Research Article
A preliminary investigation of rider position during walk, trot and canter
- Thomas Lovett, Emma Hodson-Tole, Kathryn Nankervis
-
- Published online by Cambridge University Press:
- 09 March 2007, pp. 71-76
-
- Article
- Export citation
-
The purpose of this study was to determine whether significant differences exist in the position of a horse rider when assessed at different points in the horse's stride cycle at walk, trot and canter on the right rein. Video analysis was used to determine the absolute angles of the trunk, thigh and lower leg of five subjects during the walk, rising trot and canter. The range of movement of the trunk, thigh and lower leg during each gait was also determined. At walk significant differences in the rider's trunk angle were found between limb impacts (P<0.05). At trot significant differences were found in all angles between impacts of the horse's diagonal limb pairs (P<0.05). At canter, there were no significant differences in rider position between limb impacts. The range of movement of the trunk was 5.9°, 4.1° and 4.7° for walk, trot and canter, respectively. The corresponding ranges of the thigh and lower leg were 1.9°, 7.3° and 4.4°, and 2.9°, 5.2° and 3.9°, respectively. This preliminary study has demonstrated differences in rider posture between limb impacts in walk and trot. Further work is necessary to investigate the forces acting on the rider during each gait and the postural strategies employed by riders to maintain a balanced position. Such work is a necessary forerunner to the study of rider influence on horse performance.
Time course and magnitude of fluid and electrolyte shifts during recovery from high-intensity exercise in Standardbred racehorses
- Amanda Waller, Michael I Lindinger
-
- Published online by Cambridge University Press:
- 09 March 2007, pp. 77-87
-
- Article
- Export citation
-
The present study characterized the fluid and electrolyte shifts that occur in Standardbred racehorses during recovery from high-intensity exercise. Jugular venous blood was sampled from 13 Standardbreds in racing condition, at rest and for 2 h following a high-intensity training workout. Total body water (TBW), extracellular fluid volume (ECFV) and plasma volume (PV) were measured at rest using indicator dilution techniques (D2O, thiocyanate and Evans Blue, respectively). Changes in TBW were assessed from measures of body mass, and changes in PV and ECFV were calculated from changes in plasma protein concentration. Exercise resulted in a 26.9% decrease in PV. At 10 min of recovery TBW and ECFV were decreased by 2.2% and 16.5% respectively, while intracellular fluid volume was increased by 7.1%. There was a continued loss of fluid due to sweating throughout the recovery period such that TBW was decreased by 3.9% at 90 min of recovery. This decrease in TBW was nearly equally partitioned between the extracellular and intracellular fluid compartments. Plasma Na+ and Cl− contents were decreased at 1 min of recovery, but not different from rest by 40 min of recovery. Plasma K+ content at 1 min post exercise was not different from the pre-exercise value; however, by 5 min of recovery K+ content was significantly decreased and it remained decreased throughout the recovery period. It is concluded that there are very rapid and large fluid and electrolyte shifts between body compartments during and after high-intensity exercise, and that full recovery of these shifts requires 90–120 min.
The influence of adrenaline on echocardiographic parameters of left ventricular function in the horse
- Heidrun Gehlen, Silke Marnette, Peter Stadler
-
- Published online by Cambridge University Press:
- 09 March 2007, pp. 89-96
-
- Article
- Export citation
-
The purpose of the present study was to investigate the effect of adrenaline on cardiac function parameters. The infusion of adrenaline for induction of stress, its prospective side-effects as well as its effect on left ventricular function were investigated. A clinical examination and echocardiography were performed on 10 healthy horses before and after infusion of adrenaline. During a period of 6 min, infusion of 1 μg adrenaline kg−1 min−1 led to a significant increase in mean heart rate, from 36.5 to 55 beats min−1. Echocardiography during adrenaline infusion revealed a significant thickening of the interventricular septum (during systole) as well as a significant decrease in left ventricular diameter at the papillary muscle level (during both systole and diastole), and thus an increased contractility. The left ventricular area and the left ventricular volume were significantly decreased during adrenaline infusion, expressing the increased left ventricular contractility (during both systole and diastole). Other echocardiographic parameters of regional left ventricular function changed with only low-grade significance or without any significance at all. During and after infusion of adrenaline, the horses showed sweating, muscle tremor and other symptoms of discomfort. The study revealed that the increases in heart rate and myocardial contractility after infusion of adrenaline were low compared with changes observed during physical performance. Furthermore, severe adverse effects were observed. Taking into account the possible cardiotoxic effects of adrenaline, we do not consider this method appropriate for stress induction, particularly in horses with cardiac disorders.
Dressage scoring patterns at selected British Eventing novice events
- TC Whitaker, J Hill
-
- Published online by Cambridge University Press:
- 09 March 2007, pp. 97-104
-
- Article
- Export citation
-
Subjective bias by judges within the dressage phase of eventing competition is problematic if correct evaluation of horse and rider performance is to be undertaken. The present study examines dressage penalty scoring (penalty scores are awarded for completion of a pre-set series of dressage movements) within a population of novice event horses (n = 2471). Between May and June 2003, 22 novice events within the UK were analysed, and at each event up to six competitions or sections (at the same competitive level) were run. The whole population data structure was normal in distribution, Pearson's skewness 0.314 (Kolmogorov–Smirnov Z = 1.855, P>0.05 from zero) and kurtosis at 0.425. The mean score recorded for the whole population was 37.82 penalty points (standard deviation = 5.65 and standard error = 0.11). A number of effects were observed within the population. Between-events effects were observed in three of the 22 events studied (P<0.01). Of those events running three or more sections (n = 16), within-event effects were observed for 10 events as differences (P<0.01) in mean scoring patterns between sections. All events running two sections (n = 4) were observed to exhibit differences (P<0.02) in mean scores. Differences (P>0.01) between the dressage test used at events were determined using post hoc Bonferroni tests. However, these differences were not found to have a confounding effect on the between-event observations. The study indicates that additional methodologies need to be implemented to ensure that accurate and impartial evaluation of event horses is conducted.
Changes in plasma cortisol and ascorbic acid in horses with and without recurrent airway obstruction upon exercise and ascorbic acid supplementation
- TL Cuff, RJ Williams, CM Deaton, NC Smith, BD Davies, MCG Davies-Morel, DJ Marlin, PA Harris
-
- Published online by Cambridge University Press:
- 09 March 2007, pp. 105-112
-
- Article
- Export citation
-
Diminished basal plasma cortisol concentrations and a blunted cortisol response to exercise have been observed in human asthmatics. In horses with recurrent airway obstruction (RAO), plasma concentrations of cortisol at rest are not significantly different from those of healthy horses, but the effect of exercise on endogenous cortisol concentrations has not been described. Ascorbic acid is a non-enzymatic antioxidant with proposed immune-modulating properties. In man, supplementation with ascorbic acid has been shown to attenuate the exercise-induced increase in plasma cortisol following prolonged, submaximal exercise. The relationship between cortisol and ascorbic acid has not previously been investigated in the horse. In a blinded cross-over design, five horses with RAO and six healthy non-RAO controls performed a standard exercise test following 4 weeks of supplementation with either an antioxidant (providing 10 mg ascorbic acid kg−1 day−1) or a placebo (<1 mg ascorbic acid kg−1 day−1). Venous blood samples were obtained 1 h prior to exercise and at 0, 15, 60 min and 24 h thereafter. Exercise resulted in a significant increase in plasma cortisol concentrations in both groups of horses (P<0.05). Basal and post-exercise concentrations of plasma cortisol in the RAO group (136±16 and 210±16 μmol l−1, respectively) were not significantly different from those in the non-RAO group (129±43 and 218±30 μmol l−1, respectively). Antioxidant supplementation increased basal and post-exercise concentrations of plasma ascorbic acid in RAO and non-RAO horses (P<0.05) but had no effect on plasma cortisol concentration in either group, before or after exercise (RAO: rest 157±27 μmol l−1, post-exercise 222±21 μmol l−1; non-RAO: rest 140±11 μmol l−1, post-exercise 227±35 μmol l−1). In conclusion, RAO-affected horses in remission demonstrate the same cortisol response to exercise as healthy controls. Antioxidant supplementation had no impact on post-exercise concentrations of plasma cortisol in either healthy or RAO-affected horses in remission.
Acute progressive resistance exercise alters intracardiac pressure in ponies
- KH McKeever, SE Alway, JW Farris, KW Hinchcliff, JA Lombardo
-
- Published online by Cambridge University Press:
- 09 March 2007, pp. 113-118
-
- Article
- Export citation
-
Five male ponies (3–6 years, 208±11 kg) were used to examine the haemodynamic effects of resistance exercise. The experiment consisted of a 30 min catheterization period and a 15 min equilibration period followed by the test. Initially, the ponies stood quietly on a treadmill for collection of 5 min of baseline data. They then walked at 1.9 m s−1 for 1 min sets while carrying 0 kg, 67 kg or 134 kg of weight loaded on the saddle area. Weights were applied in a randomized order using a chain hoist and sling. The ponies rested unloaded for 2 min between sets and all cardiovascular parameters returned to baseline before beginning the next set. Haemodynamic measurements (heart rate (HR), carotid artery systolic (SP), diastolic (DP), pulse (PP) and mean pressure (MAP), right atrial pressure (RAP), right ventricular pressure (RVP) and right ventricular maximum rate of pressure rise (dP/dtmax)) were recorded continuously and data collected during the last 18 s of each set were averaged and analysed. HR increased (P<0.05) with unloaded exercise (201%) and with increases in load (252 and 271% at 67 and 134 kg, respectively). RAP increased (P<0.05) with exercise, with differences (P<0.05) between the response to the 0 kg (66%), 67 kg (121%) and 134 kg (138%) loads. RVP increased (P<0.05) incrementally with load during exercise (58, 110 and 136%, respectively), with differences (P<0.05) between 0 versus 67 kg and 67 versus 134 kg. Right ventricular dP/dtmax increased (P<0.05) incrementally and showed differences (P<0.05) between loads (131, 191 and 252% at 0, 67 and 134 kg, respectively). There were increases (P<0.05) in MAP (20%), SP (20%) and DP (27) with exercise, but no difference (P>0.05) between the response to 67 versus 134 kg load (43 and 51%; 40 and 46%; 49 and 62, respectively). Pulse pressure did not change (P>0.05) from baseline values. These data suggest that resistance exercise in the form of weight carried increases intraventricular pressure through a significant increase in both cardiac pre-load and after-load.
Physicochemical analysis of acid–base status during recovery from high-intensity exercise in Standardbred racehorses
- Amanda Waller, Michael I Lindinger
-
- Published online by Cambridge University Press:
- 09 March 2007, pp. 119-127
-
- Article
- Export citation
-
The present study used the physicochemical approach to characterize the changes in acid–base status that occur in Standardbred racehorses during recovery from high-intensity exercise. Jugular venous blood was sampled from nine Standardbreds in racing condition, at rest and for 2 h following a high-intensity training workout. Plasma [H+] increased from 39.1±1.0 neq l−1 at rest to 44.8±2.7 neq l−1 at 1 min of recovery. A decreased strong ion difference ([SID]) was the primary contributor to the increased [H+] immediately at the end of exercise, while increased plasma weak ion concentration ([Atot]) was a minor contributor to the acidosis. A decreased partial pressure of carbon dioxide (PCO2) at 1 min of recovery had a slight alkalinizing effect. The decreased [SID] at 1 min of recovery was a result of a 15.1±3.1 meq l−1 increase in [lactate−], as [Na+] and [K+] were also increased by 6.5±0.7 and 1.14±0.06 meq l−1, respectively, at 1 min of recovery. It is concluded that high-intensity exercise and recovery is associated with significant changes in acid–base balance, and that full recovery of many parameters that determine acid–base status requires 60–120 min.
The reliability of force platform data from trotting horses
- JA Lynch, HM Clayton, DR Mullineaux
-
- Published online by Cambridge University Press:
- 09 March 2007, pp. 129-132
-
- Article
- Export citation
-
The aim of the present study was to quantify the inter-day reliability of force platform data from horses at the trot. The subjects were ten horses judged to be sound on the basis of clinical evaluation and similarity of ground reaction force peaks of left and right limbs. The same handler trotted horses in hand for four consecutive days over a force platform at their natural and comfortable velocity between 2.70 and 3.60 m s−1. For each horse, velocity was controlled in a range of±0.15 m s−1. Five contacts per limb were recorded on each day. Custom-written code in MATLAB was used to smooth the data and time-normalize to 101 data points. The agreement boundary was used to determine the reliability of seven force variables. Stance duration, peak vertical force and vertical impulse were the most reliable variables (<10% variability in the mean), while peak braking and propulsive forces and impulses had larger variation across the three days (>20% variability in the mean). Variables with low variability may require fewer animals, trials and days to obtain accurate data while maintaining adequate statistical power. These results may act both as a reference when studying variability in lame horses and as a guide for planning future equine kinetic studies.
Effect of training and recovery on airway inflammation in an animal model of ‘ski asthma’
- MS Davis, EC McKenzie, CM Royer, KK Williamson, M Payton, SL Nelson
-
- Published online by Cambridge University Press:
- 09 March 2007, pp. 133-138
-
- Article
- Export citation
-
Repeated strenuous exercise while breathing cold air is believed to induce chronic airway inflammation and hyperreactivity, a condition referred to in humans as ‘ski asthma’. However, the time course of development and resolution of ski asthma is unknown. We have previously shown that multi-day aerobic exercise induces airway inflammation and hyperreactivity in racing sled dogs. In the present study, a similar group of subjects was examined at multiple times during training to test the hypothesis that ski asthma spontaneously resolves during seasonal detraining, but is re-induced during training in the cold weather. At the beginning of training, bronchoalveolar lavage fluid (BALF) from detrained elite sled dogs (n = 16) had higher concentrations of lymphocytes (median 53.63 vs. 8.30 cells μl−1) and neutrophils (median 23.03 vs. 1.10 cells μl−1) compared with normal laboratory dogs (n = 5). However, there was no significant effect of training on BALF nucleated cell concentrations from exercised sled dogs (n = 11) compared with sedentary sled dogs (n = 8). In contrast to our hypothesis, our data support the contention that cold weather exercise-induced airway inflammation can persist through seasonal detraining, but that routine training does not cause significant worsening of the condition.