ABSTRACT. The authors studied the interaction between rider and horse by measuring their ensemble motions in a trot sequence, comparing 1 expert and 1 novice rider. Whereas the novice's movements displayed transient departures from phase synchrony, the expert's motions were continuously phase-matched with those of the horse. The tight ensemble synchrony between the expert and the horse was accompanied by an increase in the temporal regularity of the oscillations of the trunk of the horse. Observed differences between expert and novice riders indicated that phase synchronization is by no means perfect but requires extended practice. Points of contact between horse and rider may haptically convey effective communication between them.
22Background: Locomotion adaptation mechanisms have been observed in horses, but little 23 information is available in relation to banked and non-banked curve locomotion, which might 24 be important for correct training.
25Aim: To determine if adaptation mechanisms in horses existed when moving on a banked 26 compared to a flat curve and whether adaptation was similar in different gaits.
45The kinematics of walk, trot and canter gaits have been studied over ground and using 46 treadmills in two dimensions (Barrey et al., 1993; van Weeren et al., 1993; Buchner et al., 47 1994; Clayton, 1994; Back et al., 1996; Galisteo et al., 1998; Galisteo et al., 2001; Clayton et 48 al., 2002) and three dimensions (Chateau et al., 2004; Chateau et al., 2006; Hobbs et al., 49 2006; Clayton et al., 2007a; 2007b; Gomez Alvarez et al., 2009). From these studies 50 adaptation mechanisms have been observed during treadmill locomotion (Barrey et al., 1993; 51 Buchner et al., 1994; Gomez Alvarez et al., 2009) and other studies have reported adaptations 52 due to shoeing regimens and hoof conformation, which include Clayton et al. (1990), 53 Roepstorff et al. (1999) and van Heel et al. (2006). To date, few studies have investigated 54 adaptations in kinematics during locomotion on a curve. powered by torque about the hip joint and by back extension (Usherwood and Wilson, 2005).
61In contrast, the muscles that power sprinting in humans are loaded by weight induced 62 compression forces along the leg and a greater proportion of the maximum muscular effort 63 must be directed medio-laterally in order to develop centripetal acceleration (Usherwood and 64 Wilson, 2005). Chang and Kram (2007) found the inside leg to be particularly ineffective at 65 generating push off forces for propulsion in humans and proposed that this is due to a need to 66 optimise the alignment of the resultant GRF vector with the long axis of the leg. They the distal segments that were internally rotated at the end of the weight bearing phase. From 92 these studies it is clear that adaptations to curve motion are also found in horses, but 93 constraints placed on the limbs at faster speeds are unknown.
94Fredricson and Drevemo (1971) recognised that the characteristics of the surface, banking, 95 curve and gradient as well as surface variation will affect the trotting action. In this respect 96 they suggested that at high speed good horses can compensate for many of these factors, but 97 to the expense of wear and tear on their limbs. The risk of injury to the distal joints when 98 negotiating curves may increase further for horses performing at faster gaits and over longer 99 time periods, as Johnston et al. (1999) found stride length, stance time and joint excursion 100 during stance to increase with fatigue. Hill (2003) remarked that most catastrophic injuries in 101 racing will occur in turns and in the stretch run to the finish. In a study of 58 horses suffering 102 serious accidents during racing, Ueda et al. (...
This study evaluated lumbar spine muscle volume and Muscle Fatty Infiltrate (MFI) across two age groups of healthy adults. Twenty-four participants (young group - YG: age 18-25, n = 12; mature group - MG: age 45-60, n = 12) without low back pain underwent T1-weighted axial MRI. Muscle volume and MFI were obtained from the left and right lumbar erector spinae (ES), multifidus (M), rectus abdominis (RA) and psoas (PS) muscles. For MFI, mean pixel intensity (MPI) of muscles was reported as a percentage of subcutaneous fat MPI. Within-group comparison of left and right side muscle volume was not significantly different in the YG. In the MG, right RA and ES were significantly smaller than left (RA p = 0.049; ES p = 0.03). In both groups, left PS, M and ES MFI was significantly smaller compared to the right side and left RA MFI was significantly greater compared to right side (all p ≤ 0.001). For M volume, 81.7-84.6% of variance was explained by age, height and Body Mass Index (BMI). For ES volume, 81.6-82.8% of variance was explained by height and BMI. Age explained 18.1%-36.0% of variance in M and ES right MFI. Therefore, age and BMI are relevant factors for extensor muscle volume, but not for flexor muscle volume. Also, age significantly influences MFI for right-sided extensors only. The age effect is apparently independent of full subjective back functionality. For future spinal muscle research, the side-and muscle-specific effect of age on muscle morphology should be considered.
In order to study the mechanism of lameness transfer from fore‐ and hindlimb lamenesses 2 hypotheses were investigated. Hypothesis 1: Horses with a true supporting limb lameness in one hindlimb show a false supporting limb lameness in the ipsilateral forelimb. Hypothesis 2: Horses with a true supporting limb lameness in one forelimb show a false supporting limb lameness in the contralateral hindlimb.
Fourteen horses with fore‐ or hindlimb lameness were used for this study. Each horse was measured at the trot on a treadmill with standardised speed, before and after diagnostic blocks (9 horses), or with and without induced lameness (5 horses). The head acceleration asymmetry (HAAS) and the sacrum acceleration asymmetry (SAAS) were used for quantification of fore‐ and hindlimb lameness respectively. Changes were documented by changes of the HAAS or the SAAS.
In all 4 horses with a true hindlimb lameness a synchronous false lameness of the ipsilateral forelimb was documented. In 6 of 10 horses with a forelimb lameness a lameness transfer could be assessed according to hypothesis 2.
The results of this study show, that horses with a true severe lameness in the forelimb show a false lameness in the contralateral hindlimb, and horses with a true hindlimb lameness show a false lameness in the ipsilateral forelimb. This indicates that the location of the truly lame limb can be deduced from the distribution of 2 lamenesses on a sagittal or diagonal axis.
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