The biomechanical construction of the horse's body and activity patterns of three important muscles of the trunk in the walk, trot and canter

Abstract

The activity patterns of trunk muscles are commonly neglected, in spite of their importance for maintaining body shape. Analysis of the biomechanics of the trunk under static conditions has led to predictions of the activity patterns. These hypotheses are tested experimentally by surface electromyography (EMG). Five horses, with and without a rider, were examined in the walk, trot and canter. Footfall was synchronised with EMG by an accelerometer. Averages of ten consecutive cycles were calculated and compared by statistical methods. The start and stop times of the muscle activities of 5-10 undisturbed EMG plots were determined and the averages and standard deviations calculated. In walking, muscle activities are minor. Electromyography (EMG) activity was increased in the m. rectus during the three-limb support. When the bending moments assume their greatest values, for example while the horses' mass is accelerated upward (two times earth acceleration) in the diagonal support phases in trot and canter the m. rectus, connecting the sternum with the pubic bone is most active. The m. obl. externus is most active when the torsional and bending moments are greatest during the same support phases, but not bilaterally, because the forces exerted on one side by the (recorded) m. obl. externus are transmitted on the other side by the (not recorded) m. obl. internus. While the hindlegs touch the ground in the trot and canter, ground reaction forces tend to flex the hip joint and the lumbar spine. Therefore, the vertebral column needs to be stabilised by the ipsilateral m. longissimus dorsi, which in fact can be observed. As a whole, our EMG data confirm exactly what has been predicted by theoretical analysis.

The effect of cut-off frequency when high-pass filtering equine sEMG signals during locomotion

“…A cut-off frequency range of 30 -40 Hz is in agreement with previous equine sEMG studies that report using a HPF with a 40 Hz cut-off (Cheung et al, 1998;Kienapfel, 2015;Kienapfel et al, 2018), but do not provide a justification for why this cut-off frequency was chosen. Findings from this study indicate that, while previously employed cut-off frequencies of 10 and 20 Hz (Hodson-Tole., 2006;Crook et al, 2010;Harrison et al, 2012) are more likely to preserve the low-frequency component of the equine sEMG signal, they are not appropriate for completely attenuating the noise components.…”

“…No horse contributed to more than one group. sEMG signals from stance and swing phase were DC offset removed and, in accordance with (Kienapfel, 2015;Kienapfel et al, 2018), were HPF using a Butterworth 4 th order filter. HPF cut-off frequencies (n ranging between 10 -80 Hz), were applied to each signal in 10 Hz increments.…”

“…These studies recommend the use of a HPF cut-off frequency ≥ 20 Hz for most applications (Van Boxtel et al, 1998;Van Boxtel, 2001;De Luca et al, 2010). In equine sEMG research, HPF cut-off frequencies of 10 Hz (Harrison et al, 2012), 20 Hz (Hodson-Tole., 2006Crook et al, 2010;Harrison et al, 2012) and 40 Hz (Kienapfel, 2015;Kienapfel et al, 2018) have been reported. No known studies have employed the methods described in human literature to determine the optimal HPF cut-off frequency for equine sEMG signals.…”

Sagittal plane fore hoof unevenness is associated with fore and hindlimb asymmetrical force vectors in the sagittal and frontal planes

“…In sound trotting horses m . longissimus dorsi activity occurs from mid swing of the ipsilateral hindlimb until early stance and in the propulsive phase of stance [ 31 , 32 ]. In order to facilitate lateral bending towards the lame limb a larger, earlier contraction on the contralateral, lame side, would be expected (i.e.…”

Use of accelerometer end gyroscope in biomechanical studies of horses

“…Analiza biomechaniki tułowia w warunkach statycznych okazała się przydatna do prognozowania wzorców aktywności. Wykorzystano akcelerometr i elektromiografię powierzchniową (EMG) do ustalenia aktywności poszczególnych mięśni tułowia u 5 koni, badanych w trzech rodzajach chodu, w próbie pod jeźdźcem i bez siodła (27). Jednocześnie zastosowano pomiary przyspieszeń do określenia poprawności chodów, w tym kulawizn.…”