Comparison of Pressure Distribution under a Side and an English in Different Gaits

B. Frühwirth1, C. Peham1, T. Licka², B. Winkelmayr1, M. Scheidl³ 1Clinic for Orthopedics, Veterinary University , Vienna/ 2School of Veterinary Medicine, University of Edinburgh, Edinburgh/UK 3FH Wieselburg, Wieselburg/Austria

Introduction

Back pain and diseases of the spine are known as significant problems in equine sports and veterinary medicine. Information about the strains and stresses that a encounters while being ridden might be an important link between symptomatic description and functional diagnosis, and thus might improve prevention, treatment and management of pain. Up to now, the biomechanics of the equine back under conditions usually present today, especially while being ridden, have not yet been sufficiently investigated.

Saddles are rigid structures that transfer certain aids of the rider to the horse, and also transfer the motion of the horse back to the rider (Harmann, 1994). This transfer is presented by the pressure distribution under the saddle. Jeffcott et al. (1999) shows that the saddle mat equipment is an accurate and reliable device which produces repeatable objective results. According to Jeffcott et al. (1999) there is a need in further studies with clearly defined aims.

The aim of this study is to compare the different loads, the external forces on the back (e.g. saddle pressure) by the rider, applied during three different gaits (walk, trot, gallop) and two different (Side and English).

Materials and Methods

We measured 13 horses (age 7-25 years, 410-650 Kg, various breed, different training levels) without clinical signs of back pain. Their sex, age, breed or type, use and current training level are listened in Table 1. All horses were subjected to a clinical examination of the back. This examination included inspection when standing and walking, turning tight to the left and to the right, backing, palpation of the muscles of the back with assessment of muscle tone, palpation and percussion of the spinous processes as well as testing spinal movements (flexion, extension and lateroflexion of the thoracolumbar spine) (Licka et al. 1998).

All horses were ridden with both types of saddles in three different gaits (walk, sitting trot, gallop) by their regular (usual) rider. For this investigation the regularly used saddles of each horse were taken. The horses had been ridden with these saddles for more than one year, and all horses showed no signs of back problems. The fit of the saddles was checked by an veterinarian and the saddler of the of Vienna.

Measurements were carried out from the right side, with six cameras (sample rate 120 Hz, resolution 240 x 833 points) tracing one reflecting spherical marker placed on the horse’s right fore hoof. At least five recordings of each rider-gait- and saddle combination were taken with the ExpertVision System (Motion Analysis Corporation) with the horse moving on a 12 m long pressed sand track in an indoor riding arena.

The pressure distribution under the saddle was recorded with the PLIANCE saddle mat (NOVEL GMBH, MUNICH). The saddle mat contains 224 sensors (sample rate of each sensor 30 Hz, measurement range 0.1 - 6 N/cm², dimension 169x105x45mm, weight 800g). The sensor mat was calibrated using homogeneous air pressure by calculating the calibration curves for each individual sensor. The measurements were triggered by the rider. A minimum of 12 motion-cycles of each trial were collected. In order to normalise the pressure distribution to the duration of one motion cycle we combined the saddle mat with kinematic measurements described above. From the pressure distribution we calculated the maximum overall force (MOF) in relation to the mass of rider and saddle and the Centre of Pressure (CoP) of the overall force.

Results and Discussion

The MOF in the is significant (p<0.05) higher than in the side saddle in all gaits. See table 1.

Mean SD MOF Walk Trot Gallop Walk Trot Gallop English 12.13 24.26 27.15 1.17 4.56 4.37 Side 9.40 19.62 21.82 1.60 3.21 4.94

Table 1 shows the maximum overall forces (MOF) [N/kg].

The CoP varies significantly (p<0.05) more in the side saddle as in the english saddle in all gaits which is shown in Table 2.

Mean-x Mean-y CoP Walk Trot Gallop Walk Trot Gallop English 2.87 4.76 2.99 3.49 9.98 8.66 Side 4.77 5.29 4.17 6.26 13.11 11.75 SD-x SD-y English 0.64 3.51 1.72 1.19 4.92 1.96 Side 2.33 2.07 2.12 2.65 4.80 3.67

Table 2 shows the variation range of the Centre of Pressure (CoP) [cm].

1600

1400

1200

1000

800

Force [N] 600

400

200 Trot English Trot Side 0 1 21 41 61 81 Time [%] Figure 1 shows a typical example of the overall force during one motion cycle in gallop under an English and a Side Saddle Our results demonstrate, that force transmission is more in the English saddle (less variation of the CoP) than in the Side saddle. The rider’s weight is concentrated on a smaller area in the English saddle compared to the Side saddle. Therefore the aids given by the rider probably are more distinct and more efficient in the English saddle as in the Side saddle. The pressure on the back of the horse is reduced by the Side saddle (see fig. 1) because this saddle presumably tends to dampen the actual load more than the English saddle. The Side saddle contains double the stuffing of a regular English saddle, and therefore its stuffing deforms more easily than in English saddle. Therefore we think that the different pressure distribution of both saddle types might make it advantageous to alternate between them in training and rehabilitation of horses. In addition, it might give the chance to pronounce the variation during the training of horse and rider.

References:

HARMAN, J.C.: Practical use of a computerised saddle pressure measuring device to determine the effects of saddle pads on the horse’s back. Journal of Equine Veterinary Science 14, 606-611, 1994.

JEFFCOTT, L.B., HOLMES, M.A., TOWNSEND, H.G.G.: Validity of saddle pressure measurements using force-sensing array technology – Preliminary studies. The Veterinary Journal, 158, 113-119, 1999.

LICKA, T., PEHAM, C.: An objective method for evaluating the flexibility of the back of standing horses. Equine Veterinary journal, 30 (5), 412-415, 1998.

Acknowledgements:

This study was supported by the Austrian Science Fund Project P13915. We would like to thank Mr. Desmond O`Brien for his active participation in the measurements and for checking the fits of the saddles.