Fig. 1. Kinematic landmarks and calculated angles describing the motion of the hind limb. (A) Eight points marked with reflective paint. The abbreviations are as follows: E, eye, positioned between the eyes in the dorsal aspect; the center of the eye was digitized in the lateral aspect; PC, pectoral, positioned midway between the shoulder joints; M, a point midway between pectoral and pelvis points; PL, pelvis, midpoint between palpated positions of acetabula; H, hip acetabulum; K, knee; A, ankle; MP, foot, positioned over the metatarsal–phalangeal joint of the longest (fourth) digit. Even though all of these points were digitized, only data from the hind limb points are presented in this paper. (B) Three-dimensional angles are labeled as follows: _hip, hip angle formed by two planes containing lines PL–H and H–K; _knee, knee angle formed by two planes containing lines H–K and K–A; _ankle, ankle angle formed by two planes containing lines K–A and A–MP; _fw, angle formed between the foot (line MP–A) and the water surface; _tw, angle formed by the tibia (line K–A) to the water surface; _bw, angle formed between the torso (line PC–PL) and the water surface. Pelvic rotation was measured as a two-dimensional angle, _pr, formed by two planes containing lines H–PL and E–PL. All joint angles greater than 90° indicate joint extension, and all joint angles less than 90° indicate joint flexion. Negative values of _fw indicate a toe-up foot position, whereas positive values indicate a toe-down foot position. Angles were measured in the counterclockwise direction.

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