Reliability of surface electromyographic (sEMG) measures of equine axial and appendicular muscles during overground trot

The reliability of surface electromyography (sEMG) has not been adequately demonstrated in the equine literature and is an essential consideration as a methodology for application in clinical gait analysis. This observational study investigated within-session, intra-subject (stride-to-stride) and inter-subject reliability, and between-session reliability of normalised sEMG activity profiles, from triceps brachii (triceps), latissimus dorsi (latissimus), longissimus dorsi (longissimus), biceps femoris (biceps), superficial gluteal (gluteal) and semitendinosus muscles in n = 8 clinically non-lame horses during in-hand trot. sEMG sensors were bilaterally located on muscles to collect data during two test sessions (session 1 and 2) with a minimum 24-hour interval. Raw sEMG signals from ten trot strides per horse and session were DC-offset removed, high-pass filtered (40 Hz), full-wave rectified, and low-pass filtered (25 Hz). Signals were normalised to peak amplitude and percent stride before calculating intra- and inter-subject ensemble average sEMG profiles across strides for each muscle and session. sEMG profiles were assessed using waveform similarity statistics: the coefficient of variation (CV) to assess intra- and inter-subject reliability and the adjusted coefficient of multiple correlation (CMC) to evaluate between-session reliability. Across muscles, CV data revealed that intra-horse sEMG profiles within- and between-sessions were comparatively more reliable than inter-horse profiles. Bilateral gluteal, semitendinosus, triceps and longissimus (at T14 and L1) and right biceps showed excellent between-session reliability with group-averaged CMCs > 0.90 (range 0.90-0.97). Bilateral latissimus and left biceps showed good between-session reliability with group-averaged CMCs > 0.75 (range 0.78-0.88). sEMG profiles can reliably describe fundamental muscle activity patterns for selected equine muscles within a test session for individual horses (intra-subject). However, these profiles are more variable across horses (inter-subject) and between sessions (between-session reliability), suggesting that it is reasonable to use sEMG to objectively monitor the intra-individual activity of these muscles across multiple gait evaluation sessions at in-hand trot.

Surface EMG signal normalisation and filtering improves sensitivity of equine gait analysis

Low-frequency noise attenuation and normalisation are fundamental signal processing (SP) methods for surface electromyography (sEMG), but are absent, or not consistently applied, in equine biomechanics. The purpose of this study was to examine the effect of different band-pass filtering and normalisation conventions on sensitivity for identifying differences in sEMG amplitude-related measures, calculated from leading (LdH) and trailing hindlimb (TrH) during canter, where between-limb differences in vertical loading are known. sEMG and 3D-kinematic data were collected from the right Biceps Femoris in 10 horses during both canter leads. Peak hip and stifle joint angle and angular velocity were calculated during stance to verify between-limb biomechanical differences. Four SP methods, with and without normalisation and high-pass filtering, were applied to raw sEMG data. Methods 1 (M1) to 4 (M4) included DC-offset removal and full-wave rectification. Method 2 (M2) included additional normalisation relative to maximum sEMG across all strides. Method 3 (M3) included additional high-pass filtering (Butterworth 4th order, 40 Hz cut-off), for artefact attenuation. M4 included the addition of high-pass filtering and normalisation. Integrated EMG (iEMG) and average rectified value (ARV) were calculated using processed sEMG data from M1 – M4, with stride duration as the temporal domain. sEMG parameters, within M1 – M4, and kinematic parameters were grouped by LdH and TrH and compared using repeated measures ANOVA. Significant between-limb differences for hip and stifle joint kinematics were found, indicating functional differences in hindlimb movement. M2 and M4, revealed significantly greater iEMG and ARV for LdH than TrH (P<0.01), with M4 producing the lowest P-values and largest effect sizes. Significant between-limb differences in sEMG parameters were not observed with M1 and M3. The results indicate that equine sEMG SP should include normalisation and high-pass filtering to improve sensitivity for identifying differences in muscle function associated with biomechanical changes during equine gait.

Does equestrian knowledge and experience influence selection and training practices for showjumping horses?

Selection and training methods for showjumping horses are largely anecdotal, and performance analysis has been proposed as a method for scientifically improving competitive outcomes. To employ performance analysis in showjumping, an understanding of the tacit and explicit knowledge and practices of equestrians is required to identify relevant performance indicators. This study aimed to examine the knowledge and practices of equestrians with varying levels of experience (advanced and novice) for selecting horses, based on evaluation of movement, and training showjumping horses using an original questionnaire. It was hypothesised that differences would be present between advanced and novice responses. The questionnaire was composed of closed-end and follow-up open-end questions and 225 equestrians (66.7% advanced, 33.3% novice) participated. Closed-end responses from advanced and novice groups were analysed separately using Chi-Squared tests and open-end responses were subjected to thematic and content analysis. Closed-end responses showed significant within-group preferences (P<0.0001) for specific movement traits and training methods and between-group response differences <13% revealed that advanced and novice groups displayed similar preferences. Thematic analysis indicated different preferences for movement traits when selecting showjumping horses, as well as differences in the level of tacit knowledge between advanced and novice groups. Advanced equestrians placed greater emphasis on aesthetic forelimb traits than novice equestrians, who emphasised traits that they may be less capable of influencing, such as hindlimb impulsion and position of the horse at take-off. An emphasis on hindlimb movement and flatwork/non-jumping exercises for showjumping training was observed across both groups. Understanding equestrian tacit knowledge and its application is fundamental for developing research that is relevant to equestrians. Findings from this study may form a basis for research to identify relevant, objective performance indicators for performance analysis in showjumping, with the ultimate goal of improving competitive performance and welfare for equine athletes.

Electromyographic evaluation of approach stride, jump stride and intermediate stride in selected superficial muscles of the jumping horse: a preliminary study

The horse's ability to execute the diverse physical demands of jumping is greatly influenced by muscular adaptations to training. The aim of the study was to provide preliminary insight into potential differences in the functional activity of muscles recruited during phases of the equine jumping effort. An exploratory case study was conducted to investigate muscle activity and recruitment in one jumping horse, experienced in 1.40 m competition. Wireless sEMG electrodes were utilised to quantitatively investigate the degree of muscle activation by recording potentials from the Superficial gluteal (SG), Triceps brachii (TB) and Longissimus dorsi muscles. Data were collected as the horse executed a related combination of fences with a maximum height of 1.25 m. Mean motor unit action potential (mMUAP) and mean peak amplitude frequency (PAF) were determined for each muscle during approach, jump and intermediate strides, and were analysed using Friedman and Wilcoxon Signed Rank tests to establish whether significant differences occurred between strides. Statistical analyses did not reveal significant differences between mMUAP values for muscles investigated across strides (P≯0.05). However, significant differences were found for mean PAF values in the left SG between approach and jump strides (P<0.025), and between jump and intermediate strides (P<0.025) in the left TB. The lack of significant differences between strides may reflect the theory that the jump stride is a form of extended suspension incorporated into the canter stride and may support current anecdotal training methods of the jumping horse, which place emphasis on developing a regular and collected canter. However, results from this study were based on one horse and therefore application to the wider population of jumping horses should be undertaken with caution until further research in more subjects is conducted to support the results from this preliminary study.

Immediate postpartum complications

Two hundred and sixty-nine (5.4%) of the 4,998 patients who delivered in Westmead Hospital, New South Wales in 1985 had immediate postpartum complications. This analysis was compared with figures from a major institution in another state of Australia. Early detection and prompt management without procrastination was the key to a successful outcome in the fourth stage of labour (i.e. within 24 hours of delivery). Nearly three-quarters of the complications were due to postpartum haemorrhage (PPH). The contributory factors are analysed and discussed. Reappraisal of the indications for induction of labour, epidural analgesia and forceps delivery is necessary to reduce the incidence of postpartum haemorrhage. The study reinforces the need for undiminished vigilance in the fourth stage of labour even if the first 3 stages are uncomplicated.

Low vertical uterine incision in caesarean section

Eleven of the 3,420 Caesarean sections performed in Westmead Hospital, Sydney during a 6-year period from 1979 to 1985 were by a low vertical uterine incision. All the others were the standard transverse lower segment operation except for 1 which was a postmortem classical Caesarean section. There are indications when the preferred lower segment Caesarean section with a transverse incision should be avoided in the interest of the mother and baby. A low vertical incision has more advantages and less dangers than a classical fundal incision. It is prudent to defer the decision regarding the type of incision until the uterus is inspected intraoperatively. If access to the lower uterine segment is limited by prematurity, an obstructing lesion, a transverse lie, or if the presenting part is high and difficulty in delivering the baby is anticipated, a low vertical incision should be considered.