Preliminary report into the function of the shoulder using a novel imaging and motion capture approach
Article first published online: 8 NOV 2010
© 2010 EVJ Ltd
Equine Veterinary Journal
Special Issue: Proceedings of the 8th International Conference on Equine Exercise Physiology
Volume 42, Issue Supplement s38, pages 552–555, November 2010
How to Cite
LAWSON, S. E. M. and MARLIN, D. J. (2010), Preliminary report into the function of the shoulder using a novel imaging and motion capture approach. Equine Veterinary Journal, 42: 552–555. doi: 10.1111/j.2042-3306.2010.00289.x
- Issue published online: 8 NOV 2010
- Article first published online: 8 NOV 2010
- [Paper received for publication 17.03.10; Accepted 28.06.10]
- motion capture;
- musculo-skeletal modelling;
Reasons for performing study: The function of the forelimb is fundamental to understanding both sound and pathological locomotion. The precise movements of the equine shoulder are hidden by layers of skin and muscle and hence the shoulder is normally modelled as a simple pivot during locomotion which assumes that any translational motion is negligible.
Objectives: To record and quantify the sliding motion of the scapula during locomotion, using a novel imaging technique.
Methods: Scapula motion during locomotion in the horse was calculated by tracking the ripple of the shoulder blade's movement under an array of markers placed over the soft tissue.
Results: Interstride variability was low. Sliding of up to 80 mm in the plane of progression (cranio-caudal) was observed; however, the limits of motion varied by <5 mm in the gaits examined, despite variations in stride length. Stride length appeared to be increased by scapula rotation in the plane of progression, and this flexion-extension was largest in trot and was not significantly different between walk and canter. This was in agreement with the distance travelled by the trunk whilst the hoof was on the ground. Substantial sliding in a dorsal-ventral direction was shown and varied with the gait used, both in magnitude and timing, possibly providing a shock absorption mechanism. The sliding did not increase as much as would be expected in canter and this coincided with a more lateral positioning of the scapula and increased impact on the ribcage.
Conclusions: It has been assumed that scapula-thoracic sliding increases stride length and hence economically increases locomotor speed. The extra motion of the scapula recorded appeared to absorb shock from forelimb impact and maintain the economy of locomotion, but did not increase with speed and the muscular pretensioning implied could actually impair ventilation.