The fundamental tenets of exercise physiology are to describe energy transformations during physical work and make predictions about physical performance under different conditions. Historically, the most popular method to observe such responses during exercise has been the constant load or fixed-intensity protocol, based largely on the assumption that there is a certain threshold response of the organism under a given condition. However, constant load exercise does not fully allow for randomness or variability, as the biological system is overridden by a predetermined externally imposed load that cannot be altered. Conversely, in self-regulated (paced) exercise, there is almost an immediate reduction in power output and muscle recruitment upon commencing exercise. This observation suggests the existence of neural inhibitory command processes. This difference in regulation demonstrates the inherent importance of variability in the biological system; for in tightly controlled energy expenditure, as is the case during constant load exercise, sensory cues cannot be fully integrated to provide a more appropriate response to the given task. The collective evidence from conventional constant load versus self-regulated exercise studies suggests that energy transformations are indeed different, so that the inherent biological variability accounts for the different results achieved by the two experimental paradigms.

The phenomenon known as the lactate paradox has been a topic of heated debate since it gained worldwide attention following Operation Everest in the early 1980s. What began as the simple finding that blood lactate (blood [La]) for a given sub-maximal workload or VO2 following acclimatization to high altitude is reduced compared with sea-level values, morphed into a complex set of parameters that have been redefined several times in the nearly 30 years that the lactate paradox has been researched. Though several strong hypotheses have been proposed to, to date, no one hypothesis has been able fully to explain the lactate paradox. The goal of the current article was to bring together the most prominent studies done on the lactate paradox and illuminate the details brought forth by each. In doing so we hope to stimulate new hypotheses and research studies that will further our understanding of the lactate paradox.

Research into other sports has shown that excessive levels of anxiety can undermine motor function during performance. This study aims to investigate the effects of anxiety and self-confidence on equestrian performance. Forty riders (12 male, 28 female; 15 elite, 25 non-elite; 12 dressage, 17 showjumping, 11 eventing) completed the Revised Competitive Sport Anxiety Inventory 2 (CSAI-2R), which measures the levels of somatic and cognitive anxiety (arousal) as well as levels of self-confidence. Two-way between-subjects MANOVA tests were used to examine competence-by-discipline interactions and gender-by-discipline interactions in CSAI-2R scores. Post hoc analysis was conducted using one-way univariate ANOVA tests. Spearman's rank correlation tests were conducted between each of the CSAI-2R subscales according to competence, discipline and gender. Most important findings include lower somatic arousal and higher self-confidence in elite compared with non-elite riders, with 15.2 ± 4.4 vs. 19.0 ± 5.0, F1,34 = 5.8, P < 0.05; 31.5 ± 4.8 vs. 25.1 ± 7.4, P < 0.01, respectively. Negative correlations between cognitive arousal and self-confidence were found among elite riders, non-elite riders, showjumpers and female riders (r = − 0.69, P < 0.005; r = − 0.41, P < 0.05; r = − 0.52, P < 0.05; r = − 0.33, P < 0.05). Greater riding-specific skills in the elite rider may result in increased self-confidence. Lower levels of somatic anxiety may further increase fine motor skills in elite riders. Practical implications are that non-elite riders would benefit from sport psychological interventions increasing levels of self-confidence and reducing symptoms of somatic arousal to improve performance.

Aminocaproic acid (ACA) and Premarin® (PRE) are used to treat exercise-induced pulmonary haemorrhage (EIPH) at the racetrack based upon their putative coagulation effects. We hypothesized that neither ACA nor PRE would reduce EIPH because the literature does not substantiate coagulation deficits being manifested in EIPH. Six Thoroughbreds were run from 4 m s− 1 until fatigue (1 m s− 1s × 1 min increments; 6° inclined treadmill) after being treated with placebo, PRE (25 mg) or ACA (5 g) at 2-week intervals in a randomized crossover design. Coagulation and exercise-related variables were measured at rest and maximal effort. EIPH and inflammation were quantified via bronchoalveolar lavage fluid (BALF) 30–60 min post-exercise. EIPH was not altered by either treatment (3.8 ± 1.7 (placebo), 4.6 ± 3.2 (ACA) and 2.4 ± 1.2 (PRE) × 106 RBC ml− 1 BALF; p = 0.12), nor was coagulation. However, inflammation was decreased (5.9 ± 0.9 (placebo), 4.4 ± 0.9 (ACA) and 4.2 ± 0.4 (PRE) × 105 WBC ml− 1 BALF; both p < 0.05). There was a trend for decreased time-to-fatigue (720 ± 27 (placebo), 709 ± 24 (ACA) and 726 ± 28 (PRE) s; p = 0.09 for placebo vs. ACA) and a reduction in plasma lactate (19.5 ± 3.0 (placebo), 14.7 ± 1.0 (ACA) and 17.6 ± 2.5 (PRE) mmol l− 1; p < 0.05 for placebo vs. ACA) following ACA administration. ACA and PRE were not effective in reducing EIPH, and ACA may be detrimental to performance. However, both may mitigate exercise-induced pulmonary inflammation.

Recent research has shown that more successful performers interpret pre-competitive symptoms of anxiety as more facilitative than less successful performers. The aim of the study was to examine the effect of both trait anxiety and pre-competitive arousal intensity and direction on intermediate riding performance in the disciplines of dressage, showjumping and eventing, including whether differences exist between male and female riders. Sixty-two German equestrian riders competing in the equestrian disciplines of dressage (N = 21), showjumping (N = 25) and eventing (N = 16) were asked to complete a revised version of the ‘Wettkampf–Angst-Inventar-State’, which included directional scales for all items and the ‘Wettkampf–Angst-Inventar-Trait’ prior to competing. Final placings were used as performance indicators. Most important findings revealed that the correlation between direction of somatic state arousal and competitive placing was nearing significance (rs = − 0.23, P =0.07) and loss of focus was positively correlated to competitive placing (rs = 0.26, P < 0.05). Conclusions may be drawn that in equestrian sports positive interpretation of physical symptoms of arousal as well as the ability to remain focused on the task at hand may lead to more successful ridden performance.

The maximal lactate steady state (MLSS) has been considered the gold standard method to determine aerobic/anaerobic metabolism transition during continuous exercise executed by human beings and rats. Therefore, the aim of the present study was to determine MLSS for aerobic evaluation in swimming mice. Twenty-five adult male mice (90-day-old animals) were adapted to the deep aquatic environment at the temperature of 31 ± 1°C. The mice were submitted to five continuous exercise loads of 3, 4, 5, 6 and 7% of the body weight (bw) tied to the back, executed with 25-min duration and 48-h intervals between them. Blood samples were collected from the tail during swimming exercise (rest, 5, 10, 15, 20 and 25 min) for blood lactate concentration (LAC) determinations. The individual MLSS was considered as the highest intensity in which the increase on the LAC was equal to or below 1 mmol l− 1 from the 10th to the 25th minute of exercise. The results showed that 36% of the swimming mice presented MLSS at 4% bw, 20% at 3% bw and 6% bw, 16% at 5% bw and 8% at 7% bw. The LAC at the MLSS was 5.78 ± 0.29 mmol l− 1 (4.40–6.67 mmol l− 1). These results indicate that the MLSS of mice swimming with additional weight for the final 15 of 25 min of exercise could be determined.

While there have been several studies of heart rates (HRs) of horses during exercise in water, the effect of exercise in water of different temperatures has not been reported. While the increase in HR during exercise is primarily related to the intensity of exercise and therefore metabolic rate, increasing body temperature can also contribute to elevations in HR separate to muscle metabolic activity per se. When exercising in water, as the thermal conductivity is greater than that of air, the temperature of the water can have a marked influence on body temperature and heat exchange compared with exercise in air. The aim of the present study was to investigate the effect of water temperature on HR of horses walking for 16 min on a water treadmill in water up to the height of the scapulohumeral joint. Eight horses were studied in three separate exercise tests in water at 13, 16 and 19°C in a randomised order in an ambient temperature between 4 and 10°C. HR was recorded continuously throughout exercise. Mean HR over the 16 min exercise period was the lowest in 13°C water (79 ± 6 bpm), intermediate in 16°C water (89 ± 7 bpm) and the highest in 19°C water (92 ± 5 bpm). A one-way ANOVA and post hoc least significant difference test comparing mean HRs at each temperature showed that there was a significant difference between HRs in water at 13 and 16°C (P < 0.0001) and in water at 13 and 19°C (P < 0.0001), but not between water at 16 and 19°C (P>0.05). Individual HRs for horses during the first minute of exercise in water of 13°C were significantly different from those in water at 16°C (P < 0.0001) and 19°C (P < 0.0001). The gradients of the log HR–time relationships showed a significant difference between exercise in the latter part of exercise in 19°C when compared with 13°C (t = 34.0, P < 0.05) and 16°C (t = 67.4, P < 0.05), suggesting that cardiovascular drift is likely when exercising in temperatures of 19°C and above. In conclusion, to the best of our knowledge, this is the first study to describe the effect of water temperature in the range of 13–19°C on the HR of horses during water treadmill exercise. Further studies to investigate the effect of different water depth and temperature combinations are indicated.

Fibre type composition of skeletal muscle in horses varies due to factors like breed, age and training. Variations due to these factors in muscle fibre type composition of the Swedish cold-blooded trotter, a heavier and slower breed than the Standardbred trotter, have not previously been reported. The objective of this study was therefore to investigate muscle fibre type composition of young and racing cold-blooded trotters using both histochemical and immunohistochemical methods. Muscle biopsies (gluteus medius) were obtained from 2-year-old (n = 18) and 4–8-year-old horses (n = 6). Four of the 2-year-old horses were sampled again during their 4-year-old season. All of the horses were in professional training and the group included superior racehorses. Fibre types (I, IIA and IIB) were visualized with the myosin ATPase technique. Some samples were also stained immunohistochemically to identify MHCI, MHCIIA and MHCIIX fibres using myosin heavy chain (MHC) antibodies. The oxidative capacity of the fibres was subjectively evaluated from NADH-tetrazolium reductase stains. Type I and type IIA fibres were all identified as MHCI and MHCIIA fibres, respectively, whereas type IIB fibre population included both pure MHCIIX and hybrid MHCIIAX fibres. The older racehorses had a higher proportion of type MHCIIA and a lower proportion of type MHCIIX fibres than the 2-year-old horses. Areas of type I fibres were larger and those of type IIB fibres were smaller in racing horses compared with young horses. The proportion of type MHCIIX fibres that stained medium for oxidative capacity increased with age and training. In conclusion, training and racing induce muscular adaptations in cold-blooded trotters as in other breeds. Furthermore, immunohistochemical methods detect hybrid fibres indicating that transitions of fibre types may occur.

Previous studies of the effect of age on maximal aerobic capacity (maximal rate of oxygen consumption, VO2max) in horses have only grouped horses (young, middle-aged and old) for statistical analysis. Those experiments were not designed to determine a break point due to age. The purpose of this study was to utilize data collected over the last 15 years to test the nature of the association between age and VO2max, and secondarily, to determine whether there is a ‘breakpoint’ in the age-related decline in aerobic capacity. Data were acquired from 50 unfit Standardbred mares ranging in age from 4 to 29 years, and were used in a retrospective regression analysis in order to characterize the age-related decline in VO2max. All VO2max values were measured using the same incremental graded exercise test protocol. The data were analyzed using a curvilinear regression analysis predicting VO2max from age, and the break point was determined using univariate simple contrasts. There was a significant decline in VO2max with age (R2 = 0.554; P < 0.001). The data analysis demonstrated a notable downturn in cardiopulmonary function between the ages of 18 and 20 years (P < 0.001). Such results indicate similar responses to age between humans and horses. These results have implications for improving training methods in active older horses.

To help resolve the mechanistic bases for haematological adaptations (~28% increase in red blood cell volume) of equids to high altitude (3800 m, barometric pressure Pb, 487 mm Hg) and exercise, plasma erythropoietin concentration ([EPO]) was measured at rest and following exercise in six, moderately fit equids (four Arabians, one Quarter Horse and one Shetland Pony; four females and two males; age 9.0 ± 4.5 years (mean ± SD)). [EPO] was measured on 2 days at 225 m (i.e. ~sea level; Pb, 743 mm Hg), over the course of a 10-day altitude exposure, and then again for 2 days after return to sea level. A standard track exercise test (submaximal, speed set-to-heart rate of 110 (trot), 150 (canter), 180 (gallop) bpm) was performed 2 days pre-high-altitude exposure and on three separate days at high altitude. In addition, a maximal incremental exercise test was performed on a high-speed motor-driven treadmill at sea level and 2 days following return to sea level from high altitude. Resting [EPO] increased from 28 ± 29 at sea level to 144 ± 46 mU ml− 1 (P < 0.05) on the first day at high altitude. By day 2 at high altitude, [EPO] had returned to baseline (31 ± 24 mU ml− 1, P>0.05 vs. pre-high altitude) and did not change over the remaining 8 days at high altitude nor over the 2 days after return to sea level. [EPO] was not significantly altered by acute exercise at sea level or at 3800 m. These results indicate that [EPO] increases rapidly (though transiently) in response to hypobaric hypoxia but not to acute exercise, and that exercise does not appear to potentiate the altitude response. Thus, if any [EPO]-derived haematological adaptations to high altitude are present, these appear to result from a transient ~4-fold elevation of [EPO] rather than any sustained increase in this signalling mechanism, at least in the equid.

Football players walk a fine line between optimal training and overtraining. Manipulating nutrient intake has the potential to maximize the biochemical environment necessary to induce peak performance and proper recovery. The purpose of this study was to examine the impact of supplementing the diet of Division I football players with a proprietary nutraceutical recovery drink on changes in performance, body composition, anabolic status, muscle damage, inflammation and oxidative stress over the course of a 7-week conditioning period immediately prior to preseason camp. At the beginning (trial 1) and end (trial 2) of a 7-week training phase, body composition, vertical jump and 225 lb bench press were assessed in Division I college football players (n = 25). A 30 s Wingate Anaerobic Test plus eight 10 s intervals was used to examine power and biochemical responses. Blood samples were collected pre-, 0 and 60 min post-test for analysis of interleukin-6 (IL), 8-isoprostane (8-iso), cortisol (CORT) and resting testosterone:CORT (T:C) ratios. Athletes were randomly assigned to either an experimental group (EXP) receiving the nutraceutical drink (n = 13) or a control group (CON) receiving an isocaloric equivalent (n = 12). EXP had a significantly greater increase in peak power (P < 0.05) and significant decreases in percentage body fat and fat mass (P < 0.05). Multivariate ANOVA for repeated measures (RM MANOVA) revealed a significant test × time × group interaction (P < 0.05) for changes in CORT, IL-6 and 8-iso from trial 1 to trial 2. Follow-ups revealed no significant differences between groups at trial 1 for any of the variables. At trial 2, EXP had significantly lower CORT at rest (P = 0.01) and 60 min post-test (P = 0.001). Additionally, IL-6 was significantly different between EXP and CON at 0 (P < 0.01) and 60 min post-test (P < 0.01), with CON having an elevated IL-6 response. There were also differences in both 8-iso and creatine kinase at all time points at trial 2, with CON having higher levels (P < 0.02.). There were significant differences between groups in T:C ratio changes (P < 0.05), with EXP having an improved T:C ratio. It appears that supplementing the post-workout diet of Division I college football players with a nutraceutical recovery drink has favourable effects on body composition, peak power output and biochemical markers. Based on differences between groups that emerged at rest at trial 2, it appears that this supplement positively impacts both acute and chronic physiological responses indicative of improved recovery.

Exercise-induced pulmonary haemorrhage (EIPH) is a major health concern in performance horses, but the presence and severity of this condition in racing greyhounds has received little attention. While equids and greyhounds share many physiological attributes, there are important structural and functional differences that may help protect greyhounds from EIPH. We tested the hypothesis that greyhounds performing a simulated 503 m race would experience EIPH and that the time course of recovery would be similar to the horse, even though the severity or relative extent as indexed by the concentration of red blood cells [RBCs] in bronchoalveolar lavage (BAL) fluid would be lower in comparison with that demonstrated previously in horses. Greyhound dogs (n = 6) raced on two occasions (separated by 7 weeks) and BAL was performed 1 week before, 2 h after and each week for 4 weeks following each race to examine the [RBC], concentration of white blood cells [WBCs], WBC differentials and haemosiderophages in the lungs. Racing increased 10 min post-exercise venous blood [lactate] to 18.6 ± 0.4 mmol l− 1. No epistaxis or pink froth was observed at the nose or mouth of any of the dogs. The [RBC] in the BAL fluid was increased significantly 2 h post-race (baseline = 109.6 ± 11.7 × 103; post-race = 292.3 ± 69.9 × 103 RBC ml− 1 BAL fluid, P < 0.05) and returned to baseline 1 week post-race (149.2 ± 46.2 × 103 RBC ml− 1 BAL fluid, P>0.05 versus baseline). The number of haemosiderophages was not different for any of the measurement periods. The [WBC] in the BAL fluid decreased from baseline and race values at 2, 3 and 4 weeks post-exercise (all P < 0.05). Alveolar neutrophil concentrations were also decreased from baseline and immediate post-race values for 4 weeks post-race. The increased [RBC] in the BAL fluid post-exercise is consistent with the presence of EIPH in these greyhounds. However, the relative extent of EIPH in greyhounds (as indexed by [RBC] in the BAL fluid), as compared with that in the horse, was mild, and the lack of elevation of WBC suggests that, unlike their equine counterparts, inflammatory airway disease was absent.

The most popular techniques used for studying equine kinematics are videographic recording combined with the analysis using a commercial software package or optoelectronic systems based on emission and detection of infrared or visible light. Such systems can be expensive, complicated to use and their use may be restricted to indoor use (in the case of infrared systems) or a limited number of strides when used outdoors. Recently, there has been considerable interest in monitoring motion using inertial measuring systems. The purpose of the present study was to determine the accuracy of the Pegasus system (European Technology for Business Ltd., Codicote, UK), which determines stride frequency directly when mounted on the withers. Eight horses of different breeds and sizes (447–588 kg) were studied at walk, trot and two speeds at canter on a treadmill. Simultaneous measurements of stride were made using the Pegasus and ProReflex motion capture systems. Mean stride frequencies (n = 8 horses) for the ProReflex and Pegasus systems at walk (0.86 ± 0.05 and 0.87 ± 0.05 strides per second, respectively), trot (1.36 ± 0.07 and 1.36 ± 0.07 strides per second, respectively) and canter (7 m s− 1: 1.92 ± 0.05 and 1.92 ± 0.05 strides per second, respectively; 8 m s− 1: 1.93 ± 0.05 and 1.94 ± 0.05 strides per second, respectively) were not significantly different (P>0.05). The mean difference between the two systems for all four speeds was − 0.002 strides per second (lower 95% CI: − 0.016; upper 95% CI: 0.011; P = 0.309). In conclusion, the differences between stride frequency measurements made with the Pegasus and ProReflex systems in horses exercising at walk, trot and slow canter on a treadmill are < 1% and not likely to be of physiological significance.

Exercise places an increased demand on the body's systems, both to provide fuel for working musculature and to neutralize and dispose of toxic build-up. By-products of demanding performance are reactive free radicals. Dietary consumption of vitamin E, an antioxidant, may be a plausible way to reduce free radical damage. The present study examined the effects of supplemental dietary vitamin E on the presence of oxidation products and antioxidant capacity in blood and tissue of exercising horses. Eight Thoroughbred horses were used in a crossover design study, with one group consuming a diet containing vitamin E at the 1989 National Research Council (NRC) level recommended for horses in moderate to intense work (80 IU kg DM− 1 [National Research Council (1989). Nutrient Requirements of Horses. 5th revised edn.; Washingto, DC: National Academy Press, pp. 48]), and the second group being fed the control diet plus 3000 IU day− 1dl-α-tocopheryl acetate. The horses underwent an adaptation phase, an 8-week training programme and a final standard exercise test (SET) during which the horses ran on a 6° incline to exhaustion, and then a washout phase. Horses were then crossed over to opposite treatment groups and these phases repeated. Blood samples were collected at specific points before and after exercise during the training period and before and after performing the SET. Neither plasma vitamin E nor thiobarbituric acid-reactive substance concentrations were influenced by supplemental vitamin E. Blood Trolox-equivalent antioxidant capacity values increased (P < 0.05) following 5 weeks of training in both groups, indicating improved antioxidant capacity as horses became fitter. Vitamin E supplementation did not alter plasma reduced, oxidized or total glutathione levels, nor the percentage of glutathione in the reduced form during the training period. However, vitamin E did cause an elevation in the percentage of glutathione existing in the reduced form following a SET as compared with the control diet (P < 0.006). This is possibly due to lower plasma oxidized glutathione levels in vitamin E-treated horses (P < 0.03). This study indicates that vitamin E supplementation above NRC levels can influence certain measures of oxidative stress in intensely exercising horses, and training has the ability to improve the antioxidant status of the animal.

The gaits of the dressage horse have been described, but less information is available regarding the transitions between gaits. The objective was to describe and compare temporal variables during transitions from trot to halt (TH) and halt to trot (HT) in horses competing in different levels of dressage competitions. The experimental hypothesis was that a higher level of training is associated with the ability to make more direct transitions with fewer non-trot steps. Video recordings of TH and HT transitions were made during novice (n = 15 horses), medium (n = 15 horses) and advanced (n = 15 horses) dressage competitions and were analysed to determine the timing of footfalls and lift-offs. Duty factors, diagonal dissociations and suspension durations were calculated for eight diagonal steps preceding and following the halt. The steps were classified as trot or non-trot based on diagonal synchrony of the footfalls. Statistical analysis using a general linear model ANOVA with Tukey B post hoc tests indicated that advanced horses changed their limb coordination patterns more abruptly, and that they maintained positive diagonal dissociation and a suspension phase in the steps in closer proximity to the halt than the novice horses. There was no preference between left/right and fore/hind limbs in the order of limb placements in the TH transition. The first limb to move off from the halt was always a forelimb, with a significant preference for the right forelimb in the advanced horses.

The present study tested the hypothesis that lactate concentration ([La− ]) would differ between sample sites and between assay techniques that used different analytical substrates. Six clinically normal adult (two Thoroughbreds, three Standardbreds and one Quarter Horse) mares weighing between 435 and 560 kg were used in the study. Each mare performed an incremental exercise test (graded exercise test, GXT) where it ran on a treadmill at a fixed 6% grade. The GXT started at 3 m s− 1 for 1 min with increased in speed by 1 m s− 1 every 60 s until the horses completed the final 10 m s− 1 step. Jugular vein, pulmonary arterial and carotid arterial blood samples (14 ml) were collected before exercise and during the last 10 s of each step of the GXT. [La− ] was measured in whole blood (WB, no manipulations), total blood (TB, where the red blood cells were lysed) and plasma. Data were used to calculate the velocity to produce [La− ] of 4 mmol l− 1 (VLA4) and 10 mmol l− 1 (VLA10). Statistical analysis utilized a three-way ANOVA and, where appropriate, the Holm–Sidak or the Student Neuman–Keuls method for post hoc comparisons. The null hypothesis was rejected when P < 0.05. There was an effect of exercise intensity on [La− ] for all three methods (P < 0.001) with all means during exercise significantly greater than the resting mean, and there were differences due to method (i.e. analytical substrate) (P < 0.001) and sample site (P = 0.043). Comparisons of least-squared means (LSM ± SE) within site revealed that there was a difference (P < 0.05) between jugular vein (5.41 ± 0.24) and carotid artery (6.24 ± 0.24) and between carotid and pulmonary artery (5.98 ± 0.24). There was no difference (P>0.05) between jugular vein and pulmonary artery. Within method, there was a difference (P < 0.05) between WB (6.54 ± 0.36) and TB (5.06 ± 0.36) and between TB and plasma (6.04 ± 0.64), but there was no difference (P>0.05) between WB (6.54 ± 0.36) and plasma (6.04 ± 0.64). Further analysis of the data demonstrated that the method and sample site influenced (P < 0.05) VLA4 and VLA10.

Foot strike can be difficult to determine using kinematics alone, particularly when studying equine activities on more compliant surfaces, so this study was done with the aim of developing and validating a method to determine foot strike on an arena surface that can be used in conjunction with kinematics alone, and of applying the method in the context of measuring foot strike during jump landing on an arena surface. A low-cost contact mat was developed. The timing of the contact mat switching ‘on’ was compared to the timing of a force platform onset of 20 N, load and loading rate at foot strike. Two groups of 25 participants were used in two separate studies to validate the contact mat: the first measured the difference in timing with respect to two different activities (running and stepping down from a box), and the second measured the difference in timing with respect to 1- and 2-cm depths of an arena surface during running. In a third study, the mat was used to measure leading limb foot strike of six horses during jump landing, and these data were compared to kinematics from a palmar marker on the hoof wall. All data were recorded at 500 Hz. A consistent difference in delay was found between the mat and force platform onset, and as a result, no significant differences (P>0.05) in timing delay between different loading rates or depths were found. During jump landing, foot strike (determined from the mat) occurred after the vertical velocity minima and the acceleration maxima for the hoof marker, but it occurred before the point where the rate of vertical displacement began to reduce. In conclusion, further work is needed to enhance these techniques, but these preliminary results indicate that this method may be effective in determining foot strike for field-based applications.

Few equine studies exist comparing the effects of different forms of training. This study tested the following hypothesis: interval training (IT) results in similar or better fitness parameters in Thoroughbreds when compared to continuous incremental training (CT) of the same workload with fewer galloping strides. Two groups of five horses underwent 6 weeks of IT or CT. Fitness levels were established before and following training. Both groups showed significant increases in VO2max (P < 0.05), lactate threshold (P < 0.05), work rate corresponding to 100% VO2max (P < 0.05) and work to fatigue during an incremental and sprint exercise test (P < 0.05). The interval-trained group had a significant increase in peak lactate values (P < 0.05) and a significant decrease in body weight (P < 0.05). The increase in VO2max of the interval group was greater than the increase in VO2max of the continuous incremental group (P = 0.10), increasing 27.38 ± 8.44 and 14.64 ± 2.66%, respectively. The interval group took significantly fewer galloping strides than the continuous incremental group for all weeks of training (P < 0.05). It is considered that supramaximal IT improves equine fitness as well as CT of the same workload with fewer galloping strides.

The objective of this experiment was to test the hypothesis that ageing and training alter plasma concentrations of the peptide hormone leptin. The rationale for the study is based on prior investigations performed at Rutgers University, where published reports documented that ageing disrupts the immune and endocrine responses to acute exercise. The training period for mature young (7.3 ± 0.6 years; n = 6) and old (22 ± 0.7 years; n = 6) (mean ± SE) Standardbred mares was the duration of the summer of 2009 at the Rutgers University Equine Exercise Physiology Laboratory. Mares exercise trained in groups of six in a free-stall motorized circular equine exercise machine for 30 min, three times per week. Each mare performed a graded exercise test before beginning the training, after 8 weeks and after 16 weeks of training. There was no difference in body mass due to age (P>0.10). Training caused an increased body mass in both old and young mares (P < 0.10). There was no effect of training on rump fat thickness; therefore, the increase in body mass was primarily due to an increase in fat-free mass (muscle mass). Old mares had significantly lower plasma leptin at all sample points. As a result of training, plasma leptin was reduced in both old and young mares (P < 0.10). In conclusion, age and training appear to alter the relationship between body composition and leptin.

The equine hoof wall is a hard, keratinous structure that transmits forces generated when the hoof connects the ground to the skeleton of the horse. During locomotion the hoof capsule is known to deform, resulting in an inward curvature of the dorsal wall and expansion of the heels. However, while researchers have studied the tensile and compressive properties, there is a lack of data on the flexural properties of the hoof wall in different locations around the hoof capsule. In this study, the flexural properties and hydration status of the hoof wall were investigated in two orthogonal directions, in different locations around the hoof capsule. The hoof was divided into three regions: the dorsal-most aspect (toe), the medial and lateral regions (quarters) and the heels caudally. Beams were cut both perpendicular (transverse) and parallel (longitudinal) to the orientation of the tubules. Differences in the mechanical properties were then investigated using three-point bending tests. There were considerable differences in the flexural properties around the hoof capsule; transverse beams from the heel were 45% more compliant than those from the toe region. This corresponded with changes in the hydration of the hoof wall; beams from the heel region were more hydrated (28.2 ± 0.60%) than those from the toe (24.2 ± 0.44%; P < 0.01). Regional variation in the water content is thought to help explain differences in the flexural properties. Mechanical data are further discussed in relation to variation in the structure and loading of the hoof wall.