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First published online January 31, 2006
Journal of Experimental Biology 209, 633-644 (2006)
Published by The Company of Biologists 2006
doi: 10.1242/jeb.02061

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Effects of limb mass distribution on mechanical power outputs during quadrupedalism

David A. Raichlen

Department of Anthropology, Harvard University, 11 Divinity Avenue, Cambridge, MA 02138, USA

View larger version (26K): [in a new window]   Fig. 1. Between-group comparisons of mass-specific power outputs in the ontogenetic sample of infant baboons. In all panels, Group 1 infants (filled circles) have significantly heavier distal limb segments than Group 2 infants (open circles). (A) Mass-specific internal power (int) compared over the range of raw velocities. (B) Mass-specific int compared over the range of dimensionless velocities. (C) Manipulation of int calculations for Group 2 (see text for further explanation). (D) Mass-specific external power (ext) compared over the range of raw velocities. (E) Mass-specific ext compared over the range of dimensionless velocities. (F) Mass-specific total power (tot) compared over the range of raw velocities. (G) Mass-specific tot compared over the range of dimensionless velocities. Statistical between-group differences using ANCOVAs were found for B, D and F. These results can be found in Table 2.

View larger version (25K): [in a new window]   Fig. 2. Residuals analysis of kinematics and mechanical power. (A) Residuals of internal power vs dimensionless velocity regressed on residuals of dimensionless stride frequency vs dimensionless velocity (r=0.48; P<0.001). Group 1 is represented by filled circles and Group 2 is represented by open circles. Note that Group 1 clusters together in the negative residuals quadrant. (B) Residuals of external power vs dimensionless velocity regressed on residuals of dimensionless stride length vs dimensionless velocity (r=0.21; P<0.001). Group 1 is represented by filled circles and Group 2 is represented by open circles. Note that Group 1 clusters in the positive residuals quadrant.

View larger version (32K): [in a new window]   Fig. 3. Kinematics in infant baboons compared with dogs and horses. In all panels, the least-squares regression (LSR) line for infant baboons in black, with 95% confidence limits for the regression line in gray, is compared with the LSR line for horses (dot-dashed line) and for dogs (dashed line). (A) Dimensionless stride frequencies over the range of dimensionless velocities for the combined infant baboon sample compared with dogs and horses. LSR line for infant baboons (95% C.I. in parentheses): slope=0.64 (0.02); intercept=-0.35 (0.01); r=0.96; P<0.001. (B) Dimensionless stride lengths for the infant baboons compared with dogs and horses. LSR line for infant baboons: slope=0.35 (0.02); intercept=0.35 (0.01); r=0.86; P<0.001. (C) Internal power in infant baboons compared with dogs and horses. LSR line for infant baboons: slope=1.82 (0.05); intercept=-0.19 (0.02); r=0.96; P<0.001. (D) External power in infant baboons compared with dogs and horses. LSR line for infant baboons: slope=1.68 (0.06); intercept=0.37 (0.03); r=0.92; P<0.001. (E) Total power in infant baboons compared with dogs and horses. LSR line for infant baboons: slope=1.68 (0.07); intercept=0.42 (0.03); r=0.92; P<0.001.