Volunteers were given detailed written and verbal information about all of the study's inclusion criteria and experimental procedures. If the volunteers decided that they would like to participate in the study, they were asked to come to the research centre on another morning, where they completed a detailed screening questionnaire that assessed their current health status and medical history. In order to participate in the study, the volunteers had to meet the inclusion criteria. All suitable volunteers that were invited to participate in the study were required to sign a detailed subject information sheet and a consent form before commencing any experimental procedures.