The power calculation is based on change in Whiteley-7 scores (scale 0-100). An uncertainty of the change in Whiteley-7 scores of 25 is estimated from a pilot study and other randomised controlled trials [11,15,61]. A sample size of 70 was estimated to provide 84.9% power, at the 5% significance level, to find a difference in mean reductions in Whiteley-7 scores from baseline to 6 month follow-up of the size 20 and allowing for a drop-out rate of 20% in both groups.