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First published online October 18, 2006
Journal of Experimental Biology 209, 4389-4397 (2006)
Published by The Company of Biologists 2006
doi: 10.1242/jeb.02518

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Effect of speed on stride parameters in racehorses at gallop in field conditions

T. H. Witte^1,*, C. V. Hirst^1, and A. M. Wilson^1,2,

¹ Structure and Motion Laboratory, The Royal Veterinary College, Hawkshead Lane, Hatfield, Hertfordshire, AL9 7TA, UK
² Structure and Motion Laboratory, University College London, Royal National Orthopaedic Hospital, Brockley Hill, Stanmore, Middlesex HA7 4LP, UK

View larger version (13K): [in a new window]   Fig. 1. The sequence of stance phases drawn to scale for all four limbs of a galloping horse. One stride is shown at (A) 9 m s-1 and (B) 17 m s-1, drawn using the mean data from the six horses where a full data set existed for all four legs.

View larger version (64K): [in a new window]   Fig. 2. Hoof-mounted accelerometer and telemetry unit, antenna and battery mounted in an elasticated exercise bandage on the lateral aspect of the third metacarpal bone.

View larger version (10K): [in a new window]   Fig. 3. Stance duration as a function of speed. Values are means ± s.d. of individual horse mean data for lead and non-lead limbs (indicated by different symbols) and fore- and hindlimbs (red and blue, respectively) for the six horses for which complete data sets were available. Quadratic lines of best fit (P<0.001) are shown. These were estimated for the population using mean data. Coefficients: forelimb b0=270.33, b1=-19.1 and b2=0.5047; hindlimb b0=243.56, b1=-17.426 and b2=0.4591.

View larger version (12K): [in a new window]   Fig. 4. Protraction duration as a function of speed. Values are means ± s.d. of individual horse mean data for lead and non-lead limbs (indicated by different symbols) and fore- and hindlimbs (red and blue, respectively) for the six horses for which complete data sets were available. Quadratic lines of best fit (P<0.001) are shown. These were determined for the population for fore- and hindlimbs separately using mean data. Coefficients: forelimb b0=363.92, b1=3.9561 and b2=-0.3026; hindlimb b0=288.88, b1=13.141 and b2=-0.5954.

View larger version (6K): [in a new window]   Fig. 5. Stride frequency as a function of speed. Values are means ± s.d. of individual horse mean data for all nine horses studied. The quadratic line of best fit (P<0.001) is shown, which was estimated using mean data. Coefficients: b0=1.7052, b1=0.0305 and b2=0.0004.

View larger version (9K): [in a new window]   Fig. 6. Duty factor as a function of speed (N=9). Values are means ± s.d. of individual horse mean data for fore- and hindlimbs (red and blue, respectively). Quadratic lines of best fit (P<0.001) are shown for the population. These were calculated for fore- and hindlimbs separately, using mean data. Coefficients: forelimb b0=0.4334, b1=-0.0274 and b2=0.0008; hindlimb b0=0.5071, b1=-0.0339 and b2=0.001.

View larger version (9K): [in a new window]   Fig. 7. Predicted peak vertical force, normalised to total mass of subject (including mass of horse, riding tack and rider) as a function of speed (N=9). Values are means ± s.d. of individual horse mean data for fore- and hindlimbs (red and blue, respectively). Quadratic lines of best fit (P<0.001) are shown for the population. These were calculated for fore- and hindlimbs separately using mean data. Coefficients: forelimb b0=-2.778, b1=2.1376 and b2=-0.0535; hindlimb b0=1.3249, b1=1.5444 and b2=-0.041.

View larger version (10K): [in a new window]   Fig. 8. Stance length as a function of speed (N=9). Values are means ± s.d. of individual horse mean data for fore- and hindlimbs (red and blue, respectively). Quadratic lines of best fit (P<0.000) are shown for the population. These were calculated for fore- and hindlimbs separately, using mean data. Coefficients: forelimb b0=0.9385, b1=0.0172 and b2=0.0004; hindlimb b0=1.0002, b1=0.027 and b2=0.0003.

View larger version (16K): [in a new window]   Fig. 9. (A) Total contact duration, flight duration and limb overlap duration as a function of speed. Values are means ± s.d. of individual horse mean data. Quadratic lines of best fit (P<0.000) are shown for the population. These were calculated using mean data. Coefficients: contact: b0=633.89, b1=-41.187 and b2=1.302; flight: b0=-55.25, b1=34.405 and b2=-1.4337; overlap: b0=395.43, b1=-26.42 and b2=0.2757. (B) Contact, flight and limb overlap as a percentage of total stride duration as a function of speed. Quadratic lines of best fit (P<0.000) are shown for the population. These were estimated using mean data. Coefficients: contact: b0=117.12, b1=-7.5431 and b2=0.2901; flight: b0=-17.116, b1=7.5431 and b2=-0.2901; overlap: b0=65.381, b1=-3.1195 and b2=-0.0215.