The effect of three different head–neck positions on the average EMG activity of three important neck muscles in the horse

Abstract

Summary The Knowledge of muscle activity in common head–neck positions (HNPs) is a necessary precondition for making judgements on HNPs. The aim of the study was to record the surface electromyography activities of important muscles of the horse's neck in various HNPs. The electrical activities of the m. splenius, brachiocephalicus and trapezius were recorded on both sides. Five horses, both with and without a rider, were examined in all three gaits on both hands in three different HNPs: a ‘free’ position, a ‘gathered’ (head higher, neck more flexed) position with the noseline in front of the vertical and a ‘hyperflexed’ position. Averages of ten consecutive gait cycles in each HNP were evaluated and compared by standard statistical methods. No difference between ridden and unridden horses could be detected. The m. brachiocephalicus was in the hyperflexed position in all gaits significantly (p < 0.01) more active than in the gathered and free position, which were not significantly different. By contrast, the m. splenius was in the hyperflexed position less active than in the free position (p < 0.02), in which it always showed the highest activity. In walking, the muscle activities in the free and gathered positions deviated significantly (p < 0.01). The m. trapezius was in the hyperflexed posture during walking significantly less active than in the free (p < 0.01) and gathered (p < 0.01) positions with the strongest activities in the free position. Again, the free and gathered positions differed significantly (p < 0.01). In trot, the same pattern occured, although the gathered and hyperflexed positions did not differ significantly. In the canter, the activities of the m. trapezius showed no differences between HNPs. In HNPs with the noseline in front of the vertical, the muscles of the topline (m. splenius, m. trapezius) are activated and trained. In the hyperflexed position, however, a major muscle of the lower topline (m. brachiocephalicus) is activated and trained.

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

“…Its bending moments will assume their greatest values, if the neck is stretched or if acceleration forces are transmitted through the forelimbs, especially in the canter. Both require increased muscle activities, which indeed have been observed by Kienapfel ().…”

“…In a heavy beam, which is supported like body stem of horse on anterior and posterior limbs, we can expect tensile forces—that is muscle activity—along the ventral side of the belly as well as along the dorsal side of the anterior thorax and proximal neck. The latter has indeed been found in an earlier study (Kienapfel, ). If the same beam is supported near its rear (caudal) end by a forwardly inclined leg, with ground contact underneath its belly, tensile forces will occur at the posterior back and rear margin of the beam.…”

“…Between the supports, the trunk tends to sag ventrally downwards, so that compressing forces occur along the upper margin and tension at the lower. This distribution of internal forces is in agreement with the arrangement of the compression‐resistant skeleton (vertebral column and sternum, pelvis, (Preuschoft & Fritz, )) and the tension‐producing musculature (neck, cranial thoracic dorsal musculature and several shoulder muscles, as detailed in Kienapfel ()). Aside from the muscles, there exist very strong strands of connective tissue, which can take over at least part of the tensile forces, and are claimed by several researchers (Gellman & Bertram, ; Nickel, Schummer, Seiferle, & Frewein, ; Slijper, ; Zschokke, ) to do so.…”

“…Former investigations have shown that in the phase of forelimb support, the dorsal neck muscles (m. splenius, anterior part of m. trapezius) are active (Kienapfel, ).…”

Effect of different head and neck positions on kinematics of elite dressage horses ridden at walk on treadmill

“…Further, at walk the horse moves with substantially less muscle activity in the lower back and abdomen (Wakeling et al, 2007;Zsoldos et al, 2010), and with larger lateral movement of the body center of mass, compared to trot (Buchner et al, 2000). Maintaining a defined, non-natural, HNP alters neck muscle activity compared to the free position (Kienapfel, 2014), which may affect the coordination between the neck and trunk movements and necessitate increased core muscle tension. Both effects influence the normal gait mechanics of the walk, as evidenced by the finding in this and earlier studies that a restrained HNP decreases stride length at this gait (Gómez et al, 2006;Rhodin et al, 2005;Weishaupt et al, 2006).…”