Human heart rate monitors (HRMs) are frequently used in equine studies to measure heart rate (HR) and interbeat intervals (IBIs). However, to date, the most commonly used HRM (the Polar® system) in horses has not been validated against simultaneously recorded electrocardiogram (ECG) signals during a range of ambulatory conditions. Polar® S810i and ECG IBIs were simultaneously recorded from six horses under three conditions commonly included in behavioural observation: standing at rest, loose in the stable and at liberty in a field. Following recording, Polar® IBI data were corrected for error processing in cardiac data. Corrected and uncorrected Polar® data were then compared with simultaneously recorded ECG data using a variety of commonly measured time and frequency domain parameters (e.g. HR variability (HRV)). Polar® data collected while horses were stabled or in the field were significantly different from ECG data, even following correction of the data, and therefore, it may not be possible for the two systems to be used interchangeably. This study indicates the need for caution while using Polar® S810i for collecting HRV data, unless horses are stationary, and even when the IBI data are corrected for measurement error.

This study investigated intra-oral behaviours in horses wearing different bits with and without rein tension. Six riding horses wore a bridle and three bits: jointed snaffle, KK Ultra and Myler comfort snaffle. Lateral fluoroscopic images (30 Hz) were recorded for 20 s for each bit with loose reins and with 25 ± 5 N bilateral rein tension. The videos were analysed to determine time spent in the following behaviours: mouth quiet, gently mouthing the bit, retracting the tongue, bulging the dorsum of the tongue over the bit, lifting the bit and other behaviours that were performed infrequently. Repeated-measures ANOVA indicated that behaviours did not differ between bits, so bit type was not predictive of behaviour, but there were significant effects of horse and rein tension. Horses spent less time quiet and more time mouthing the bit, retracting the tongue and bulging the tongue over the bit when tension was applied.

While temporal variable measurements have assisted in objectively defining and distinguishing between four-beat stepping gaits performed by gaited horses, kinematic research describing joint motion of the gaited horse is limited. The objective of this study was to measure the temporal variables and the forelimb kinematics of the flat walk and fox trot of the Missouri Fox Trotter (MFT) to provide a more comprehensive description of these gaits and to assist in distinguishing between them. Reflective markers placed along the lateral aspect of the right forelimb and the zygomatic process of the temporal bone were tracked at 60 Hz as eight MFTs were ridden at a flat walk and fox trot for ten strides. Student's paired t-tests were performed to compare means of analysed parameters between gaits on finding that the fox trot was a faster stepping gait (fox trot velocity: 3.17 ± 0.03 m s− 1, flat walk velocity: 1.75 ± 0.06 m s− 1) with a shorter stride duration (fox trot: 0.63 ± 0.03 s, flat walk: 1.17 ± 0.06 s) and greater stride frequency (fox trot: 1.59 ± 0.09 strides s− 1, flat walk: 0.09 ± 0.04 strides s− 1) than the flat walk (P < 0.05). Both gaits were performed with similar stride length (fox trot: 2.0 ± 0.03 m, flat walk: 1.95 ± 0.05 m), but the fox trot had an irregular rhythm with diagonal couplets (diagonal advanced placement: 0.10 ± 0.01 s, lateral advanced placement: 0.23 ± 0.02 s). Vertical head excursions, protraction/retraction angles and joint angle-time curves for the shoulder, elbow, carpus and forelimb fetlock were similar between gaits. Shoulder peak flexion of the fox trot occurred later in the stride (fox trot: 38 ± 5%, flat walk: 20 ± 3%; P < 0.05), but the timing of the other peak flexion and extension joint angles were similar between gaits. The fox trotting carpus flexed more (fox trot: 136 ± 3°, flat walk: 147 ± 4°) than the carpus of the flat walk (P < 0.05), but the other peak flexion and extension joint angles were comparable between gaits. Measured temporal and kinematic variables assisted in defining the fox trot and flat walk and differences between variables can be applied in distinguishing between the two gaits.

This study hypothesized that ginger (Zingiber officinale) and cranberry (Vaccinium macrocarpon) extracts would alter the physiological response to exercise as well as markers of muscle damage, and mRNA expression for the inflammatory cytokines tumour necrosis factor-α (TNF-α), interferon-γ (IFN-γ) and interleukin-6 (IL-6) after an exhaustive bout of exercise in horses. Nine unfit Standardbred mares (age 10 ± 4 years, ~450 kg) completed three graded exercise tests (GXTs) in a crossover design, where they were assigned to the initial order of treatment in a randomized fashion. The GXTs were conducted between 07.00 and 12.00 hours, 7 days apart. Mares received either water (2 l), cranberry (~30 g in 2 l of water) or ginger (~30 g in 2 l of water) extract 1 h prior to testing. Blood samples were taken prior to dosing (pre-exercise), at the end of each step of the GXT, at the end of the exercise and at 2, 5 and 30 min, 1, 2, 4 and 24 h post-GXT. Plasma total protein (TP) concentration and haematocrit (HCT) were analysed immediately following the tests. Analysis of creatine kinase (CK) and aspartate aminotransferase (AST) was done commercially. There was no effect of treatment (P>0.05) on VO2max, run-time to fatigue, core temperature, TP or HCT. CK was substantially elevated (P < 0.05) in the ginger group at 4 h post-GXT. All CK levels returned to baseline 24 h post-GXT. No change (P>0.05) was noted in AST. A slight increase (P < 0.05) in CK was seen in all groups at 2 h post-GXT. The cranberry group had significantly lower TNF-α mRNA expression than the control and ginger groups. Ginger appeared to influence (P < 0.05) the upregulation and expression of IFN-γ mRNA at 30 min post-GXT, but, more strikingly, significantly decreased recovery time defined as the time for VO2 to recover from the peak observed at fatigue to a post-exercise plateau (ginger = 101 ± 3 s, water = 130 ± 14 s, cranberry = 131 ± 16 s). No effect of treatment or exercise (P>0.05) was seen on IL-6 mRNA expression. Results suggest that cranberry extract blunts the upregulation and expression of TNF-α mRNA, while ginger extract reduces cardiovascular recovery time in horses completing a short, exhaustive bout of exercise.

The aim of this study was to investigate the effect of high-intensity training on lactate transporters (monocarboxylate transporters (MCTs)) in Thoroughbred horses. Five Thoroughbreds (three males and two geldings; 3–10 years old; 478 ± 13 kg) ran at 100% maximal oxygen uptake (VO2max) for 1 min (3 days per week, 3 weeks) or 2 min (2 days per week, 4 weeks) on a treadmill for 7 weeks. VO2max and ability to sustain an incremental all-out test of maximal running were measured, and muscle samples were obtained from the gluteus medius muscle at rest before and after the training. The performance in the all-out test and VO2max were increased after the training. The protein content of MCT1 and MCT4 in the gluteus medius muscles was not significantly altered. However, MCT1 showed a relationship with the duration of maximal exercise after the training. The changes in MCT4 showed a relationship with the increase in exercise duration by the training. These results suggest that in Thoroughbreds, although the overall changes in MCT protein after endurance training are small, MCT1 and MCT4 can play important roles in the capacity to sustain maximal exercise.

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.