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Clayton, H. M. (1994). Comparison of the stride kinematics of the collected, working, medium and extended trot in horses. Equine Vet J, 26(3), 230–234.
Abstract: Highly-trained dressage horses were studied to test the hypothesis that stride length is altered independently of stride duration in the transitions between the collected, working, medium and extended trot. Six well-trained dressage horses were filmed at a frame rate of 150 frames/s performing the collected, working, medium and extended trots in a sand arena. Temporal, linear and angular data were extracted from the films, with 4 strides being analysed for each horse and gait type. There were no significant asymmetries between the left and rights limbs or diagonals when data from the whole group were pooled, but 3 horses showed asymmetries in one or more variables (P < 0.01). Analysis of variance and post-hoc tests indicated that the speed increased significantly (P < 0.01) from the collected (3.20 m/s) to the working (3.61 m/s) to the medium (4.47 m/s) to the extended (4.93 m/s) trot. The increases in speed were associated with a significant increase in stride length from 250 cm in the collected trot, to 273 cm in the working trot, 326 cm in the medium trot and 355 cm in the extended trot (P < 0.01). The lengthening of the stride was a result of increases between each gait type in the over-reach distance, whereas the diagonal distance was significantly longer in the extended than the collected trot only (P < 0.01). The stride duration tended to decrease as speed increased, and the difference became significant between the collected and extended trots (P < 0.01).
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Geutjens, C. A., Clayton, H. M., & Kaiser, L. J. (2008). Forces and pressures beneath the saddle during mounting from the ground and from a raised mounting platform. The Veterinary Journal, 175(3), 332–337.
Abstract: The objective was to use an electronic pressure mat to measure and compare forces and pressures of the saddle on a horse's back when riders mounted from the ground and with the aid of a mounting platform. Ten riders mounted a horse three times each from the ground and from a 35 cm high mounting platform in random order. Total force (summation of forces over all 256 sensors) was measured and compared at specific points on the force-time curve. Total force was usually highest as the rider's right leg was swinging upwards and was correlated with rider mass. When normalized to rider mass, total force and peak pressure were significantly higher when mounting from the ground than from a raised platform (P < 0.05). The area of highest pressure was on the right side of the withers in 97% of mounting efforts, confirming the importance of the withers in stabilizing the saddle during mounting.
Keywords: Electronic saddle mat; Total force; Peak pressure; Equestrian; Kinetics
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Clayton, H. M., Larson, B., Kaiser, L. A. J., & Lavagnino, M. (2011). Length and elasticity of side reins affect rein tension at trot. The Veterinary Journal, 188(3), 291–294.
Abstract: This study investigated the horse’s contribution to tension in the reins. The experimental hypotheses were that tension in side reins (1) increases biphasically in each trot stride, (2) changes inversely with rein length, and (3) changes with elasticity of the reins. Eight riding horses trotted in hand at consistent speed in a straight line wearing a bit and bridle and three types of side reins (inelastic, stiff elastic, compliant elastic) were evaluated in random order at long, neutral, and short lengths. Strain gauge transducers (240 Hz) measured minimal, maximal and mean rein tension, rate of loading and impulse. The effects of rein type and length were evaluated using ANOVA with Bonferroni post hoc tests. Rein tension oscillated in a regular pattern with a peak during each diagonal stance phase. Within each rein type, minimal, maximal and mean tensions were higher with shorter reins. At neutral or short lengths, minimal tension increased and maximal tension decreased with elasticity of the reins. Short, inelastic reins had the highest maximal tension and rate of loading. Since the tension variables respond differently to rein elasticity at different lengths, it is recommended that a set of variables representing different aspects of rein tension should be reported.
Keywords: Horse; Equitation; Training; Rein aids
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Bonin, S. J., Clayton, H. M., Lanovaz, J. L., & Johnston, T. (2007). Comparison of mandibular motion in horses chewing hay and pellets. Equine Vet. J., 39(3), 258–262.
Abstract: Summary Reasons for performing study: Previous studies have suggested that temporomandibular joint (TMJ) kinematics depend on the type of food being masticated, but accurate measurements of TMJ motion in horses chewing different feeds have not been published. Hypothesis: The temporomandibular joint has a larger range of motion when horses chew hay compared to pellets. Methods: An optical motion capture system was used to track skin markers on the skull and mandible of 7 horses as they chewed hay and pellets. A virtual marker was created on the midline between the mandibles at the level of the 4th premolar teeth to represent the overall motion of the mandible relative to the skull during the chewing cycle. Results: Frequency of the chewing cycles was lower for hay than for pellets. Excursions of the virtual mandibular marker were significantly larger in all 3 directions when chewing hay compared to pellets. The mean velocity of the virtual mandibular marker during the chewing cycle was the same when chewing the 2 feeds. Conclusions: The range of mediolateral displacement of the mandible was sufficient to give full occlusal contact of the upper and lower dental arcades when chewing hay but not when chewing pellets. Potential relevance: These findings support the suggestion that horses receiving a diet high in concentrate feeds may require more frequent dental prophylactic examinations and treatments to avoid the development of dental irregularities associated with smaller mandibular excursions during chewing.
Keywords: horse; temporomandibular joint; mastication; kinematics
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Clayton, H. M. (1993). Development of conditioning programs for dressage horses based on time-motion analysis of competitions. J Appl Physiol, 74(5), 2325–2329.
Abstract: The time-motion characteristics of Canadian basic- and medium-level dressage competitions are described, and the results are applied in formulating sport-specific conditioning programs. One competition was analyzed at the six levels from basic 1 to medium 3. Each test was divided into a series of sequences based on the type and speed of activity. The durations of the sequences were measured from videotapes. The basic-level tests had fewer sequences, and they were shorter in distance and duration than the medium tests (P < 0.10), but the average speed did not differ between the two levels. It is recommended that horses competing at the basic levels be conditioned using 5-min exercise periods, with short (10-s) bursts of lengthened trot and canter included at basic 2 and above. In preparation for medium-level competitions, the duration of the work periods increases to 7 min, 10- to 12-s bursts of medium or extended trot and canter are included, and transitions are performed frequently to simulate the energy expenditure in overcoming inertia.
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Clayton, H. M., Hampson, A., Fraser, P., White, A., & Egenvall, A. (2018). Comparison of rider stability in a flapless saddle versus a conventional saddle. Plos One, 13(6), e0196960.
Abstract: The purpose of a saddle is to improve the rider's safety, security, and comfort, while distributing the forces exerted by the rider and saddle over a large area of the horse's back without focal pressure points. This study investigates the effects on rider stability of an innovative saddle design that differs from a conventional saddle in having no flaps. Five horses were ridden by their regular rider in their usual saddle and in a flapless saddle. A pressure mat (60 Hz) placed between the saddle and the horse's back was used to determine the position of the center of pressure, which represents the centroid of pressure distribution on the horse's back. Data were recorded as five horses were ridden at collected and extended walk, trot and canter in a straight line. Data strings were split into strides with 5 strides analysed per horse/gait/type. For each stride the path of the rider's center of pressure was plotted, maximal and minimal values in the anteroposterior and mediolateral directions were extracted, and ranges of motion in anteroposterior and mediolateral directions were calculated. Differences between the conventional and flapless saddles were analysed using mixed models ANOVA. Speed and stride length of each gait did not differ between saddles. Compared with the conventional saddle, the flapless saddle was associated with significant reductions in range of motion of the rider's center of pressure in the mediolateral direction in all gaits and in the anteroposterior direction in collected trot, extended trot and extended canter. The improved stability was thought to result from the absence of saddle flaps allowing the rider's thighs to lie in more adducted positions, which facilitated the action of the lumbopelvic-hip musculature in stabilizing and controlling translations and rotations of the pelvis and trunk. The closer contact between rider and horse may also have augmented the transfer of haptic information.
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Clayton, H. M. (1995). Comparison of the stride kinematics of the collected, medium, and extended walks in horses. Am J Vet Res, 56(7), 849–852.
Abstract: Six horses, highly trained for dressage competition, were used to study the stride kinematics of the walk, and to compare the kinematics of the collected, medium, and extended walks. Horses were filmed in a sagittal plane at a rate of 150 frames/s; temporal, linear, and angular data were extracted from the films. Results of ANOVA and Duncan's multiple range test indicated that the speed of the collected walk (1.37 m/s) was significantly (P < 0.01) slower than that of the medium (1.73 m/s) and extended (1.82 m/s) walks, values for which were not significantly different from each other. The increase in speed was associated with a significant increase in stride length, from 157 cm in the collected walk to 193 cm in the extended walk. This was a result of an increase in the over-tracking distance, whereas there was no significant difference in the distance between lateral placements of the limbs. Stride duration decreased (P < 0.01) from the collected walk (1,159 ms) to the extended walk (1,064 ms). Angles of the metacarpal and metatarsal segments, measured on the palmar/ plantar aspect, were higher at impact and lower at lift off in the collected than in the extended walk (P < 0.01). This indicated greater range of angular motion of this segment during the stance phase in the extended walk. Only 1 of the 6 horses had a regular 4-beat rhythm of the footfalls, with equal time elapsing between the lateral and diagonal footfalls.
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Dutto, D. J., Hoyt, D. F., Clayton, H. M., Cogger, E. A., & Wickler, S. J. (2004). Moments and power generated by the horse (Equus caballus) hind limb during jumping. J Exp Biol, 207(Pt 4), 667–674.
Abstract: The ability to jump over an obstacle depends upon the generation of work across the joints of the propelling limb(s). The total work generated by one hind limb of a horse and the contribution to the total work by four joints of the hind limb were determined for a jump. It was hypothesized that the hip and ankle joints would have extensor moments performing positive work, while the knee would have a flexor moment and perform negative work during the jump. Ground reaction forces and sagittal plane kinematics were simultaneously recorded during each jumping trial. Joint moment, power and work were determined for the metatarsophalangeal (MP), tarsal (ankle), tibiofemoral (knee) and coxofemoral (hip) joints. The hip, knee and ankle all flexed and then extended and the MP extended and then flexed during ground contact. Consistent with our hypothesis, large extensor moments were observed at the hip and ankle joints and large flexor moments at the knee and MP joints throughout ground contact of the hind limb. Peak moments tended to occur earlier in stance in the proximal joints but peak power generation of the hind limb joints occurred at similar times except for the MP joint, with the hip and ankle peaking first followed by the MP joint. During the first portion of ground contact (approximately 40%), the net result of the joint powers was the absorption of power. During the remainder of the contact period, the hind limb generated power. This pattern of power absorption followed by power generation paralleled the power profiles of the hip, ankle and MP joints. The total work performed by one hind limb was 0.71 J kg(-1). Surprisingly, the knee produced 85% of the work (0.60 J kg(-1)) done by the hind limb, and the positive work performed by the knee occurred during the first 40% of the take-off. There is little net work generated by the other three joints over the entire take-off. Velocity of the tuber coxae (a landmark on the pelvis of the animal) was negative (downward) during the first 40% of stance, which perhaps reflects the negative work performed to decrease the potential energy during the first 40% of contact. During the final 60% of contact, the hip, ankle and MP joints generate positive work, which is reflected in the increase of the animal's potential energy.
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