It is well documented that spending large amounts of time each day in sedentary behaviour is associated with increased risks of a variety of health impairments. The time engaged in sedentary behaviours is generally high in Europe, and has increased over recent decades during both work and leisure. This has resulted in considerable research and societal attention over the last decade.

Sedentary behaviour in the workplace varies between occupations. It is high among office workers, and is likely to be high for job groups with lower education with constrained sittingbased working tasks like long-haul drivers and surveillance work in manufacturing. However, the question of whether spending large amounts of time in occupational sedentary behaviour is a causal risk factor for health impairments remains to be settled.

An important reason for this could be the poor validity and reliability of many of the methods used to assess sedentary behaviour such as self-report and interviews. Another reason might be that the sedentary behaviour is often not measured in accordance with its proposed definition "

any waking behaviour characterised by a low energy expenditure (≤1.5 METs) while in a sitting or reclining posture". Measurements of sedentary behaviour should therefore capture its two main components, namely posture and energy expenditure.

Observational methods are also used to assess sedentary behaviour, but they are costly, time-consuming, and may lead to observational-bias. Measurements using wearable devices ("wearables") are thus recommended due to their objective nature, and their ability to be relatively low cost and to have little impact on the daily life of the participant.

Numerous suitable small wearables, with long battery life and high data storage capacity, have become commercially available in recent years. However, none of the commercially available wearables can independently assess occupational sedentary behaviour in accordance with its definition (i.e. a sitting or lying posture with low energy expenditure). Therefore, deciding on how to assess sedentary behaviour is currently not easy.

The wide variety of devices with the potential to assess sedentary behaviour is likely to leave practitioners and researchers wondering - "How can I choose the measurement system bestsuited to my aim, preferences, funding, and skills?" However, no practically useful guidance for researchers and practitioners exists on how to assess occupational sedentary behaviour.

This report provides an overview of relevant technical systems and their general capabilities and gives examples of their appropriate use when assessing occupational sedentary behaviour. The report emphasises factors such as the target population, the need for accuracy, data accessibility, wearing comfort, expert knowledge for analyses, assessment duration, the number of participants needed, budget available, and the need for information on time patterns of sedentary and non-sedentary behaviour, including moderate and vigorous physical activity. Importantly, the need for assessing body posture, energy expenditure, or both, should be critically evaluated based on the work tasks undertaken by the target population and the aim of the project.

The report highlights needs for developing of cheap, feasible wearables combining precise posture and energy assessments for a valid and reliable assessment of sedentary behaviour at work, which fulfils the current needs of both researchers and practitioners alike.