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First published online December 14, 2007
Journal of Experimental Biology 211, 150-162 (2008)
Published by The Company of Biologists 2008
doi: 10.1242/jeb.010678

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Locomotor function of forelimb protractor and retractor muscles of dogs: evidence of strut-like behavior at the shoulder

David R. Carrier^1,*, Stephen M. Deban² and Timna Fischbein¹

¹ Department of Biology, 201 South Biology Building, University of Utah, Salt Lake City, UT 84112, USA
² Department of Biology, 4202 East Fowler Avenue, SCA 110, University of South Florida, Tampa, FL 33620, USA

View larger version (31K): [in this window] [in a new window]   Fig. 1. Illustrations of the extrinsic appendicular muscles of the canid pectoral girdle, showing the location of the electrode placements used in this study. (A) Lateral view of the m. trapezius pars thoracica (1), m. trapezius pars cervicalis (2), m. omotransversarius (3), m. cleidobrachialis (4), m. pectoralis profundus (5) and m. latissimus dorsi (6, 7). (B) Ventral view of the m. cleidobrachialis (4), m. pectoralis profundus (5) and m. pectoralis superficialis descendens (8).

View larger version (44K): [in this window] [in a new window]   Fig. 2. Mean normalized electromyograms (EMGs) from six dogs when they trotted with 12% of body mass carried in a backpack located over their pectoral girdle (i.e. anterior-trunk loading manipulation). For each muscle, the black line represents the average EMG when the dogs trotted on the level without added mass (control) and the gray line represents the average EMG when the dogs carried the added mass. For each dog, the trotting speed was the same during the control and added mass trials. The error bars are the standard error of the mean for each sampling bin.

View larger version (42K): [in this window] [in a new window]   Fig. 3. Mean normalized EMGs from six dogs when they trotted uphill on an incline of 14° to the horizontal (i.e. fore/aft force manipulation). For each muscle, the black line represents the average EMG when the dogs trotted on the level (control) and the gray line represents the average EMG when the dogs trotted on the incline. For each dog, the trotting speed was the same during the control and incline trials. The error bars are the standard error of the mean for each sampling bin.

View larger version (47K): [in this window] [in a new window]   Fig. 4. Mean normalized EMGs from six dogs when they trotted downhill on an incline of 14° to the horizontal (i.e. fore/aft force manipulation). For each muscle, the black line represents the average EMG when the dogs trotted on the level (control) and the gray line represents the average EMG when the dogs trotted on the incline. For each dog, the trotting speed was the same during the control and incline trials. The error bars are the standard error of the mean for each sampling bin.

View larger version (45K): [in this window] [in a new window]   Fig. 5. Mean normalized EMGs from six dogs when they trotted with 2% of body mass added to each wrist (i.e. distal limb mass manipulation). For each muscle, the black line represents the average EMG when the dogs trotted on the level (control) and the gray line represents the average EMG when the dogs trotted with the added mass attached to the distal forelimbs. For each dog, the trotting speed was the same during the control and added mass trials. The error bars are the standard error of the mean for each sampling bin.