Order effects can be easily accounted for by means of counterbalancing experimental conditions using well-designed schemes. Finally, it is suggested to include baseline characteristics of sleep systems used at home as well as information on preferred sleep postures. The former has shown to be a predicting factor of sleep on a newly introduced sleep system [126]; subjects sleeping on an old mattress are more likely to benefit from a new mattress. Information on preferred sleep postures should be incorporated in the comparison of results because it is known that supine sleepers have different mattress requirements than lateral or prone sleepers [71].