D. R. Mullineaux

Energetic and kinematic consequences of weighting the distal limb

REASON FOR PERFORMING STUDY It is well known that adding a load to a horses back increases its energetic costs of locomotion, but the magnitude of increase obtained by loading the most distal portion of limb has not been measured. OBJECTIVES To measure oxygen consumption in horses with mass added to the back and hooves. Because such mass distribution alters inertial parameters of the limbs, kinematic measurements were made to quantify the magnitude of change in limb movement. METHODS Steady-state oxygen consumption was measured in 6 horses with a load of 2.4 kg. The load was either carried on the back or distributed equally between the 4 limbs. Modified bell boots kept the mass at the level of P3. Horses trotted on a treadmill at speeds ranging from 2 to 5 m/sec (in 0.5 m/sec increments). High-speed (250 Hz) digital images were recorded in a sagittal plane and the positions of retroreflective markers located on standard positions on the limbs were digitised for kinematic analysis. RESULTS Loading of the distal limbs produced a 6.7% increase in metabolic rate, an order of magnitude higher than when the mass was added over the back. Although the stride period was 2% longer in horses with loads on the distal limbs, time of contact and duty factor were not different. Distal limb loading increased the range of motion in hind- but not forelimbs. CONCLUSIONS The costs of swinging the limbs in the horse are considerable and the addition of weights to the distal limb can have a profound effect on not only the energetics of locomotion but also the kinematics, at least in the hindlimb. POTENTIAL RELEVANCE The use of weighted shoes, intended to increase animation of the gait, increases the metabolic effort of performance horses a disproportionate amount. The additional mass also increases the joint range of motion and, potentially, the likelihood of injury.

Ground reaction forces and limb function in tölting Icelandic horses.

REASONS FOR PERFORMING STUDY Gaited horses employ 4-beat stepping (singlefoot) gaits that extend into speeds typical of trots. Ground reaction force (GRF) patterns of these specialised gaits have not been reported; therefore, appraisal of these gaits using nongaited horse kinetics may lead to clinical misjudgements. HYPOTHESIS GRFs of tölting Icelandic horses will be comparable in profile and magnitude with those of trotting horses. METHODS Forelimb and hindlimb GRFs were obtained for 10 Icelandic horses ridden at a tölt. These data were evaluated across 3 speed ranges: <2, 2.5-5 and >5 m/sec. RESULTS Virtually all vertical force tracings were single-peaked. Forelimbs typically had greater peak vertical forces and impulses compared with hindlimbs. Support duration and forelimb vertical impulse were correlated negatively with speed, whereas peak vertical, braking and propulsive forces and hindlimb braking and propulsive impulses were correlated positively with speed. CONCLUSIONS GRF profiles of tölting Icelandic horses are more similar to profiles of trots than walks, suggesting that tölts follow bouncing mechanics. POTENTIAL RELEVANCE Greater overlap of limb support in 4-beat gaits (even at high speeds) is associated with lower peak vertical force magnitudes of tölts compared with those reported for trots at comparable speeds, which may help limit the occurrence of overloading injuries in Icelandic horses.

Effects of athletic taping of the fetlock on distal limb mechanics

REASONS FOR PERFORMING STUDY Athletic taping is used frequently by human athletes to stabilise, maintain or strengthen soft tissue structures, but empirical evidence supporting any changes in equine kinematics is lacking. OBJECTIVES To assess the effects of athletic taping of the fetlock applied by an experienced athletic trainer on forelimb mechanics in healthy horses. HYPOTHESES That athletic taping of the distal forelimb reduces 1) hyperextension of the fetlock joint during stance, 2) flexion of the fetlock joint during swing and 3) ground reaction forces during stance. METHODS Ground reaction force and kinematic data were obtained for 6 healthy horses trotting at 3 m/sec for 4 sequential conditions (baseline, untaped; pre-exercise, taped; post exercise, taped post 30 mins trotting exercise; transfer, 4 h after tape removal). Data were analysed using 2-way mixed ANOVAs (condition; joint). RESULTS A statistically significant interaction was identified for the fetlock during the swing phase (mean +/- s.d. peak flexion at baseline 157 +/- 4 degrees, reduced with taping to 172 +/- 4 degrees; P<0.05) compared with no differences across conditions for the other joints. Peak vertical force reduced significantly (P<0.05) with taping. CONCLUSIONS Athletic taping of the fetlock does not alter the kinematics of the forelimb during stance, but does limit flexion of the fetlock during the swing phase. The decreased peak vertical force may be due to an increased proprioceptive effect. POTENTIAL RELEVANCE Reduced peak vertical forces may be of benefit in preventing or reducing injury. Further investigation remains necessary before it can be concluded that taping should be applied for tendinous or ligamentous rehabilitation in equine patients.

Three‐dimensional carpal kinematics of trotting horses

REASONS FOR PERFORMING STUDY Descriptions of 3D kinematics assist in understanding joint function and dysfunction, and are an essential step toward 3D inverse dynamic analysis. OBJECTIVES To measure 3D carpal joint motion during trotting. METHODS Three-dimensional trajectories of bone-fixed markers on the radius and third metacarpus of the right forelimb of 3 healthy horses were recorded at 120 Hz using a 6-camera analysis system. Joint kinematics were calculated in terms of helical angles between the 2 segments using a spatial attitude method. RESULTS All horses showed carpal extension and internal rotation of the metacarpus relative to the radius as the carpus assumed the close-packed position. In late stance, the carpus began a cycle of flexion that continued through midswing, accompanied by a small cycle of internal rotation. The direction of abduction/adduction varied between horses. The predominant rotational movement was flexion/extension, which showed a range of motion of 15 +/- 6 degrees in stance and 76 +/- 13 degrees in swing. CONCLUSIONS Carpal motions were generally similar between horses with the exception of abduction/adduction. POTENTIAL RELEVANCE Knowledge of carpal joint motion should assist in understanding the pathogenesis of carpal injuries. However, it seems probable that real differences exist between individuals; therefore, further investigations of the effect of conformation on carpal motion should be performed in a much larger population of horses.

The effects of a single acupuncture treatment in horses with severe recurrent airway obstruction

Summary Reasons for performing study: Acupuncture may be recommended for horses with ‘heaves’ because it is being increasingly applied to treat human asthma. Therefore, its efficacy was investigated in horses with this asthmalike disease. Objective: To evaluate the efficacy of a single acupuncture treatment for the relief of airway obstruction in heaves-affected horses. Methods: The efficacy of a single acupuncture treatment was tested in 10 heaves-affected horses, and the effect of removal from the dusty stall environment in 5 heaves-affected horses. Before treatment, horses were stabled to induce airway obstruction and, apart from trips to the laboratory for pulmonary function measurements, they remained stabled for the duration of each treatment. The severity of airway obstruction was quantified by measurement of lung function before treatment (baseline), and at 20, 60, 120 and 240 mins and 24 h after the following treatments administered in random order: halter restraint and patting, a single acupuncture treatment by an experienced acupuncturist, and a single acupuncture treatment using predetermined points (recipe) by a veterinarian with no acupuncture training. In a second study, horses were untreated and remained either in their stall or in a paddock for all measurements of lung function, after baseline readings were made. Results: In the first study, after all treatments, there was a temporal improvement in maximal change in pleural pressure, pulmonary resistance, dynamic compliance, respiratory rate, and tidal volume that lasted less than 24 h. There was no specific effect of acupuncture treatment. In the second study, removal from the dusty environment did not produce an improvement in lung function in the first 6 h. We conclude that most of the improvements in lung function observed in the study were due to handling. Conclusions: Assessed objectively, a single acupuncture treatment during an attack of heaves causes no more improvement in lung function than does handling the horse. Potential relevance: Acupuncture should not replace conventional medical treatments for heaves.

Mepivacaine local anaesthetic duration in equine palmar digital nerve blocks.

REASONS FOR PERFORMING STUDY Perineural analgesics are used for lameness diagnosis but the duration of effect, knowledge of which would provide valuable information when performing subsequent blocks, is unknown. OBJECTIVE To evaluate the duration of a palmar digital nerve block using force plate measurements. METHODS Ten horses diagnosed with unilateral navicular syndrome were trotted at range of 3 +/- 0.15 m/sec over a force plate to record ground reaction forces for 5 trials of each forelimb. Data were recorded before nerve block, and then at 15 mins, 1, 2 and 24 h post nerve block. RESULTS Before nerve block, peak vertical force (mean +/- s.e.) was significantly higher in the contralateral forelimb (CL = 5345 +/- 188 N) than in the lame forelimb (L = 4256 +/- 204 N; P<0.05). At 15 mins post nerve block there was no significant difference between the 2 forelimbs (CL = 5140 +/- 184 N; L = 5126 +/- 129 N), and this remained the case for 1 h. By 2 h, the mean score for the lame leg had decreased (L = 4642 +/- 182 N) but was still greater than preblock. By 24 h, vertical forces had returned to preblock values. CONCLUSIONS The palmar digital nerve block was fully effective between 15 mins and 1 h. The analgesic effect began to subside between 1 and 2 h but sufficient analgesia persisted to affect gait characteristics beyond 2 h. POTENTIAL RELEVANCE When using a palmar digital nerve block, it is important to perform lameness evaluations between 15 mins and 1 h to be sure of effective nerve blockade.

Three‐dimensional analysis of patterns of skin displacement over the equine radius

REASONS FOR PERFORMING STUDY Surface markers are usually used to track bone movement. However, skin movement related to the bone has a large effect on the analysis of skeletal kinematics. A 2-dimensional (2D) skin displacement correction model has been successfully developed, but no 3D skin displacement model exists. OBJECTIVES To develop a 3-dimensional (3D) skin displacement model for the equine radial segment during trot. METHODS The 3D trajectories of 6 skin-based markers and a bone-fixed triad were captured at trot in 4 horses. Skin displacements in the bone-based coordinate system were calculated using a singular-value decomposition method. The truncated Fourier series models were developed for the skin displacements using a generalised cross-validatory spline. RESULTS Mean + /- s.d. of peak skin displacement of the 3 markers on the proximal radius as percentage of radial length was 10.7 +/- 0.5, 4.6 +/- 1.5 and 14.5 +/- 2.9% in x, y and z direction, respectively. For the 3 markers on the distal radius, the equivalent displacements were 4.7 +/- 0.6, 1.7 +/- 0.8 and 7.3 +/- 18% in x, y and z direction, respectively. CONCLUSIONS The 3D skin displacement model for correction of skin marker motion over the equine radius relative to the bone can be established using a truncated Fourier series, which has previously been used successfully to develop 2D models. POTENTIAL RELEVANCE This method of determining 3D skin displacement correction needs to be extended to the entire fore- and hindlimbs to provide a more sensitive measure of kinematic analysis. Accurate descriptions of the 3D motions of the limb segments and interactions between adjacent segments at the joints are necessary for understanding of the mechanics of different gaits and the gait aberrations that manifest as lameness.

Tennis: Criterion validity of an isokinetic dynamometer to assess shoulder function in Tennis players

Abstract Isokinetic dynamometry is used in the assessment and rehabilitation of shoulder function in tennis players. The aim of this study was to validate a newly installed Biodex III Isokinetic Dynamometer for internal and external shoulder rotation. A non‐injured male performed this movement which replicates an integral section of the tennis service action (Cohen et al., 1994). Three maximal trials were performed at six randomly assigned angular velocities (0.52, 1.05, 1.57, 2.09, 2.62 and 3.14 rad.s‐1) with 90s rest between each set. Trials were recorded using an on‐line motion analysis system and kinematic data were obtained. Kinematic angular displacement of the lever arm was slightly greater (≥0.01 rad.s‐1) than for the isokinetic dynamometer at all test angular velocities. Mean angular velocities from the kinematic data were almost identical to those from the isokinetic dynamometer but less than the target values, and this difference (e.g. 2.55 rad.s‐1 at 3.14 rad.s‐1) was greater at higher angular velocities owing to the greater acceleration phases required. Peak angular velocity was similar on the isokinetic dynamometer to the target values, but substantially less than those from the kinematic data (e.g. 0.68 rad.s‐1 at 0.52 rad.s‐1). This suggests that the isokinetic data are over‐smoothed and may mask important information. In summary, criterion validity of this isokinetic dynamometer is supported for displacement and mean angular velocity, but not for peak angular velocity. Shoulder rotations in tennis are often at angular velocities greater than the Biodex can reproduce, but for the purpose of monitoring the shoulder strength and range of motion of tennis players and providing safe functional rehabilitation, the use of slower angular velocities is acceptable.Isokinetic dynamometry is used in the assessment and rehabilitation of shoulder function in tennis players. The aim of this study was to validate a newly installed Biodex III Isokinetic Dynamometer for internal and external shoulder rotation. A non-injured male performed this movement which replicates an integral section of the tennis service action (Cohen et al., 1994). Three maximal trials were performed at six randomly assigned angular velocities (0.52, 1.05, 1.57, 2.09, 2.62 and 3.14 rad x s(-1)) with 90 s rest between each set. Trials were recorded using an on-line motion analysis system and kinematic data were obtained. Kinematic angular displacement of the lever arm was slightly greater (> or = 0.01 rad x s(-1)) than for the isokinetic dynamometer at all test angular velocities. Mean angular velocities from the kinematic data were almost identical to those from the isokinetic dynamometer but less than the target values, and this difference (e.g. 2.55 rad x s(-1) at 3.14 rad x s(-1)) was greater at higher angular velocities owing to the greater acceleration phases required. Peak angular velocity was similar on the isokinetic dynamometer to the target values, but substantially less than those from the kinematic data (e.g. 0.68 rad x s(-1) at 0.52 rad x s(-1)). This suggests that the isokinetic data are over-smoothed and may mask important information. In summary, criterion validity of this isokinetic dynamometer is supported for displacement and mean angular velocity, but not for peak angular velocity. Shoulder rotations in tennis are often at angular velocities greater than the Biodex can reproduce, but for the purpose of monitoring the shoulder strength and range of motion of tennis players and providing safe functional rehabilitation, the use of slower angular velocities is acceptable.