First published online January 12, 2004
Journal of Experimental Biology 207, 667-674 (2004)
Published by The Company of Biologists 2004
doi: 10.1242/jeb.00808
Moments and power generated by the horse (Equus caballus) hind limb during jumping
Darren J. Dutto1,*,
Donald F. Hoyt2,
Hilary M. Clayton3,
Edward A. Cogger4 and
Steven J. Wickler4
1 Department of Kinesiology and Health Promotion, California State
Polytechnic University, Pomona, CA 91768, USA
2 Department of Biological Sciences, California State Polytechnic
University, Pomona, CA 91768, USA
3 College of Veterinary Medicine, Michigan State University, East Lansing,
MI 48824, USA
4 Department of Animal and Veterinary Science, California State Polytechnic
University, Pomona, CA 91768, USA
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Fig. 1. The picture shows the reflective marker set-up with four joints of the hind
limb. The locations of the knee and hip joints were mathematically determined
using the geometrical relationships of the limb segments. Digitized
coordinates were used to determine the knee, and the mathematically derived
coordinates of the knee and the digitized coordinates of the tuber coxae were
used to calculate the hip coordinate (see Materials and methods). The location
of the hip (xh, yh) was determined
using the coordinates of the knee (xk,
yk) and tuber coxae (xt,
yt), and the lengths of the pelvis
(lpelvis) and thigh (lthigh) segments.
If two circles are drawn with the tuber coxae and knee joint as origins and
radius equivalent to the length of the appropriate segments, there will be two
places where the circumferences of the circles overlap (or one if the segments
are oriented in a straight line). The rearmost of these two intersections was
taken as the location of the hip joint.
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Fig. 2. Representation of the inertial moment relative to the joint moments for one
jumping trial. The solid symbols are the total joint moment for each
identified joint. The open symbols represent the inertial moments. Notice that
the inertial moments are clustered near zero throughout the trial. MP,
metatarsophalangeal joint.
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Fig. 3. Joint moments (relative to body mass) are presented. (A) Observed moments
at the hip for each of the test animals. Each curve represents the mean of the
trials for that animal, with the number of trials ranging between five and
eight for the different animals. The five curves are very similar across
animals. (B) Moments for the MP (metatarsophalangeal), ankle, knee and hip
joints of the hind limb. Each curve represents the mean of 29 trials (solid
line) ± S.D. (shaded area) across all horses. For both
plots, positive values represent extensor moments and negative values
represent flexor moments for each joint.
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Fig. 4. Mean angular position data for all trials of the hind limb joints are
presented (29 trials included in the mean). Each curve represents a mean
(solid line) ± S.D. (crossbars) for the respective joint.
Decreasing angles represent joint flexion and increasing angles represent
joint extension. MP, metatarsophalangeal joint.
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Fig. 5. Joint power (relative to body mass) for the MP (metatarsophalangeal),
ankle, knee and hip joints of the hind limb during ground contact. Each curve
is the mean of 29 trials (solid line) ± S.D. (shaded area)
of the power. Positive values represent power generation and negative values
represent power absorption.
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Fig. 6. Net power created by the hind limb during the jump. The curve represents
the mean of 29 trials (solid line) ± S.D. (shaded area) of
the summed power from the four joints of the hind limb.
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Fig. 7. During the first 40% of contact (when the total power is primarily
negative), the mean horizontal velocity of the tuber coxae increased and the
mean vertical velocity changed from negative to approximately 0. The resultant
velocity remains essentially constant (the same value at the beginning and end
of the time period) during the first 40% of contact. During the last 60% of
contact, the horizontal velocity remains essentially constant until near the
end, and the vertical velocity substantially increases; thus, the resultant
velocity increases almost continuously over the final 60% of contact. 40% of
contact is indicated by the vertical line. Velocity values represent the mean
across all trials.
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Fig. 8. The horizontal ground reaction force is only negative for the first 25% of
ground contact, which means that the force vector stays anterior to the knee
(the leg) throughout ground contact. Horizontal velocity decreases slightly
during the first 25% of contact, which coincides with the negative (braking)
horizontal force. For comparison, the mean horizontal force during trotting at
3.25 m s-1 (which is a speed very similar to mean speed during the
jump) is shown. The amount of braking that occurs during trotting is greater
(larger area) than during jumping. The braking impulse during trotting is
roughly twice that of jumping (0.06 Ns kg-1 vs 0.03 Ns
kg-1). The curve represents the mean horizontal force for all
trials.
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© The Company of Biologists Ltd 2004
