This study tested the hypothesis that phenylbutazone would block the exercise-induced increase in cytokine markers of inflammation in blood. Blood samples were obtained from unfit Standardbred mares (age 10 ± 4 years, ~500 kg) before and after three different trials (standing control (CON), n = 9; exercise with phenylbutazone (EX-bute), n = 9; and exercise with water, n = 9). Comparisons were made for data collected in three trials, one where each horse underwent an incremental exercise test (graded exercise test (GXT)) where they were administered water as a placebo, a GXT following phenylbutazone administration (2 g given orally 2 h before the GXT) or standing parallel control where they stood quietly in stalls. During the GXT, horses ran on a treadmill (1 m s− 1 increases each min until fatigue, 6% grade). Blood samples were obtained 30 min before exercise, immediately after exercise and at 0.5, 1, 2, 4 and 24 h post-GXT or at matched time points during the parallel control trials. Samples were analysed using real-time PCR for measurement of mRNA expression of interferon-γ (IFN-γ), tumour necrosis factor-α (TNF-α) and interleukin (IL)-6 in samples collected during all three trials, and for IL-1 and IL-10 in samples collected for the CON and EX-bute trials. Data were analysed using ANOVA for repeated measures, and where appropriate, post hoc separation of means utilized the Student–Newman–Keuls test. The null hypothesis was rejected when P < 0.05. There were no changes (P>0.05) in IL-1, IL-6, IFN-γ or TNF-α during CON or following phenylbutazone administration. During the water trial, exercise resulted in significant increases in IFN-γ, IL-1 and TNF-α. It was concluded that high-intensity exercise results in a transient increase in the expression of inflammatory cytokines in blood that is blocked when phenylbutazone is administered to horses.

Successful completion of endurance exercise is facilitated by conditioning that enhances the capacity of the cardiovascular and musculoskeletal systems to maintain a high level of aerobic activity. Insufficiency or disease in these systems may be diagnosed using routine haematology and serum chemistry testing. Pre-race blood samples obtained from 82 endurance-trained sled dogs were used to test the hypothesis that common haematological and serum chemistry values could identify subjects with occult disease, decreasing the likelihood of their finishing a multi-day exercise challenge. Multivariate logistic regression was used to identify the combinations of specific biomarkers that best predicted the eventual outcome of the exercise challenge for an individual dog. This analysis constructed six different predictive formulas. In all cases, the formulae contained the pre-race values for creatine kinase and some measurement of erythrocyte abundance. When a probability of 0.4 was used as a cut-off value, all dogs with values below the cut-off did not complete the race. These results suggest that in a population of healthy, aerobically conditioned subjects, routine clinical biomarkers can be used to identify subjects unsuited to performance for endurance exercise.

The primary purpose of this study was to test the predictions of the dual-mode model using arm ergometry as the exercise modality. It was hypothesized that changes in affect during exercise would be greater in high (105% VT)- and low (80% VT)-intensity exercise conditions than in a control condition, while differences in affect would be observed between exercise conditions. Study participants were 24 physically active men. A within-subjects design was used. Affect was measured using the Activation–Deactivation Adjective Check List and the State Anxiety Inventory. Cognitive (i.e. self-efficacy and enjoyment) and physiological (i.e. heart rate, pain and perceived exertion) mediators of the exercise–affect relationship were also examined. Results showed that during exercise, changes in affect were greater in the exercise conditions than the control condition, and affective valence in the exercise conditions declined relative to the control condition. In partial support of the dual-mode model, self-efficacy mediated the relationship between below-VT exercise and affect, whereas pain mediated the relationship between above-VT exercise and affect. These findings highlight the importance of exercise intensity to the affective benefits of exercise.

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.

Nutritional management studies to improve the performance of Mangalarga Marchador (MM) horses during the marcha test are limited. This study was designed to test the hypothesis that chelated trivalent chromium (CR) feed supplementation may reduce the suitability of the length of the interval between concentrate feeding and the marcha test among MM horses. A total of 12 healthy mares (4.25 ± 0.62 years) were randomly assigned to one of six dietary treatments (0 or 10 mg Cr by concentrate, fed 0.5, 2 or 4 h before exercise), according to a completely randomized design, with a split-plot arrangement. The diet was Cynodon pasture and concentrate (50:50 ratio). The first 29 days of the trial were for diet, Cr and exercise adaptation; during the next 15 days, horses were submitted to three 50-min field marcha tests, once a week. Heart rate (HR) was measured before, during and until 25 min after the exercise. Respiratory rate and rectal temperature were measured; blood samples were collected before, at the end and 25 min after the test. There was no effect of Cr by concentrate feeding strategy on any physiological variables (P>0.05). Supplementation of Cr increased glycaemia before and soon after the second marcha test (P < 0.01). In addition, Cr reduced HR during the second marcha test and decreased the time to first post-exercise HR recovery (P < 0.05). Insulinaemia was greater when the concentrate was provided 2 h prior to the test (P < 0.05). Concentrate provided 0.5 and 2 h before the test reduced plasma triacylglycerol in the first and second tests, respectively. The interval between concentrate feeding and marcha tests should not be decreased in horses supplemented with Cr. Horses should be fed more than 2 h before that test. Cr supplementation during training may improve the cardiac performance of MM mares during the marcha test.

The tension applied to the girth is usually based on an individual's experience rather than by scientific measurement or procedure. The equine thorax is a dynamic structure, and therefore the actual readings of girth tensions at rest and during exercise (actual tension) are likely to vary from the tension to which the girth was intended to be tightened at rest while standing (intended tension). This study was undertaken to determine the variability of girth tensions at rest and during exercise. A total of 19 Hanoverian horses were lunged on a 20 m circle in walk, trot and canter on both reins. In a randomized design, each horse was exposed to intended tensions 6, 10, 14 and 18 kg (saddle and girth at appropriate intended tensions). Girth tension was measured and recorded continuously using an in-line load cell. Intended girth tensions were not significantly different with mean actual girth tensions while standing. Actual girth tensions increased significantly (P < 0.001) between walk, trot and canter at all tensions except rest to trot at tension 6 kg, where the significance level was P < 0.01. Actual girth tension was significantly higher (P < 0.001) on the left rein at tension 14 kg in walk and trot, and at tensions 6, 10 and 14 kg during canter, and there was an overall trend for higher actual girth tensions on the left rein for the other tensions. As the thorax is a dynamic structure, girth tension variation could be due to multiple factors such as respiration, breath holding, muscular contraction, back flexion and extension, speed, gait and vertical acceleration of the saddle. Girth tension is a relatively new area of research, and as there are many opportunities for further research, a better understanding of the impact the girth has on the horse could help to improve performance and welfare.