. Bulletin of the Museum of Comparative Zoology at Harvard College. Zoology. 290 Bulletin Museum of Comparative Zoology, Vol. 156, No. 1 400 S 200 Hind limb Fore limb. Ankle Shoulder Elbow Wrist Figure 3. Stress (force/cross-sectional area [/4J) developed in limb muscles of dogs and turkeys. Stresses are presented for the extensors at the joint indicated, with the exception of the wrist values, which represent flexor stresses. Values are means and standard deviations. m/s in the turkeys. Despite the large dif- ference in absolute speed, the average GRF developed during stance was similar in th
. Bulletin of the Museum of Comparative Zoology at Harvard College. Zoology. 290 Bulletin Museum of Comparative Zoology, Vol. 156, No. 1 400 S 200 Hind limb Fore limb. Ankle Shoulder Elbow Wrist Figure 3. Stress (force/cross-sectional area [/4J) developed in limb muscles of dogs and turkeys. Stresses are presented for the extensors at the joint indicated, with the exception of the wrist values, which represent flexor stresses. Values are means and standard deviations. m/s in the turkeys. Despite the large dif- ference in absolute speed, the average GRF developed during stance was similar in the two species, ± X body weight in the bird and ± X body weight in the dog. This suggests that the animals were operating at similar duty fac- tors, one of the criteria that has been used to determine equivalent speeds in running mammals (Biewener, 1983). The turkeys were able to run at faster speeds with duty factors similar to those of dogs because they have longer legs. The small difference in average GRF at the speeds used in this study indicates that some of the difference in estimated muscle stress may be due to a 15—20% difference in the magnitude of GRF between the dogs and turkeys. DISCUSSION Patterns of Force Development and Limb Design The results of the present study dein- onstrate that the timing of muscle force Table 1. Muscle force per unit peak ground reaction force (GRF), total GRF and muscle FORCE IN MULTIPLES OF BODY WEIGHT (BW), MUSCLE CROSS-SECTIONAL AREA (Acs), AND MUSCLE STRESS FOR DOG AND TURKEY HIND LIMBS. Muscle force per GRF Peak GRF per BW Muscle force per BW A,., (CU1-) Muscle stress (kN/m-) Hip Turkey ± ± ± ± 180 ± 28 Dog ± ± ± ± 59 ± 28 Ratio * * * Knee Turkey ± ± ± ± 248 ± 65 Dog ± ± ± ± 71 ± 20 Ratio * * * * Ankle Turkey ± ± 16.
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