Participants are also required to restrict herbal extracts, food supplements and polyphenols such as dark chocolate, fruit rich in polyphenols and antioxidants to less than three portions for 24 hrs beforehand. A 24 hour pre test food diary is completed to assist in compliance. Participants are also advised to have a good night's sleep - at least 6−8 h during the night before the study day - and should not be more stressed than usual. These aspects are confirmed before participants are allowed to commence their sessions.