Jan Christian Brønd

Jan Christian Brønd
University of Southern Denmark | SDU · Institute of Sports Science and Clinical Biomechanics

Phd

About

95
Publications
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2,301
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Publications

Publications (95)
Article
Full-text available
Wearable technologies open up new avenues for the assessment of individual physical activity behaviour. Particularly, free-living heart rate (HR) data assessed by optical sensors are becoming widely available. However, while an abundancy of scientific information and guidance exists for the processing of raw acceleration data, no universal recommen...
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Background The widespread ownership of digital devices among adolescents presents challenges and opportunities in schools, particularly during recess. This study aimed to examine the association of screen use during recess with physical activity behaviours. Methods The study was based on a population-based cross-sectional study including 1347 adol...
Article
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Physical activity (PA) reduces the risk of negative mental and physical health outcomes in older adults. Traditionally, PA intensity is classified using METs, with 1 MET equal to 3.5 mL O2·min⁻¹·kg⁻¹. However, this may underestimate moderate and vigorous intensity due to age‐related changes in resting metabolic rate (RMR) and VO2max. VO2reserve acc...
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Aim To provide detailed descriptions of the amount of daily physical activity (PA) performed by people with multimorbidity and investigate the association between the number of conditions, multimorbidity profiles, and PA. Methods All adults (≥18 years) from The Lolland-Falster Health Study, conducted from 2016 to 2020, who had PA measured with acc...
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Physical inactivity increases risks of cardiovascular disease, poor mental health, and morbidity. School-based physical activity (PA) promotion can reach children from differing backgrounds in a large proportion of their waking hours. Education outside the classroom (EOtC) is an PA-integrating pedagogical approach that aligns PA with the primary go...
Article
The Danish Christmas Seal Homes offer a 10-week residential stay for socially vulnerable children. We aimed to examine the effects on body composition and cardiometabolic fitness variables of the standard program (SG) and whether substituting physical activity sessions with sessions from a football-based health education program is beneficial for t...
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Objectives A new school policy mandating 45 min physical activity daily during school was introduced in Denmark in 2014. We aimed to evaluate the effect of this policy on BMI in school-aged children. It was hypothesized that the school policy would decrease BMI, especially in the obese fraction of the population (90th percentile BMI). Study design...
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OBJECTIVE: This study aimed to examine differences in heart rate variability (HRV) across accelerometer-derived position, self-reported sleep, and different summary measures (sleep, 24h-HRV) in free-living settings using open-source methodology. APPROACH: HRV is a biomarker of autonomic activity. As it is strongly affected by factors such as physic...
Article
Purpose: To study the effectiveness of a preschool staff-delivered motor skills intervention on body composition and physical activity over a 2.5-year time frame. Methods: In this pragmatic parallel cluster randomized controlled trial (16 preschools), outcome data were collected after 6 (body composition only), 18, and 30 months of intervention....
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The accurate estimation of energy expenditure from simple objective accelerometry measurements provides a valuable method for investigating the effect of physical activity (PA) interventions or population surveillance. Methods have been evaluated previously, but none utilize the temporal aspects of the accelerometry data. In this study, we investig...
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Objective To evaluate the feasibility of a mobile health-supported intervention in patients with cardiovascular diseases after completion of a cardiac rehabilitation programme. Methods The feasibility study was performed in two hospitals and one municipality in Region Zealand, Denmark. Eligible participants were ≥18 years old, participated in a su...
Article
There are currently several methods available to generate summary measures from acceleration, while ActiGraph (AG) counts as the first method to be used at large scale. The recent disclosure of the AG counts method exposes its intrinsic properties, which has not been accessible before. The intrinsic properties are the raw acceleration processing el...
Article
In 2022, it became possible to produce ActiGraph counts from raw accelerometer data without use of ActiLife software. This supports the availability and use of transparent, open-source methods for producing physical behavior outcomes from accelerometer data. However, questions remain regarding the implications of the availability of open-source Act...
Article
Background : Accelerometer time may drift, whereas global positioning system time does not (due to constant satellite communication), potentially impacting linkage of these data; the impact of this issue on outcome measures is unknown. Our study assessed if time drift is consistent between devices and/or data collection waves and the impacts on com...
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Background Sedentary behavior (SB) is a determinant of health in older adult people. Educational level is a primary driver of health disparities and is demonstrated to be a reliable measure of socioeconomic position. We aimed to examine the associations between educational level and self-reported along with device-measured SB in older adults living...
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We recently developed a novel keratin-derived protein (KDP) rich in cysteine, glycine, and arginine, with the potential to alter tissue redox status and insulin sensitivity. The KDP was tested in 35 human adults with type-2 diabetes mellitus (T2DM) in a 14-wk randomised controlled pilot trial comprising three 2×20 g supplemental protein/day arms: K...
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Background Education can create better opportunities for health, and vice versa. Using a so-called ‘add-in’ approach, school-based physical activity (PA) promotion and prevention of sedentary behaviours can increase pupils’ wellbeing and learning and, on the longer term, reduce the risk of non-communicable diseases. A PA ‘add-in’ approach involves...
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Introduction This study aimed to describe objectively measured physical activity patterns, including daily activity according to day type (weekdays and weekend days) and the four seasons, frequency, distribution, and timing of engagement in activity during the day in individuals with diabetes and prediabetes and compared with individuals with no di...
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Purpose Education outside the classroom (EOtC) is a physical activity (PA)-integrating pedagogical approach that aligns PA with the primary goals of schools and is therefore thought to present an acceptable, feasible, and efficacious model for school-based PA. The aim of this study was to investigate the efficacy of an EOtC intervention that aims t...
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Aim Evidence suggests low-grade inflammation (LGI) to be associated with multimorbidity. Furthermore, there are links between inflammation markers, physical activity (PA), and labour market participation. The aims of this study were to examine the association between PA and LGI in people with multimorbidity and if this association was moderated by...
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Objective This study aimed to investigate directional influences in the association between adiposity and physical activity (PA) from pre-puberty to early adulthood. Methods In the Calex-study, height, weight, body fat and leisure-time physical activity (LTPA) were measured at age11.2-years, 13.2-years and 18.3-years in 396 Finnish girls. Body fat...
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Diet-induced weight loss is associated with improved beta-cell function in people with type 2 diabetes (T2D) with remaining secretory capacity. It is unknown if adding exercise to diet-induced weight loss improves beta-cell function and if exercise volume is important for improving beta-cell function in this context. Here, we carried out a four-arm...
Article
Aim: The objective of the current study was to examine whether physical activity and sedentary behavior were associated with appetite among community-dwelling older adults. Methods: Cross-sectional analysis was performed on three cohort studies: the Longitudinal Aging Study Amsterdam (LASA); the Health, Aging and Body Composition Study (HABC Stu...
Article
Children and adolescents with cerebral palsy (CP) show a reduced physical activity (PA) level compared with their typically developed peers. This study aimed to identify potential predictors of objectively evaluated habitual PA using data from a national clinical registry—the Cerebral Palsy Follow-Up Program (CPFP)—and proxy-reported questionnaires...
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Wearable physical activity sensors are widely used in research and practice as they provide objective measures of human behavior at a low cost. An important challenge for accurate assessment of physical activity behavior in free-living is the detection non-wear. Traditionally, heuristic algorithms that rely on specific interval lengths have been em...
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Introduction Habitual physical activity behaviors of individuals with new-onset type 2 diabetes are largely unknown. We aimed to investigate accelerometer-derived physical activity behaviors in individuals with newly diagnosed type 2 diabetes. We also examined sociodemographic and health-related correlates of a high-risk physical activity profile....
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Background: Early mobilisation of mechanically ventilated patients during their stay at an Intensive Care Unit (ICU) can improve physical recovery. Yet an objective and specified description of physical activities while in the ICU is lacking. Therefore, our aim was to describe the objectively assessed type, quantity, and daily variation of physica...
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Background A new Danish school policy with a requirement for 45 min physical activity daily during school hours was introduced in 2014. The objective of this natural experiment was to evaluate the effect of this nationwide school policy on physical activity in Danish children and adolescents. Methods Four historical studies completed between 2009...
Article
Background: It remains unclear if a low-carbohydrate, high-fat (LCHF) diet is a possible treatment strategy for type 2 diabetes mellitus (T2DM), and the effect on nonalcoholic fatty liver disease (NAFLD) has not been investigated. Objective: To investigate the effect of a calorie-unrestricted LCHF diet, with no intention of weight loss, on T2DM...
Preprint
Full-text available
Diet-induced weight loss improves beta-cell function in persons with type 2 diabetes (T2D) with remaining secretory capacity. It is unknown if adding exercise to a diet-induced weight loss improves beta-cell function and if exercise volume is important for improving beta-cell function in this context. In this four-armed randomized trial (Clinicaltr...
Article
Full-text available
Background: Tape-mounted Axivity AX3 accelerometers are increasingly being used to monitor physical activity of individuals, but studies on the integrity and performance of different attachment protocols are missing. Purpose: The purpose of this paper was to evaluate four attachment protocols with respect to skin reactions, adhesion, and wear time...
Article
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Background: Effective and sustainable implementation of physical activity (PA) in type 2 diabetes (T2D) health care has in general not been successful. Efficacious and contemporary approaches to support PA adherence and adoption are required. Objective: The primary objective of this study was to investigate the effectiveness of including an app-...
Article
ActiGraph sampling frequencies of more than 30 Hz may result in overestimation of activity counts in both children and adults, but research on free-living individuals has not included the range of sampling frequencies used by researchers. Objective: We compared count- and raw-acceleration-based metrics from free-living children and adolescents ac...
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Background PL is increasingly regarded as a ‘cause of the causes’ to health promotion. Cross-sectional studies have shown associations between children’s PL, physical activity (PA) behaviors and well-being. This presentation aims to present empirical evidence from a large-scale research project in Denmark assessing children’s physical literacy. Res...
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Study design: A method development and validation study. Objectives: The purpose of this study was to develop and test a method for step detection using accelerometer data in patients with lumbar spinal stenosis. There are two objectives: (1) to describe a method for step detection from accelerations measured at the wrist, hip, lower back, thigh...
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Background Technological advances have recently made possible the estimation of maximal oxygen consumption (VO2max) by consumer wearables. However, the validity of such estimations has not been systematically summarized using meta-analytic methods and there are no standards guiding the validation protocols. Objective The aim was to (1) quantitativ...
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Background Physical literacy (PL) is a multi-dimensional concept that provides a holistic understanding of movement and physical activity. PL contains an affective, a physical, and a cognitive domain, which together lay the foundation for the individual’s capacity and the tendency for participating in physical activities currently and throughout li...
Preprint
Full-text available
Wearable physical activity sensors are widely used in research and practice as they provide objective measures of human behavior at a low cost. An important challenge for accurate assessment in free-living is the detection non-wear. Traditionally, heuristic algorithms that rely on specific interval lengths have been employed to detect non-wear time...
Article
ActiGraph counts are commonly used for characterizing physical activity intensity and energy expenditure and are among the most well-studied accelerometer metrics. Researchers have recently replicated the counts processing method using a mechanical setup, now allowing users to generate counts from raw acceleration data. Purpose : The purpose of thi...
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Purpose To investigate separate and combined effects of vitamin D supplementation during the extended winter and increased dairy protein intake on muscle strength and physical function in children, and furthermore to explore potential sex differences. Methods In a 2 × 2-factorial, randomized winter trial, 183 healthy, 6–8-year-old children receive...
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Importance: Children and adults spend large amounts of their leisure time using screen media, which may affect their health and behavior. Objective: To investigate the effect of reducing household recreational screen media use on physical activity and sleep in children and adults. Design, setting, and participants: This was a cluster randomize...
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Introduction To enhance health and prevent secondary consequences for patients with cardiovascular disease (CVD), maintenance of an active lifestyle following participation in cardiac rehabilitation (CR) is important. However, levels of physical activity often decrease after completion of a structured CR programme. Models that support long-term beh...
Article
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Background Consumer wearables and smartphone devices commonly offer an estimate of energy expenditure (EE) to assist in the objective monitoring of physical activity to the general population. Alongside consumers, healthcare professionals and researchers are seeking to utilise these devices for the monitoring of training and improving human health....
Preprint
Full-text available
Background Physical literacy (PL) is a multi-dimensional concept that provides a holistic understanding of movement and physical activity. PL contains an affective, a physical, and a cognitive domain, which together lay the foundation for the individual’s capacity and the tendency for participating in physical activities currently and throughout li...
Article
Aims: To investigate the efficacy and safety of a non-calorie-restricted low-carbohydrate diet (LCD) on glycemic control, body composition, and cardiovascular risk factors in patients with type 2 diabetes (T2D) instructed to maintain their non-insulin antidiabetic medication and physical activity. Material and methods: In an open-label RCT, pati...
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With the emergence of machine learning for the classification of sleep and other human behaviors from accelerometer data, the need for correctly annotated data is higher than ever. We present and evaluate a novel method for the manual annotation of in-bed periods in accelerometer data using the open-source software Audacity®, and we compare the met...
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Background Sedentary behaviour, which may have increased among GPs due to increasing use of telemedicine, is associated with many illnesses and increased all-cause mortality. Aim To explore levels of sedentary behaviour among GPs and General Practice Specialty Trainees (GPSTs). Design & setting Sequential, cross-sectional design (initial online s...
Article
Background: ActiGraph is a commonly used, research-grade accelerometer brand, but there is little information regarding intermonitor comparability of newer models. In addition, while sampling rate has been shown to influence accelerometer metrics, its influence on measures of free-living physical activity has not been directly studied. Purpose: To...
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Background Advancements in screen media devices has transformed the way families engage with screen media. Although these modern devices offer many opportunities, e.g. communication and research online, an in-depth understanding of how these devices affect our health, is lacking. Before a definite randomized controlled trial, the SCREENS pilot stud...
Article
Objectives This study examined the link between accelerometer recordings and cardiac pathophysiology measured with right heart cauterization at rest and with exercise in patients with HFrEF. Background Patient-worn accelerometers are increasingly being used in patients with heart failure with reduced ejection fraction (HFrEF) to assess activity an...
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Combining accelerometry from multiple independent activity monitors worn by the same subject have gained widespread interest with the assessment of physical activity behavior. However, a difference in the real time clock accuracy of the activity monitor introduces a substantial temporal misalignment with long duration recordings which is commonly n...
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Purpose: Evidence of shared physical activity (PA) habits within families is inconsistent. The present study aimed at examining intra-family resemblance in PA during different time segments of the week. Method: This cross-sectional study used data from the Danish household-based population study Lolland-Falster Health Study. We assessed time spe...
Preprint
BACKGROUND Effective and sustainable implementation of physical activity (PA) in type 2 diabetes (T2D) health care has in general not been successful. Efficacious and contemporary approaches to support PA adherence and adoption are required. OBJECTIVE The primary objective of this study was to investigate the effectiveness of including an app-base...
Article
Full-text available
The main aim of this study was to assess the criterion validity of the Sedentary Behavior Questionnaire (SBQ) to measure SB in community-dwelling older adults using thigh-measured accelerometry as the criterion method. 801 participants (75.6 ± 6.1 years old, 57.6% females) provided valid thigh-based accelerometer data (activPAL/Axivity) and complet...
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The inter-relationship between physical activity, sedentary behaviour and sleep (collectively defined as physical behaviours) is of interest to researchers from different fields. Each of these physical behaviours has been investigated in epidemiological studies, yet their codependency and interactions need to be further explored and accounted for i...
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Background: Older adults are recommended to sleep 7-8 h/day. Time in bed (TIB) differs from sleep duration and includes also the time of lying in bed without sleeping. Long TIB (≥9 h) are associated with self-reported sedentary behavior, but the association between objectively measured physical activity, sedentary behavior and TIB is unknown. Met...
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Assessing vital signs such as heart rate (HR) by wearable devices in a lifestyle-related environment provides widespread opportunities for public health related research and applications. Commonly, consumer wearable devices assessing HR are based on photoplethysmography (PPG), where HR is determined by absorption and reflection of emitted light by...
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Consumer wearable and smartphone devices provide an accessible means to objectively measure physical activity (PA) through step counts. With the increasing proliferation of this technology, consumers, practitioners and researchers are interested in leveraging these devices as a means to track and facilitate PA behavioural change. However, while the...
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Background Evidence of intra-family resemblance in physical activity (PA) is lacking. The association between parent and child PA appears weak, the influence of age and gender on this association is uncertain, and no studies have investigated the degree of resemblance in family members’ PA behaviours such as walking, sitting/lying, and biking. Thus...
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Background: The objective and accurate assessment of children’s sedentary and physical behavior is important for investigating their relation to health. The purpose of this study is to validate a simple and robust method for the identification of sitting, standing, walking, running and biking performed by preschool children, children and adolescent...
Article
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Aims To investigate the effect of the sodium-glucose co-transporter-2 inhibitor empagliflozin on N-terminal pro-b-type natriuretic peptide (NT-proBNP) in patients with heart failure (HF) and reduced ejection fraction (HFrEF). Methods and Results Empire HF was an investigator-initiated, multi-centre, double-blinded, placebo-controlled, randomised t...
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Background: Childhood represents an important life stage for establishment of physical activity (PA) habits. Parents are assumed to play an important role in influencing children's PA. Earlier reviews have mainly focused on parental modelling, encouragement, and support for PA, rather than the actual PA levels of parents. Therefore, the purpose of...
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Background: During the recent decade presence of digital media, especially handheld devices, in everyday life, has been increasing. Survey data suggests that children and adults spend much of their leisure on screen media, including use of social media and video services. Despite much public debate on possible harmful effects of such behavioral sh...
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Sampling rate (Hz) of ActiGraph accelerometers may affect processing of acceleration to activity counts when using a hip-worn monitor, but research is needed to quantify if sampling rate affects actual acceleration (mg's), when using wrist-worn accelerometers and during non-locomotive activities. Objective: To assess the effect of ActiGraph sampl...
Article
Purpose: Examine the association between physical activity and neuromuscular and physical function in patients with multiple sclerosis when also considering disease severity. Methods: 91 patients with multiple sclerosis were enrolled. Assessments included physical activity by 7-day thigh-worn accelerometry, knee extensor neuromuscular function by...