Comparability of measured acceleration from accelerometry-based activity monitors

Accelerometers that provide triaxial measured acceleration data are now available. However, equivalence of output between brands cannot be assumed and testing is necessary to determine whether features of the acceleration signal are interchangeable.National Osteoporosis Societ

A data-driven, meaningful, easy to interpret, standardised accelerometer outcome variable for global surveillance

This is the author accepted manuscript. The final version is available from Elsevier via the DOI in this record.Objectives: Our aim is to demonstrate how a data-driven accelerometer metric, the acceleration above which a person’s most active minutes are accumulated, can a) quantify the prevalence of meeting current physical activity guidelines for global surveillance and b) moving forward, could inform accelerometer-driven physical activity guidelines. Unlike cut-point methods, the metric is population-independent (e.g. age) and potentially comparable across datasets. Design: Cross-sectional, secondary data analysis. Methods: Analyses were carried out on five datasets using wrist-worn accelerometers: children (N=145), adolescent girls (N=1669), office workers (N=114), pre- (N=1218) and post- (N=1316) menopausal women, and adults with type 2 diabetes (N=475). Open-source software (GGIR) was used to generate the magnitude of acceleration above which a person’s most active 60, 30 and 2 minutes are accumulated: M60ACC; M30ACC and M2ACC, respectively. Results: The proportion of participants with M60ACC (children) and M30ACC (adults) values higher than accelerations representative of brisk walking (i.e., moderate-to-vigorous physical activity) ranged from 17-68% in children and 15%-81% in adults, tending to decline with age. The proportion of pre-and postmenopausal women with M2ACC values meeting thresholds for bone health ranged from 6-13%. Conclusions: These metrics can be used for global surveillance of physical activity, including assessing prevalence of meeting current physical activity guidelines. As accelerometer and corresponding health data accumulate it will be possible to interpret the metrics relative to age- and sex- specific norms and derive evidence-based physical activity guidelines directly from accelerometer data for use in future global surveillance. This is where the potential advantages of these metrics lie

A small amount of precisely measured high intensity habitual physical activity predicts bone health in pre- and post-menopausal women in UK Biobank.

Background: Physical inactivity is a highly modifiable risk factor for the development of osteoporosis but, due to a lack of research that has precisely and objectively meaured physical activity (PA) relevant to bone, the specific contribution that PA can make to bone health is poorly understood. This study examined whether a more precise measure of PA relelvant to bone was associated with meaures of bone health in pre- and post-menopausal women in UK Biobank. Methods: Time spent at intensities specific to bone health [≥750 milli-gravitational units (mg) and ≥1000 mg] were analysed from raw tri-axial acceleration data averaged over 1-second epochs from 7-day monitoring of habitual PA using accelerometry-based activity monitors (100 Hz; AX3, Axivity, UK) of 1218 pre- and 1316 post-menopausal healthy women. In a cross-sectional analysis, associations between categories of time (<1, 1–2 and ≥2 minutes) spent above the intensity thresholds and calcaneal quantitative ultrasound measures of bone health (bone mineral density T-score, BMDT-score; speed of sound, SOS; and broadband ultrasound attenuation, BUA) were examined. Results: Compared with <1 minute, spending 1–2 or ≥2 minutes/day at intensities ≥1000 mg in pre-menopausal and ≥750 mg in post-menopausal women was positively associated with BMDT-score, SOS and BUA. Conclusion: Brief bursts of high-intensity PA relevant to bone health can be captured by applying bone-specific thresholds of intensity to raw tri-axial accelerations averaged over 1-second epochs. Accumulating 1–2 minutes/day of high-intensity PA, equivalent to running in pre-menopausal women and slow jogging in post-menopausal women, is associated with better bone health

Comparability of measured acceleration from accelerometry-based activity monitors

Background: Accelerometers that provide triaxial measured acceleration data are now available. However, equivalence of output between brands cannot be assumed and testing is necessary to determine whether features of the acceleration signal are interchangeable. Purpose: This study aimed to establish the equivalence of output between two brands of monitor in a laboratory and in a free-living environment. Methods: For part 1, 38 adults performed nine laboratory-based activities while wearing an ActiGraph GT3X+ and GENEActiv (Gravity Estimator of Normal Everyday Activity) at the hip. For part 2, 58 children age 10–12 yr wore a GT3X+ and GENEActiv at the hip for 7 d in a free-living setting. Results: For part 1, the magnitude of time domain features from the GENEActiv was greater than that from the GT3X+. However, frequency domain features compared well, with perfect agreement of the dominant frequency for 97%–100% of participants for most activities. For part 2, mean daily acceleration measured by the two brands was correlated (r = 0.93, P \u3c 0.001, respectively) but the magnitude was approximately 15% lower for the GT3X+ than that for the GENEActiv at the hip. Conclusions: Frequency domain-based classification algorithms should be transferable between monitors, and it should be possible to apply time domain-based classification algorithms developed for one device to the other by applying an affine conversion on the measured acceleration values. The strong relation between accelerations measured by the two brands suggests that habitual activity level and activity patterns assessed by the GENE and GT3X+ may compare well if analyzed appropriately

Comparability of measured acceleration from accelerometry-based activity monitors

Background: Accelerometers that provide triaxial measured acceleration data are now available. However, equivalence of output between brands cannot be assumed and testing is necessary to determine whether features of the acceleration signal are interchangeable. Purpose: This study aimed to establish the equivalence of output between two brands of monitor in a laboratory and in a free-living environment. Methods: For part 1, 38 adults performed nine laboratory-based activities while wearing an ActiGraph GT3X+ and GENEActiv (Gravity Estimator of Normal Everyday Activity) at the hip. For part 2, 58 children age 10–12 yr wore a GT3X+ and GENEActiv at the hip for 7 d in a free-living setting. Results: For part 1, the magnitude of time domain features from the GENEActiv was greater than that from the GT3X+. However, frequency domain features compared well, with perfect agreement of the dominant frequency for 97%–100% of participants for most activities. For part 2, mean daily acceleration measured by the two brands was correlated (r = 0.93, P \u3c 0.001, respectively) but the magnitude was approximately 15% lower for the GT3X+ than that for the GENEActiv at the hip. Conclusions: Frequency domain-based classification algorithms should be transferable between monitors, and it should be possible to apply time domain-based classification algorithms developed for one device to the other by applying an affine conversion on the measured acceleration values. The strong relation between accelerations measured by the two brands suggests that habitual activity level and activity patterns assessed by the GENE and GT3X+ may compare well if analyzed appropriately

Four biomechanical and anthropometric measures predict tibial stress fracture: A prospective study of 1065 Royal Marines

Copyright © 2016 BMJ Publishing GroupBackground: Tibial stress fractures cause a significant burden to Royal Marines recruits. No prospective running gait analyses have previously been performed in military settings. Aim: We aimed to identify biomechanical gait factors and anthropometric variables associated with increased risk of TSF. Methods: 1065 Royal Marines recruits were assessed in week-2 of training. Bilateral plantar pressure and 3D lower limb kinematics were obtained for barefoot running at 3.6 m.s-1, providing dynamic arch index, peak heel pressure and lower limb joint angles. Age, bimalleolar breadth, calf girth, passive hip internal/external range of motion and body mass index (BMI) were also recorded. Ten recruits who sustained a TSF during training were compared with 120 recruits who completed training injury-free using a binary logistic regression model to identify injury risk factors. Results: Four variables significantly (p<0.05) predicted increased risk of TSF (odds ratios and 95% CI): smaller bimalleolar width (0.73, 0.58-0.93), lower BMI (0.56, 0.33-0.95), greater peak heel pressure (1.25, 1.07-1.46) and lower range of tibial rotation (0.78, 0.63-0.96). Summary: Reduced impact attenuation and ability to withstand load were implicated in tibial stress fracture risk

A history of hookworm vaccine development

The human hookworms Necator americanus and Ancylostoma duodenale remain among the most common infections of humans in areas of rural poverty in the developing regions of the world, with an estimated 1 billion people infected with one or more of these parasites. Herein, we review the nearly 100 years of research, development, animal testing, and fieldwork that have led to our current progress in recombinant hookworm vaccines. We begin with the identification of hookworm at the start of the 20th century in Southern US, then discuss the progress in developed countries to eliminate human hookworm infection, and then the industrial development and field use in the 1970s a canine hookworm vaccine(Ancylostoma caninum), and finally our progress to date in the development and clinical testing of an array of recombinant antigens to prevent human hookworm disease from N. americanus infection. Special attention is given to the challenges faced in the development of a vaccine against a blood-feeding nematode, including the epidemiology of infection (high prevalence of infection), pathogenesis (chronic infection that increases with the age of the host), and a robust immune response that fails to confer the protection in the host and a concomitant absence of correlates of protection by a successful vaccine could be developed and tested. Finally, we provide the optimal and acceptable profiles of a human hookworm vaccine, including the proposed indication, target population, and route of administration, as developed by the Human Hookworm Vaccine Initiative, the only group currently working on vaccines targeting this parasite