Background: Activity trackers can potentially stimulate users to increase their physical activity behavior. The aim of this study was to examine the reliability and validity of ten consumer activity trackers for measuring step count in both laboratory and free-living conditions.Method: Healthy adult volunteers (n = 33) walked twice on a treadmill (4.8 km/h) for 30 min while wearing ten different activity trackers (i.e. Lumoback, Fitbit Flex, Jawbone Up, Nike+ Fuelband SE, Misfit Shine, Withings Pulse, Fitbit Zip, Omron HJ-203, Yamax Digiwalker SW-200 and Moves mobile application). In free-living conditions, 56 volunteers wore the same activity trackers for one working day. Test-retest reliability was analyzed with the Intraclass Correlation Coefficient (ICC).Validity was evaluated by comparing each tracker with the gold standard (Optogait system for laboratory and ActivPAL for free-living conditions), using paired samples t-tests, mean absolute percentage errors, correlations and Bland-Altman plots.Results: Test-retest analysis revealed high reliability for most trackers except for the Omron (ICC .14), Moves app (ICC .37) and Nike+ Fuelband (ICC .53). The mean absolute percentage errors of the trackers in laboratory and free-living conditions respectively, were: Lumoback (−0.2, −0.4), Fibit Flex (−5.7, 3.7), Jawbone Up (−1.0, 1.4), Nike+ Fuelband (−18, −24), Misfit Shine (0.2, 1.1), Withings Pulse (−0.5, −7.9), Fitbit Zip (−0.3, 1.2), Omron (2.5, −0.4), Digiwalker (−1.2, −5.9), and Moves app (9.6, −37.6). Bland-Altman plots demonstrated that the limits of agreement varied from 46 steps (Fitbit Zip) to 2422 steps (Nike+ Fuelband) in the laboratory condition, and 866 steps (Fitbit Zip) to 5150 steps (Moves app) in the free-living condition.Conclusion: The reliability and validity of most trackers for measuring step count is good. The Fitbit Zip is the most valid whereas the reliability and validity of the Nike+ Fuelband is low.
Activity trackers like Fitbit are used for self-tracking of physical activity by an increasing number of individuals. Comparing physical activity scores with peers can contribute to the desired behavioural change. However, for meaningful social comparison a high inter-device reliability is paramount. This study aimed to determine the inter-device reliability of Fitbit activity trackers in measuring steps. Ten activity trackers (Fitbit Ultra) were worn by a single person (male,46 years) during eight consecutive days. Inter-device reliability was assessed on three different levels of aggregation (minutes, hours, days) with various methods, including intra-class correlation coefficient (ICC), Bland-Altman plots, limits of agreement (LOA) and Mixed Model Analysis. Results showed that the inter-device reliability of the Fitbit in measuring steps is good at all levels of aggregation (minutes, hours, days), but especially when steps were measuredper day. This implies that individuals can reliably compare their daily physical activity scores with peers.
De technische en economische levensduur van auto’s verschilt. Een goed onderhouden auto met dieselmotor uit het bouwjaar 2000 kan technisch perfect functioneren. De economische levensduur van diezelfde auto is echter beperkt bij introductie van strenge milieuzones. Bij de introductie en verplichtstelling van geavanceerde rijtaakondersteunende systemen (ADAS) zien we iets soortgelijks. Hoewel de auto technisch gezien goed functioneert kunnen verouderde software, algorithmes en sensoren leiden tot een beperkte levensduur van de gehele auto. Voorbeelden: - Jeep gehackt: verouderde veiligheidsprotocollen in de software en hardware beperkten de economische levensduur. - Actieve Cruise Control: sensoren/radars van verouderde systemen leiden tot beperkte functionaliteit en gebruikersacceptatie. - Tesla: bij bestaande auto’s worden verouderde sensoren uitgeschakeld waardoor functies uitvallen. In 2019 heeft de EU een verplichting opgelegd aan automobielfabrikanten om 20 nieuwe ADAS in te bouwen in nieuw te ontwikkelen auto’s, ongeacht prijsklasse. De mate waarin deze ADAS de economische levensduur van de auto beperkt is echter nog onvoldoende onderzocht. In deze KIEM wordt dit onderzocht en wordt tevens de parallel getrokken met de mobiele telefonie; beide maken gebruik van moderne sensoren en software. We vergelijken ontwerpeisen van telefoons (levensduur van gemiddeld 2,5 jaar) met de eisen aan moderne ADAS met dezelfde sensoren (levensduur tot 20 jaar). De centrale vraag luidt daarom: Wat is de mogelijke impact van veroudering van ADAS op de economische levensduur van voertuigen en welke lessen kunnen we leren uit de onderliggende ontwerpprincipes van ADAS en Smartphones? De vraag wordt beantwoord door (i) literatuuronderzoek naar de veroudering van ADAS (ii) Interviews met ontwerpers van ADAS, leveranciers van retro-fit systemen en ontwerpers van mobiele telefoons en (iii) vergelijkend rij-onderzoek naar het functioneren van ADAS in auto’s van verschillende leeftijd en prijsklassen.
met Vrije Universiteit Brussel, Faculteit Lichamelijke opvoeding en Kinesitherapie, in kader van Movement and Rehabilitation Fellowship aan de VUB van lector Harriet Jager-Wittenaar.
The production, use, disposal and recovery of packaging not only generates massive volumes of waste, it also consumes raw materials, water and energy (Fitzpatrick et al. 2012). Simultaneously, consumers have shown an increasing interest in products incorporating sustainable and social attributes (Kletzan et al., 2006). As a result, environmentally friendly packaging, also called ecofriendly or sustainable packaging, has become mainstream. In this context, packaging is more than just ensuring the product's protection and easing transportation, it is also a communicative tool (Palmer, 2000) and it becomes associated with multiple drivers of the purchasing process. Consequently, companies face pressure to innovate responding to consumer demands, and focusing on sustainable solutions that reduce harmful materials and favour green alternatives for both, the product and the packaging. Although the above has triggered research on consumer choice for sustainable products and alternatives on sustainable packaging, the relation between sustainable packaging and consumer behaviour remains underexplored. This research unpacks this relationship, i.e., empirically verifies which dimensions (recyclability, biodegradability, reusability) of sustainable packaging are perceived and valued by consumers. Put differently, this research investigates consumer behaviour towards the functions of sustainable packaging in terms of product protection, convenience, reliability of information and promotion, and scrutinises the perceived credibility of the associated ethical responsibility claims. It aims to identify those packaging materials and/or sustainability characteristics perceived as more sustainable by consumers as well as the factors influencing actual consumer choice towards sustainable packaged products. We aim to gain more insights in the perceptual frame that different types of consumers apply when exposed to sustainable packaging. To this end, we will make use of revealed preference methods to measure consumer valuations of sustainable packaged products. This game-theoretic approach should provide a more complete depiction of consumers' perceptions and preferences.
