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NOTICE: this is the author’s version of a work that was accepted for publication in the Clinical Rehabilitation. Changes resulting from the publishing process, such as copy-editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. A definitive version of this work was published by Sage Publications in the Clinical Rehabilitation, 28(8): 754-761, 2014, this version can be found at http://dx.doi.org/10.1177/0269215514520774 (Please note: access via this link may only be available with a subscription).