bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of trotting speed, load and incline on hindlimb stance‐phase kinematics
Authors: HOYT D. F. , MOLINARI M. , WICKLER S. J. , COGGER E. A.
Published: June 2010

The objective was to understand how the stance‐phase kinematics of the hindlimb of trotting horses change with speed under 3 conditions (level, loaded and incline), to compare our results with the predictions of the spring‐mass model and to help focus our future studies of muscle function. Video recordings were made of 5 Arabian horses trotting on a treadmill. Five consecutive strides were digitised and averaged for each trial. The angle‐time diagrams were qualitatively similar to those reported previously. As speed increases, the range of motion of the hindlimb increases, as predicted by the spring‐mass model. This is the result of increased range of motion in the coxofemoral and tarsal joints. The hindlimb does not ‘land short ‐ take off long’. When trotting up an incline, the hindlimb undergoes a greater range of motion because of increased retraction resulting from increased extension of the coxofemoral joint. At hoof contact on an incline, the 3 proximal joints are more flexed than on the level. Carrying a load had no effect on kinematics. These results suggest that there may be larger changes in strain with speed in muscles acting at the coxofemoral and tarsal joints than at the femorotibial joint, and that locomotion up an incline will change muscle strain more than carrying a load.
Analysis of trotter gait on the track by accelerometry and image analysis
Authors: LELEU C. , GLORIA E. , RENAULT G. , BARREY E.
Published: June 2010

The aim of this study was to describe the correlation between the phases of the limb cycle of trotters on the track and specific points on the acceleration curves obtained from a new gait analysis system. We compared kinematic data obtained by video image analysis and 3‐dimensional acceleration recordings made on 3 French trotters in training. They trotted on a race track at speeds of 8.33, 10 and 11.66 m/s, with a final stretch at maximum speed. Their locomotion was recorded with a synchronised video camera at a frame frequency of 200 Hz and with the Equimétrix gait analysis system. The gait variables were calculated using 3‐dimension acceleration data recorded at the sternum (dorso‐ventral, longitudinal and lateral axes) at a sampling rate of 100 Hz.

Three phases of the stride were clearly identified on the dorsoventral acceleration signal: hoof‐landing, midstance phase and toe‐off. Braking and propulsion phases were identified on the corresponding longitudinal acceleration signal. The weight‐bearing diagonal was identified by observing the lateral signal. The stride temporal variables (stride, stance, braking and propulsion durations for both diagonals), measured by video analysis and by acceleration signal analysis, were not significantly different (P>0.05). The identification of specific points on the acceleration pattern allowed an accurate temporal analysis of the stride. Potential applications could be the determination of locomotor factors related to racing performance or assessment of locomotor disorders at high speed.
Biomechanical implications of uphill training on the aetiology of tendinitis
Authors: TAKAHASHI T. , KAI M. , HADA T. , ETO D. , MUKA K. , ISHIDA N.
Published: June 2010

It has been reported that a small decrease in the strain in the superficial digital flexor tendon (SDFT) occurs if the toe is raised during walking. Although walking on a slope appears similar to raising the toe, it is unclear whether uphill exercise decreases the strain in the SDFT. Because the force or strain on tendons is one of the important factors leading to tendon stress injury, we hypothesised that reducing the force in the SDFT during exercise may prevent tendinitis. The purpose of this study was to determine the effects of treadmill inclination on the force in the SDFT in the walking horse. ‘Arthroscopically implantable force probes’ (AIFP) were implanted into the SDFT of the forelimb of 4 horses. The AIFP output was recorded during walking on a treadmill inclined at 0%, 3%, 8% and then 0% again. When the inclination increased from 0 to 8%, the first peak of force in the SDFT decreased significantly, the second increased significantly, but the maximal force and the area under the force‐time curve did not change. In conclusion, uphill walking on an inclined treadmill did not decrease the maximal force in the SDFT or the area under the force‐time curve, however, the patterns of force were altered.

Future research should focus on the force distributions of tendons and ligaments at faster gaits, because the effects of a change in hoof angle and slope may be greater at faster gaits.
Movements of thoracic and abdominal compartments during ventilation at rest and during exercise
Authors: MARLIN D. J. , SCHROTER R. C. , CASHMAN P. M. M. , DEATON C. M. , POOLE D. C. , KINDIG C. A. , McDONOUGH P. , ERICKSON H. H.
Published: June 2010

The present investigation utilised simultaneous measurements of chest (Ch) and abdominal (Ab) circumferences and respiratory airflow to test the hypothesis that Ch circumferential expansion contributes proportionally little to tidal volume in the running Thoroughbred. During exercise, there were only small changes in Ch and Ab circumference and no increase with increasing tidal volume. At rest, walk and trot, the flow, Ch and Ab signals were in phase. However, during canter and gallop, the Ch and Ab changes were 180° out of phase with each other and both were out of phase with airflow. In contrast to exercise, increase in ventilation at rest achieved by administration of lobeline resulted in a 4–6‐fold increase in tidal volume; large excursions of the chest were always in phase with airflow. Furthermore, 3 horses showed an increase in chest circumference, demonstrating that chest stiffness per se does not preclude chest circumferential expansion. In conclusion, in the absence of significant increases in either Ch or Ab expansion during running, elongation of the thoracoabdominal segment may be the main determinant of tidal volume.
Dynamic upper airway changes and arterial blood gas parameters during treadmill exercise
Authors: DURANDO M. M. , MARTIN B. B. , HAMMER E. J. , LANGSAM S. P. , BIRKS E. K.
Published: June 2010

The primary goal was to investigate the relationship between dynamic upper airway abnormalities and arterial blood gas tensions during exercise. Horses that completed a high‐speed treadmill examination consisting of upper‐airway videoendoscopy, blood gas evaluation and electrocardiogams and, postexercise, echocardiograms and tracheal washes, were included. An age‐matched group of fit, healthy Thoroughbreds, trained to run on a high‐speed treadmill, served as controls for blood gas values at specific exercise speeds.

One hundred and nineteen horses completed the treadmill examination. Sixty (50%) were Thoroughbreds (TB), 51 (43%) Standardbreds (STD) and 8 (7%) other breeds. Mean ± s.d. age TB 3.8 ± 2.2 years and STD 4.0 ± 1.7 years, with no gender predilection. Fifty‐four horses (45%) had abnormal upper respiratory tract (URT) abnormalities alone or in combination with abnormalities in another body system. Thirty‐eight (70%) were TB, 14 (26%) were STD and 2 (4%) were other breeds. Of these, 24 (45%) had exercising Pao2 values significantly lower than those observed in healthy TB. Nineteen (35%) horses also had significantly elevated exercising PaCo2. Only 14 (12%) horses had abnormal clinical findings in the URT alone, and of these, only 3 (21%) had an abnormally low Pao2 and/or elevated Paco2. Multiple URT abnormalities were more commonly associated with abnormal exercising blood gases than were single disorders, but pharyngeal collapse (PC) was much more commonly associated with abnormal values if only one disorder was detected. Fifty‐five percent (n = 65) of all cases admitted had no evidence of URT disease. Twenty‐two (35%) were TB and 37 (57%) were STD. Twenty (31%) of these had abnormally low Pao2 and 14 (22%) had elevated PaCo2 values. Seventy percent (14) of the horses with abnormal Pao2 were STD, while almost 80% (11) of the horses with elevated Paco2 were STD.

These data suggest that dynamic URT dysfunction can adversely affect gas exchange during exercise. While multiple abnormalities were more commonly associated with gas exchange problems than were single disorders, pharyngeal collapse, either alone or in combination with other URT problems, was the disorder most frequently associated with blood gas abnormalities. Additionally, URT disease was more commonly seen in TB, and the proportion of URT diagnoses in horses with abnormal blood gases reflected this percentage, while STD without URT disease had a much higher incidence of abnormal blood gases than did TB without URT abnormalities.
Evidence of an association between inflammatory airway disease and EIPH in young Thoroughbreds during training
Authors: NEWTON J. R. , WOOD J. L. N.
Published: June 2010

In an epidemiological study of risk factors for exercise‐induced pulmonary haemorrhage (EIPH) in young Thoroughbreds in the UK, in which 148 horses contributed 1614 horse‐months of data, there were 64 (4%) episodes of endoscopically visible tracheal bleeding and 824 (51%) episodes of increased quantities of haemosiderophages in tracheal washes. There were increases in prevalence and risk of EIPH by both definitions with age from < 2‐> 4 years, season of sampling from winter (Nov‐Jan) to autumn (Aug‐Oct) and several different measures of airway inflammation, including tracheal mucus, neutrophil proportion, inflammation score and fungal material in tracheal washes. There was considerable variability in the prevalence of EIPH between trainers. EIPH in the preceding month significantly increased the risk of the condition the following month. There was no evidence that EIPH was associated with infection of the airways with even large numbers ofStreptococcus zooepidemicusorPasteurella‐like spp., which are significantly associated with airway inflammation in younger racehorses. Multiple logistic regression modelling that took account of random variability between horses and the effects of each trainer and an episode the preceding month, confirmed that after controlling for the other risk factors, EIPH was still significantly associated with increasing age, different seasons, airway inflammation and evidence of airway fungal material.
Hyperhydration prior to moderate‐intensity exercise causes arterial hypoxaemia
Authors: LEON L. SOSA , HODGSON D. R. , EVANS D. L. , RAY S. P. , CARLSON G. P. , ROSE R. J.
Published: June 2010

The second day of a 3‐day event is the most physically demanding of the 3 days. If this is performed under hot and humid environmental conditions, detrimental effects on cardiovascular and thermoregulatory function and, therefore, on exercise capacity, may occur due to exercise‐induced dehydration. We hypothesised that the administration of fluid equivalent to 6% of the horse's bodyweight prior to a simulated second day of a 3‐day event would increase plasma volume and limit increases in core temperature. Seven Standardbred geldings underwent a training protocol prior to the study. A standardised exercise test was developed for each horse so that exercise intensity at each phase would be the same percentage of the maximal heart rate for all horses. The exercise test involved 4 phases: Phase A involved 30 min exercise at 3.7 m/s (∼25% V̇O2max); Phase B 4 min exercise at 8 m/s (∼60% V̇O2max); and Phase C 50 min at 3.7 m/s, after which there was a 10 min rest. Phase D involved 14 min at 7.3 m/s (55% V̇O2max). In a cross‐over design, horses were grouped randomly and allocated to either exercise with no fluid (control) or ∼26 I isotonic fluid by nasogastric tube, 120 min prior to exercise. Arterial and mixed venous blood samples were collected prior to exercise, towards the end of each of the phases and during the rest period. The administration of fluid prior to exercise resulted in a pre‐exercise bodyweight gain of 21.3 ± 1.2 kg. Hyperhydration resulted in a greater degree of arterial hypoxaemia than the control group in Phases B and D, but not in Phases A and C or at rest. During Phases B and D, mean PaO2 values in the horses that received fluid were about 15 torr lower than in the control group, but there were no differences in PaCO2 values between the 2 groups. In both arterial and mixed venous blood, pH and HCO3‐ were significantly lower in the group that were hyperhydrated. We concluded that the most likely cause of the more severe arterial hypoxaemia in the hyperhydrated group during the intense exercise phase was some degree of pulmonary oedema, from the extravasation of the administered fluid.

Hyperhydration prior to exercise may be detrimental to respiratory function and therefore care must be taken in administration of large volumes of fluid prior to exercise.
The effect of a tongue‐tie in horses with dorsal displacement of the soft palate
Authors: FRANKLIN S. H. , NAYLOR J. R. J. , LANE J. G.
Published: June 2010

Tongue‐ties are frequently used in an attempt to prevent dorsal displacement of the soft palate (DDSP). The aim of this study was to determine the efficacy of a tongue‐tie in horses clinically affected with the disorder. Videoendoscopic recordings and measurements of respiratory airflow were made simultaneously during high intensity treadmill exercise in 6 Thoroughbred racehorses with confirmed DDSP, with and without a tonguetie. DDSP was confirmed in all 6 horses without the tongue‐tie but occurred in only 4 horses with the tongue‐tie in place. In one horse the palate displaced only on slowing down after intense exercise and in the other horse DDSP did not occur although palatal instability remained. The presence of the tongue‐tie did not result in any significant alteration in run‐time to fatigue or in any of the respiratory variables measured. The results suggest that the use of a tongue‐tie may prevent DDSP in individual horses although it is not effective in the majority, consistent with the widely accepted anecdotal reports of success rates for its use. Where DDSP was not prevented, application of a tongue‐tie did not improve ventilation.
Exercise‐induced pulmonary perfusion redistribution in heaves
Authors: HARMEGNIES N. F. , DUVIVIER D. H. , VANDENPUT S. N. , ART T. , LEKEUX P. M. , VOTION D. M.
Published: June 2010

This study aimed to compare exercise‐induced pulmonary perfusion redistribution in healthy vs. ‘heavey’ horses using scintigraphy, a minimally invasive technique. Six healthy (A) and 5 ‘heavey’ horses in remission (BI) and during clinical signs of disease (BII) were investigated. Dimensions of the exercising pulmonary perfusion (QE) images were expressed in percent of the resting perfusion (QR) images. Computed QEto QRratios (QE/QR) images enabled the definition of the region more perfused at exercise than at rest (R1).

In all groups, exercise induced a major enlargement of the Q image but a larger increase of the lung height was found in ‘heavey’ horses. Compared to A, ‘heavey’ horses showed a larger R1region with a significantly higher QE/QR. Location of R1pointed out the dorsal lung region as a major site of pulmonary perfusion redistribution for all groups.

This work demonstrated (1) the feasibility of using scintigraphy for studying exercise‐induced pulmonary perfusion redistribution; (2) perfusion redistribution to the dorsal lung with exercise and (3) an intensified redistribution in ‘heavey’ horses, either clinically affected or not.
Thermoregulatory‐induced compromise of muscle blood flow in ponies during intense exercise in the heat: a contributor to the onset of fatigue?
Authors: McCONAGHY F. F. , HODGSON D. R. , HALES J. R. S. , ROSE R. J.
Published: June 2010

Cardiac output (Q) and tissue blood flows (BF) were measured in four ponies at rest, after 30 min of moderate exercise (ME) (∼30% V̇O2max) and following moderately intense exercise (M‐IE) (∼65%) until fatigue, in a mildly hot (MH) environment (dry bulb temperature = 41°C, wet bulb temperature = 27.5°C). Exercise at both intensities resulted in increases in Q (15.6 ± 1.7 [rest] vs. 35.8 ± 2.6 [ME] vs. 48.6 ± 3.9 [M‐IE] l/min) and V̇O2(4.7 ± 0.9 vs. 24.5 ± 1.2 vs. 55.8 ± 5.8 ml/kg/min). When compared to ME, M‐IE resulted in decreases in BF to the skin (∼15%), nonworking muscle (46%), fat (93%), gut (56%), kidneys (57%), CNS (31–66%) and an increase in BF to respiratory (68%), limb (98.5%) and cardiac (50%) muscles. In contrast, BF to working muscle during ME in thermoneutral (TN) conditions (McConaghyet al.2002) was higher than found during ME in MH. We calculated that limb BF was ∼25% lower for ME in MH vs. ME in TN. Similarly, we estimated that limb BF during M‐IE in MH was ∼25% lower than for M‐IE in TN. Attenuation of the increases in muscle BF during exercise in the heat may be a determinant of the onset of fatigue.
Effects of somatotropin and training on indices of exercise capacity in Standardbreds
Authors: GERARD M. P. , HODGSON D. R. , LAMBETH R. R. , RAY S. P. , ROSE R. J.
Published: June 2010

The recent availability of recombinant equine somatotropin (eST) has led to concern about its use as an ergogenic aid in racehorses. This study was undertaken to investigate the changes in exercise capacity in maturing horses in a training programme, and to assess whether eST is an ergogenic aid to this group. We tested the hypothesis that the combination of training and eST, compared to training alone, would further improve exercise capacity in maturing Standardbreds, by virtue of ST's anabolic effects and potential to enhance cardiac function, circulating fluid volume and red cell mass. Twelve, untrained Standardbreds (mean ± s.d. 20.7 ± 1.1 months) were paired according to similar bodyweight and then assigned randomly to treatment or control group. The horses underwent a 12 week treadmill training programme. Methionyl eST (10 μg/kg for the first 7 days, then 20 μg/kg) was administered once daily, i.m., for 42 consecutive days (Weeks 4 to 9 inclusive) to 6 horses in the treatment group. All horses performed a standardised maximal exercise test to fatigue at Weeks 0, 3, 6, 9, and 12. During each exercise test V̇O2, Vco2, plasma lactate concentrations ([La]), heart rates, blood volume and total run time were measured.

There was no significant effect of eST administration on V̇O2max, V200, VLA4, LA9, red cell volume (RCV), plasma volume (PV), or run time to fatigue. Combining the data for all horses, training significantly altered the V̇O2max(mean ± s.d. 98.2 ± 11.1 ml/kg/min in Week 0 to 117.6 ± 4.8 ml/kg/min in Week 12), VLA4(5.1 ± 0.8 m/s to 7.4 ± 1.0 m/s), LA9(12.7 ± 3.9 mmol/l to 7.1 ± 1.9 mmol/l), RCV (46.3 ± 4.7 ml/kg to 63.5 ± 5.0 ml/kg), PV (46.0 ± 4.8 ml/kg to 57.0 ± 6.3 ml/kg), and run time to fatigue (431.8 ± 30.9 to 490.2 ± 30.5 s), but not V200(5.0 ± 0.5 m/s to 5.2 ± 1.1 m/s). The administration of eST to young Standardbred horses in training did not significantly improve their exercise capacity or indices of fitness. However, these maturing horses demonstrated a rapid physiological response to training exercise. Further research is required to determine the relationship between exercise capacity and ST in the horse.
Evaluation of binding of fibrinogen and annexin V to equine platelets in response to supramaximal treadmill exercise
Authors: KINGSTON J. K. , BAYLY W. M. , MEYERS K. M. , SELLON D. C. , WARDROP K. J.
Published: June 2010

There is evidence that equine platelet reactivity is altered by strenuous exercise. Changes in platelet reactivity could impact haemostasis following exercise‐induced injury and may play a role in the pathophysiology of exercise‐induced pulmonary haemorrhage. Interpretation of results of previous studies is hindered by potentialin vitro‐induced changes in platelet activity through the choice of anticoagulant and the use of platelet inhibitors. The present study was undertaken to re‐evaluate the effect of exercise on equine platelets using methodologies that minimisein vitro‐induced changes in platelet activation.

The percentage of platelet‐neutrophil aggregates increased significantly (P = 0.01) from mean ± s.e. 3.5 ± 0.6% at rest to 7.2 ± 1.3% during exercise. There were no significant changes in binding of anti‐fibrinogen antibody or annexin V to platelets in response to exercise.

An inability to detect increased binding of fibrinogen or annexin V may be a result of poor test sensitivity or low statistical power. Alternatively, activated platelets may be quickly removed from the circulation and miss detection. The significance of increased numbers of platelet‐neutrophil aggregates in association with exercise is currently unknown and warrants further investigation.
Effect of body incline on cardiac performance
Authors: McDONOUGH P. , KINDIG C. A. , HILDRETH T. S. , BEHNKE B. J. , ERICKSON H. H. , POOLE D. C.
Published: June 2010

Maximal cardiac performance is improved in man during upright compared to supine exercise. Whether cardiac performance in quadrupeds is dependent upon body position is unknown. Therefore, we undertook the present investigation to determine if peak cardiac output (Qpeak) would be influenced by body inclination in the Thoroughbred horse. To test the hypothesis, four Thoroughbred horses performed an incremental exercise protocol (speed increased by 1 m/s/min to fatigue) on both a level (L) and inclined (I: 6°) treadmill. Specifically, we hypothesised that Qpeak would be increased on the incline, as this represents a progression towards upright exercise. Cardiac output was determined using the Fick relationship from continuous measurements of pulmonary V̇O2 and paired arterial (carotid artery or transverse facial) and mixed venous (pulmonary artery) samples. Qpeak was significantly increased on the incline (L: 279 ± 20; I: 336 ± 17 l/min; P<0.05), while CaO2 was not significantly different (L: 25.5 ± 1.1; I: 25.4 ± 1.9 ml/100 ml), and therefore, whole body O2 delivery (QO2) was significantly increased (L: 70.7 ± 4.9; I: 84.4 ± 3.1 l/min; P<0.05). In conclusion, within the scope of this investigation, these data suggest that cardiac performance, as judged by increased Qpeak and QO2, is enhanced in the inclined body position. Furthermore, these findings provide preliminary information that level and incline treadmill exercise tests may yield significantly different results in the Thoroughbred horse and consequently this factor should be considered when interpreting exercise testing and performance data.
Drinking salt water enhances rehydration in horses dehydrated by frusemide administration and endurance exercise
Authors: BUTUDOM P. , SCHOTT H. C. , DAVIS M. W. , KOBE C. A. , NIELSEN B. D. , EBERHART S. W.
Published: June 2010

Because the primary stimulus for thirst is an increase in plasma tonicity, we hypothesised that dehydrated horses would drink a greater total volume of fluid voluntarily during the first hour of recovery when they were initially offered salt water. To test this hypothesis, bodyweight (bwt), fluid intake (FI) and [Na+] were measured in 6 Arabian horses offered 3 rehydration solutions. After dehydration was induced by frusemide administration (1 mg/kg bwt, i.v.) followed by 45 km treadmill exercise, water (W), 0.45% NaCl and 0.9% NaCl were offered, in a randomised order, during the initial 5 min after completing exercise. Horses were subsequently placed in a stall and further intake of plain water during the first hour of recovery was measured. By the end of exercise, horses lost 5.2 ± 0.2, 5.6 ± 0.3 and 5.7 ± 0.2% (P>0.05) bwt and FI during the first 5 min of recovery was 10.5 ± 0.7, 11.6 ± 0.8 and 11.6 ± 1.5 l (P>0.05) for W, 0.45% NaCl and 0.9% NaCl, respectively. After 20 min of recovery, [Na+] had decreased with W but remained unchanged from the end exercise values for both saline solutions. During the initial hour of recovery, further water intake was 0.9 ± 0.4, 5.0 ± 0.5 and 6.9 ± 0.7 l (P<0.05) for W, 0.45% NaCl and 0.9% NaCl, respectively. Therefore, total FI was 11.4 ± 0.5, 16.6 ± 0.7 and 18.5 ± 1.7 l (P<0.05) for W, 0.45% NaCl and 0.9% NaCl, respectively, and persisting bwt loss after 60 min of recovery was greater (P<0.05) for W (3.5%) than for the 2 saline solutions (2.4% for 0.45% NaCl and 1.9% for 0.9% NaCl). In conclusion, providing salt water as the initial rehydration fluid maintained an elevated [Na+] and resulted in greater total FI and recovery of bwt loss during the first hour of recovery, in comparison to offering only plain water.
Potassium and lactate uptake by noncontracting tissue during strenuous exercise
Authors: SCHOTT H. C. , BOHART G. V. , EBERHART S. W.
Published: June 2010

Efflux of potassium (K+) and lactate (lac−) from active skeletal muscle during high intensity exercise leads to increased plasma [K+] and [lac−] in venous and arterial blood. The exercise‐induced increases in these ions in human athletes is ameliorated, in part, by uptake by noncontracting tissue, reflected by an increase in the arteriovenous difference across these tissues from rest to exercise. To test the hypothesis that these ions are taken up by noncontracting tissue in strenuously exercising horses, plasma [K+] and [lac−] were measured in blood samples collected simultaneously from the carotid artery (CA), femoral vein (FV), and transverse facial vein (TFV) in 5 unconditioned Standardbred horses performing 4.5 min of strenuous treadmill exercise. Further, the arteriovenous differences ((a‐v)diff) in [K+] and [lac−] were calculated across active tissue (CA‐FV) and noncontracting tissue (CA‐TFV). After 3 min of strenuous exercise, plasma [K+] in FV blood (mean ± s.e. 7.1 ± 0.2 mmol/l) was greater (P<0.05) than in CA blood (6.8 ± 0.2 mmol/l) and both of these concentrations were greater (P<0.05) than a value of 5.7 ± 0.1 mmol/l in TFV blood. Similarly, plasma [lac−] increased to 20.6 ± 0.8 and 21.1 ± 0.8 mmol/l in CA and FV blood, respectively, and these concentrations were greater (P<0.05) than a value of 19.1 ± 0.8 mmol/l in TFV blood. The magnitude of the (a‐v)difffor both [K+] and [lac−] increased (P<0.05) across active and noncontracting tissue during highspeed exercise but the directions were opposite, supporting release by active tissue and uptake by noncontracting tissue. These results confirm that uptake of K+and lac−by noncontracting tissue contributes to regulation of the plasma concentrations of these ions in strenuously exercising horses.
Effect of sodium bicarbonate administration on metabolic responses to maximal exercise
Authors: SCHUBACK K. , ESSÉN‐GUSTAVSSON B. , PERSSON S. G. B.
Published: June 2010

Administration of bicarbonate has been shown to cause metabolic alkalosis both in man and in horses and is, therefore, thought to increase the buffering capacity of the body and thereby delay the onset of fatigue. However, results regarding the influence of sodium bicarbonate loading on performance both in human athletes and in horses are conflicting. The aim of this study was, therefore, to investigate the metabolic response to a standardised treadmill exercise test to fatigue, in horses given bicarbonate (0.6 g/kg bwt), in comparison to horses given placebo (water). Five Standardbred trotters performed the test on 2 occasions. Venous blood samples were collected before and after administration of test substance, during exercise and during recovery. Muscle biopsy specimens were taken at rest, postexercise and at 15 min of recovery. The increases in pH and concentration of bicarbonate in the blood and the shift seen in base excess showed that the administration of sodium bicarbonate caused metabolic alkalosis. Exercise caused similar decreases in muscle ATP, CP and glycogen and similar increases in muscle IMP, lactate and plasma lactate and uric acid concentrations both in the placebo‐ and bicarbonate‐treated group. The effect upon postexercise muscle and plasma metabolites was similar with both test treatments. Duration of exercise did not change after sodium bicarbonate intake. In conclusion, sodium bicarbonate caused metabolic alkalosis, but did not affect the metabolic response or duration of exercise.
Changes in selected physiological and laboratory measurements in elite horses competing in a 160 km endurance ride
Authors: II H. C. SCHOTT , MARLIN D. J. , GEOR R. J. , HOLBROOK T. C. , DEATON C. M. , VINCENT T. , DACRE K. , SCHROTER R. C. , JOSE‐CUNILLERAS E. , CORNELISSE C. J.
Published: June 2010

Reason for performing study:Limited information exists about the physiological changes and clinical problems that occur in elite horses competing in high‐speed 160 km endurance races.

Objectives:To provide initial data describing changes in physiological and laboratory measurements in horses competing in a high‐speed, 160 km endurance race under temperate conditions and to compare data between horses that successfully completed the race and those that failed to finish.

Methods:Body mass (BM) was measured, blood samples were collected, and veterinary examinations performed on horses before, during, and at the finish of a CEI*** 160 km endurance race.

Results:Of 36 horses participating in the study, 22 (61%) completed the race. Twelve horses were eliminated for lameness and 2 for persistent heart rate elevation. Mean speed of finishers was 15.2 km/h. Mean ± s.d. BM loss of finishers at the end of the race (5.7 ± 2.6%) was not different (P = 0.58) from BM loss of nonfinishers at elimination (6.7 ± 3.4%). Similarly, there were no significant differences in heart rate or veterinary assessment of hydration at the race end for finishers as compared to the elimination point for nonfinishers. PCV increased while sodium, chloride and potassium concentrations decreased with exercise but differences between finishers and nonfinishers were not detected. In contrast, both total and ionised calcium concentrations decreased in successful horses but remained unchanged in nonfinishers.

Conclusions:Elite endurance horses are more likely to be eliminated from competition for lameness than metabolic problems; however, it remains unclear whether these conditions are entirely distinct. The magnitude of the decrease in sodium concentration in both finishers and nonfinishers was greater than in previous reports of 160 km rides.

Potential relevance:These data should be of use for both organisers and participants in elite 160 km endurance races. The tendency toward hyponatraemia as well as the difference in calcium concentrations between finishers and nonfinishers warrant further study.
Equine locomotor analysis on vet‐gates in endurance events
Authors: RIBER C. , CUESTA I. , MUÑOZ A. , GATA J. , TRIGO P. , CASTEJÓN F. M.
Published: June 2010

Reasons for performing the study:Fatigue during endurance rides might induce changes in gait pattern that could be difficult to distinguish from subtle lameness.

Objectives:To assess changes in gait patternen route, in fore‐(FL) and hindlimbs (HL) and establish differences between excellent (EP) and good performers (GP).

Methods:Seventy‐five sound and fit horses that completed endurance rides of 80 km were filmed at trot in the vet‐gates (VGs) prior to competitions (VG0), and at 29 km (VG1), 59 km (VG2) and 80 km (VG3). Mean gait velocity (V), stride length (SL), duration (SD) and frequency (SF) were measured. Also, stance (StD), swing (SwD), braking (BrD) and propulsion (PrD) durations were determined in the 4 limbs and expressed as % of SD.

Results:Horses trotted with a significant lower V at VG3 in comparison to VG0 (mean ± s.d. 2.3 ± 0.6 m/sec, 3.3 ± 0.6m/sec) and showed a shorter SL (1.5 ± 0.4 m and 2.2 ± 0.3 m in VG0 and VG3). Regression analysis confirmed that the reduced SL at VG3 was due to the lower V. Horses in VG3 presented longer FL‐StD (46.2 ± 4.7%, 38.1 ± 4.6%), BrD (22.0 ± 2.5%, 16.9 ± 2.5%) and PrD (24.1 ± 2.2%, 21.5 ± 2.47%) compared to VG0. In VG0, HL‐PrD (23.0 ± 3.0%) and HL‐BrD (18.7 ± 1.8%) were longer than FL‐PrD (21.5 ± 2.47%) and FL‐BrD (16.9 ± 2.5%). EP showed fastest V and longer SL at VG0, and VG3 than GP (P<0.05).

Conclusions:Sound endurance horses undergo changes in gait pattern during competition, mainly due to reduction of V. Some differences exist between FL and HL, and EP show higher V and SL in the VGs.

Potential relevance:Understanding of the locomotor effect of fatigue will provide an objective basis for the assessment of soundness during endurance events.
A nonsurgical method allowing continuous core temperature monitoring in mares for extended periods, including during endurance exercise
Authors: SMITH J. E. , BARNES A. L. , MALONEY S. K.
Published: June 2010

Reasons for performing study:Body temperature can be a useful measure of how well the horse responds to thermal challenges of exercise and environment. Currently there is little information available about how body temperature changes throughout an endurance ride, and no nonsurgical methods to evaluate internal temperature of exercising horses during prolonged periods and during long distances.

Objective:To develop and test a nonsurgical method, using temperature loggers, of continuously recording internal temperature during exercise and over an extended period.

Methods:Loggers were inserted transcervically into the uterus of mares to measure internal temperature. A total of 9 mares were implanted for periods of 3 days to 6 weeks. The internal temperature was recorded while horses underwent their normal training and competition. Loggers were validated against rectal temperature over a range of internal temperatures while mares were alternatively exercised and rested.

Results:The technique proved to be straightforward and accurate. There were no ill effects observed and all mares retained the loggerin uterountil removal manually, except for one mare, which expelled the logger when she came into oestrus. The intrauterine and deep rectal temperatures were highly correlated and increased during exercise and decreased with aggressive cooling after exercise.

Conclusions:The technique is a useful and accurate nonsurgical method for prolonged monitoring of internal temperature in mares, including those animals in athletic competition.

Potential relevance:This method allows more intensive studies of core temperature during prolonged exercise in competition and under different environmental conditions. It also enables comparison to be made of different methods of cooling of horses post exercise.
Effect of conditioning horses with short intervals at high speed on biochemical variables in blood
Authors: LINDNER A. , SIGNORINI R. , BRERO LUCIANA , ARN E. , MANCINI R. , ENRIQUE A.
Published: June 2010

Reasons for performing study:There is limited published work on the effect of training using intensive and short intervals of exercise to condition horses for racing.

Objectives:To examine the effect of conditioning horses 1, 2 or 3 x a week using 2 short fast exercise intervals on blood lactate (LA), plasma ammonia (NH3) and urea (urea) as well as creatine kinase (CK) activity.

Methods:Thoroughbreds (age 4–5 years) were conditioned at near maximal speed (12–14 m/sec) over 100 m, on 2 occasions separated by a 10 min period at walk, on dirt track (conditioning exercise; CE) during a 6 week conditioning period (CP). The CE was undertaken either once (5 horses), twice (5 horses) or 3 times a week (4 horses) during a CP. Before, every 2 weeks during and after the CP, blood was drawn during the CE at 0, 2 and 4 min after each run and additionally 6 min after the 2nd run to measure blood LA and determine the maximal LA post exercise (LAmax). Plasma NH3was measured in the same samples and the maximal NH3post exercise (NH3max) determined. Additional blood samples were taken from the horses when stabled before the CE, and 12 and 24 h after to measure urea and CK activity in plasma.

Results:There was no differential effect of the number of weekly CE on LAmax, NH3max, LA and NH3immediately after exercise (LAO and NH30). Conditioning did not have an effect on LAmaxand LAO after the 1st interval (P>0.05), but LAO after the 2nd interval was lower after conditioning. NH3maxafter the 1st and 2nd exercise interval decreased in response to the conditioning, but not NH3immediately after exercise (P>0.05). Median plasma CK activity 12 h after exercise was higher than before exercise and returned to pre‐exercise levels 24 h post exercise when horses were exercised once and twice/week. In contrast, the median plasma CK activity of horses exercising 3 times/week remained at the pre‐exercise level 12 and 24 h post exercise (P>0.05).

Conclusion:Conditioning horses with 2 intervals of 100 m at near maximal speed had a positive effect on blood LA and plasma NH3.

Potential relevance:With the type of exercise examined, the fitness of racing horses can be maintained and eventually improved. In further studies the effect of increasing the number of runs in one exercise session should be investigated.
The workload of riding‐school horses during jumping
Authors: Van OLDRUITENBORGH‐OOSTERBAAN M. M. SLOET , SPIERENBURG A. J. , Van den BROEK E. T. W.
Published: June 2010

Reasons for performing the study:As there are no reports on the real workload of horses that jump fences, this study was undertaken in riding‐school horses.

Objective:To compare the workload of horses jumping a course of fences with that of horses cantering over the same course at the same average speed without jumping fences. The workload variables included heart rate (HR), packed cell volume (PCV), acid‐base balance (venous pH, pCO2, HCO3−) and blood lactate (LA), glucose, total protein and electrolyte concentrations.

Methods:Eight healthy riding‐school horses performed test A (a course of approximately 700 m with 12 jumps from 0.8‐1.0 m high at an average speed of approximately 350 m/min) and test B (same course at the same speed, but without the rails) in a crossover study with at least 4 h between the 2 tests. Before each test the horses were fitted with a heart rate meter (Polar Electro)1. Blood samples were taken from the jugular vein at rest prior to the test, after warm‐up before starting the course, immediately after the course and after recovery. All samples were analysed immediately.

Results:The mean ± s.d maximal HR (beats/min) during the course (184 ± 17 and 156 ± 21, respectively) and the mean HR after recovery (75 ± 6 and 63 ± 7, respectively) were significantly higher in test A compared to test B (P=0.001 and P=0.007 respectively). The mean LA concentrations after the course and after recovery (mmol/1) were significantly higher in test A (3.6 ± 2.7 and 1.0 ± 0.9, respectively) compared to test B (0.9 ± 0.5 and 0.3 ± 0.1, respectively), (P=0.016 and P = 0.048 respectively). The mean PCV (1/1) after the course and after recovery was also significantly different between tests A (0.48 ± 0.04 and 0.39 ± 0.03, respectively) and B (0.42 ± 0.04 and 0.36 ± 0.03, respectively) (P<0.01). The mean pH and the mean HCO3′ (mmol/1) after the course were significantly lower in test A (7.40 ± 0.04 and 28.9 ± 1.4, respectively) compared to test B (7.45 ± 0.03 and 30.4 ± 2.3, respectively) (P<0.05).

Conclusions:This study indicates that in riding‐school horses jumping fences, even at a low level competition, provokes a significant workload compared to cantering the same distance and speed without fences.

Potential relevance:This study makes it clear that the extra workload of jumping fences should be taken into account in the training programmes of jumping horses. Further research with more experienced horses jumping higher fences will reveal the workload for top‐level jumping horses.
Body composition in young Standardbreds in training: relationships to body condition score, physiological and locomotor variables during exercise
Authors: LELEU C. , COTREL C.
Published: June 2010

Reasons for performing study: Body composition is an essential factor in athletic performance of human sprinters and long distance runners. However, in horses, many questions remain concerning relationships between body composition and performance in the different equine activities.

Objectives:To determine relationships between body composition, body score, physiological and locomotor variables in a population of young Standardbreds in training.

Methods:Twenty‐four 2‐year‐old Standardbreds were studied, body condition on a scale 0–5 and bodyweight recorded, and height at withers measured. Percentage of fat (%F), fat mass (FM) and fat free mass (FFM) were estimated echographically. During a standardised exercise test on the track, velocity, heart rate, respiratory frequency and blood lactate concentrations were measured. V4and V200(velocity for a blood lactate concentration of 4 mmol/1 and velocity of 200 beats/min) calculated. Basic gait variables were measured at 3 different speeds with an accelerometric device.

Results:Body composition variables: %F and FM were significantly related to body condition score and physiological variables. Body score was highly correlated to %F (r=0.64) and FM (r = 0.71). V4was negatively correlated to %V (r=‐0.59) and FM (r = ‐0.60), P<0.05. V200was also negatively related to %F and FM, (r=‐0.39 and r = ‐0.37, respectively, P<0.1). No relationships were found between body composition and gait characteristics.

Conclusions:Body composition was closely related to indirect measurements of aerobic capacity, which is a major factor of athletic performance in middle distance running horses.

Potential relevance:As in human athletes, trainers should take special note to evaluate optimal bodyweight and body composition of race horses to optimise performance.
Optimal active recovery intensity in Standardbreds after submaximal work
Authors: DAHL S. , COTREL C. , LELEU C.
Published: June 2010

Reasons for performing study: A retrospective study concerning spontaneous active recovery intensity, i.e. at a freely chosen speed, after a submaximal exercise in trotters showed that the mean intensity demanded by trainers corresponds to 40–50% of maximal heart rate (max HR; unpublished data). However, in human athletes, optimal active recovery intensity was found to be about 60–70% of max HR. Is the spontaneous recovery optimal after a submaximal exercise in trotters?

Objectives:To compare different recovery intensities and define the most efficient one.

Methods:Thirty‐seven trotters performed a standardised exercise test on the track. Horses were randomly divided into 4 groups of recovery: passive recovery (n=10), 10 min walk recovery (n=10,100 m/min), 10 min slow trot recovery (n=9, 250 m/min) and 10 min fast trot recovery (n = 8, 420 m/min). Before, during and 1 h after exercise, speed, heart rate, blood lactate concentration were measured as well as respiratory frequency and rectal temperature. Creatine kinase (CK) was measured 1, 3 and 5 h after exercise.

Results:Walk, slow trot and fast trot recovery corresponded respectively to 45–50%, 55–60% and 65–70% of max HR. Heart rate and blood lactate concentration were significantly lower after the 10 sec recovery with increasing intensity of recovery.

Conclusion:The most efficient intensity of recovery was the 10 min fast trot recovery (65–70% max HR) as this type of recovery allows the optimal blood lactate disappearance.

Potential relevance:Considering the usual habits of trainers or drivers, recovery intensity after trot races should be increased in intensity to optimise its efficiency.
Use of a global positioning and heart rate monitoring system to assess training load in a group of Thoroughbred racehorses
Authors: KINGSTON J. K. , SOPPET G. M. , ROGERS C. W. , FIRTH E. C.
Published: June 2010

Reasons for performing study: Training is an important variable for determining athletic success. Nonetheless, there has been minimal scientific evaluation of racehorse training programmes. Training of racehorses focuses on running the horses at certain speeds using a combination of a stopwatch and rider's ‘feel’ for a horse's work intensity. Consequently, actual work intensity for individual horses is not clearly defined.

Objectives:To 1) utilise a combined global positioning system (GPS) and heart rate monitor system to quantify training intensity and physiological responses of a group of racehorses undergoing training and racing; and 2) compare the workload measured by the GPS to that timed and recorded daily by a racehorse trainer.

Methods:Nineteen racehorses age 3 years were followed through a traditional training and racing programme over a 4 month period. Daily GPS and heart rate data together with the trainer's timing and distance data were collected while the horses were trained. Data were analysed using an ANOVA for repeated measures.

Results:The combined GPS/heart rate monitoring system detected different heart rate responses in individual horses subjected to the same training workouts. The average speeds detected with the GPS system were in agreement with average speeds timed by the trainer. However, peak speeds reached during training were significantly greater (P<0.05) than those estimated with stopwatch timing. The horses average training speeds increased significantly over the duration of the training period.

Conclusions and potential relevance:The results from this study show that a GPS/heart rate monitor system provides a reliable measure of daily workload in horses during training. This technology provides a detailed picture of horses' training sessions and has the potential to provide a greater insight into the types of training that may predispose horses to injury.
Correlation of race earnings with velocity at maximal heart rate during a field exercise test in Thoroughbred racehorses
Authors: GRAMKOW H. L. , EVANS D. L.
Published: June 2010

Reasons for performing study:Running ability of Thoroughbred racehorses is correlated with maximal oxygen uptake, and the velocity at maximal oxygen uptake is highly correlated with the velocity at maximal heart rate (VHRmax).

Objective:To investigate the relationship between VHRmaxand racing performance, expressed as ‘peak dollars earned per race start’.

Methods:Heart rate (HR) and velocity were recorded in 25 Thoroughbred racehorses during trotting and subsequent fast gallops in the field at velocities of 15–16 m/sec. Velocity was recorded by a global positioning system (GPS). Maximal HR (HRmax) and maximal velocity (Vmax) were identified, and a linear regression of HR on velocity for trotting and galloping data was constructed to derive VHRmax. Horses followed the training programme designed by one trainer, had at least 6 race starts and were clinically sound at the time of testing. Race earnings were expressed as the peak dollars per start in the horse's race career. Data were normalised using the results for the square root of ‘peak dollars earned per race start’ and the significance of associations between variables was determined by correlation coefficient and least square analyses.

Results:Horses with higher VHRmaxearned significantly more dollars per race start (r = 0.41, P<0.05), and horses with VHRmaxless than 14.5 m/sec had mean earnings of less than A$2500 per race. There were no correlations between race earnings and either HRmaxor Vmax.

Conclusion:Field studies of the relationship between HR and velocity with a GPS enable identification of horses with limited earnings.

Potential relevance:This study demonstrates that a field test of fitness of Thoroughbred racehorses that correlates with retrospective racing ability is feasible. The technique has potential application in commercial training environments assisting with decisions concerning racing careers of individual racehorses.