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REFEREED PAPERS FROM THE IOTH SYMPOSIUM

EFFECTS OF URGING BY THE RIDER ON GALLOP STRIDE CHARACTERISTICS OF QUARTER HORSES

N.R. Deuel, MS,PhD 1 and L.M. Lawrence, MS,PhI~

SUMMARY

The effects of urging by the rider on the limb contact patterns of the gallop stride were documented using high- speed cinematography. The subjects were 4 Quarter Horse fillies, approximately 30 months old, that were raised, housed, fed and trained alike. Both sides of each horse were filmed simultaneously (243 frames/sec) while horses galloped individually along a 1.5-m-wide track, with the same rider and equipment. The experimental urging treatment consisted of the rider'goading the horse with a riding crop on the leading shoulder approximately once per stride, attempting to maintain similar body positions for each trial. Gallop kinematic variables determined by film analysis for 34 strides without rider urging and 28 strides with rider urging included velocity, stride frequency, stride length and limb contact timing variables adjusted for velocity effects. Urging by the rider had no detectable effect on the average velocity of 12.6 m/see, although rider urging increased (P<.05) stride frequency and decreased (P<.05) stride length. Hind limb contact and non- contact durations were unaffected by treatment, but for each forelimb, contact durations decreased (P<.05) and non-contact durations were increased (P<.05) with rider urging. Horses altered the forelimb timing patterns of the gallop stride in response to urging by the rider.

INTRODUCTION

A vast amount of anecdotal and qualitative information is available concerning the effects of horseback riders on the movement patterns of their mounts.4'11 In the 1800s, Capprilli recognized the important biomechanical consequences of the position of the rider's center of mass in relation to that of the horse, 1° and the jockey's weight has long been an important consideration in racetrack handicapping. It has been shown that by carrying a rider on its back, a horse's energy expenditure increases in proportion to the increase in total mass of horse and rider, a Despite millennia of practical investigations,

Authors' addresses: 1Department of Animal and Nutritional Sciences, University of New Hampshire, Durham, New Hampshire 03824 USA; 2Depaltment of Animal Sciences, University of Illinois, Urbana, Illinois 61801 USA. Address correspondence to Dr. Deuel. Acknowledgement: Thanks are extended to Dr. J.L. Groppel of the University of Illinois Depaament of Physical Education for filming equipment and technical assistance.

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there have been relatively few studies that objectively document gait patterns of horses, and virtually none that quantify the biomechanical effects of the rider on the horse? ,e

In order to objectively evaluate gait patterns of individual horses, the magnitude and type of effects of rider actions on equine motion patterns must be known. Riding crops, "bats," "'sticks" and whips of various types have been employed by riders for centuries as a signal to their horses to move more quickly. We included urging by the rider as a treatment in a multi-factored experiment with the intention of encouraging horses to gallop at their individual maximal velocities and to obtain a wide range of galloping velocities for analysis. The specific purpose of this study was to document the effects of urging by the rider on the limb contact patterns of the equine gallop stride.

MATERIALS AND METHODS

The experimental protocol has been detailed in previous reports from this research, 1-a but are briefly summarized here. The subjects were 4 Quarter Horse fillies, approximately 30 months old (mean wt 508 kg), that were raised, housed, fed and trained alike. The same rider, saddle and bridle (total wt 76 kg), were used throughout the 12-week training period and on 3 filming dates. Both sides of each horse were filmed simultaneously by high-speed cameras a (243 framesJsec) aimed perpendicular to the line of motion, while horses galloped individually along a 1.5-m-wide track.

The experimental urging treatment consisted of the rider goading the horse on the leading shoulder with a riding crop approximately once per stride, attempting to maintain similar body positions for each trial. During the trials in which rider urging was absent, the rider carded the crop but did not use it.

One stride was analyzed per run down the track. Tempo- ral measurements were accomplished by frame counts of limb contact phases in projected film images, b Linear distance measurements were completed by digitization ° of projectJ~d film frames with methods that minimized influences of cam-

"Redlake Locam Model 51, Campbell, CA 95008 USA: Eastman Ektachrome 16-ram Video News Film, High Speed 7250, Daylight ASA 250/25 DIN, Eastman Kodak Co., Rochester, NY 14650 USA. nMotion Analyzer, Model M-16: Vanguard Instrument Corp., Melville, NY 11746 USA. CEleetronic Digitizer/Graphics Calculator, Model 1224, resolution .25 rmn, absolute accuracy + .50 mm; Numonics Corp., Lansdale, PA 19446 USA.

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TABLE 1

Effect of Urging by the Rider on Gal lop St r ide L imb Contacts

Rider urging" Item Absent Present

Probability Urging effecP

Number of strides 34 28 Velocity (m/sec) 12.52 + .17 12.66 + .20 .326 Stride freq. (sec-') 2.50 + .03 2.56 + .03 .032 Stride length (m) 5.08 + .04 5,02 + .04 .034

Step lengths (m) Hindstep .84 ± .03 .84 ± .03 .859 Midstep 2.00 + .04 2.05 +.05 .148 Forestep 1.05 + .01 1.04 ± .01 .508 Airbome step 1.25 ± .04 1.22 ± .04 .301

Limb contact phases (sec) Hind trail .110 + .001 .110 ± .002 .551 Hind lead .101 ± .001 .101 + .002 .837 Fore trail .100 + .001 .096 + .002 .012 Fore lead .100 + .001 .096 + .002 .002

Limb non-contact phases (aec) Hind trail .269 ± .001 .268 + .002 .298 Hind lead .278 + .002 .277 + .002 .827 Fore trail .279 + .001 ,282 + .002 .043 Fore lead .279 ± .001 .282 ± .002 .008

Sequential contact phase durations (aec)

Hind trail unipedal .062 + .002 .063 + .002 .630 Hind bipedal .036 + ,002 ,038 + .002 .356 Hind lead unipedal .038 + .003 .038 + .004 .881 Fore trail diagonal bipedal .025 + .003 .025 + .004 .896 Fore trail unipedal .039 + .003 .040 + .003 .626 Fore bipedal .025 ± .001 .022 ± .001 .016 Fore lead unipedal .073 ± .001 .072 + .002 .670 Airbome .077 ± .003 .077 + .003 .990

Sums of contact phases (sec) Total unipedal .201 + .006 Total bipedal .086 ± .004

.204 + .007 .461

.085 + .005 .658

Contact ratios (sec:aec) Hind lead:total hind .621 + .011 .618 +.012 .658 Fore lead:total fore .560 + .006 .571 + .007 .027 Total fore:total hind 1.058 + .015 1.036 + .017 .029

aLeast square means + standard errors from N=122 observations bprobability of no difference between rider urging absent and present

era lens distortion and perspective error, using conversion factors of 4.63 and 4.70 projected cm/real meter for horses' right and left sides, respectively. Gallop kinematic variables determined for 34 strides without rider urging and 28 strides with rider urging included velocity, stride frequency, stride length, step lengths and limb contact timing variables.

General linear regression techniques9 were used to patti- Volume 8, Number 3, 1988

don out the effects of velocity, gallop lead, individual variation and urging treatment on dependent limb contact variables. Type HI sums of squures probabilities were considered significant at P<.05. The effects of velocity,1 individual variation, 2 and lead a on gallop stride limb contact variables in this group of horses have been reported previously.

R E S U L T S

There was no significant difference in velocity according to urging treatment although rider urging was associated with an increase (P<.05) in stride frequency and a decrease (P<.05) in stride length (Table 1). Stride duration was reduced by approximately 2% and stride length was reduced by approximately 1% when urging by the rider was imposed.

Effects of rider urging on other variables were determined on the basis of a constant (average) velocity. Hind limb contact and non-contact durations were not significantly affected by urging treatment, but for each forelimb, contact durations were shorter (P<.05; Figure 1) and non-contact durations were longer (F.05; Figure 2) with rider urging. Fore bipedal contact durations were shorter (P<.05) when rider urging was present (Figure 3).

The reductions (P<.05) in stride duration and reductions (P<.05) in contact durations of both fore limbs occurred at the expense of the duration of fore bipedal contact in the gallop stride cycle. On the basis of a constant velocity, rider urging was associated with a 14% reduction in fore bipedal contact duration, a 3% to 4% reduction in the contact durations of the forelimbs and a 1% increase in the forefimb non-contact durations.

The ratio of leading forelimb contact to total forelimb contact durations was smaller (P<.05) with rider urging, but the contact ratio for the hind limbs was not significantly

DURATION (5EC) .120

Y / / / / / A

URGING /.115 ~ R T

HIND TIL~IL HIND LEND FO~ TRAIL F ~ LEAD G^LLOP LIHD CONTACT PHASES

Figure 1: l~.ffect or absence (34 strides) o r presence (28 strides) of urging by the r ider on durations in seconds (mean + SE) of hoof contact phases for the l imbs of 4 Quar ter Horse fillies, velocity 12.6 mlsec. *P<.05, **P<.Ol.

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tI~IND

PT"J'7"~/A

LI~tND PeE~NT

DURATION (SEE)

.ae5

.2m

.2'/5

it NIHD TRML HIND LEkl FO~ TRAIL

BAt.LOP LIKa NON-CONTACT PHASES FORE LF.~

Figure 2: Effect of absence 0 4 strides) or presence (28 strides) of urging by the rider on durations in seconds (mean + SE) of hoof non-contact phases for the limbs of 4 Quarter Horse fillies, velocity 12.6 m/see. *P<.0$.

ouRtcr D3N (SEE) t~IND

'tI~IND .~7

IH * l t IlL I1_ + n" F I t3" * FL fL t l l E f l ~ GALLOP STRIDE SEQUENTIAL PHASES

Figure 3: Effect of absence (34 stride s) or presence (28 strides) of urging by the rider on duratiom in seconds (mean + SE) of sequential gallop stride limb contact phases of hind (H) and fore (F), leading (L) and tratling (T) limbs of 4 Quarter Horse filles, velocity 12.6 m/sec. *P<.0$.

affected by treatment. The ratio of total fore contact to total hind contact was reduced (P<.05) when rider urging was present.

There were no significant interactions between gallop lead and rider urging effects for any limb contact variable measured, so the effects of rider urging were not different for left and fight gallop leads. Individual differences in responses to urging were detectable (Horse*urging treatment interaction P<.05) only for midstep length and hind trail non-contact duration.

DISCUSSION

Urging by the rider did not have the anticipated effect of significantly increasing galloping velocity of these horses. This means either that urging had no detectable influence on submaximal velocity, or that even in the absence of rider urging the subjects were galloping close to their individual maximal velocities. The kinematic responses to the urging 242

treatment demonstrate alterations in limb timing patterns, with a possible redistribution of weight off of the forelimbs as a behavioral reaction by the galloping horses to being goaded on the leading shoulder with a riding crop. An alternative explanation for the observed gait alterations is that they represent the influence of minor redistributions in the fider's body weight or other biomechanical factors associated with the activity of the rider while using the riding crop.

It should be noted that in this study, the urging action was a crop applied on the horse's shoulders. In many equine athletic competitions, riders use crops exclusively on the horse's rump. These effects may be substantially different from those of a crop used on the forequarters. In gyrnkhana and rodeo speed events, e.g., barrel racing and pole bending, the rules of competition expressly prohibit striking the horse in front of the saddle.

The results should not be interpreted to mean that urging by the rider cannot influence galloping velocity in other circumstances, e.g., in a race. The horses in this experiment were not unduly fatigued, as might be expected near the end of a race. During the final drive to the finish line, jockeys fre- quently make extensive use of their whips to encourage maximal efforts of their mounts. The intention is to reduce the extent of the decrease in velocity that typically occurs near the end of a race/Minor influences on velocity in that portion of a race could mean the difference between winning or losing. As little as a 0.1 m/sec difference in average velocity of 2 horses over the course of a 400 m ( 1/4 mile ) race would result in 4 m (13 ft) between the two at the finish line.

CONCLUSIONS

This study provided objective evidence of the influence of urging by a rider on the limb motion patterns of the equine gallop stride. Specifically, the action of the rider of goading the horse on the leading shoulder with a riding crop was associated with a reduction in gallop stride length and also a reduction in stride duration at the expense of fore bipedal contact duration. Limb contact durations for both forelimbs were reduced and the fore: hind contact ratio was reduced with rider urging, indicating a possible redistribution of weight off of the forelimbs. However, urging by the rider on the shoulder did not significantly influence gallop velocity nor any hind limb contact variables of the gallop stride. This information may have applicability in the design and interpretation of future equine biomechanical studies that are performed under field conditions during actual sporting competitions wherein crops or whips are used by riders.

The influences of rider urging were fairly consistent within this small homogeneous group of horses. Individual-

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ized responses to rider urging are expected to be of greater magnitude in a larger, more heterogeneous sample of horses, or with different riders. Urging on the right and left sides had similar effects. Additional objective studies are needed to determine typical biomechanical effects of a rider on the motion patterns of horses. Particularly valuable would be research on the magnitude and distribution of forces imposed by a rider and saddle in the dynamic loading of horses' backs, and also studies of the biomechanical consequences of a rider's application of forces of variable magnitude and direc- tion through the reins to the bit.

REFERENCES

1. Deuel NR, Lawrence I.aM: Gallop velocity and limb contact variables of Quarter Horses. J EqVet Sci 6(3)143, 1986.

2. Deuel NR, Lawrence LM: Individual variation in the Quarter

Horse gallop. In: Equ/ne ExercisePhysiology2, pp 564-573. Ed GiUespie JR and Robinson NE, Edwards Brothers, Ann Arbor, MI, 1987a.

3. Deuel NR, Lawrence LM: Laterality in the gallop gait of horses. J Biomech 20(6)645-649, 1987b.

4. Fredricson I, Gemandt A, Hediund G, Sederholm L: Horses and Jump/ng. Arco Publ Co; NY, pp 118, 1976.

5. Leach DH, Crawford WH: Guidelines for the future of equine locomotion research. Eq Vet ,l 15(2)103, 1983.

6. Leach DH, Dagg At: A reviewof research on equine locomotion and biomechanics. EqVet J 15(2)93, 1983.

7; Leach DH.:and::Springinga:E: Gait fatigue in the racing Thoroughbred. J Equine Med Sur& 3:436, 1979.

8. Pagan JD, Hintz HF: Equine energetics H: Energy expenditure in horses during submaximal exercise. JAnimSci 63:822, 1986.

9. SAS: Statistical Analysis System User's Guide: Statistics, pp 139- 200. SAS Institute, Cavj, NC, 1982.

10. Thomson KS~ How to Siton a horse. American Scientist, 75(1)69, 1987.

11. Xenophon: Hints for the rider (365 BC). The Horseman's Companion pp 92-97, Ed Williams D, St Martin's Press, New York, NY, 1980.

NECK AND SHOULDER MOTION OF THE GALLOP STRIDE

N.R. Deuel, MS, PhD, 1 and L.M. Lawrence, MS, PhD 2

S U M M A R Y

The motion patterns of the neck and shoulders during the gallop stride were documented using high-speed cinematography. The gallop stride characteristics of 4 Quarter Horse fillies, approximately 30 months of age, were used as a model. Horses were housed and fed together and received the same amount and type of limited training; and were all ridden with the same tack and by the sameperson. Both sides of each horse were filmed simultaneously (243 frames/sec) while galloping individually along a 1.5-m-wide track. Kinematic variables describing 29 strides (mean velocity 13.1 m/sec, stride frequency 2.6 strides/see, stride length 5.1 m) included linear and temporal measurements of the maximum and minimum heights of the wing of the atlas, spine of the scapula, shoulder joint and elbow joint; maximum and minimum angles with respect to the horizon of the neck, shoulder and arm segments; and maximum and minimum relative angles between the neck and shoulder, and shoulder and arm segments. Differences (P<.05) between the leading and trailing sides of the body were identified for 12 of a total of 27 spatial measurements

Authors' Addresses: 1Department of Animal and Nutritional Sciences, University of New Hampshire, Durham, New Hampshire 03824 USA; 2Departmeut of Animal Sciences, University of Illinois, Urbana, Illinois 61801 USA. Address correspondence to Dr. DeueL Acknowledgement: Thanks are extended to Dr. J.L. Groppel of the Univer- sity of Illinois, Department of Physical Education for filming equipment and technical assistance.

Volume 8, Number 3, 1988

reported for the neck, shoulder and arm, including minimum height of the scapula spine, maximum height of the scapula spine and elbow joint, maximum absolute angle of the shoulder segment, and minimum angle between neck and shoulder segments. O f 18 temporal measurements reported involving the neck, shoulder, and arm, 14 differed (P<.05) between leading and trailing sides. Kinematic events describing the motion of the leading and trailing shoulder and ann segments were ordered and tabulated in the temporal sequence of the normal gallop stride. Results indicated that the motion patterns of the shoulder and arm segments were highly specific to the leading and trailing sides of the body in the equine gallop stride. The work required for vertical displacement of the center of mass in galloping was estimated to be approximately 98,500 J/kin or 23.5 kcal/km; equivalent to approximately 6 percent of the total energy expenditure for galloping 1 km.

INTRODUCTION

The conformation of the neck and shoulder has long been considered of critical importance in equine locomotion. According to Hayes, ? "the more we seek for speed and ability to jump cleverly in an animal, the longer should be his neck" and "the more oblique are the shoulders, the greater ability will a horse have to raise and advance his forelegs. Also, oblique shoulders are valuable aids to speed at the gallop." More recently, Rooney 14 speculated on the biomechanical

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