Fig. 5. Mean kinematic profiles of the forelimb in chipmunks (triangles), red squirrels (squares) and flying squirrels (circles). Protraction brings the forelimbs closer to the head and is indicated by an increasing angle. A protraction angle of 90° indicates that the forelimbs have been brought forward to the level of the occiput. All three species exhibit similar values for forelimb protraction, bringing the forelimbs from approximately 45° at the onset of hand-off to approximately 65° at toe-off. Forelimb abduction moves the forelimbs away from the midline of the body and is indicated by an increasing angle. Forelimb adduction moves the forelimbs closer to the midline of the body and is indicated by a decreasing angle. An abduction angle of 90° indicates that the forelimbs are fully abducted to the level of the occiput, while an angle of 0° indicates that the forelimbs are fully adducted to the midline. Flying squirrels abduct to approximately 72° before losing contact with the platform. The other two species show a decrease in the abduction angle, indicating that they are adducting the forelimbs during the propulsive phase. Values are means ± S.E.M., N=5 trials per species.

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