Analysis of the Coordination of the Trunk Tilting Angle and Bilateral Lower Limbs According to the Stirrups Length during Trot in Equestrian: Asymmetric Index Development of Overall Movement Index Algorithm

Abstract

Purpose : The purpose of this study was to analyze the coordination of the trunk tilting angle and bilateral lower limbs according to the stirrups length during trot in equestrian.Methods : Participants selected as subject were consisted of adult male(n=7, mean age: 45.00±3.78 yrs, mean height: 172.50±2.44 cm, mean body mass: 76.95±4.40 kg, mean, mean leg length: 97.30±2.60 cm). They were divided into 3-types of stirrups lengths(67 cm, 72 cm, 77 cm) during trot. The variables analyzed were consisted of the trunk front-rear angle, lower limb joint(Right·Left hip, knee, ankle), overall movement index(OMI) of the lower limbs(thigh, shank, foot) and asymmetry index(AI%) during trot.Results : The average angle in hip and knee joint showed more extended posture according to the increase of stirrups lengths and ankle angle showed more plantarflexion posture according to increase of stirrups length during 1 stride in trot. Also, average angle showed more extended posture in right hip and ankle joint than that of left. The angle of knee joint didn't show significant difference statistically between right and left. Also asymmetric index in average angle of hip, knee and ankle joint didn't show significant difference statistically in between lower limbs, but hip joint showed higher asymmetric index in stirrup length of 77 cm and ankle joint showed higher asymmetric index in stirrup length of 67 cm than that of the others respectively. The FR angle in trunk of horse-rider showed relative backward leaning motions at stirrup length of 67 cm and 77 cm than that of stirrup length of 72 cm during stance and swing phase. OMI in thigh, shank, and foot limbs didn't show significant difference statistically according to the stirrups length of right and·left lower limbs, but left lower limbs showed higher index than that of right lower limb. Stirrup length of 72 cm in shank and foot limbs showed higher index than that of stirrup length of 67 cm and 77 cm. But stirrup length of 72 cm showed higher asymmetric index than that of stirrups length of 67 cm and 77 cm.Conclusions : When considering the above, 72 cm(ratio of lower limb 74.04%) stirrup lengths could be useful in posture correction and stabilization than 67cm(ratio of lower limb 68.69%) and 77 cm(ratio of lower limb 79.18%) stirrup lengths during trot in horse back riding.

Comparison of stirrup lengths chosen for flatwork by novice and experienced riders

“…Throughout their equestrian career, riders are taught that the correct leg position aligns the heel vertically below the hip, with the angulations of the intervening joints compressing or extending to accommodate different stirrup lengths (Hyun and Ryew, 2015). With practise and through the development of muscle memory this becomes a reproducible posture that serves as a reference position that the rider returns to after being perturbed by the movements of the horse.…”

“…Although the authors did not further investigate the cause or effects, an illustration in the paper shows a lower position of the right foot in a subject with greater external rotation of the right hip. Another study found that the hip and ankle joints were more extended in the right leg than the left leg when riding at a longer stirrup length (Hyun and Ryew, 2015). The possibility of a relationship between the positional asymmetries and the rider's handedness pattern has not yet been investigated.…”

“…It has also been suggested that stirrup length can be estimated before mounting by placing the knuckles against the stirrup bar and pulling the stirrup into the armpit (The Pony Club, 1993). Shorter stirrups are associated with greater flexion of the rider's hip, knee and ankle joints (Hyun and Ryew, 2015), which can then act as springs to support the body weight during galloping and jumping where the rider is 'out of the saddle' (i.e. the rider's seat is not in contact with the saddle).…”

“…If the rider has symmetrical posture and movements, it is thought to facilitate the development of straightness in the horse (Hobbs et al, 2014). However, Hyun and Ryew (2015) found that, in spite of having equal stirrup lengths, the angles of the hip and ankle joints increased more in the right leg than the left when the stirrups were lengthened. It has also been reported that the right hip shows more external rotation than the left during riding (Gandy et al, 2014).…”

Motor ability of forelimb both on- and off-riding during walk and trot cadence of horse

“…In addition to the above, preceded studies reported the interaction effect among horse-saddle-rider ( Greve and Dyson, 2013 ; Harman, 1999 ), position-transition analysis of rider during walk-trot-gallop ( Lovett et al, 2005 ) and interaction between horse and rider ( Münz et al, 2014 ). In recent studies, Hyun and Ryew (2015a , 2015b) reported that keeping stirrup length of 74.04% to lower limb length was more effective in stabilization and posture correction of rider. But there was no study about stride mechanism of horse according to on- or off-riding during walk and trot when reviewed the above studies about stability and effectiveness of riding posture related with motor ability of horse.…”