bluuebunny/crossref_metadata_2025 huggingface dataset:
Associations between exercise‐induced pulmonary haemorrhage, right ventricular dimensions and atrioventricular valve regurgitation in conditioned National Hunt racehorses
Authors: YOUNG L. E. , HELWEGEN M. M. G. H. J. , ROGERS K. , KEARNS L. , SCHREIBER C. , WOOD J. L. N.
Published: June 2010

Reasons for performing study:Exercise‐induced pulmonary haemorrhage (EIPH) and tricuspid (TR) and mitral valve regurgitation (MR) are conditions with high prevalence in conditioned Thoroughbreds. Stress failure of pulmonary capillaries, leading to EIPH, is most likely when pulmonary vascular pressure is increased, and mitral regurgitation can result in pulmonary venous hypertension.

Hypothesis:There might be an association between MR and EIPH and the right ventricle (RV) of horses known to suffer repeated episodes of EIPH, as their hearts would be subject to higher pulmonary vascular pressures and cardiac output during training and hence increased RV afterload and preload.

Methods:An echocardiographic and auscultation study was conducted in 121 race‐fit National Hunt Thoroughbreds. Cardiac auscultation and echocardiography were performed. A guided M‐mode image of the RV just below the tricuspid valve was obtained from a right parasternal location and colour flow Doppler (CFD) used to interrogate the tricuspid valve and right atrium. The mitral valve was similarly examined from the left hemithorax. Severity of TR and MR by CFD was graded. Binary data on EIPH, based on whether the horse was perceived to have a clinically significant problem with EIPH, were determined retrospectively for each horse by the horses' primary care veterinary surgeon from medical and other records. Data were analysed using a standard logistic regression analysis approach.

Results:EIPH was significantly and positively associated with the systolic and diastolic dimensions of the RV (P=0.017 and 0.011 respectively) and this association was not sensitive to the effects of age or weight. There were no significant associations between EIPH and TR or MR by auscultation or CFD (TR: auscultation P=0.1; CFD P=0.2 and MR: auscultation P=0.07; CFD P = 0.37).

Conclusions and clinical relevance:This study was limited by the method used to classify EIPH, but there was no association between EIPH and horse age, weight, TR or MR in this population of Thoroughbreds. Nevertheless, RV internal dimension was greater in horses obviously affected by EIPH, suggesting that factors resulting in EIPH may directly or indirectly affect RV remodelling in athletic horses.
Effect of repeated exercise and recovery on heart rate variability in elite trotting horses during high intensity interval training
Authors: COTTIN F. , BARREY E. , LOPES P. , BILLAT V.
Published: June 2010

Reasons for performing study:Interval training is a commonly used training method for trotting horses. In addition, trainers are provided with efficient and inexpensive heart rate monitor devices for the management of training.

Hypothesis:Since the high frequency (HF) frequency peak (fHF) of heart rate variability (HRV) corresponds to the breathing frequency in combination with stride frequency during trotting, it is hypothesised that modifications of breathing and stride frequencies induced by repeated exercise could be detected fromfHF.

Methods:RR interval time series of 7 trotting horses were recorded during an interval training session. Interval training was made up of 5 successive 800 m high‐velocity trotting runs (H1, H2…H5) separated by 1 min recovery bouts at low speed (R1, R2.R5). Fast Fourier transform (FFT) and Poincaré plot analysis techniques were applied to RR series.

Results:Repeated exercise had significant effects on HRV components during interval training. Despite constant trotting velocities during high‐speed and recovery, repetition induced a decrease in mean RR interval (H1: 295 ± 19 vs. H5: 283 ± 15 msec, P<0.05) and in the root mean square of successive differences in RR series (RMSSD; H1: 6.31 ± 1.28 vs. H5: 5.31 ± 1.31 msec, P<0.05). Furthermore, high‐speed and recovery repetitions induced an increase infHF (H1: 1.37 ± 0.35 vs. H5: 1.62 ± 0.40 Hz and R1: 0.22 ± 0.02 vs. R4: 0.64 ± 0.38 Hz, P<0.05). Hence, recovery induced a decrease in the s.d. of the successive RR series (SDRR; R3: 10.5 ± 3.96 vs. R5: 6.17 ± 2.65 msecs, P>0.05) and in the long term index of Poincaré plot (SD2; R1: 43.29 ± 28.90 vs. R5: 18.19 ± 9.35 msecs, P<0.05).

Conclusions:The observed increase infHF during the interval training could be induced by alterations of the coupling between breathing and stride frequency linked to the emergence of fatigue. The decrease in SD2 and SDRR during successive recovery bouts could be linked with a deterioration of the recovery pattern.

Potential relevance:HRV can provide breathing frequency data of Standardbreds during training without any respiratory device. Furthermore, HRV could provide useful makers of the emergence of fatigue states during training.
The effect of long‐term exercise on glucose metabolism and peripheral insulin sensitivity in Standardbred horses
Authors: de GRAAF‐ROELFSEMA E. , Van GINNEKEN M. E. , Van BREDA E. , WIJNBERG I. D. , KEIZER H. A. , Van der KOLK J. H.
Published: June 2010

Reasons for performing study:To study the possible long‐term effect of improved glucose tolerance in horses after long‐term training, as the impact of exercise training on glucose metabolism is still unclear in the equine species. It is not known whether there is a direct long‐term effect of training or if the measurable effect on glucose metabolism is the residual effect of the last exercise session.

Objectives:To determine the chronic effect on glucose metabolism and peripheral insulin sensitivity of long‐term training in horses by use of the euglycaemic hyperinsulinaemic clamp technique.

Methods:Eleven Standardbred horses were acclimatised to running on the high‐speed treadmill for 4 weeks (Phase 1) followed by training for 18 weeks with an alternating endurance (˜ 60% HRmax) high intensity training programme (˜ 80% HRmax) (Phase 2). Training frequency was 4 days/week. At the end of Phase 1, a euglycaemic hyperinsulinaemic clamp was performed 72 h after the last bout of exercise in all horses. At the end ofPhase 2, the horses were clamped 24 h or 72 h after the last bout of exercise.

Results:Glucose metabolism rate did not change significantly after 18 weeks of training, measured 72 h after the last exercise bout (0.018 ± 0.009 and 0.022 ± 0.006 mmol/kg bwt/min, respectively). Peripheral insulin sensitivity also did not change significantly following training (7.6 ± 5.7 times 10−6and 8.0 ± 3.1 times 10−6, respectively). The same measurements 24 h after the last bout of exercise showed no significant differences.

Conclusions:Results indicated that long‐term training in Standardbreds neither changed glucose metabolism or insulin sensitivity 72 h after the last bout of exercise.

Potential relevance:The fact that the beneficial effect of increased insulin sensitivity after acute exercise diminishes quickly in horses and no long‐term effects on insulin sensitivity after chronic exercise have as yet been found in horses, implies that exercise should be performed on a regular basis in horses to retain the beneficial effect of improved insulin sensitivity.
Effects of short‐term training on insulin sensitivity and skeletal muscle glucose metabolism in Standardbred horses
Authors: STEWART‐HUNT L. , GEOR R. J. , McCUTCHEON L. J.
Published: June 2010

Reasons for performing study:Increased insulin sensitivity occurs after a period of exercise training, but the mechanisms underlying this training‐associated increase in insulin action have not been investigated.

Objective:To examine the effects of short‐term endurance training (7 consecutive days) and a subsequent period of inactivity (5 days) on whole body insulin sensitivity and GLUT‐4 protein and the activities of glycogen synthase (GS) and hexokinase (HK) in skeletal muscle. It was hypothesised that training would increase insulin sensitivity in association with increased GLUT‐4 protein and activities of GS and HK, but that these changes would be transient, returning to baseline after 5 days of inactivity.

Methods:Seven mature Standardbred horses completed training consisting of 7 consecutive days of 45 min of treadmill exercise at a speed that elicited 55% of pretraining maximal aerobic capacity (VO2peak). Insulin sensitivity was determined by rate of glucose disposal (M) during the last 60 min of a 120 min euglycaemic‐hyperinsulinaemic clamp (EHC) performed before (‐2 days) and at 1 and 6 days following training. VO2peakwas measured before (UT) and after (TR) training and the period of inactivity (IA).

Results:Training resulted in a 9% increase in mean VO2peak(P<0.05) that was maintained following inactivity (IA). Mean M values were more than 2‐fold higher (P<0.05) in TR than in UT. Mean M was also higher (P<0.05) in IA when compared to UT. GLUT‐4 protien abundancewas more than 10‐fold higher in TR and IA (P<0.001) than in UT. Pre‐EHC GS activity and GS fractional velocity were increased (P<0.05) in TR when compared to UT and IA. Pre‐EHC HK activity was increased (P<0.05) in IA when compared to UT and TR. Muscle glycogen was 66% lower (P<0.05) in TR than in UT and IA.

Conclusions:Short‐term training resulted in increases in whole body insulin sensitivity, and GLUT‐4 protein content and glycogen synthase activity in skeletal muscle. The enhancements in insulin sensitivity, GLUT‐4 protein and glycogen synthase activity were still evident after 5 days of inactivity.

Potential relevance:Insulin resistance in equids has been associated with obesity and predisposition to laminitis. Regular physical activity may mitigate risk of these conditions via enhancement of insulin sensitivity and/or control of bodyweight.
Frusemide results in an extracellular to intracellular fluid shift in horses
Authors: FORRO M. , LINDINGER M. I.
Published: June 2010

Reasons for performing study:Frusemide (Lasix) is commonly used diuretic in horse racing and equine clinical practice. While pharmacology, pharmacodynamics, renal and haematological effects of frusemide have been studied in horses, its effects on the distribution of fluid within the horse remain unknown.

Objective:To quantify the effects of frusemide on extracellular and intracellular fluid shifts.

Methods:Horses were infused with 1 mg/kg body mass (n=7) or 2 mg/kg (n = 9) i.v. frusemide. Total body water (TBW), extracellular fluid volume (ECFV) and plasma volume (PV) were measured using D2O, NaSCN and Evans blue dilution. Change in ECFV was assessed from the change in plasma [protein] and from repeated infusion/dilution of NaSCN.

Results:Frusemide resulted in a 0.020 ± 0.002 1/kg decrease in TBW within 120 min. At 120 min after frusemide infusion the ECFV losses were nearly double the TBW losses, therefore ECFV loss in excess of TBW loss is seen as an increase in ICFV.

Conclusions:Frusemide resulted in a net shift of fluid (electrolytes and water) from the extracellular to intracellular fluid compartment.

Potential relevance:The fluid shifts that occur within horses administered frusemide has not previously been characterised. The intracellular shift of fluid is of performance and clinical significance.
Effect of exercise on blood oxidant/antioxidant markers in Standardbred horses: comparison between treadmill and race track tests
Authors: de MOFFARTS B. , KIRSCHVINK N. , ART T. , PINCEMAIL J. , LEKEUX P.
Published: June 2010

Reasons for performing study:Interest in establishing oxidant/antioxidant profiles in competition horses is increasing. Earlier studies performed in horses have mainly been performed under laboratory conditions using a treadmill and it is not known to what extent laboratory results of oxidant/antioxidant studies might be transposed to field conditions.

Objective:To compare the impact on the blood oxidant/antioxidant status of a standardised exercise test including a run up to fatigue performed on a treadmill (TM) and on a racetrack (RT) in healthy and trained Standardbred horses.

Material and methods:During TM and RT tests the following blood antioxidant markers were analysed in jugular venous blood at rest and 15 mins (E15) after an intense bout of exercise: uric acid (UA), ascorbic acid (AA), superoxide dismutase (SOD), glutathione peroxidase (GPx), glutathione (reduced: GSH and oxidised: GSSG), glutathione redox ratio (GRR) and protein thiol (PSH). Running time to fatigue (RTF), velocity during the last exercise stage (Vmax), final heart rate (HRfinal) and venous lactic acid (LA) were also recorded.

Results:Vmaxwas significantly (P<0.05) higher during the RT, whereas LA was significantly lower. HRfinaland RTF did not differ significantly between TM and RT. Exercise induced a significant increase (R vs. E15) of UA and AA in both tests, whereas GSH and PSH decreased significantly. GPx, SOD, GSSG and GRR remained unchanged. Differences between TM and RT were significant at E15 for UA, AA and PSH.

Conclusions:Comparison of oxidant/antioxidant profiles from laboratory and field studies are difficult to standardise and should be interpreted with caution.

Potential relevance:For the same RTF and final HR, the TM induced stronger changes in blood lactate and in blood oxidant/antioxidant balance than did RT.
Changes in arterial, mixed venous and intraerythrocytic concentrations of ions in supramaximally exercising horses
Authors: BAYLY W. M. , KINGSTON J. K. , BROWN J. A. , KEEGAN R. D. , GREENE S. A. , SIDES R. H.
Published: June 2010

Reasons for performing study:Horses experience major perturbations in acid‐base balance during supramaximal exercise. Ion movement in and out of erythrocytes (RBCs) is believed to be important in maintaining acid‐base balance but it is unclear as to the extent to which this happens, nor how it affects single measurements of ion concentrations in arterial and venous blood.

Objectives:To clarify the role RBCs play in mitigating perturbations in acid‐base balance during high speed exercise in horses, and to describe associated differences in arterial (a) and mixed venous (v) concentrations of key ions.

Methods:Six exercise‐trained Thoroughbreds galloped to fatigue at speeds calculated to have an oxygen demand that was 115% of the VO2max. Blood samples (a and v) were collected pre‐exercise, during warm‐up, at fatigue, and immediately post exercise. Packed cell volume (PCV), pH, PCO2, and plasma concentrations of bicarbonate (HCO3−), chloride (Cl−), sodium (Na+), potassium (K+), and lactate (Lac−) and strong ion difference (SID) were determined, and RBC concentrations of Lac−and electrolytes calculated for each sample. Data were analysed using a 2‐way ANOVA for repeated measures testing for effects of sampling time and site (P<0.05).

Results:Plasma and RBC [Cl−] were increased with hypercapnoea and acidaemia. [HCO3−]v was greater than pre‐exercise values at fatigue, although [HCO3−]a was lower. Hyperkalaemia and decreased RBC [K+] were evident at fatigue, as was an increased RBC [Na+]. Plasma [K+] started to decrease as soon as exercise ceased and Na+began to move back onto RBCs in exchange for K+. Concentrations of all measures of Lac−rose from fatigue to post exercise. The SID decreased with exercise and was higher in v at fatigue and post exercise, reflecting the decrease in pH.

Conclusions:RBCs act as a repository for lactate, and therefore the increase in PCV facilitates the maintenance of the muscle to plasma Lac−diffusion gradient during exercise.

Potential relevance:This serves to keep intramuscular [Lac−] lower than it would otherwise be and, because of the link between Lac−accumulation, pH decrease and the onset of fatigue, may help delay the onset of fatigue.
Plasma concentrations of myeloperoxidase in endurance and 3‐day event horses after a competition
Authors: ART T. , FRANCK T. , GANGL M. , VOTION D. , KOHNEN S. , DEBY‐DUPONT G. , SERTEYN D.
Published: June 2010

Reason for performing study: In man, exercise of any type has been shown to induce neutrophil degranulation and respiratory burst activity, as well as an increase in plasma myeloperoxidase (MPO), a specific enzyme of neutrophil azurophilic granules with a strong oxidative activity. Until now, it is not known whether this is the same in horses.

Objectives: To study whether degranulation of blood neutrophils may be induced by exercise by measuring the total concentration of MPO and assess the possible influence of type of competition on this exercise‐induced adjustment.

Methods: Blood was sampled before, and 30 min after, the course, in 9 ponies performing thePhase Dof a national 3‐day event championship (CIC*), and in 7 endurance horses participating at the European endurance championship 2005. White blood cells and granulocytes, total plasma proteins, creatine phosphokinase (CK), and total MPO contents were determined from blood samples. In addition, blood was taken from all ponies and 4 of the endurance horses 5 min after completion of the course to give some idea of the intensity of exercise.

Results: The mean blood lactate was 15.8 ± 5.8 mmol/1 after the CIC* and 2.7 ± 0.2 mmol/1 after the 160 km course. Performing both competitions induced a significant increase in CK and MPO. After the endurance course, the number of granulocytes significantly increased. Whilst there was no significant correlation between the measurements in CIC* ponies, MPO was significantly correlated with granulocyte count (r2= 0.776) and CK (r2= 0.586) in endurance horses.

Conclusions: Intense exercise induces an activation of blood granulocytes, with degranulation of neutrophils and release of MPO. The plasmatic MPO concentration after endurance was higher than the values reported in some inflammatory pathological conditions.

Potential relevance: This phenomenon may partly contribute to the occurrence of an exercise‐induced oxidative stress and to the alteration of muscular membrane permeability. Further studies should be conducted to assess the possible relationship between MPO concentration and markers of oxidative stress in performance horses.
Myosin heavy chain fibre type composition in foals: analyses at the mRNA and protein level
Authors: EIZEMA K. , Van der WAL D. E. , Van den BURG M. M. M. , DINGBOOM E. G. , EVERTS M. E.
Published: June 2010

Reasons for performing study:An optimal developed musculoskeletal system is vital for the performance of the horse. Previously, we showed that in them. gluteus mediusfrom adult untrained horses, identical mRNA and protein expression patterns were found in the majority of fibres. However, co‐expression of IIa and IId/x myosin heavy chain (MyHC) was substantially more common at the protein than at the mRNA level, suggesting a transcriptionally controlled fine‐tuning of these 2 genes.

Objective:To analyse the MyHC transcripts and proteins (including the cardiac alpha isoform) in the same muscle during post natal development when the muscle is adapting to movement and load.

Methods:Biopsies were taken from them. gluteus mediusof 2 Dutch Warmblood foals at 0, 2, 4, 22 and 48 weeks of age. mRNA was compared to protein expression on a fibre‐to‐fibre basis usingin situhybridisation and immunofluorescence. The MyHC slow (I), alpha, IIa and IId/x isoforms were analysed.

Results:At all ages the expression of the mRNA and protein MyHC isoforms was almost identical. Surprisingly, co‐expression of the IIad isoform was also detected at the mRNA level especially early in life. The transcript of the alpha isoform was only detectable at young age, indicating silencing of the gene around birth.

Conclusion:During the first year of life, MyHCs are continuously adapting at the mRNA and protein level. Additionally, the regulation of hybrid fibres is different from that in adult fibres.

Potential relevance:We postulate that interfering in this process by e.g. early training will be levelled out by the maturation of the muscle.
Prevalence of polysaccharide storage myopathy in horses with neuromuscular disorders
Authors: McCUE M. E. , RIBEIRO W. P. , VALBERG S. J.
Published: June 2010

Reasons for performing study:Controversy exists as to the prevalence of polysaccharide storage myopathy (PSSM) in breeds of horses and its impact on performance.

Objectives:To determine 1) the prevalence of PSSM in horses that presented with a neuromuscular disorder, as well as breed, sex and age distributions and clinical signs 2) effect of diagnostic criteria on prevalence, breed distribution and age of horses diagnosed with PSSM.

Methods:Fresh frozen biopsies (n = 1426) submitted to the Neuromuscular Diagnostic Laboratory at the University of Minnesota were searched to identify horses diagnosed with PSSM. Horses with and without histological evidence of PSSM were compared. Biopsies were classified asGrade 1, containing aggregates of granular glycogen orGrade 2, containing periodic acid Schiff's (PAS) positive inclusions, traditionally resistant to amylase digestion.

Results:Horses (n = 572: 40.1%) were identified with PSSM, of which 62.9% were Quarter Horse related breeds (QHR), 11.5% Draught breeds (DB) and 8.9% Warmblood breeds (WB). Exertional rhabdomyolysis was more prevalent in QHR than DB and WB, whereas QHR were less likely to have muscle atrophy compared to DB. QHR were less likely to have gait abnormalities than DB and WB. The highest within breed prevalence of PSSM was in DB at 63/116, WB 58/111 and QHR 360/753. Exclusion ofGrade 1criteria decreased the overall prevalence of PSSM to 21.7% of biopsy submissions, and decreased the within breed prevalence in each breed category. The within breed prevalence decreased most substantially in the breeds less commonly diagnosed with PSSM, Thoroughbreds (4.5%) and Arabians (2.5%).

Conclusion:PSSM is a common cause of neuromuscular disease in QHR, DB and WB related breeds. Inclusion of granular glycogen as the sole diagnostic criterion may increase the sensitivity of this diagnostic test, but conversely it may decrease the specificity of the diagnosis resulting in the inclusion of horses of Thoroughbred, Arabian and other breeds.

Potential relevance:PSSM is an important differential diagnosis for QHR, WB and DB presenting with signs of rhabdomyolysis, gait abnormalities and muscle atrophy.
Muscle, tendon, and somatotropin responses to the restriction of muscle blood flow induced by KAATSU‐walk training
Authors: ABE T. , KEARNS C. F. , FILHO H. C. MANSO , SATO Y. , McKEEVER K. H.
Published: June 2010

Objective:The efficacy of KAATSU training has been demonstrated in human athletes, both as a therapeutic method as well as a training aid. The purpose of this study was to investigate the effects of slow walk training combined with restriction of muscle blood flow (KAATSU) on muscle and tendon size.

Methods:Six healthy, unfit Standardbred mares performed walking (240 m/min for 10 min and then 5 min recovery) with KAATSU, and 6 mares performed walking without KAATSU. A specially designed elastic cuff1was placed at the most proximal position of the forelegs and inflated to a pressure of 200–230 mmHg throughout the walking and recovery sessions. The training was conducted once a day, 6 days/week for 2 weeks. Skeletal muscle thickness and tendon thickness were measured using B‐mode ultrasound at baseline and after 2 weeks of training. Venous blood samples were obtained before the first acute exercise and 5, 15 and 60 min afterwards. Serum somatotropin concentration was determined using a commercially available equine‐specific ELISA kit.

Results:The acute increase in plasma somatotropin was 40% greater (P<0.05) in the KAATSU‐walk group than in the Control‐walk group 5 min after exercise and remained elevated (P<0.05) at 15 and 60 min post exercise compared with the Control‐walk group. After 2 weeks of training, muscle thickness increased (P<0.05) 3.5% in the KAATSU‐walk group but did not change in the Control‐walk group (0.7%). Tendon thickness did not change (P>0.05) in either group.

Conclusions:These data demonstrate that KAATSU training can induce muscle hypertrophy in horses and suggest that KAATSU training may provide significant therapeutic/rehabilitative value in horses, as has been shown in man.
Effect of head and neck position on vertical ground reaction forces and interlimb coordination in the dressage horse ridden at walk and trot on a treadmill
Authors: WEISHAUPT M. A. , WIESTNER T. , von PEINEN K. , WALDERN N. , ROEPSTORFF L. , Van WEEREN R. , MEYER H. , JOHNSTON C.
Published: June 2010

Reasons for performing study:Little is known in quantitative terms about the influence of different head‐neck positions (HNPs) on the loading pattern of the locomotor apparatus. Therefore it is difficult to predict whether a specific riding technique is beneficial for the horse or if it may increase the risk for injury.

Objective:To improve the understanding of forelimb‐hindlimb balance and its underlying temporal changes in relation to different head and neck positions.

Methods:Vertical ground reaction force and time parameters of each limb were measured in 7 high level dressage horses while being ridden at walk and trot on an instrumented treadmill in 6 predetermined HNPs: HNP1 ‐ free, unrestrained with loose reins; HNP2 ‐ neck raised, bridge of the nose in front of the vertical; HNP3 ‐ neck raised, bridge of the nose behind the vertical; HNP4 ‐ neck lowered and flexed, bridge of the nose considerably behind the vertical; HNP5 ‐ neck extremely elevated and bridge of the nose considerably in front of the vertical; HNP6 ‐ neck and head extended forward and downward. Positions were judged by a qualified dressage judge. HNPs were assessed by comparing the data to a velocity‐matched reference HNP (HNP2). Differences were tested using pairedttest or Wilcoxon signed rank test (P<0.05).

Results:At the walk, stride duration and overreach distance increased in HNP1, but decreased in HNP3 and HNP5. Stride impulse was shifted to the forehand in HNP1 and HNP6, but shifted to the hindquarters in HNP5. At the trot, stride duration increased in HNP4 and HNP5. Overreach distance was shorter in HNP4. Stride impulse shifted to the hindquarters in HNP5. In HNP1 peak forces decreased in the forelimbs; in HNP5 peak forces increased in fore‐ and hindlimbs.

Conclusions:HNP5 had the biggest impact on limb timing and load distribution and behaved inversely to HNP1 and HNP6. Shortening of forelimb stance duration in HNP5 increased peak forces although the percentage of stride impulse carried by the forelimbs decreased.

Potential relevance:An extremely high HNP affects functionality much more than an extremely low neck.
Functional anatomy of the caudal thoracolumbar and lumbosacral spine in the horse
Authors: STUBBS N. C. , HODGES P. W. , JEFFCOTT L. B. , COWIN G. , HODGSON D. R. , McGOWAN C. M.
Published: June 2010

Reasons for performing study:Research in spinal biomechanics and functional anatomy has advanced back pain research in man. Yet, despite the performance limiting nature of back pain in horses, there are few data for the equine spine.

Objectives:To describe aspects of functional anatomy of the equine thoracolumbar and lumbosacral (LS) spine and potential effects on performance.

Methods:The first study investigated variations in LS vertebral formula bypost mortemexamination of 120 horses. Midline vertebral transection was carried out on 65 Thoroughbred (TB), 24 Standardbred (SB) and 31 other breeds. The second study investigated morphology and biomechanics of the deep stabilising epaxial muscles of 13 horses using MRI (n=3), anatomical dissection (n=11) and biomechanical analysis (n = 6). The spinous process angular orientation relative to the vertebral body, was analysed at vertebrae T13, T18, L3, L5, L6 and S1.

Results:LS variations were found in 33.3% of the total group, 40.0% TB and 45.2% others, but 0% SB. Sacralisation of lumbar vertebra (L) 6 with LS motion between L5 and L6 occurred in 32.3% TB and 29.0% others. Five segmentalmultifidusfascicles were identified originating from spinous processes and vertebral laminae running craniocaudally onto the mammillary processes and lateral border of the sacrum, crossing between 1–5 intervertebral discs.Sacrocaudalis dorsalis(SCD)lateralismuscle was an extension ofmultifidusfrom L4, L5 and L6 depending on the vertebral formula whereas SCD medialismmoriginated from S3. Both inserted on caudal vertebrae. Based on the location and direction of fibres, the principal action of the deep epaxial muscles was dorsoventral sagittal rotation. This action was dependent on vertebral spinous process/body orientation. We hypothesise that equinemultifidusand SCDlateralismuscles act as caudal sagittal rotators of their vertebra of origin, as is the case in man, allowing dynamic stabilisation during dorsoventral motion.

Conclusion:Equinemultifidusanatomy and function are comparable to that of man. The high prevalence of anatomical variations in the LS spine may affect maximal dorsoventral motion, the stability of the LS joint and, therefore, have consequences for athletic performance. Further studies of these structures are warranted in appropriately selected poorly performing horses.
The effect of head and neck position on the thoracolumbar kinematics in the unridden horse
Authors: ÁLVAREZ C. B. GÓMEZ , RHODIN M. , BOBBERT M. F. , MEYER H. , WEISHAUPT M. A. , JOHNSTON C. , Van WEEREN P. R.
Published: June 2010

Reasons for performing study:In many equestrian activities a specific position of head and/or neck is required that is dissimilar to the natural position. There is controversy about the effects of these positions on locomotion pattern, but few quantitative data are available.

Objectives:To quantify the effects of 5 different head and neck positions on thoracolumbar kinematics of the horse.

Methods:Kinematics of 7 high level dressage horses were measured walking and trotting on an instrumented treadmill with the head and neck in the following positions: HNP2=neck raised, bridge of the nose in front of the vertical; HNP3=as HNP2 with bridge of the nose behind the vertical; HNP4=head and neck lowered, nose behind the vertical; HNP5=head and neck in extreme high position; HNP6 = head and neck forward and downward. HNP1 was a speed‐matched control (head and neck unrestrained).

Results:The head and neck positions affected only the flexion‐extension motion. The positions in which the neck was extended (HNP2, 3, 5) increased extension in the anterior thoracic region, but increased flexion in the posterior thoracic and lumbar region. For HNP4 the pattern was the opposite. Positions 2, 3 and 5 reduced the flexion‐extension range of motion (ROM) while HNP4 increased it. HNP5 was the only position that negatively affected intravertebral pattern symmetry and reduced hindlimb protraction. The stride length was significantly reduced at walk in positions 2, 3, 4 and 5.

Conclusions:There is a significant influence of head/neck position on back kinematics. Elevated head and neck induce extension in the thoracic region and flexion in the lumbar region; besides reducing the sagittal range of motion. Lowered head and neck produces the opposite. A very high position of the head and neck seems to disturb normal kinematics.

Potential relevance:This study provides quantitative data on the effect of head/neck positions on thoracolumbar motion and may help in discussions on the ethical acceptability of some training methods.
Head and body centre of mass movement in horses trotting on a circular path
Authors: CLAYTON H. M. , SHA D. H.
Published: June 2010

McPhail Equine Performance Centre, College of Veterinary Medicine, Michigan State University, East Lansing, Michigan 48824, USA.

Reasons for performing study:Horses are often worked along a circular trajectory but the mechanics of turning have not been reported.

Objective:To develop a methodology for kinematic analysis of horses during circling and to report preliminary findings describing movements of the total body centre of mass (COMbody).

Methods:Seventy‐five skin markers, distributed over the head, neck, trunk and limbs of 5 sound horses, were tracked in a global coordinate system at 120 Hz as the horses trotted around a small circle. Based on segmental inertial data, 3D positions of the segmental centres of mass and COMbodywere calculated. Movements of COMbodywere measured relative to the cylindrical vertical plane, the radius of which was defined by a marker overlying the sixteenth thoracic vertebra.

Results:During trotting, COMbodywas high at the start and end of the diagonal stance phases and low in midstance. All horses leaned to the inside of the circle, with a tilt angle of mean ± s.d. 14.8 ± 2.8° during the entire stride. In the transverse direction, COMbodyswung from side to side reaching its most inward position around the time of contact of the inside forelimb and its most outward position around the time of contact of the outside forelimb. The centre of mass of the head and neck segments (COMhead/neck) had a symmetrical, double sinusoidal pattern in the vertical direction. All horses had the same motion pattern for COMhead/neckin the transverse direction but the mean position relative to the circle line varied between horses.

Conclusions:Horses lean to the inside when turning around a small circle. COMhead/neckand COMbodyshowed 2 vertical oscillations in each stride, whereas there was a single mediolateral excursion that was not symmetrical to the inside and outside of the circle line.

Potential relevance:This study provides a first step toward understanding the mechanics of locomotion during turning, which has implications in the aetiology of injuries, the response to lungeing as a diagnostic technique and the incorporation of circles into rehabilitation exercises.
Harnessed vs. mounted Standardbreds on the track: changes in gait and physiological variables
Authors: MOTTINI V. , LELEU C. , COTREL C.
Published: June 2010

Reasons for performing study:It has become apparent through analysis of elite races over the past 20 years that mounted races are always slower than harnessed races when performed by the same horses over the same distances on the same tracks.

Objectives:To investigate and compare physiological and gait variables in mounted and harnessed activities in trotters.

Methods:Ten trotters were taken at random in 2 standardised field exercise tests one week apart: a harnessed and a mounted test with standardised weight jockeys and drivers. Speed, heart rate (HR), respiratory frequency (RF), blood lactate concentration (La), stride characteristics (length, frequency [SF], symmetry, regularity, dorsoventral displacement of the sternum and vertical, longitudinal and lateral activities measuring the amount of deceleration and acceleration along the 3 axis) were measured.

Results:Pairedttests and an analysis of variance were calculated between the 2 conditions and revealed that V4(speed for a La of 4 mmol/1), V200(speed for a HR of 200 beats/min), stride length, trot symmetry, lateral activity were lower in the mounted condition. In contrast, RF, SF, dorsoventral displacement, vertical and longitudinal activities were significantly higher in mounted horses compared to harnessed horses.

Conclusion:The significant physiological and biomechanical differences between pulling whilst harnessed and being ridden reflect an increase in the energy requirement of locomotion in the mounted condition compared to the harnessed condition. Trotting mounted at maximal speed is more demanding for the horse than harnessed as reflected by the lower V4and V200and some gait variables change in relation to this phenomenon.

Potential relevance:This study demonstrates that trotting mounted at sub‐maximum and maximum speed is more demanding for the horse when ridden and that it modifies some gait variables, either as a result or even as a possible cause.
Correlation between routine radiographic findings and early racing career in French Trotters
Authors: ROBERT C. , VALETTE J.‐P. , DENOIX J.‐M.
Published: June 2010

Reasons for performing study:The relationship between the presence of radiological abnormalities and subsequent racing performance is controversial. However, as training is expensive and time consuming, it would save time and money to identify subjects with osteo‐articular lesions not compatible with a normal racing career on the basis of routine radiographic screenings at yearling age.

Objectives:To evaluate the impact of osteo‐articular lesions on racing ability in French Trotters and identify radiographic changes associated with failure in ‘qualification’, in order to provide objective criteria for selection of horses based on their osteo‐articular status.

Hypothesis:The influence of radiographic findings (RF) on racing ability depends on their nature, location, clinical relevance and number.

Methods:The limbs of 202 French Trotters were radiographed just before they started training. All the RF were graded according to a standardised protocol depending on their severity. The success in ‘qualification’ (first race in career of French Trotters) was the criteria used to assess racing ability. Breeders and trainers were questioned about the causes for horses not racing.

Results:Overall 113 (55.9%) horses qualified. Osteoarticular lesions were directly responsible for nonqualification in 31% of the horses. Subjects with more than one abnormal RF, with abnormal RF on the fore‐, hind‐fetlock or proximal tarsus were less likely to qualify. Dorsal modelling in the front fetlock and osteochondrosis of the lateral trochlear ridge of the femur also significantly reduced the qualification rate.

Conclusions:Most RF are compatible with beginning a racing career, but severe RF or multiple abnormal RF significantly compromise future racing career.

Potential relevance:This study supports the use of routine radiographic programmes for detection of osteoarticular lesions in yearlings. A synthetic radiographic score, based on both the severity and the number of lesions, could be useful for breeders and trainers as complementary information to select their horses.
Evaluation of race distance, track surface and season of the year on exercise‐induced pulmonary haemorrhage in flat racing Thoroughbreds in Brazil
Authors: COSTA M. F. M. , THOMASSIAN A.
Published: June 2010

Reasons for performing study:To our knowledge no studies evaluating risk factors to EIPH have been undertaken with such a population of horses in Brazil, which is one of the few countries in the racing community to accept the use of frusemide (FUR) as a prerace medication for bleeders. We also compared national results with those already in the literature.

Objectives:To verify the influence of variables such as distance of the race, racetrack surface, going and season of the year in the recurrence and severity of EIPH and its effect on the finishing position of flat racing Thoroughbreds in Brazil.

Methods:2118 post race respiratory endoscopies were recorded, in a total of 1003 individual horses. All horses in the study were certified bleeders (deemed positive by registered veterinarians following one or more endoscopies) and were administered FUR prior to each race. Data was analysed using both ordinary logistic regression and multiple logistic regression.

Results:The results suggest that race distance, season of the year and racetrack surface affect the recurrence of EIPH. Also, despite the use of FUR, the majority (62%) of horses continued to display some degree of haemorrhage.

Conclusions:There was a tendency for horses that remained positive despite the use of FUR to finish unplaced in a race. Horses which had a significant reduction in bleeding and became HPIE negative after the use of FUR, tended to finish in top positions. It was not possible to determine a pattern of severity of EIPH in horses with more than one endoscopy. Further studies are required to improve our understanding of this syndrome and its correlations to performance in the racing Thoroughbred, together with the role of FUR and its possible enhancing performance effects and efficacy in consistently diminishing EIPH.

Potential relevance:This study enabled a better understanding of the use of FUR in Brazilian Thoroughbred racehorses and showed there was a tendency towards improvement in performance after administrion of FUR in bleeders. The fact that a large number of horses remained positive for EIPH despite the use of FUR should encourage the scientific community to search for better ways of reducing, or preventing, this syndrome.
The effect of inspired gas density on pulmonary artery transmural pressure and exercise induced pulmonary haemorrhage
Authors: DEATON C. M. , BROWN‐FELTNER H. , HENLEY W. E. , ROBERTS C. A. , LEKEUX P. , SCHROTER R. C. , MARLIN D. J.
Published: June 2010

Reasons for performing study:Pulmonary capillary stress failure, largely as a result of high pulmonary vascular pressures, has been implicated in the aetiology of EIPH. However, the role of the respiratory system in determining the magnitude of EIPH has received little attention.

Hypothesis:Horses breathing a gas of greater density than air will exhibit greater transmural pulmonary arterial pressures (TPAP) and more severe EIPH, and horses breathing a gas of lower density than air will exhibit lower TPAP and less severe EIPH, both compared with horses breathing air.

Methods:Following a warm‐up, 8 Thoroughbred horses were exercised for 1 min at 10, 11 and 12 m/sec (5° incline) breathing air or 21% oxygen/79% helium or 21% oxygen/79% argon in a randomised order. Heart rate, respiratory rate, pulmonary arterial pressure and oesophageal pressure were measured during exercise. Bronchoalveolar lavage fluid (BALF) was collected from the dorsocaudal regions of the left and right lungs 40 min post exercise and red blood cell (RBC) counts were performed.

Results:The exercise tests induced mild EIPH. Maximum changes in oesophageal pressure were lower on helium‐oxygen compared to argon‐oxygen (P<0.001). TPAP and median RBC counts did not differ between gas mixtures. BALF RBC counts from the left lung correlated with counts from the right lung (P<0.0001). However BALF RBC counts from the left lung were higher than those from the right lung (P = 0.004).

Conclusion:As alterations in pulmonary arterial and oesophageal pressure caused by changes in inspired gas density were of similar magnitude, TPAP remained unchanged and there was no significant effect on EIPH severity.

Potential relevance:Manipulations that decrease swings in intrapleural pressure may only decrease the degree of EIPH in horses severely affected by the condition.
Correlations between exercising arterial blood gas values, tracheal wash findings and upper respiratory tract abnormalities in horses presented for poor performance
Authors: DURANDO M. M. , MARTIN B. B. , DAVIDSON E. J. , BIRKS E. K.
Published: June 2010

Reasons for performing study: There are limited data on the correlations between arterial blood gas (ABG) values, tracheal wash (TW) cytology and upper respiratory tract (URT) abnormalities.

Objectives: To identify horses with abnormal exercising ABG, and compare the proportions of horses with abnormal ABG and TW cytology, mucus or URT dysfunction with those with normal ABG results and abnormal TW cytology, mucus or URT dysfunction.

Methods: Medical records of 813 horses presenting to the treadmill facility that had a complete treadmill examination, including ABG analysis, TW and URT endoscopy were selected. Diagnoses, ABG results, TW cytology and URT endoscopy were compared.

Results: Two hundred and eleven horses met the study criteria of a complete treadmill examination and could have ABG evaluated. There were no significant differences in the age distribution of horses having normal and abnormal ABG or upper respiratory tract (URT) examinations. There was a significantly higher percentage of geldings with abnormal ABG analysis. In the horses with abnormal URT examinations, there were no differences in the proportion of horses having mucus vs. no mucus. However, in the horses with normal URT, there were a higher percentage of horses with visible mucus in the group with abnormal ABG analysis. The majority of horses had abnormal TW cytology and evidence of prior EIPH, with no differences in proportions between the groups.

Conclusions: Because such a large percentage of horses had evidence of inflammation and/or evidence of prior EIPH on TW cytology, it was not possible to determine the effect of these findings on gas exchange. Mucus was present in a larger percentage of cases with abnormal ABG analysis and normal URT examinations, suggesting that the presence of mucus may affect gas exchange. Standardbreds may be more likely to have abnormal gas exchange than Thoroughbreds. A larger number of horses is needed to determine the significance of these findings.

Potential relevance: Abnormal TW cytology and endoscopic visualised mucus may contribute to impairment of gas exchange, but they do not specifically predict abnormal ABG analysis.
Haematological and respiratory gas changes in horses and mules exercised at altitude (3800 m)
Authors: GREENE H. M. , HURSON M. J. , WICKLER S. J.
Published: June 2010

Reason for performing study:Despite the common use of equids as visitors to high altitude mountainous environments, there are a paucity of carefully orchestrated scientific approaches. Further, again as a function of a common perceived advantage of mules over horses in these similar environments there are needs for controlled comparisons between these 2 equids.

Objective:To measure haematological and respiratory function in horses and mules at low altitude (225 m), at rest and post exercise. In addition the rate and magnitude of these changes were followed over a 13 day period at high altitude (3800 m) to contrast acclimatisation.

Methods:Resting and exercise venous blood samples (1 min post exercise) were obtained from 6 horses and 5 mules housed at 225 m (LA) and then transported to 3800 m (HA) for 13 days. The standardised exercise tests at both LA and HA consisted of trotting (3.0 m/sec) up an incline (6%) for 2 km. Data were analysed with repeated measures ANOVA (comparison of altitude acclimatisation and species) for changes in haematological and respiratory gases.

Results:At low altitude, no group differences were found with both resting (P=0.69) and exercising (P=0.74) heart rates. Resting PCV was 8% lower in the mules (P=0.02) and 20% lower during exercise (P=0.02). Horses had significantly higher 2,3‐diphosphoglycerate (2,3‐DPG)/g Hb at both rest (P=0.003) and exercise (P=0.03). Exercise at HA increased PCV (P=0.03) in both groups, but the increase was attenuated in the mules compared to horses. The increase with 2,3‐DPG/g Hb was expressed at HA in both groups (P=0.001) and was also attenuated in mules (P=0.03). Both groups were alkalotic compared to LA (P=0.001), and there were no group differences (P = 0.95).

Conclusion:Of the variables measured, the most notable distinction between species was identified for only PCV and 2,3‐DPG with both higher in horses, at both LA and HA. While the attenuated response of PCV in mules for the same exercise might argue for an improved adaptation to altitude, the lower 2,3‐DPG might not. Other variables during the exercise bout were not different between species.