SummaryReason for performing study: The rectus abdominis (RA) and oblique external abdominal (OEA) muscles are both part of the construction of the equine trunk and thought to be essential for the function of the spine during locomotion. Although RA activity at trot has previously been investigated, the relationship between OEA and RA at walk and trot has not yet been described. Objectives: To document abdominal muscle activities during walk and trot, and test the hypothesis that muscle activity at walk would be smaller than at trot. Materials and methods: Six horses (8-20 years old, 450-700 kg) were used for surface electromyography (EMG) measurements, with EMG electrodes placed caudal to the sternum (RA) and at the level of the 16th rib (OEA). On all hooves, the withers and the sacrum reflective markers were placed to determine motion cycles. Normal distribution of data was tested using a Kolmogorov-Smirnov test and Student's t test was used to compare left-right and walk-trot differences (P<0.05). Results: Minimum, maximum and mean EMG values recorded at walk were significantly higher at trot than at walk in all horses for OEA and in 5/6 horses for RA. At walk, EMG activity ranged from 8-44 mV (RA) and 7-54 mV (OEA). At trot, EMG activity ranged from 18-150 mV (RA) and 27-239 mV (OEA). There were statistically significant differences between maximum activities of left and right OEA and RA muscles at walk in all horses, and in 4/6 horses at trot. Conclusions: Muscle activities of OEA and RA are smaller at walk than at trot. At walk, the OEA/RA ratio is lower than at trot. There are more significant correlations between muscle activities of both RA and OEA and limb movements at walk than at the trot.

The study of muscle activity using surface electromyography (sEMG) is commonly used for investigations of the neuromuscular system in man. Although sEMG has faced methodological challenges, considerable technical advances have been made in the last few decades. Similarly, the field of animal biomechanics, including sEMG, has grown despite being confronted with often complex experimental conditions. In human sEMG research, standardised protocols have been developed, however these are lacking in animal sEMG. Before standards can be proposed in this population group, the existing research in animal sEMG should be collated and evaluated. Therefore the aim of this review is to systematically identify and summarise the literature in animal sEMG focussing on (1) species, breeds, activities and muscles investigated, and (2) electrode placement and normalisation methods used. The databases PubMed, Web of Science, Scopus, and Vetmed Resource were searched systematically for sEMG studies in animals and 38 articles were included in the final review. Data on methodological quality was collected and summarised. The findings from this systematic review indicate the divergence in animal sEMG methodology and as a result, future steps required to develop standardisation in animal sEMG are proposed.

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SummaryReason for performing study: The motion of the atlantooccipital, cervical vertebral and cervicothoracic joints play an important role in equestrian sports and they are also common sites for lesions limiting performance in horses. Objectives: To calculate inverse kinematics based on cervical vertebral motion and to develop a model close to the measured neck movements. Materials and methods: Measurements were recorded in 6 horses without neck pain. Reflective markers were placed on both cristae facialis, both sides of cervical vertebra 1, 3 and 6 on the withers and hooves. The neck model was reconstructed from CT scans of the osseus structures and was developed in SIMM (Software for Interactive Musculoskeletal Modelling). Inverse kinematics calculation was done in OpenSim. Three degrees of freedom: Flexion-extension (FE), axial rotation (AR) and lateral bending (LB) were considered. The simulated motion was generated from the recorded motion of the skin markers. The differences in angular range of motion (ROM) of the joints were analysed using paired sample t tests. Results: From the model, the smallest FE ROM was in the C5-C6 joint (2°Ϯ 1°) and the largest was in the C3-C4 joint (11°Ϯ 5°). The smallest AR ROM was in the C5-C6 joint (2°Ϯ 1°) and largest AR ROM was in the atlantoaxial joint (7°Ϯ 2°). The smallest LB ROM was in the C5-C6 joint (2°Ϯ 1°) and the largest LB ROM was in the cervicothoracic joint (18°Ϯ 5°). There were significant differences between the ROM of joints in 51 of 168 comparisons (P<0.05). Conclusions:The result of the motion of each joint gives an insight into the biomechanics of the equine neck. The small FE ROM at C5-C6 illustrates the pathogenetical relevance of the model for the development of osteoarthritis. The calculated data also provides a source for inverse dynamics.evj_265 516..522

SummaryReasons for performing study: Skeletal muscle activity can be concentric or eccentric, anisometric or isometric and correlation of the equine splenius muscle activity with the movement of its effector joints at walk and trot has not yet been fully characterised. Objective: Investigating activity of the splenius muscle together with kinematics of head and cranial neck at walk and trot.

Accurately measuring body temperature in horses will improve the management of horses suffering from or being at risk of developing postrace exertional heat illness. PTSM has the potential for measuring body temperature accurately, safely, rapidly, and noninvasively. This study was undertaken to investigate the relation between the core body temperature and PTSM temperatures prior to, during, and immediately after exercise. The microchips were implanted into the nuchal ligament, the right splenius, gluteal, and pectoral muscles, and these locations were then compared with the central venous temperature, which is considered to be the “gold standard” for assessing core body temperature. The changes in temperature of each implant in the horses were evaluated in each phase (prior to, during, and immediately postexercise) and combining all phases. There were strong positive correlations ranging from 0.82 to 0.94 (p < 0.001) of all the muscle sites with the central venous temperature when combining all the phases. Additionally, during the whole period, PTSM had narrow limits of agreement (LOA) with central venous temperature, which inferred that PTSM is essentially equivalent in measuring horse body temperature. Overall, the pectoral PTSM provided a valid estimation of the core body temperature.

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