements were found between L4-L5 vertebras. The biggest load protractile spine muscle experiences in the sport sitting position. Maximum vertebrae rotation and linear variation values in wheeling regime with 1.5 Bar tyres pressure and at a speed of 10 km/h are 0.46° and 0.46 mm. Maximum vertebrae rotation and linear variation values for a 23 year old, 1.74 m high and 73 kg of mass (bicycle mass~7 kg) man in wheeling regime with 3.5 Bar tyres pressure and at a speed of 30 km/h are 3.9° and 1.23 mm. The biggest variation of rotation in sagittal plane between two nearest lumbar spines is about 1°. Because of this displacement the frontal part of last mentioned disc is compressed with 530 N more and dorsal disc part as much less.

Bedroom media, sedentary time and screen-time in children: a longitudinal analysis

BACKGROUND

Having electronic media in the bedroom is cross-sectionally associated with greater screen-time in children, but few longitudinal studies exist. The aim of this study was to describe longitudinal patterns of ownership and examine cross-sectional and longitudinal associations of bedroom media with children's sedentary behaviour.

METHODS

Data are from the Sport, Physical activity and Eating behaviour: Environmental Determinants in Young people (SPEEDY) study, collected at 3 time-points: baseline (2007, T0; age 10.3 ± 0.3 years), 1-year (T1y) and 4-year (T4y) follow-up. For each assessment, 1512 (44.9% male), 715 (41.0% male), and 319 (48.3% male) participants provided valid accelerometer data. Outcome variables were accelerometer-assessed sedentary time and self-reported screen-time. The presence of a television or computer in the bedroom was self-reported by participants and a combined bedroom media score calculated as the sum of such items. Cross-sectional and longitudinal associations between bedroom media and each outcome were examined using multi-level linear regression.

RESULTS

Bedroom TV ownership fell from 70.9% at T0 to 42.5% at T4y. Having a TV in the bedroom (beta; 95% CI*100, T0: -1.17; -1.88, -0.46. T1y: -1.68; -2.67, -0.70) and combined bedroom media (T0: -0.76; -1.26, -0.27. T1y: -0.79; -1.51, -0.07) were negatively associated with objectively measured weekly sedentary time at T0 and T1y. Having a computer in the bedroom (beta; 95% CI, T0: 0.15; 0.02, 0.29. T4y: 0.35; 0.10, 0.60) and combined bedroom media (T0: 0.09: 0.01, 0.18. T4y: 0.20; 0.05, 0.34) were positively associated with screen-time at T0 and T4y. Relative to participants without a computer throughout the study, children that had a computer in their bedroom at T0 but not at T4y (beta; 95% CI for change in screen-time: -8.02; -12.75, -3.29) reported smaller increases in screen-time.

CONCLUSIONS

The bedroom media environment changes with age and exhibits a complex relationship with children's sedentary behaviour. Modifying children's bedroom media environment may impact upon screen-time but appears unlikely to influence overall sedentary time.

Effectiveness and feasibility of lowering playground density during recess to promote physical activity and decrease sedentary time at primary school

BACKGROUND

This pilot study aimed at investigating the effectiveness of lowering playground density on increasing children's physical activity and decreasing sedentary time. Also the feasibility of this intervention was tested.

METHODS

Data were collected in September and October 2012 in three Belgian schools in 187, 9-12 year old children. During the intervention, playground density was decreased by splitting up recesses and decreasing the number of children sharing the playground. A within-subject design was used. Children wore accelerometers during the study week. Three-level (class - participant - measurement (baseline or intervention)) linear regression models were used to determine intervention effects. After the intervention week the school principals filled out a questionnaire concerning the feasibility of the intervention.

RESULTS

The available play space was 12.18 ± 4.19 m²/child at baseline and increased to 24.24 ± 8.51 m²/child during intervention. During the intervention sedentary time decreased (-0.58 min/recess; -3.21%/recess) and moderate-to-vigorous physical activity (+1.04 min/recess; +5.9%/recess) increased during recess and during the entire school day (sedentary time: -3.29%/school day; moderate-to-vigorous physical activity +1.16%/school day). All principals agreed that children enjoyed the intervention; but some difficulties were reported.

CONCLUSIONS

Lowering playground density can be an effective intervention for decreasing children's sedentary time and increasing their physical activity levels during recess; especially in least active children.

Daily physical activity patterns of children with delayed eating behaviors

Night eating syndrome (NES) is a delayed pattern of energy intake. It is unknown if symptoms associated with this syndrome are accompanied by a delayed pattern of physical activity. This study examines the relationship between physical activity patterns and delayed eating behaviors in children. Children from the QUALITY cohort (n = 269, 45% female, aged 8-11 y) completed the Night Eating Questionnaire (NEQ), which measures NES symptoms on a continuous scale and identifies single NES symptoms. Daily accelerometer data were transformed into mean counts per wear-time minute for each hour of the day. Children with high NEQ scores had higher levels of daily (p < 0.001) and evening physical activity (p = 0.05) and reached 75% of their total daily physical activity 20 minutes later than children with low NEQ scores (p < 0.05). Excessive evening snacking and a strong urge to eat in the evening or at night were the symptoms most related to these physical activity patterns. Children with delayed eating behaviors had higher levels of physical activity in the late morning and evening and a delayed physical activity pattern compared to children with no or fewer symptoms. Future research is needed to determine if physical activity plays a role in the onset or maintenance of night eating.

Walking cadence and cardiovascular risk in children and adolescents: NHANES, 2005-2006

BACKGROUND

Peak cadence (steps/minute) has been presented as an indicator of children's and adolescents' best natural daily effort.

PURPOSE

The goal of the study was to determine the relationship between peak walking cadence and cardiovascular disease (CVD) risk factors in children and adolescents.

METHODS

Data from the 2005-2006 National Health and Nutrition Examination Survey on accelerometer, high-density lipoprotein cholesterol, BMI, and blood pressure from 1817 children and adolescents (aged 8-18 years) were analyzed in 2012. Participants were stratified based on CVD risk factors (0, 1, and ≥2) and age (8-11, 12-15, and 16-18 years). Age-specific trends were evaluated in peak 1-minute cadence (steps/minute recorded for the highest single minute in a day) and peak 30-minute and 60-minute cadence (average of the highest steps/minute recorded for the specified number of minutes, not necessarily consecutive) across strata.

RESULTS

Across ascending age groups, peak 1-minute, 30-minute, and 60-minute cadence ranged from 123 to 111, 87 to 82, and 74 to 68 steps/minute, respectively. Peak 60-minute cadence means trended lower across groups of children with higher numbers of risk factors (p=0.02) in the age group 8-11 years; means similarly trended lower for all peak cadence indicators (all p for trend <0.01) in the age group 12-15 years; analogous trends were also significant in the age group 16-18 years.

CONCLUSIONS

Results varied with age; however, children and adolescents who on average had higher peak cadence indicators tended to have fewer CVD risk factors. These cross-sectional data suggest that a simple indicator of best natural daily effort may play an important role in early progression of unfavorable cardiometabolic health.

Accelerometer-determined physical activity and walking capacity in persons with Down syndrome, Williams syndrome and Prader-Willi syndrome

In this study we describe by use of accelerometers the total physical activity (PA), intensity pattern and walking capacity in 87 persons age 16-45 years with Down syndrome (DS), Williams syndrome (WS) and Prader-Willi syndrome (PWS). Participants were recruited from all over Norway, and lived either with their parents or in community residences with support. On average the participants generated 294 counts per minute (cpm) or 6712 steps per day, with most of the day spent in sedentary activity, 522 min/day, followed by 212 min/day in light PA, 71 min/day in lifestyle activity and 27 min/day in moderate-to-vigorous physical activity (MVPA). Inactivity was prevalent, as only 12% meet the current Nordic recommendations for PA. When compared, no differences for total physical activity or time in MVPA were observed between the three groups. However, participant with DS spent a mean of 73 min/day less and 43 min/day less in sedentary activities compared to participants with PWS and WS, respectively, (p=0.011, 95% CI: -10.9; -80.1). In addition the DS-group spent a mean of 66 min/day more in light PA than the PWS-group and 41 min/day more than the WS-group, (p<0.001, 95% CI: 29.3; 79.7). Participants with PWS spent on average 30 min/day less in lifestyle activities compared to both participants with DS and WS, (p<0.001, 95% CI: -14.2; -45.4). No association between total PA and BMI were observed. Males were more active than females across all diagnoses. Males accumulated on average 85 counts per minutes more than females, (p=0.002, 95% CI: 33.3; 136.7), 2137 more steps per day, (p=0.002, 95% CI: 778; 3496). The mean walking capacity during six-minutes was 507 m (SD 112 m) for males and 466 m (SD 88 m) for females. Distance walked during testing decreased with 33.6 m when comparing normal or underweight participants to overweight participants, and 78.1 m when comparing overweight to obese participants (p<0.001 95% CI: -40.4; -85.8). When adjusted for BMI no differences in walking capacity between the three genetic conditions were observed.

Obesity increases risk of declining physical activity over time in women: a prospective cohort study

OBJECTIVE

Research indicates that risk of obesity increases as physical activity (PA) decreases; however, the reciprocal effect has been rarely studied. The present investigation was conducted to determine the contribution of obesity on objectively measured PA over 20 months.

DESIGN AND METHODS

A prospective cohort design with 254 middle-aged women was employed. Body fat percentage (BF%) was measured using Bod Pod, and obesity was defined as BF% ≥32%. PA was assessed objectively using 7-day accelerometry at baseline and ∼20 months later at follow-up.

RESULTS

Of the 254 subjects, 124 were obese (49%) at baseline. Mean BF% was 32.1 ± 7.8 and average age was 41.7 ± 3.1 years. Mean weekly PA was 2.79 ± 0.85 million activity counts for all participants. Over the 20-month period, PA decreased significantly more in obese women (-8.1% ± 27.1%) than in nonobese women (0.3% ± 31.7%) after adjusting for confounders (F = 5.3, P = 0.022). Moderate plus vigorous PA levels also decreased more in obese women (-28.1 ± 73.6 min/week) than in nonobese women (-5.9 ± 66.8 min/week), after adjusting for covariates (F = 7.84; P = 0.0055).

CONCLUSIONS

It appears that obese women tend to reduce PA over time at a faster rate than nonobese women. Evidently, obesity is a risk factor for decreasing PA over time in middle-aged women.

The independent and combined associations of physical activity and sedentary behavior with obesity in adults: NHANES 2003-06

OBJECTIVE

To examine the combined influence of moderate-to-vigorous physical activity (MVPA) and sedentary behavior on obesity in US adults.

DESIGN AND METHODS

Cross-sectional analyses were undertaken on a nationally representative sample of 5,083 adults from the April 2003 and June 2005 National Health and Nutrition Examination Survey. Self-reported TV time was divided into low, moderate, and high categories. Accelerometer-derived total sedentary and MVPA minutes divided into low, moderate, and high tertiles. The independent associations between MVPA, TV, and total sedentary time and obesity were examined using logistic regression. Participants were then cross tabulated into nine MVPA-sedentary behavior groups, and logistic regression was used to examine the combined influence of MVPA and sedentary behavior on the odds of being obese.

RESULTS

MVPA was consistently inversely associated with obesity, regardless of sedentary behavior [odds ratio (OR) = 1.80-4.00]. There were inconsistent positive associations between TV time and risk of obesity in men, but not between total sedentary time and risk of obesity in either men or women.

CONCLUSIONS

Obesity was more strongly related to MVPA than either TV time or total sedentary time in US adults. Small differences in daily MVPA (5-10 min) were associated with relatively large differences in risk of obesity.

Effect of a school-based active play intervention on sedentary time and physical activity in preschool children

Early childhood is a critical time for promoting physical activity. Few studies have investigated the effect of interventions in this population. The aim of this study was to investigate the effect of a school-based active play intervention on preschool children's sedentary time and physical activity. Preschool children were recruited from randomly selected preschools. Schools were randomly assigned to an intervention or comparison group. One teacher per intervention school received training from active play professionals in the delivery of a 6-week active play programme. Comparison schools continued their usual practice. Children wore a uni-axial accelerometer for 7 days at baseline, immediately after and at 6-month post-intervention. No significant intervention effects were observed for sedentary time or physical activity. However, sex and hours spent at school were significant predictors of physical activity. Children who spent fewer hours (half-day children) at school were significantly more active than their full-day counterparts. Physical activity during the intervention classes was high even though neither daily physical activity nor sedentary time changed. Notably children who spent more time at preschool were less active suggesting that preschool was not as conducive to physical activity engagement as other environments.

Leveraging knowledge from physiological data: on-body heat stress risk prediction with sensor networks

The paper demonstrates that wearable sensor systems, coupled with real-time on-body processing and actuation, can enhance safety for wearers of heavy protective equipment who are subjected to harsh thermal environments by reducing risk of Uncompensable Heat Stress (UHS). The work focuses on Explosive Ordnance Disposal operatives and shows that predictions of UHS risk can be performed in real-time with sufficient accuracy for real-world use. Furthermore, it is shown that the required sensory input for such algorithms can be obtained with wearable, non-intrusive sensors. Two algorithms, one based on Bayesian nets and another on decision trees, are presented for determining the heat stress risk, considering the mean skin temperature prediction as a proxy. The algorithms are trained on empirical data and have accuracies of 92.1±2.9% and 94.4±2.1%, respectively when tested using leave-one-subject-out cross-validation. In applications such as Explosive Ordnance Disposal operative monitoring, such prediction algorithms can enable autonomous actuation of cooling systems and haptic alerts to minimize casualties.

Reliability and validity of the multimedia activity recall in children and adults (MARCA) in people with chronic obstructive pulmonary disease

Objective

To determine the reliability and validity of the Multimedia Activity Recall for Children and Adults (MARCA) in people with chronic obstructive pulmonary disease (COPD).

Design

People with COPD and their carers completed the Multimedia Activity Recall for Children and Adults (MARCA) for four, 24-hour periods (including test-retest of 2 days) while wearing a triaxial accelerometer (Actigraph GT3X+®), a multi-sensor armband (Sensewear Pro3®) and a pedometer (New Lifestyles 1000®).

Setting

Self reported activity recalls (MARCA) and objective activity monitoring (Accelerometry) were recorded under free-living conditions.

Participants

24 couples were included in the analysis (COPD; age 74.4±7.9 yrs, FEV₁ 54±13% Carer; age 69.6±10.9 yrs, FEV₁ 99±24%).

Interventions

Not applicable.

Main Outcome Measure(s)

Test-retest reliability was compared for MARCA activity domains and different energy expenditure zones. Validity was assessed between MARCA-derived physical activity level (in metabolic equivalent of task (MET) per minute), duration of moderate to vigorous physical activity (min) and related data from the objective measurement devices. Analysis included intra-class correlation coefficients (ICC), Bland-Altman analyses, paired t-tests (p) and Spearman's rank correlation coefficients (r_s).

Results

Reliability between occasions of recall for all activity domains was uniformly high, with test-retest correlations consistently >0.9. Validity correlations were moderate to strong (r_s = 0.43–0.80) across all comparisons. The MARCA yields comparable PAL estimates and slightly higher moderate to vigorous physical activity (MVPA) estimates.

Conclusion

In older adults with chronic illness, the MARCA is a valid and reliable tool for capturing not only the time and energy expenditure associated with physical and sedentary activities but also information on the types of activities.

Interactive drivers of activity in a free-ranging estuarine predator

Animal activity patterns evolve as an optimal balance between energy use, energy acquisition, and predation risk, so understanding how animals partition activity relative to extrinsic environmental fluctuations is central to understanding their ecology, biology and physiology. Here we use accelerometry to examine the degree to which activity patterns of an estuarine teleost predator are driven by a series of rhythmic and arrhythmic environmental fluctuations. We implanted free-ranging bream Acanthopagrus australis with acoustic transmitters that measured bi-axial acceleration and pressure (depth), and simultaneously monitored a series of environmental variables (photosynthetically active radiation, tidal height, temperature, turbidity, and lunar phase) for a period of approximately four months. Linear modeling showed an interaction between fish activity, light level and tidal height; with activity rates also negatively correlated with fish depth. These patterns highlight the relatively-complex trade-offs that are required to persist in highly variable environments. This study demonstrates how novel acoustic sensor tags can reveal interactive links between environmental cycles and animal behavior.

Energy expenditure compared to physical activity measured by accelerometry and self-report in adolescents: a validation study

Background

Physical inactivity is responsible for 5.3 million deaths annually worldwide. To measure physical activity energy expenditure, the doubly labeled water (DLW) method is the gold standard. However, questionnaires and accelerometry are more widely used. We compared physical activity measured by accelerometer and questionnaire against total (TEE) and physical activity energy expenditure (PAEE) estimated by DLW.

Methods

TEE, PAEE (TEE minus resting energy expenditure) and body composition were measured using the DLW technique in 25 adolescents (16 girls) aged 13 years living in Pelotas, Brazil. Physical activity was assessed using the Actigraph accelerometer and by self-report. Physical activity data from accelerometry and self-report were tested against energy expenditure data derived from the DLW method. Further, tests were done to assess the ability of moderate-to-vigorous intensity physical activity (MVPA) to predict variability in TEE and to what extent adjustment for fat and fat-free mass predicted the variability in TEE.

Results

TEE varied from 1,265 to 4,143 kcal/day. It was positively correlated with physical activity (counts) estimated by accelerometry (rho  = 0.57; p = 0.003) and with minutes per week of physical activity by questionnaire (rho  = 0.41; p = 0.04). An increase of 10 minutes per day in moderate-to-vigorous intensity physical activity (MVPA) relates to an increase in TEE of 141 kcal/day. PAEE was positively correlated with accelerometry (rho  = 0.64; p = 0.007), but not with minutes per week of physical activity estimated by questionnaire (rho  = 0.30; p = 0.15). Physical activity by accelerometry explained 31% of the vssariability in TEE. By incorporating fat and fat-free mass in the model, we were able to explain 58% of the variability in TEE.

Conclusion

Objectively measured physical activity significantly contributes to the explained variance in both TEE and PAEE in Brazilian youth. Independently, body composition also explains variance in TEE, and should ideally be taken into account when using accelerometry to predict energy expenditure values.

Association of physical activity and sedentary behavior with biological markers among U.S. pregnant women

BACKGROUND

To examine the association between objectively measured light-intensity and moderate-to-vigorous-intensity physical activity (MVPA), sedentary behaviors, and biological markers in a national sample of U.S. pregnant women, as few studies have examined these relationships among this population.

METHODS

The sample of noninstitutionalized U.S. civilians was selected by a complex, multistage probability design. Data from the 2003-2006 National Health and Examination Survey were used. Two hundred six pregnant women were included in the data analysis. Physical activity and sedentary data were objectively measured via accelerometry (ActiGraph 7164). Biomarker data was obtained in the mobile examination center from urine, blood samples, blood pressure, and anthropometric measurements. Urine and blood samples were obtained to determine pregnancy status, C-reactive protein (CRP), high-density lipoprotein (HDL) cholesterol, total cholesterol, and cotinine as well as fasting glucose, fasting triglycerides, and fasting low-density lipoprotein (LDL) cholesterol data. Multivariable regression was employed to examine the association between physical activity, sedentary behavior, and biomarker levels.

RESULTS

There was a positive association between sedentary behavior and CRP levels (beta coefficient [b]=0.001, p=0.02) and LDL cholesterol (b=0.12, p=0.02). There was an inverse association between light-intensity physical activity and CRP (b=-0.003; p=0.008) and diastolic blood pressure (b=-0.03; p=0.02), with those engaging in higher levels of MVPA having higher HDL cholesterol (b=6.7; p=0.01).

CONCLUSION

Physical activity and sedentary behavior were favorably associated with various biomarkers among pregnant women, suggesting that healthcare providers should encourage pregnant women to participate in safe forms of physical activity behaviors while also reducing their amount of time spent in sedentary behaviors.

Elementary school practices and children's objectively measured physical activity during school

OBJECTIVE

To examine the relation of physical activity practices covering physical education (PE), recess, and classroom time in elementary schools to children's objectively measured physical activity during school.

METHODS

Participants were 172 children from 97 elementary schools in the San Diego, CA and Seattle, WA USA regions recruited in 2009-2010. Children's moderate-to-vigorous physical activity (MVPA) during school was assessed via accelerometry, and school practices were assessed via survey of school informants. Multivariate linear mixed models were adjusted for participant demographics and unstandardized regression coefficients are reported. The 5 practices with the strongest associations with physical activity were combined into an index to investigate additive effects of these practices on children's MVPA.

RESULTS

Providing ≥ 100 min/week of PE (B=6.7 more min/day; p=.049), having ≤ 75 students/supervisor in recess (B=6.4 fewer min/day; p=.031), and having a PE teacher (B=5.8 more min/day; p=.089) were related to children's MVPA during school. Children at schools with 4 of the 5 practices in the index had 20 more min/day of MVPA during school than children at schools with 0 or 1 of the 5 practices (p<.001).

CONCLUSIONS

The presence of multiple school physical activity practices doubled children's physical activity during school.

Understanding physical activity and motivations for children with developmental coordination disorder: an investigation using the theory of planned behavior

Developmental coordination disorder (DCD) is a neurodevelopmental condition, affecting approximately 5-6% of children. Previous research has consistently found children with DCD being less physically active compared to typically-developing (TD) children; however, the psychosocial factors associated with physical activity for children with DCD are poorly understood. The purpose of this study was to examine how theory-based physical activity cognitions impacts physical activity behaviors for children with and without DCD. Participants included a sample of boys (N=61, Mage=13.25 ±.46) with DCD (n=19) and without DCD (n=42), drawn from a larger prospective cohort study. A questionnaire with psychosocial measures was first administered, and accelerometers were used to assess their physical activity behavior over the subsequent week. Findings indicate that DCD was significantly associated with lower physical activity (F(1,58)=6.51, p<.05), and poorer physical activity cognitions (F(4,56) Wilks Lambda=2.78, p<.05). Meditational analyses found attitudes (B=.23, p<.05) and subjective norms (B=.31, p<.05) partially mediating the relationship between DCD and physical activity. Overall, this study further confirms that the activity deficit that exists among boys with DCD, and that the relationship is partially mediated through some physical activity cognitions. Interventions should target the perceived approval of influential people, and the personal evaluations of physical activity for boys with motoric difficulties. These findings further emphasizes the discrepancy in physical activity that exist between boys with DCD and TD boys, and highlight the need to better understand the psychological factors related to physical activity for children with DCD.

Identification of behaviour in freely moving dogs (Canis familiaris) using inertial sensors

Monitoring and describing the physical movements and body postures of animals is one of the most fundamental tasks of ethology. The more precise the observations are the more sophisticated the interpretations can be about the biology of a certain individual or species. Animal-borne data loggers have recently contributed much to the collection of motion-data from individuals, however, the problem of translating these measurements to distinct behavioural categories to create an ethogram is not overcome yet. The objective of the present study was to develop a “behaviour tracker”: a system composed of a multiple sensor data-logger device (with a tri-axial accelerometer and a tri-axial gyroscope) and a supervised learning algorithm as means of automated identification of the behaviour of freely moving dogs. We collected parallel sensor measurements and video recordings of each of our subjects (Belgian Malinois, N=12; Labrador Retrievers, N=12) that were guided through a predetermined series of standard activities. Seven behavioural categories (lay, sit, stand, walk, trot, gallop, canter) were pre-defined and each video recording was tagged accordingly. Evaluation of the measurements was performed by support vector machine (SVM) classification. During the analysis we used different combinations of independent measurements for training and validation (belonging to the same or different individuals or using different training data size) to determine the robustness of the application. We reached an overall accuracy of above 90% perfect identification of all the defined seven categories of behaviour when both training and validation data belonged to the same individual, and over 80% perfect recognition rate using a generalized training data set of multiple subjects. Our results indicate that the present method provides a good model for an easily applicable, fast, automatic behaviour classification system that can be trained with arbitrary motion patterns and potentially be applied to a wide range of species and situations.

A new virtual instrument for estimating punch velocity in combat sports

For improving the performance in combat sport, especially percussion, it is necessary achieving high velocity in punches and kicks. The aim of this study was to evaluate the applicability of 3D accelerometry in a Virtual Instrumentation System (VIS) designed for estimating punch velocity in combat sports. It was conducted in two phases: (1) integration of the 3D accelerometer with the communication interface and software for processing and visualization, and (2) applicability of the system. Fifteen karate athletes performed five gyaku zuki type punches (with reverse leg) using the accelerometer on the 3rd metacarpal on the back of the hand. It was performed nonparametric Mann-Whitney U-test to determine differences in the mean linear velocity among three punches performed sequentially (p <0.05). The maximum velocities measured varied in the range of 10 and 10.2 m/s and the mean velocities from 6 to 6.8 m/s. There was no difference on the mean velocity for the tested punches. The VIS demonstrated regularity and proper functionality for assessing punches in combat sport.

Human pose recovery for rehabilitation using ambulatory sensors

In this paper, an approach for lower-leg pose recovery from ambulatory sensors is implemented and validated in a clinical setting. Inertial measurement units are attached to patients undergoing physiotherapy. The sensor data is combined with a kinematic model within an extended Kalman filter framework to perform joint angle estimation. Anthropometric joint limits and process noise adaptation are employed to improve the quality of the joint angle estimation. The proposed approach is tested on 7 patients following total hip or knee joint replacement surgery. The proposed approach achieves an average root-mean-square error of 0.12 radians at key poses.

Comparisons of apparent mass responses of human subjects seated on rigid and elastic seats under vertical vibration

The apparent mass (AM) responses of human body seated on elastic seat, without and with a vertical back support, are measured using a seat pressure sensing mat under three levels of vertical vibration (0.25, 0.50 and 0.75 m/s(2) rms acceleration) in 0.50-20 Hz frequency range. The responses were also measured with a rigid seat using the pressure mat and a force plate in order to examine the validity of the pressure mat. The pressure mat resulted in considerably lower AM magnitudes compared to the force plate. A correction function was proposed and applied, which resulted in comparable AM from both measurement systems for the rigid seat. The correction function was subsequently applied to derive AM of subjects seated on elastic seat. The responses revealed lower peak magnitude and corresponding frequency compared to those measured with rigid seat, irrespective of back support and excitation considered.

Measuring physical activity during US Army Basic Combat Training: a comparison of 3 methods

BACKGROUND

An understanding of the demands of physical activity (PA) during US Army Basic Combat Training (BCT) is necessary to support Soldier readiness and resilience. The purpose of this study was to determine the agreement among 3 different PA measurement instruments in the BCT environment.

METHODS

Twenty-four recruits from each of 11 companies wore an ActiGraph accelerometer (Actigraph, LLC, Pensacola, FL) and completed a daily PA log during 8 weeks of BCT at 2 different training sites. The PA of one recruit from each company was recorded using PAtracker, an Army-developed direct observation tool. Information obtained from the accelerometer, PA log, and PAtracker included time spent in various types of PA, body positions, PA intensities, and external loads carried. Pearson product moment correlations were run to determine the strength of association between the ActiGraph and PAtracker for measures of PA intensity and between the PAtracker and daily PA log for measures of body position and PA type. The Bland-Altman method was used to assess the limits of agreement (LoA) between the measurement instruments.

RESULTS

Weak correlations (r=-0.052 to r=0.302) were found between the ActiGraph and PAtracker for PA intensity. Weak but positive correlations (r=0.033 to r=0.268) were found between the PAtracker and daily PA log for body position and type of PA. The 95% LoA for the ActiGraph and PAtracker for PA intensity were in disagreement. The 95% LoA for the PAtracker and daily PA log for standing and running and all PA types were in disagreement; sitting and walking were in agreement.

CONCLUSIONS

The ActiGraph accelerometer provided the best measure of the recruits' PA intensity while the PAtracker and daily PA log were best for capturing body position and type of PA in the BCT environment. The use of multiple PA measurement instruments in this study was necessary to best characterize the physical demands of BCT.

Moderate-to-vigorous physical activity in individuals with psoriasis: associations with body surface area and subjective disease severity

AIM

Psoriasis is associated with serious comorbidities such as cardiovascular disease, type 2 diabetes, and metabolic syndrome. These comorbidities are related to low physical activity in the general population. Limited research has evaluated physical activity in psoriasis, and thus, the purpose of this investigation was to compare physical activity between individuals with and without psoriasis as well as explore the associations between measures of psoriasis severity and physical activity.

METHODS

Cross-sectional study using data from the 2003-2006 National Health and Nutrition Examination Survey. Self-reported psoriasis diagnosis and psoriasis severity were regressed on moderate/vigorous physical activity, as measured objectively by accelerometers. Measures of psoriasis severity included rating of psoriasis as a problem in life and body surface area involvement.

RESULTS

A total of 4316 individuals had data on psoriasis, moderate/vigorous physical activity, and relevant covariates, with 3.6% (population weighted) of participants (N.=117) reporting a diagnosis of psoriasis. A psoriasis diagnosis was not associated with moderate/vigorous physical activity, and furthermore, body surface area involvement was not associated with moderate/vigorous physical activity among participants with psoriasis. However, every tertile increase in psoriasis as a problem in life was associated with 28% less moderate/vigorous physical activity, which remained significant after adjusting for covariates and removing outliers.

CONCLUSION

While a diagnosis of psoriasis and body surface area involvement do not appear to be associated with less moderate/vigorous physical activity, individuals that rate their psoriasis to be a large problem engage in less moderate/vigorous physical activity.

Quantification of physical activity performed during US Army Basic Combat Training

PURPOSE

During US Army Basic Combat Training (BCT), graduation requirements, including physical readiness training (PRT), are standardized across training sites. However, there are concerns that the standardization may not be closely followed. Therefore, the purpose of this study was to measure and compare physical activity (PA) performed by recruits at 2 Army BCT sites.

METHODS

Twenty-four recruits per company from 11 companies (n=144 at Fort Jackson, SC; n=120 at Fort Sill, OK) wore an accelerometer and completed a daily PA log. The PA of one recruit from each company was recorded using an Army-developed direct observation tool (PAtracker). Amounts of time spent in various activity types, intensities, body positions, and in carrying external loads were obtained from the accelerometer, PA log, and PAtracker. Independent samples t tests were used to compare PA percentage time (%T) across training sites. Repeated measures analysis of variance was used to examine weekly differences in time spent in moderate to vigorous intensity PA during morning PRT.

RESULTS

Physical activity was measured for 47 days at Fort Jackson and 44 days at Fort Sill. Differences in the percentage of time spent in various physical activities between the 2 sites ranged from 0.4% to 15.3% (2.0-93.7 minutes). At Fort Jackson, time spent in moderate to vigorous PA during PRT significantly increased each week for the first 4 to 6 weeks of BCT. No difference was observed in PAtracker data between the 2 training sites in the percentage of time recruits spent in calisthenics (3.9%±3.6% vs 3.8%±3.0%, P=.700), and only a small difference was observed in percentage of time recruits spent running (1.2%±1.7% vs 1.6%±2.0%, P=.037).

CONCLUSION

Army recruits at the 2 BCT sites spent similar amounts of time in each PA variable, regardless of the training site and measurement method.

Sedentary behaviour and clustered metabolic risk in adolescents: the HELENA study

BACKGROUND AND AIMS

Although sedentary behaviours are linked with mortality for cardiovascular reasons, it is not clear whether they are negatively related with cardio-metabolic risk factors. The aim was to examine the association between time engaged in television (TV) viewing or playing with videogames and a clustered cardio-metabolic risk in adolescents.

METHODS AND RESULTS

Sedentary behaviours and physical activity were assessed in 769 adolescents (376 boys, aged 12.5-17.5 years) from the HELENA-CSS study. We measured systolic blood pressure, HOMA index, triglycerides, TC/HDL-c, VO₂max and the sum of four skinfolds, and a clustered metabolic risk index was computed. A multilevel regression model (by Poisson) was performed to calculate the prevalence ratio of having a clustered metabolic risk. In boys, playing >4 h/day with videogames (weekend) and moderate to vigorous PA (MVPA) was associated with cardio-metabolic risk after adjustment for age, maternal education and MVPA. In contrast, TV viewing was not associated with the presence of cardio-metabolic risk.

CONCLUSION

In boys, playing with videogames may impair cardio-metabolic health during the adolescence. Adolescents should be encouraged to increase their participation in physical activity of at least moderate intensity to obtain a more favourable risk factor profile.

Assessing the contribution of parks to physical activity using global positioning system and accelerometry

PURPOSE

Parks offer a free option for physical activity in many communities. How much time people spend using parks and the contribution that parks makes to their physical activity is not known. This study describes patterns of park use and physical activity among a diverse adult sample.

METHODS

From five US states, 248 adults enrolled in or near 31 study parks. Participants wore a global positioning system (GPS) monitor (Qstarz BT-Q1000X) and an ActiGraph accelerometer (GT1M) concurrently for 3 wk. Parks were mapped from local and national park shape files. Park visits and travel to and from the parks were derived from the objective data.

RESULTS

Participants visited parks a median of 2.3 times per week, and park visits lasted a median of 42.0 min. Overall, participants engaged in a median of 21.7 min·d-1 of moderate activity and 0.1 min·d-1 of vigorous activity, with an average of 8.2% of all moderate and 9.4% of all vigorous activity occurring within the parks. Among those with at least one park visit (n = 218), counts per minute, moderate, moderate-to-vigorous physical activity (MVPA), number and time in MVPA bouts per day, and sedentary behavior were all higher on days when a park was visited compared with days when a park was not visited. Considering several definitions of active travel, walking or bicycling to and from the park added an additional 3.7-6.6 mean minutes of MVPA per park visit.

CONCLUSIONS

Parks contributed as a place and destination for physical activity but were underused. One of the next steps in this line of inquiry is to understand characteristics of parks used more often as a place and destination for physical activity.

Validity of a combined heart rate and motion sensor for the measurement of free-living energy expenditure in very active individuals

OBJECTIVES

The correct assessment of energy expenditure in very active individuals is important to ensure that dietary energy intake is sufficient. We aimed to validate a combined heart rate (HR) and motion sensor in estimating total (TEE) and activity energy expenditure (AEE) in males and females with high physical activity levels.

DESIGN

Cross-sectional.

METHODS

Doubly-labelled water (DLW) was used to assess 7-day TEE in 12 male and female elite junior basketball players, aged 16-17 years. Resting energy expenditure (REE) was assessed with indirect calorimetry and AEE was calculated (AEE=TEE-RMR-0.1×TEE). Simultaneously, TEE and AEE were measured by combined HR and motion sensing. Individual HR calibration was performed with step-test. TEE and AEE were estimated from accelerometry and HR with individual (ACC+HRstep) and group calibration (ACC+HRgroup).

RESULTS

No mean differences were found between TEE and AEE from the ACC+HRstep and ACC+HRgroup with DLW. TEE values (kJ/day) from ACC+HRgroup and ACC+HRstep explained TEE from DLW by ∼60% and 53%, respectively whereas AEE (kJ/day) estimated by ACC+HRgroup and ACC+HRstep explained 53% and 41% of the variability of AEE from the reference method. Concordance correlation coefficients for TEE and AEE using ACC+HRgroup were 0.74 and 0.69, correspondingly while for ACC+HRstep values of 0.69 and 0.45 were found. Large limits of agreement were found for TEE and AEE using both ACC+HRgroup and ACC+HRstep.

CONCLUSIONS

ACC+HR models are a valid alternative to estimate TEE but not AEE in a group of highly active individuals however the considerable rate of equipment failure (∼50%) limits its usefulness.

Objectively measured physical activity and inflammatory markers among US adults with diabetes: implications for attenuating disease progression

OBJECTIVE

To examine the association between objectively measured physical activity and markers of inflammation (ie, white blood cell count, neutrophil count, and C-reactive protein level) among a national sample of adults with diabetes.

PATIENTS AND METHODS

Data from the 2003-2006 National Health and Nutrition Examination Survey cycles were used. The data were evaluated from November 25, 2012, to May 3, 2013. Participants wore an accelerometer for 4 days or longer to assess physical activity, with blood samples obtained to assess the aforementioned inflammatory markers.

RESULTS

Accelerometer-derived light physical activity and moderate to vigorous physical activity were inversely associated with white blood cell and neutrophil counts, whereas time spent in moderate to vigorous physical activity was inversely associated with C-reactive protein levels.

CONCLUSION

Adults with diabetes engaging in more physical activity have lower degrees of inflammation, suggesting that physical activity may reduce disease progression through mitigating inflammation, which is an important finding because increased inflammation among those with diabetes can worsen disease progression, including diabetic end-organ damage.

Assessing sitting across contexts: development of the multicontext sitting time questionnaire

PURPOSE

To describe the development and preliminary evaluation of the Multicontext Sitting Time Questionnaire (MSTQ).

METHOD

During development of the MSTQ, contexts and domains of sitting behavior were utilized as recall cues to improve the accuracy of sitting assessment. The terms "workday" and "nonworkday" were used to disambiguate occupational and discretionary sitting. An expert panel evaluated content validity. Among 25 participants, test-retest reliability of the MSTQ items was assessed with intraclass correlation coefficients (ICCs). Convergent validity was assessed versus relative and absolute accelerometer-estimated sedentary time and activity log using Pearson (r) or Spearman (p) correlation coefficients where appropriate.

RESULTS

Pilot testing revealed Web-based MSTQ administration was rapid, scalable, and inexpensive. Most items in the MSTQ demonstrated acceptable reliability (ICCs > .70). Compared with accelerometer-estimated sedentary time relative to total wear time, the MSTQ exhibited a low correlation on workdays (r = .34) and a moderately high correlation on nonworkdays (r = .61).

CONCLUSIONS

The systematic development of the MSTQ resulted in several improvements over previous tools and may serve as a model for purpose-driven questionnaire design. Additional validation is needed to conclusively determine the utility of the MSTQ.