Reducing sedentary behaviour and increasing physical activity among 10-year-old children: overview and process evaluation of the `Switch-Play' intervention - JO SALMON, KYLIE BALL, DAVID CRAWFORD, MICHAEL BOOTH AMANDA TELFORD, CLARE HUME, DAMIEN JOLLEY and ANTHONY WORSLEY (Health Promotion International, Vol. 20 No. 1 2005, 2005)