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Topic:Biomechanics
Biomechanics in horses refers to the study of the mechanical principles that govern movement and physical function in equine species. This field encompasses the analysis of gait, locomotion, and the forces exerted by and upon the horse's musculoskeletal system. Biomechanical studies often involve the use of motion capture technology, force plates, and computer modeling to assess how horses move and how various factors, such as conformation, training, and health status, influence their performance and soundness. Research in equine biomechanics contributes to understanding injury prevention, rehabilitation, and performance optimization. This page compiles peer-reviewed research studies and scholarly articles that explore the mechanics of movement, the impact of external and internal forces, and the applications of biomechanical analysis in equine care and management.
The gait of pacers. 2: factors influencing pacing speed. Standardbred pacers were studied at four different nominated speeds and selected gait kinematics were analysed to determine factors which contribute to pacing speed. A deterministic model is proposed in which pacing speed is a function of stride length and stride timing variables. Stance length and suspension time remained relatively constant over the different pacing speeds. Variables which discriminated best between pacing speeds were suspension length and overlap time. At near maximal speed, the pacers increased speeds with increased stride length. This was attributed to an increased suspen...
Evaluation of equine locomotion during different degrees of experimentally induced lameness. II: Distribution of ground reaction force patterns of the concurrently loaded limbs. Force plate and high-speed film data from a group of six walking horses were used to study the distribution of the ground reaction forces (GRF) of the concurrently loaded limbs. Three different degrees of supporting lameness were induced in a forelimb or a hindlimb using modified horse shoes. In all experiments the alterations in the distribution in the transverse horizontal GRF (Fx) were small. During unilateral forelimb lameness, the decreased longitudinal horizontal GRF (Fy) was compensated by an increase of the Fy forces of the contralateral forelimb and the ipsilateral hindlimb. The decre...
Monitoring the effects of treadmill exercise on bone by non-invasive means during a progressive fitness programme. Six Standardbred horses underwent a 14-week training programme on a treadmill. The training schedule consisted of five weeks of slow work of six to 12 km/day at 5 m/sec. This was followed by a nine week interval programme increasing in its intensity so that for the last three weeks the horses did three to four intervals/day from 600 to 1000 m at or above maximum heart rate. Ultrasound velocity through the third metacarpus showed a significant increase as a result of training. There was also a significant increase in modulus of elasticity, but no change in bone mineral content, bone mineral den...
Evaluation of equine locomotion during different degrees of experimentally induced lameness. I: Lameness model and quantification of ground reaction force patterns of the limbs. Force plate data from walking horses were used to evaluate the locomotion of a group of six horses during experimentally induced lameness in a forelimb or a hindlimb. By tightening or loosening screws in modified horseshoes the resulting pressure pain on the sole enabled induction and release of three different degrees of supporting lameness within a period of 2 h. The ground reaction force (GRF) patterns of the different recording sessions were compared with control data of the same horse as well as with the 'standard' horse data using a quantitative evaluation procedure involving 93 GRF para...
Kinetics and kinematics of the equine hind limb: in vivo tendon loads and force plate measurements in ponies. Loads on the suspensory ligament, deep digital flexor tendon, superficial digital flexor tendon, and long digital extensor tendon of the equine hind limb were determined in ponies by use of implanted strain gauges consisting of silicone rubber tubes filled with mercury. Recordings were made simultaneously with force plate measurements and high-speed film recordings while the ponies were walking. The relationship between strain gauge signals and tendon loads was obtained from tension-strain tests performed after death of the ponies. The suspensory ligament and the 2 digital flexor tendons were ...
Kinetics and kinematics of the equine hind limb: in vivo tendon strain and joint kinematics. Strains of the suspensory ligament and deep digital flexor, superficial digital flexor, and long digital extensor tendons in the equine (pony) hind limb were recorded in vivo, using implanted strain gauges consisting of silicone rubber tubes filled with mercury. The relationship between strain gauge signals and tendon strains was obtained from tension-strain tests performed on isolated tendons after death of the ponies. During normal walking, maximal tendon strain (elongation over initial length, relative to the length of the structures at first ground contact) was 3.1% in the suspensory ligam...
Effects of frequency and airway pressure on gas exchange during interrupted high-frequency, positive-pressure ventilation in ponies. Cardiovascular effects and pulmonary gas exchange were compared during conventional mechanical ventilation (CMV) and interrupted high-frequency, positive-pressure ventilation (IHFPPV) in 6 anesthetized ponies in dorsal recumbency. When the peak airway pressure (Paw) was held constant at control values attained during CMV (18 to 20 cm of H2O), and the ventilator frequency of IHFPPV was varied over the range, 2.5 to 12.5 Hz, significant (P less than 0.05) changes from control values were observed only in the ratio of dead-space volume to tidal volume (VD/VT) and in the respiratory minute volume ...
Quantification of skin displacement near the carpal, tarsal and fetlock joints of the walking horse. A technique enabling simultaneous visualisation of skin and underlying bony structures in the walking horse was used to quantify skin displacements on the lateral surface of carpal, tarsal and fetlock joints. The technique employed implanted light-emitting-diodes (LEDs) for marking the bone, and self adhesive spot labels for marking the overlying skin. Photographic recordings were made. Skin displacement was measured in six Dutch Warmblood horses. Mean total displacements and mean displacement per degree of change of joint angle were calculated. Displacements at the level of the fetlock joints...
Distribution of ground reaction forces of the concurrently loaded limbs of the Dutch Warmblood horse at the normal walk. The distribution of the ground reaction forces (GRF) over the concurrently loaded limbs of the normally walking horse was determined from 'representative' GRF patterns of all limbs, which were plotted in correct time order after analysis of simultaneously taken high-speed film. This procedure visualises the GRF patterns of each of the four limbs in relation to the GRF pattern(s) of the one or two concurrently loaded limb(s) during a complete stride. In 15 clinically sound horses the mean averaged GRF data and temporal stride parameters showed an almost complete symmetry between both the foreli...
In vitro comparison of three fixation methods for humeral fracture repair in adult horses. The stiffness, load to failure, and bending moments of adult intact equine humeri and humeri repaired with 3 fixation techniques were determined in vitro. Bones were tested in axial compression (30 pairs), mediolateral 3-point bending (15 pairs), and caudocranial 3-point bending (15 pairs). An oblique osteotomy of 1 humerus of each pair was performed to simulate the long spiral oblique fractures that occur clinically in horses. Bones were repaired in 3 ways: group 1--nylon band cerclage fixation (20 bones); group 2--multiple intramedullary pinning (20 bones); and group 3--nylon band cerclage f...
Determination and repeatability of maximum oxygen uptake and other cardiorespiratory measurements in the exercising horse. A rapid incremental treadmill exercise test was used to determine the repeatability of the following measurements in exercising horses: maximal oxygen consumption (VO2max), maximal heart rate (HRmax), velocity at a heart rate of 200 beats/min (V-200), oxygen consumption at a heart rate of 200 beats/min (VO2-200), oxygen consumption at HRmax (VO2-HRmax), work rate at a heart rate of 200 beats/min (W-200), work rate at HRmax (W-HRmax) and treadmill velocity at HRmax (V-HRmax). Six Standardbred geldings were exercised on three separate occasions on a treadmill set at an inclination of 6 degrees. ...
Measurements of bone strain in foals with altered foot balance. Two to 7 days after birth, 9 foals were anesthetized, and strain gauges were applied to lateral and medial aspects of the third metacarpal bone of the left forelimb. In 5 of these foals, strain gauges also were applied to the radius of the left forelimb. Four to 6 days later, foals were walked (5 sets of 10 to 20 strides), and compressive and tensile strains in the bone beneath strain gauges were recorded on paper and diskette. After recording base-line data, a wedge was fitted to the hoof of the limb with the strain gauges, in such a way that the lateral bearing surface was raised, and strain...
Variability of fiber size, capillary density and capillary length related to horse muscle fixation procedures. Muscle samples were taken from the superficial part of the semitendinosus muscle of four standardbred horses to compare the effects of three different fixation procedures on fiber size and capillarity. Infiltration fixation in an extended position of the muscle was compared to immersion fixation and infiltration fixation in a flexed position of the limb. The capillary length density was used to estimate muscle capillarity. Infiltration fixation was found to be a viable alternative to perfusion fixation of muscles for morphometry of fiber size and capillary length density allowing muscle tissue...
Breathing strategy of the adult horse (Equus caballus) at rest. To investigate the mechanism underlying the polyphasic airflow pattern of the equine species, we recorded airflow, tidal volum, rib cage and abdominal motion, and the sequence of activation of the diaphragm, intercostal, and abdominal muscles during quiet breathing in nine adult horses standing at rest. In addition, esophageal, abdominal, and transdiaphragmatic pressures were simultaneously recorded using balloon-tipped catheters. Analysis of tidal flow-volume loops showed that, unlike humans, the horse at rest breathes around, rather than from, the relaxed volume of the respiratory system (Vr...
The use of H(orse) INDEX: a method of analysing the ground reaction force patterns of lame and normal gaited horses at the walk. The amplitudes, impulses and times of occurrence of a number of selected peaks in the ground reaction force tracings of 17 horses with various clinical histories were compared with those of 20 horses used to establish values for the 'standard' Dutch Warmblood horse. The resulting factors were combined, using different weighting factors, into indices characterising each limb. The symmetry between the loading of the forelimbs and the hindlimbs was used to calculate amplitude and peak-time symmetry indices. Limb and symmetry indices were combined in one H(orse) INDEX. This method of quantifying t...
Calibration of the mercury-in-silastic strain gauge in tendon load experiments. A calibration method is presented by which the signals of mercury-in-silastic strain gauges (MISS), implanted in the tendons of in vitro loaded equine hindlegs, were converted to tendon loads. The relationships between MISS-signals and tendon loads were obtained from tensile-force tests applied to the tendons. Special attention was paid to the correction of the MISS-signals for amplitude-shifts resulting from internal repositioning of the MISS after tendon isolation and temperature differences. Shift corrections equivalent to tendon strains up to 2.8% were necessary in the in vitro experiment....
Central to peripheral sound propagation in excised lung. The time it takes audible sound to travel from the trachea to the pleura in five intact, excised horse lungs and one dog lung inflated with several gases was measured. Regression estimates of sound speed at total lung capacity (TLC) using straight line distance from the carina to the pleura are: helium, 775 +/- 60.5 m/s (means +/- 95% confidence limits); air, 282 +/- 23.5; carbon dioxide, 219 +/- 25.5; sulfur hexafluoride, 142 +/- 43.5. With the exception of sulfur hexafluoride, these speeds are 15%-20% less than the free-field speed of sound in each gas. Total airway length did not predict ti...
Functional design of horse hoof keratin: the modulation of mechanical properties through hydration effects. Tensile moduli and J-integral fracture toughness values were determined for horse hoof-wall keratin at four hydration levels. The stiffness of hoof-wall was influenced by water content to a greater degree than is the stiffness of other mammalian hard keratins. Young's modulus increased from 410 MPa at 100% relative hydration (RH) to 14.6 GPa at 0% RH. Fracture toughness was maximal (22.8 kJ m-2) at an intermediate hydration (75% RH), which represents a two-fold increase over both fully hydrated and dehydrated material. Maximum fracture toughness occurred at a hydration level which is within th...
Identification of hindleg lameness. The use of markers placed over the tuber coxae on each side of a horse to aid identification of the relative movement of these structures at the trot, for teaching and research purposes, is described. In each case of hindleg lameness studied, the tuber coxae on the lame side showed a consistent increase in vertical displacement relative to that of the contralateral limb, and a characteristic pattern of movement throughout the stride irrespective of the site or cause of pain.
Early development of gait asymmetries in trotting standardbred colts. Ten trotting Standardbred colts were recorded by high-speed cinematography at the ages of eight, 12 and 18 months. The horses were trotting on a treadmill operating at 4.0 m/secs. Five horses were subjected to a programme of intensified training from eight months of age, whereas the others were not trained and acted as controls. The films were analysed on a semi-automatic film-reading equipment and a number of variables used to demonstrate the gait symmetry were calculated and scaled by computer. Certain differences between left and right diagonal and contralateral pair of limbs, respectively,...
Multivariate statistical analysis of stride-timing measurements of nonfatigued racing Thoroughbreds. Standard univariate and bivariate statistical methods and two multivariate methods, stepwise regression and factor analyses, were used to analyze 17 stride-timing measurements of 22 racing Thoroughbreds filmed at the beginning of races. All horses were in a right-lead transverse gallop. Data were extracted from frame-by-frame analysis of 16-mm film taken with a high-speed camera. The mean stride duration was 0.405 s and the mean stride frequency was 2.47 strides/s. Stride duration had a higher correlation to the suspension-phase duration (r = 0.864) than to stride-stance-phase duration (r = 0....
In vitro strength of the suspensory apparatus in training and resting horses. Forty-eight limbs of 12 freshly euthanized horses were used to generate data on the strength of the equine suspensory apparatus. The point of failure of the suspensory apparatus of each limb was determined. Immediately before euthanasia, 6 of the 12 horses (thoroughbreds and standardbreds) had been engaged in active training or racing, and six horses in stall and/or pasture activity. In the actively training or racing horses, the point of acute failure of the suspensory apparatus was within the proximal sesamoid bones in 20 (83%) limbs (resulting in 17 apical fractures, 2 basilar fractures, an...
Some biomechanical aspects of the structure of the equine tarsus. The morphology of the bones of the equine tarsus has distinct kinematical and kinetic implications which are primarily expressed in the helical motion of the talocrural joint and in the transmission of forces by the rigid conformation of the subtalar articulations.
Quantification of equine ground reaction force patterns. A method was developed to quantify the ground reaction force pattern of the horse. A number of selected force amplitudes and peak-time positions in the normalized stance phase of left and right contralateral limbs were used to calculate symmetry indices. Data from each limb were compared with those of a 'standard horse' resulting in limb indices. The combination of amplitude and peak-time symmetry and limb indices yielded one H(orse)INDEX. These indices were useful for comparison of different horses and for the evaluation of lameness and treatment.
The ground reaction force pattern from the hindlimb of the horse simulated by a spring model. A model consisting of a spring loaded by a time-dependent mass is presented simulating the vertical and longitudinal horizontal ground reaction force patterns obtained from the hindlimb of a walking horse.
