Data measured during ex vivo tests on the surfaces of porcine discs. A: Data shown are for time during Cycle 1 of indenter translation on disc pair 22 (R = right, L = left). Discs 22R and 22L were oriented with medial aspect over pressure transducer #1. Compressive stresses (MPa) are plotted on vertical axes and color-coded according to the key. B: Instantaneous tractional force and thickness data recorded for disc pair 22. Indenter position (x) and velocity (✱) were the same for all discs. Instantaneous tractional forces (Discs 22, R = ■, L = □) and disc thickness (Discs 22, R = ◆, L = ◇) were recorded during movement.