Fig. 6. Mean kinematic profiles of elbow extension and flexion (true angle in three dimensions) during turtle swimming. (A) Trachemys scripta, (B) Apalone spinifera. The format and method of profile calculation are the same as in Fig. 4. Larger angles indicate greater elbow extension: 180° would indicate a straight elbow joint. The bold vertical line in each plot demarcates recovery phase (R) from thrust phase (T).