Narelle C. Stubbs

Dynamic mobilisation exercises increase cross sectional area of musculus multifidus

REASON FOR PERFORMING STUDY In human subjects with back pain, the deep spinal stabiliser m. multifidus is inhibited ipsilaterally leading to atrophy, asymmetry and intervertebral instability. Specific physiotherapeutic exercises are required to reactivate m. multifidus. This study assesses the effect of dynamic mobilisation exercises on size and symmetry of m. multifidus in the equine caudal thoracic and lumbar spine. HYPOTHESES Regular performance of dynamic mobilisation exercises over a period of 3 months increases cross sectional area (CSA) and left-right symmetry of m. multifidus muscles in the caudal thoracic and lumbar spine. METHODS Eight horses performed dynamic mobilisation exercises (3 cervical flexions, one cervical extension and 3 lateral bending exercises to the left and right sides) with 5 repetitions/exercise/day on 5 days/week for 3 months during which time they were not ridden. Left and right m. multifidus CSA was measured ultrasonographically at 6 levels from T10 to L5 at the start (initial evaluation) and end (final evaluation) of the 3 month study. Changes in CSA of the right and left m. multifidus muscles and symmetry of m. multifidus CSA on the right and left sides between the 2 evaluations were sought using analysis of variance (P<0.05). RESULTS Between the initial evaluation and final evaluation m. multifidus CSA increased significantly at all 6 spinal levels on both right and left sides. Asymmetries in m. multifidus CSA between the right and left sides decreased between the initial and final evaluations. CONCLUSIONS Hypertrophy of multifidus occurred over a 3 month period during which dynamic mobilisation exercises were the only exercise performed. POTENTIAL RELEVANCE Dynamic mobilisation exercises maybe a useful rehabilitative technique for horses in which m. multifidus has atrophied in response to back pain.

Effect of trotting speed and circle radius on movement symmetry in horses during lunging on a soft surface

OBJECTIVE To determine whether body lean angle could be predicted from circle radius and speed in horses during lunging and whether an increase in that angle would decrease the degree of movement symmetry (MS). ANIMALS 11 medium- to high-level dressage horses in competition training. PROCEDURE Body lean angle, head MS, and trunk MS were quantified during trotting while horses were instrumented with a 5-sensor global positioning system-enhanced inertial sensor system and lunged on a soft surface. Speed and circle radius were varied and used to calculate predicted body lean angle. Agreement between observed and predicted values was assessed, and the association between lean angle and MS was determined via least squares linear regression. RESULTS 162 trials totaling 3,368 strides (mean, 21 strides/trial) representing trotting speeds of 1.5 to 4.7 m/s and circle radii of 1.8 to 11.2 m were conducted in both lunging directions. Differences between observed and predicted lean angles were small (mean ± SD difference, -1.2 ± 2.4°) but significantly greater for circling to the right versus left. Movement symmetry values had a larger spread for the head than for the pelvis, and values of all but 1 MS variable changed with body lean angle. CONCLUSIONS AND CLINICAL RELEVANCE Body lean angle agreed well with predictions from gravitational and centripetal forces, but differences observed between lunging directions emphasize the need to investigate other factors that might influence this variable. For a fair comparison of MS between directions, body lean angle needs to be controlled for or corrected with the regression equations. Whether the regression equations need to be adapted for lame horses requires additional investigation.

Dynamic mobilisations in cervical flexion: Effects on intervertebral angulations

REASONS FOR PERFORMING STUDY Based upon human data, it is probable that many conditions associated with neck pain in horses may benefit from performing mobilisation exercises as part of the rehabilitation protocol. OBJECTIVES To compare sagittal plane intervertebral angulations in a neutral standing position with the angulations at end range of motion in 3 dynamic mobility exercises performed in cervical flexion. METHODS Sagittal plane motion of the head, neck and back were measured in 8 sound horses standing in a neutral position and in 3 end-of-range neck flexion positions: chin-to-chest, chin-between-carpi, and chin-between-fore fetlocks. Skin markers on the head, transverse processes of C1-C6, and dorsal spinous processes of T6, T8, T10, T16, L2, L6, S2 and S4 were tracked and adjacent markers connected to form rigid segments. Intersegmental angles, measured between segments on the ventral surface, in the 4 positions were compared using repeated measures ANOVA with Bonferroni post hoc tests (P<0.05). RESULTS The largest angular differences involved the cranial and caudal cervical joints with smaller angular differences (<10°) in the mid-neck. The angle at C1 was significantly more extended for chin-between-carpi (98 ± 11°) and chin-between-fetlocks (132 ± 11°) than for the neutral position (86 ± 8°) or chin-to-chest (92 ± 8°) positions. The intersegmental angle at C6 indicated progressive lowering of the neck from neutral through chin-to-chest and chin-between-carpi to chin-between-fetlocks. The intersegmental angles from T6-L1 were more flexed by 3-7° in the cervical flexions compared with the neutral position with the differences being significant for at least one of the dynamic mobilisations at each vertebral level. CONCLUSIONS The articulations at the extremities of the cervical vertebral column are primarily responsible for sagittal plane position and orientation of the head and neck. Dynamic cervical flexion also flexes the thoracic intervertebral joints. POTENTIAL RELEVANCE The results indicate that dynamic mobilisation exercises performed in cervical flexion have applications in mobilising the cervical and thoracic intervertebral joints, which may have some clinical applications in rehabilitation.

Evaluation of intersegmental vertebral motion during performance of dynamic mobilization exercises in cervical lateral bending in horses

OBJECTIVE To identify differences in intersegmental bending angles in the cervical, thoracic, and lumbar portions of the vertebral column between the end positions during performance of 3 dynamic mobilization exercises in cervical lateral bending in horses. ANIMALS 8 nonlame horses. PROCEDURES Skin-fixed markers on the head, cervical transverse processes (C1-C6) and spinous processes (T6, T8, T10, T16, L2, L6, S2, and S4) were tracked with a motion analysis system with the horses standing in a neutral position and in 3 lateral bending positions to the left and right sides during chin-to-girth, chin-to-hip, and chin-to-tarsus mobilization exercises. Intersegmental angles for the end positions in the various exercises performed to the left and right sides were compared. RESULTS The largest changes in intersegmental angles were at C6, especially for the chin-to-hip and chin-to-tarsus mobilization exercises. These exercises were also associated with greater lateral bending from T6 to S2, compared with the chin-to-girth mobilization or neutral standing position. The angle at C1 revealed considerable bending in the chin-to-girth position but not in the 2 more caudal positions. CONCLUSIONS AND CLINICAL RELEVANCE The amount of bending in different parts of the cervical vertebral column differed among the dynamic mobilization exercises. As the horses chin moved further caudally, bending in the caudal cervical and thoracolumbar regions increased, suggesting that the more caudal positions may be particularly effective for activating and strengthening the core musculature that is used to bend and stabilize the horses back.

Hindlimb response to tactile stimulation of the pastern and coronet

REASONS FOR PERFORMING STUDY Lightweight tactile stimulators attached to the hind pasterns increase the height of the hind hoof flight arc but details of the induced changes in swing phase kinematics and kinetics have not been investigated. HYPOTHESES Stimulators on the hind pasterns are associated with increased hindlimb joint flexions and increased positive work performed by the hip and tarsal musculature. MATERIALS AND METHODS Nine nonlame horses trotted 4 times with and without 55 g tactile stimulators loosely attached around the hind pasterns. Height of the flight arc and peak flexion angles of the hindlimb joints were measured and net positive and negative work performed across each joint during the swing phase were calculated using inverse dynamics analysis and compared across paired conditions. RESULTS Speed and stride duration did not change but stimulators were associated with a reduction in hind stance duration. The flight arc was higher with stimulators due to increased flexions of the stifle, tarsal, metatarsophalangeal and distal interphalangeal joints. Positive work increased in the tarsal musculature, but not in the hip musculature, and negative work increased across the stifle, metatarsophalangeal and distal interphalangeal joints. POTENTIAL RELEVANCE The effects of tactile stimulation of the hind pasterns on joint motion and muscle activation may be used in physiotherapy and rehabilitation to restore or increase flexion of the hindlimb joints with the exception of the hip joint. The ability to stimulate concentric activity of the tarsal musculature may have therapeutic applications in conditions such as toe dragging.

Swing phase kinematics of horses trotting over poles.

REASONS FOR PERFORMING STUDY Trotting over poles is used therapeutically to restore full ranges of limb joint motion. The mechanics of trotting over poles have not yet been described, hence quantitative evidence for the presumed therapeutic effects is lacking. OBJECTIVES To compare limb kinematics in horses trotting over level ground, over low poles and over high poles to determine changes in joint angulations and hoof flight arcs. STUDY DESIGN Repeated measures experimental study in sound horses. METHODS Standard motion analysis procedures with skin-fixed reflective markers were used to measure swing phase kinematics from 8 horses trotting on level ground, over low (11 cm) and high (20 cm) poles spaced 1.05 ± 0.05 m apart. Spatiotemporal variables and peak swing phase joint flexion angles were compared using repeated measures ANOVA (P<0.05) with Bonferroni correction for pairwise post hoc testing. RESULTS Peak heights of the fore and hind hooves increased significantly and progressively from no poles (fore: 13.8 ± 3.8 cm; hind: 10.8 ± 2.4 cm) to low poles (fore: 30.9 ± 4.9 cm; hind: 24.9 ± 3.7 cm) and to high poles (fore: 41.0 ± 3.9 cm; hind: 32.7 ± 4.0 cm). All joints of the fore- and hindlimbs contributed to the increase in hoof height through increased swing phase flexion. The hooves cleared the poles due to increases in joint flexion rather than by raising the body higher during the suspension phases of the stride. CONCLUSIONS The increases in swing phase joint flexions indicate that trotting over poles is effective for activating and strengthening the flexor musculature. Unlike the use of proprioceptive stimulation devices in which the effects decrease over time due to habituation, the horse is required to elevate the hooves to ensure clearance whenever poles are present. The need to raise the limbs sufficiently to clear the poles and place the hooves accurately requires visuomotor coordination, which may be useful in the rehabilitation of neurological cases. The Summary is available in Chinese - see Supporting information.

Evaluation of biomechanical effects of four stimulation devices placed on the hind feet of trotting horses

OBJECTIVE To compare effects of 4 types of stimulation devices attached to the hind feet on hoof flight, joint angles, and net joint powers of trotting horses. ANIMALS 8 clinically normal horses. PROCEDURES Horses were evaluated under 5 conditions in random order: no stimulators, loose straps (10 g), lightweight tactile stimulators (55 g), limb weights (700 g), and limb weights with tactile stimulators (700 g). Reflective markers on the hind limbs were tracked during the swing phase of 6 trotting trials performed at consistent speed to determine peak hoof heights and flexion angles of the hip, stifle, tarsal, and metatarsophalangeal joints. Inverse dynamic analysis was used to calculate net joint energies. Comparisons among stimulators were made. RESULTS Peak hoof height was lowest for no stimulators (mean ± SD, 5.42 ± 1.38 cm) and loose straps (6.72 ± 2.19 cm), intermediate for tactile stimulators (14.13 ± 7.33 cm) and limb weights (16.86 ± 15.93 cm), and highest for limb weights plus tactile stimulators (24.35 ± 13.06 cm). Compared with no stimulators, net tarsal energy generation increased for tactile stimulators, limb weights, and limb weights plus tactile stimulators, but only the weighted conditions increased net energy generation across the hip joint. CONCLUSIONS AND CLINICAL RELEVANCE The type and weight of foot stimulators affected the magnitude of the kinematic and kinetic responses and the joints affected. These findings suggest that different types of foot stimulators are appropriate for rehabilitation of specific hind limb gait deficits, such as toe dragging and a short stride.

Muscle fibre type distribution of the thoracolumbar and hindlimb regions of horses: relating fibre type and functional role

BackgroundAlthough the majority of equine muscles have a mixed fibre type distribution indicative of diverse functional roles, the predominance of a fibre type can indicate the primary function of a muscle. The deep epaxial musculature has an important role in core spinal stability in humans, reflected as a predominantly muscle fibre type (MFT) I or postural fibre type. The fibre type of the deep epaxial musculature has not been determined in horses. The objective of the study was to determine the MFT distribution in selected muscles of thoracolumbar and hindlimb region of horses. This included deep epaxial and hypaxial muscles that were hypothesised to have a postural stabilising role. A second objective was to examine differences in MFT distribution between horses bred for endurance (Arabian) and sprinting (Quarter horse). Muscle biopsy samples were obtained from selected thoracolumbar and hind limb muscles of 5 Quarter horses, 4 Arabians, and 2 Thoroughbreds. The myosin heavy chain distribution was determined by gel electrophoresis. Mann–Whitney rank test was used to compare the proportional MFT and differences between breeds.ResultsMm. sacrocaudalis dorsalis medialis and diaphragm had the highest proportion of MFT-I. The remaining deep epaxial muscles and the hypaxial muscle m. psoas minor had approximately equal MFT I and II proportions. Mm. psoas major, iliocostalis, longissimus dorsi and the hind limb muscles contained mostly MFT-IIX. The fibre type distribution was similar between Arabians and Quarter horses, although Quarter horses had more MFT-IIX fibres in psoas major (P = 0.02) while Arabians had more MFT-I fibres in m. longissimus dorsi (P = 0.03).ConclusionsThe fibre type distribution of the deep epaxial muscles, mm psoas minor and diaphragm varied from approximately equal MFT-I and II proportions to predominantly MFT-I suggesting a postural stabilising role possibly important in core spinal stability. In contrast the fibre type proportions of mm psoas major, iliocostalis, longissimus dorsi and the hind limb muscles were mainly MFT-II suggesting a locomotory role. Knowledge of fibre type distribution in such a clinically important area can direct diagnosis, prevention and treatment of muscular or neuromotor dysfunction.

Swing phase kinematic and kinetic response to weighting the hind pasterns.

REASONS FOR PERFORMING STUDY It is considered that specific exercises to strengthen limb musculature would be helpful. OBJECTIVE To describe swing phase kinematic and kinetic changes in the hindlimbs of trotting horses in response to the addition of leg weights to the hind pasterns. METHODS Six horses were prepared by placing reflective skin markers on the hindlimbs, the withers and fore hooves. Horses were evaluated at trot for 6 trials with and without leg weights (700 g) attached around the pasterns, with the 2 conditions applied in random order. The markers were tracked to determine peak heights of the flight arc of the hind hooves and swing phase joint angulations. Inverse dynamic analysis was used to calculate positive and negative work done across each joint in the first and second halves of the swing phase. Comparisons between conditions were made using paired t tests (normally distributed data) or the Wilcoxon rank-sum test (non-normally distributed data). RESULTS Peak height of the flight arc of the hind hooves was significantly higher with leg weights as a result of increased flexions of the stifle, tarsal and metatarsophalangeal joints. Increased positive (concentric) work was performed by the hip and tarsal musculature to protract and raise the limb in early swing, then to retract and lower the limb in late swing. Increased negative (eccentric) work was performed across the stifle and metatarsophalangeal joints to control their movements in response to increases in inertia and momentum due to the weights. CONCLUSIONS The addition of weight to the hind pasterns stimulates increased muscular activity across all the hindlimb joints from the hip to the metatarsophalangeal joint. CLINICAL SIGNIFICANCE The addition of weight to the hind pasterns may have therapeutic applications in activating and strengthening the hindlimb musculature. This is particularly relevant in the hip region, which appears more sensitive and responsive to the effect of weights than to tactile stimulation alone.

Gross anatomy of the deep perivertebral musculature in horses

OBJECTIVE To determine the gross morphology of the multifidus, longus colli, and longus thoracis muscles in the cervical and cranial thoracic portions of the equine vertebral column. SAMPLE 15 horse cadavers. PROCEDURES The vertebral column was removed intact from the first cervical vertebra (C1) to the seventh thoracic vertebra (T7). After removing the superficial musculature, detailed anatomic dissections of the multifidus, longus colli, and longus thoracis muscles were performed. RESULTS The multifidus cervicis muscle consisted of 5 bundles/level arranged in lateral, medial, and deep layers from C2 caudally into the thoracic portion of the vertebral column. Fibers in each bundle attached cranially to a spinous process then diverged laterally, attaching caudally on the dorsolateral edge of the vertebral lamina and blending into the joint capsule of an articular process articulation after crossing 1 to 4 intervertebral joints. The longus colli muscle had ventral, medial, and deep layers with 5 bundles/level from C1 to C5 that attached cranially to the ventral surface of the vertebral body, diverged laterally and crossed 1 to 4 intervertebral joints, then attached onto a vertebral transverse process as far caudally as C6. The longus thoracis muscle consisted of a single, well-defined muscle belly from C6 to T5-T6, with intermediate muscular attachments onto the ventral aspects of the vertebral bodies, the intervertebral symphyses, and the craniomedial aspects of the costovertebral joint capsules. CONCLUSIONS AND CLINICAL RELEVANCE Results indicated that there were multiple, short bundles of the multifidus cervicis, multifidus thoracis, and longus colli muscles; this was consistent with a function of providing sagittal plane intersegmental vertebral column stability.