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First published online February 29, 2008
Journal of Experimental Biology 211, 945-956 (2008)
Published by The Company of Biologists 2008
doi: 10.1242/jeb.006692

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High-speed gallop locomotion in the Thoroughbred racehorse. II. The effect of incline on centre of mass movement and mechanical energy fluctuation

K. J. Parsons^*, T. Pfau, M. Ferrari and A. M. Wilson

Structure and Motion Laboratory, The Royal Veterinary College, University of London, North Mymms, Hatfield, Hertfordshire AL9 7TA, UK

View larger version (72K): [in this window] [in a new window]   Fig. 1. Examples of experimental records at 10 m s–1 (A,C,E) and 12 m s–1 (B,D,F) for horse 1. Red represents incline data and blue represents level data. Craniocaudal acceleration (A,B), craniocaudal velocity (C,D) and craniocaudal displacement (E,F) of the trunk for strides recorded at each speed are presented and the figure demonstrates the integration procedure. Acceleration data is integrated to provide velocity data and displacement data for each stride. LF=lead fore; NLF=non-lead fore; LH=non-lead hind; NLH=non-lead hind.

View larger version (50K): [in this window] [in a new window]   Fig. 2. Displacement range (A), minimum and maximum velocity (B) and minimum and maximum acceleration (C) from 8 m s–1 to 12 m s–1 for dorsoventral (left) and craniocaudal (right) movement on the level (blue triangles) and incline (red circles) for the six horses. For each speed category mean ± 1 s.e.m. (displacement) or median and interquartile range (velocity and acceleration) are calculated from all strides. A linear function was fitted to the data and is shown as a red solid line (incline data) and a blue broken line (level data).

View larger version (52K): [in this window] [in a new window]   Fig. 3. Displacement range (A), minimum and maximum velocity (B) and minimum and maximum acceleration (C) from 8 m s–1 to 12 m s–1 for pitch (left column) and heading (right column) on the level (blue triangles) and incline (red circles) for the six horses. For each speed category mean ±1 s.e.m. (displacement) or median and interquartile range (velocity and acceleration) are calculated from all strides. A linear function was fitted to the data and is shown as a red solid line (incline data) and a blue broken line (level data).

View larger version (23K): [in this window] [in a new window]   Fig. 4. Stride data (mean ± s.e.m. as shading, N=6) of the sum of the vertical kinetic (KEdv) and linear potential energy (PE) during level (blue broken line) and incline (red solid line) galloping at a mean speed of (A) 10 m s–1 (n level=56 and n incline=60) and (B) 12 m s–1 (n level=60 and n incline=28). Presented data are averages of all strides from all horses within the speed range. Aerial phases (vertical grey bar) were estimated to be during the time when the curve was approximately constant. Stance phases of individual feet are presented for illustrative purposes as black bars in the lower panels. LF=lead fore; NLF=non-lead fore; LH=non-lead hind; NLH=non-lead hind.

View larger version (23K): [in this window] [in a new window]   Fig. 5. Stride data (mean ± s.e.m. as shading, N=6) of changes in craniocaudal kinetic (KEcc) energy during level (blue broken line) and incline (red solid line) galloping at a mean speed of (A) 10 m s–1 (n level=56 and n incline=60) and (B) 12 m s–1 (n level=60 and n incline=28). Presented data are averages of all strides from all horses within the speed range. For illustrative purposes the minimum craniocaudal kinetic energy has been subtracted from external mechanical energy. Estimated aerial phase (vertical grey bar); stance phases of individual feet are presented for illustrative purposes as black bars in the lower panels (LF=lead fore; NLF=non-lead fore; LH=non-lead hind; NLH=non-lead hind).

View larger version (18K): [in this window] [in a new window]   Fig. 6. Stride data (mean ± s.e.m. as shading) of changes in total potential energy (PE) during level (blue broken line) and incline (red solid line) galloping at a mean speed of (A) 10 m s–1 (n level=56 and n incline=60) and (B) 12 m s–1 (n level=60 and n incline=28). Aerial phase (vertical grey bar); stance phases of individual feet are presented for illustrative purposes as black bars in the lower panels (LF=lead fore; NLF=non-lead fore; LH=non-lead hind; NLH=non-lead hind). Note s.e.m. shading is not clearly visible as the standard errors are small.

View larger version (23K): [in this window] [in a new window]   Fig. 7. Stride data (mean ± s.e.m. as shading) of changes in total linear mechanical energy MElin(CoM) during level (blue broken line) and incline (red solid line) galloping at a mean speed of (A) 10 m s–1 (n level=56 and n incline=60) and (B) 12 m s–1 (n level=60 and n incline=28). For illustrative purposes the minimum total energy has been subtracted from external mechanical energy. Estimated aerial phase (vertical grey bar); stance phases of individual feet are presented for illustrative purposes as black bars in the lower panels (LF=lead fore; NLF=non-lead fore; LH=non-lead hind; NLH=non-lead hind).

View larger version (30K): [in this window] [in a new window]   Fig. 8. Linear mechanical work Wlin(CoM) (A), Linear mechanical cost MCTlin(CoM) (B), rotational mechanical work Wrot (C), rotational mechanical cost MCTrot (D), linear + rotational mechanical work Wlin(CoM)+rot (E) and linear + rotational mechanical cost MCTlin(CoM)+rot (F) for six galloping horses on the level (blue triangles) and incline (red circles) at a speed range of 8 m s–1 to 12 m s–1. For each speed category values are mean ±1 s.e.m. (N=6) for individual horses. A linear function was fitted to the data and is shown as a red solid line (incline data) and a blue broken line (level data).

View larger version (12K): [in this window] [in a new window]   Fig. 9. Negative linear work () (percentage of total linear work) as a function of gradient. A linear regression line (red) has been fitted to the data.