Randomization was performed on a cluster level to
minimize contamination between the participants; for details
see Andersen et al. [24]. In short, the clusters were naturally
occurring groups of employees working together on a daily
basis, being located at the same floor, same office or the like.
To ensure the comparability of the training groups and the
reference group, the geographical sites were categorized into
13 strata [24].Adjustments were made in respect to the cluster
allocation due to 26 participants being relocated to other
work sites between the time of randomization and the startup
of the different interventions (approx. 3 weeks) in order
to have these participants follow the intervention for the
cluster of their new colleagues.