The invention relates to optimising the performance of a user at a sport or exercise activity by providing provide different separation distances between the user's upper and lower jaw and enable a user to select the apparatus which gives the optimal performance. An oral apparatus 12 includes at least one bite portion 14 configured to receive a bite pad 16, wherein a plurality of bite pads 16 with different depths are provided. The bite pad 16 may be situated between the teeth of the upper jaw and lower jaw. The depth of the bite pad 16 may be between 1 and 12 mm. The apparatus may comprise a mouthguard such that the separation distance (B, fig 11) is the distance between the surface of the pad (30, fig 11) and the base of the mouthguard (36, fig 11). A kit may be provided comprising two apparatuses each having a bite pad of different depths.
