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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.
Mechanical properties of suture materials in vitro and after in vivo implantation in horses. Tensile testing of reproducible loops of size 5 braided polyester, size 2 polyglycolic acid, size 2 monofilament nylon, and size 2 polydioxanone sutures was performed in vitro and after subcutaneous implantation in horses for 7, 14, and 28 days. Maximum breaking strength, energy absorption, and percentage elongation to breakage point were measured. Size 5 braided polyester had the highest maximum breaking strength and energy absorption over 28 days. Polydioxanone had better mechanical performance over 28 days than did polyglycolic acid. On day 28, none of these parameters was measurable in pol...
Characterizing bone strain distributions in vivo using three triple rosette strain gages. Three triple-element rosette strain gages were attached to the equine third metacarpal midshaft to record site-specific strains engendered by locomotion. The distribution of strains acting upon the midshaft cross section were characterized using a combined beam theory and finite element model analysis that did not presume the manner by which the bone was inertially loaded. A medium-speed trot (3.6 ms-1) was chosen as a representative speed and gait, with normal and shear strains, and strain energy density (SED) distributions determined throughout the stance and subsequent swing phase. Importan...
Mechanical properties of small airways in excised pony lungs. We evaluated the pressure-flow relationships in collaterally ventilating segments of excised pony lungs by infusing N2, He, Ne, or SF6 at known flows (V) through a catheter wedged in a peripheral airway. Measurements were made at segment- (Ps) to-airway opening (Pao) pressure differentials of 3-15 cmH2O when the lungs were held at transpulmonary pressures of 5, 10, and 15 cmH2O. The data were analyzed both by calculating collateral resistance (Ps-Pao/V) and by constructing Moody-type plots of normalized pressure drop [(Ps-Pao)/(1/2 rho U2, where rho is density and U is velocity)] against Reyno...
Evaluation of support bandaging during measurement of proximal sesamoidean ligament strain in horses by use of a mercury strain gauge. Liquid mercury strain gauges were implanted in the forelimb proximal sesamoidean ligaments (PSL) of 8 adult horses. The gauges measured PSL strain while horses were standing with or without external support. In 6 of the horses, the gauges also measured PSL strain in horses at a walk, with or without external support. Gauges were enclosed within sliding polypropylene tubes to prevent nonaxial deformation. Each gauge was placed in 1 arm of a low-resistance half-bridge circuit. To provide temperature compensation, a dummy gauge was placed in the adjacent arm of the bridge circuit and was implante...
The synchronization of ventilation and locomotion in horses (Equus caballus). Ciné film and synchronized records of respiratory flow were obtained from Thoroughbred racehorses cantering on a treadmill at speeds of 9 and 11 m s-1. Horses and some other galloping and hopping mammals link their breathing and locomotion, taking exactly one breath per stride. Three theoretical mechanisms by which the movements of locomotion might drive ventilation are considered. (i) Flexion of the lumbosacral joint and the resulting forward sweep of the pelvis pushes the viscera against the diaphragm. However, back flexion lags behind ventilation at 11 m s-1 and could not exclusively drive...
Suspensory apparatus prosthesis in the horse. Part 1: In vitro mechanical properties. Mechanical properties of equine suspensory apparatus preparations and three braided synthetic prostheses were evaluated in vitro. Force versus displacement plots and failure modes were recorded from single load-to-failure testing in 18 cadaver limbs before and after replacement of each suspensory apparatus with a prosthesis. Mean load at failure, energy to failure, and stiffness values of polytetrafluoroethylene (PTFE) prostheses were lower than those of the suspensory apparatus and aramid prosthesis. The PTFE prosthesis failed by elongation or rupture of the prosthesis. Mechanical properties ...
The response of equine cortical bone to loading at strain rates experienced in vivo by the galloping horse. The behaviour of cortical bone under load is strain rate-dependent, i.e. it is dependent on the rate at which the load is applied. This is particularly relevant in the galloping horse since the strain rates experienced by the bone are far in excess of those recorded for any other species. In this study the effect of strain rates between 0.0001 and 1 sec-1 on the mechanical properties of equine cortical bone were assessed. Initially, increasing strain rates resulted in increased mechanical properties. Beyond a critical value, however, further increases in strain rate resulted in lower strain to...
Healing of transected equine superficial digital flexor tendons with and without tenorrhaphy. Healing of transected superficial digital flexor tendons was evaluated mechanically and histologically in eight horses. Tendons sutured with polyglyconate had higher loads at failure than nonsutured tendons at weeks 5 and 9. The tendon stress at failure (force per unit area) was higher in the sutured tendons at week 5 but not at week 9, reflecting the increased size of the scar at week 9. Histologically, scars after tenorrhaphy were consistently more mature than nonsutured tenotomy scars. The mean maturity score for sutured tendons was higher than for nonsutured tendons at weeks 5 and 9. Overa...
Modelling exercise-induced pulmonary hemorrhage in racing thoroughbreds. Exercise-induced pulmonary hemorrhage (EIPH) affects a large portion of racing thoroughbred horses. Sites of hemorrhage and causal mechanisms remain unestablished. Our mathematical model was constructed to test the hypothesis that EIPH could be caused by a combination of respiratory and circulatory mechanical factors occurring during exercise. Various physiological data for respiration, blood circulation and exercise were incorporated into the model. Results show that inhalation pressure drops across airway resistances become great enough during exercise to cause rupture of capillaries for bot...
Elbow extensor muscles of the horse: postural and dynamic implications. Based on histochemical and immunohistochemical evidence, horse elbow extensor muscles are composed of two morphologically distinct muscle groups. The long and lateral heads of the triceps brachii are large, predominantly type II (presumed fast) muscles. The long and lateral heads of the triceps together account for 96% of the weight of the elbow extensors (long head of triceps is 81%). The long and lateral heads contain three histochemical fiber types: types I, IIa and IIb. Type I muscle fibers account for approximately 18 and 27% of the fibers in the long and lateral heads of the triceps, res...
Effects of treadmill exercise on cortical bone in the third metacarpus of young horses. The effects of exercise and relative inactivity on cortical bone were compared in young horses. Two groups were used; one was given a 14-week programme of exercise (n = 6) and the other kept as unexercised controls (n = 6). The first nine weeks of exercise involved trotting and cantering (2 to 4 km d-1 at speeds up to 12 m s-1) on a treadmill set at an incline of 3 degrees. Over the next five weeks the horses were trained at near maximal speeds (that is, up to 14.5 m s-1) with no incline of the treadmill. At the end of the programme marked differences in cortical porosity and distribution of s...
Common horse sense. This research article corrects a common misconception about the energy metabolism in horses during short sprinting and long-distance running events, emphasizing that short sprints are primarily powered by anaerobic activity, […]
Embryo recovery from mares exposed to a year-to-year artificially prolonged daylength. The aim of the experiment was to determine the effect of a year-to-year prolonged daylength on the patterns of equine reproductive activity and results of embryo recovery. Experiments using Konik Polski mares were conducted over four reproduction seasons. Five mares were exposed to a regimen of artificially prolonged daylength (APD) and another five mares in a control group were kept under conditions of natural daylight. Both the control and experimental groups were examined for appearance of estrus, ovulation and also for the state of their coats. A single stallion was used for breeding all o...
Osteochondrosis in the horse–searching for the key to pathogenesis. This paper reviews current developments in equine osteochondrosis complex and the clinical syndromes associated with it. Although the primary lesion has been defined as a failure of endochondral ossification, its definitive cause is unknown and appears to involve heredity, growth rate, nutrition, mineral imbalance, endocrinological dysfunction and biomechanical trauma. Despite the international importance of osteochondrosis in horses, surprisingly few controlled investigations have been performed on its pathogenesis. The studies that have been conducted suggest that local effects on differenti...
The use of high-speed treadmills for lameness and hoof balance evaluations in the horse. Examination for lameness remains the most important component of the clinical evaluation for poor performance. Although conventional examinations can be used to diagnose many causes of lameness, treadmill video gait analysis and dynamic hoof balance evaluations have proved to be useful not only for evaluating lameness but also for maintenance of long-term soundness. Treadmill lameness evaluations offer a major advantage compared to conventional evaluations because of the stationary position of the exercising horse relative to the people performing the examination. Lameness is suspected if asym...
Advances in motion analysis. Time magnification in motion photography allows the observation of events in the stride cycle that normally are beyond the resolution of the human eye. Quantitative analysis goes a stage further by measuring the stride in terms of timing, distance, and angular variables. Motion analysis is a good technique for detecting left-right asymmetries of gait, and the nature of the asymmetries has some value in locating the site of a lameness. Repeated analyses of the same horse allow an objective assessment of the effects of local anesthesia, surgical treatment, or medication. It is anticipated that t...
Treadmill exercise testing. Treadmill installation and training protocols used for clinical evaluations of equine athletes. The use of motorized treadmills has made it possible to evaluate equine poor performance with sophisticated diagnostic techniques during peak exercise. Treadmill exercise tests currently being used for clinical evaluations include treadmill gait analysis, dynamic hoof balancing, endoscopic evaluation of upper airway function, and exercise performance profiling. Large motorized treadmills (1 to 1.5 m in width and 4 to 5 m in length) are best suited for clinical evaluations. Ideally, the treadmill should be installed in-ground using a pit. This type of installation results in the tread surface b...
Quantitative evaluation of the remodeling response of the proximal sesamoid bones to training-related stimuli in Thoroughbreds. Eight untrained 2-year-old Thoroughbred horses were used in a study of the remodeling response of the proximal sesamoid bone (PSB) to training-related stimuli. Two horses each were assigned to 1 of 4 groups: group 1, untrained, pasture turnout (control); group 2, modified-classically trained, dirt track; group 3, classically trained, dirt track; and group 4, classically trained, wood chip track. Horses were given fluorochromic bone labels every 28 days during training. All horses were euthanatized after 5 months of training, and the proximal sesamoid bones (PSB) were removed. A midsagittal sec...
A mechanical trigger for the trot-gallop transition in horses. It is widely thought that animals switch gaits at speeds that minimize energetic cost. Horses naturally switched from a trot to a gallop at a speed where galloping required more energy than trotting, and thus, the gait transition actually increased the energetic cost of running. However, by galloping at this speed, the peak forces on the muscles, tendons, and bones, and presumably the chance of injury, are reduced. When the horses carried weights, they switched from a trot to a gallop at a lower speed but at the same critical level of force. These findings suggest that the trot-gallop transiti...
Identification of subclinical tendon injury from ground reaction force analysis. In this study a method of analysing ground reaction forces was developed to help in the diagnosis of subclinical flexor tendon injury. A Kistler force plate was used to obtain records from a population of Thoroughbreds in National Hunt training over a period of two years. Characteristic features of the force patterns generated were measured and shown to have low variance, both between horses and over a period of two racing seasons in animals that were sound throughout the trial. Specific changes in the loading pattern of the limb, which correlated with injury of the superficial digital flexor ...
Desmotomy of the accessory ligament of the superficial digital flexor muscle in equine cadaver limbs. Effects of longitudinal compression before and after transection of the accessory ligament of the superficial digital flexor (SDF) muscle were measured in eight equine cadaver forelimbs. When compression was increased from 890 N to 3115 N, the metacarpophalangeal (MCP) and carpal joints hyperextended 20 degrees and 4 degrees, respectively, and strain in the SDF and deep digital flexor tendons was increased 3.5% and 1.4%, respectively. The accessory ligament did not elongate. Immediately after transection of the accessory ligament at 3115 N load, a 2.8 mm gap formed between the transected ends ...
Mechanical properties of the isolated equine trachea. In order to study the in vitro mechanical properties of the equine trachea submitted to the compressive pressures observed in vivo, the pressure-volume relationship was determined in intra- and extra-thoracic tracheal segments taken post mortem from 29 healthy horses (one to 15 years old; 352 to 651 kg). At the same time, the cross-sectional lumen area (X-SA) at the mid-point of the segment was measured using a slit-lamp transillumination and photographic measurement by endoscopy. The tracheal specific compliance (Cs) as well as the relative changes in X-SA and in the sagittal and transverse d...
Viscoelastic shear properties of the equine medial meniscus. Recent studies have shown that the meniscus is highly anisotropic in tension and that its compressive creep behavior can be modeled using biphasic theory. In this study, an alternative approach is used, where viscoelastic shear properties of the meniscal fibrocartilage are measured to determine the anisotropy and inhomogeneity of this tissue with respect to specimen location and fiber orientation. Medial menisci were obtained from eight skeletally-mature horses. Nine test specimens were taken from the circumferential midsubstance of each meniscus, at three circumferential and three axial posit...
Technique for continuous stride analysis of horses exercising on a treadmill. A technique for continuous computerised recording and analysis of the stride of horses on a treadmill is described. Advantages of the system are low cost, the use of normal shoes and the calculation of stride parameters in real time.
Osteopenic effects of forelimb immobilisation in horses. Methods for the non-invasive assessment of bone quality were used to monitor the osteopenia induced by immobilising a forelimb in a cast. These techniques included the measurement of ultrasound velocity, single photon absorptiometry and radiographic photodensitometry. Serial measurements were made before, during and after an eight week period of immobilisation of the left forelimb of four adult standardbreds in a light fibreglass cast which included the foot and extended above the carpus. The measurements continued for 12 weeks after the removal of the cast. The results indicated a trend to de...
Pathway of ultrasound waves in the equine third metacarpal bone. The velocity of ultrasound waves through bone has been used widely as a non-invasive method for assessing bone quality. Accurate measurement of velocity depends on accurate assessment of the distance travelled by the sound wave. It has been argued that the sonic pathway is deflected around the marrow cavity and so does not follow a straight line through the bone; therefore, correction factors have been developed to account for the extra distance travelled. This hypothesis was examined in vitro using sections from the equine third metacarpal bone. Two 1 MHz transducers used with the transmittin...
