Marco Giurgiu, Simon Kolb, Carina Nigg, Alexander Burchartz, Irina Timm, Marlissa Becker, Ellen Rulf, Ann-Kathrin Doster, Elena Koch, Johannes B J Bussmann, ClaudioNigg, Ulrich W Ebner-Priemer, Alexander Woll. Assessment of 24-hour physical behaviour in children and adolescents via wearables: a systematic review of free-living validation studies. 

The full article can be found here


Tell us more about yourself and the author team

My name is Dr Marco Giurgiu. I am a sports scientist at the Karlsruhe Institut of Technology (KIT), with a research focus on the 24-hour assessment of physical behaviour (i.e., sleep, sedentary behaviour and physical activity) and its antecedents and consequences on health outcomes.


Our group, headed by Prof. Ulrich Ebner-Priemer, is characterized by its methodological focus on Ecological Momentary Assessment (EMA), aiming to learn more about momentary mechanisms in daily life (e.g., the association between physical behaviour and mental health). One important part is integrating device-based assessments of 24-hour physical behaviour in our mHealth approach while selecting commercial or research wearables that provide valid measurements. Our project was supported by internal KIT groups (headed by Prof. Alexander Woll) as well as by external groups from the Erasmus MC in Rotterdam (Assoc. Prof. Hans Bussmann) and the University of Bern (Prof. Claudio Nigg).


What is the story behind your study?

Continuous assessment of 24-hour physical behaviour is an essential part of our methodological mHealth approach. Especially the integrative 24-hour perspective is a common aim for different research disciplines (eg, sport and exercise, public health, psychology) to measure all aspects simultaneously. Due to the COVID-19 restriction, we were partly unable to collect data. This situation has led to some free resources, and we started a comprehensive literature search (including five electronic databases) about the validity of wearables. As our main purpose, we would like to raise researchers’ and consumers’ attention to the quality of published validation protocols while aiming to identify and compare specific consistencies/inconsistencies between validation protocols. To evaluate the quality of the studies, we followed core principles, recommendations, and expert statements with published quality criteria (eg, study duration, number of included participants, selection of criterion measure, and data synchronization). As a secondary aim, we would like to provide a comprehensive and historical overview of which wearable has been validated for which purpose and whether they show promise or not for being used in further studies.


In your own words, what did you find?

Across all 76 included studies, we identified 51 different commercial and research-graded Wearables. Some of them are not available anymore. However, from a historical perspective, it was interesting to see that most of the included studies focused on intensity outcomes such as steps or energy expenditure, whereas quite less studies validated outcomes including sleep (e.g., total sleep time) or postural outcomes (e.g., sitting, lying, standing). Therefore, we identified no wearable that validated all three aspects of the 24-hour physical behaviour construct in children/adolescents during free-living conditions. Moreover, our results revealed that thirty of the 51 included wearables were validated only once. Overall, most studies do not meet currently published core principles regarding study quality. In particular, no reviewed study that validated a biological state or posture/activity type outcome was classified as ‘low risk’.


What was the main challenge you faced in your study?

The main challenge was processing a large number of validation studies. We found (including all age groups) over 13.000 articles. Still, after the screening process, there were 194 full texts to screen and discuss for eligibility. Given the high heterogeneity across different wearables and study protocols, we needed several discussion rounds to harmonize them into one article. Since it was a non-founded project, the realization was only possible through organized and motivated teamwork.


If there is one take-home message from your study, what would that be?

The measurement of physical behaviour has changed significantly in recent years due to technological possibilities. The use of device-based data is can be seen as the gold standard. The small portable devices can record various parameters with a high frequency over a longer period. Also, the relevance of capturing different facets of physical behaviour simultaneously is becoming increasingly important from a health perspective. Accordingly, future studies will likely be interested in capturing the full 24-hour cycle of physical behaviour. Our review can be seen as a summary of how existing devices have been accurately validated to measure each construct. An important finding from the results shows that many wearables have been validated in only one study so far with partly low study quality. This aspect should be considered when selecting wearables in health studies.

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