An original technique of tendon load direct measurement, which can be used in the moving horse, has been developed. This completely non-invasive process is based on the propagation of an ultrasonic wave in the tendon under study, where the direct relationship between the speed of the wave and the loads applied to the tendon is shown. After experimental demonstration of this relationship through in vitro tests (on isolated tendons and limbs), prototypes adapted to the measurement of the in vivo loads which are exerted on the superficial digital flexor tendon (SDFT) in the walking and trotting horse were manufactured. The measurement resolution and their reproducibility were evaluated in 5 horses. The estimated resolution was 0.02 micro seconds, which approximately corresponded to 60 Newton. Interstride variability and the variability related to the probe repositioning were approximately 6% of the range of tendon loading during the stance phase. Significant differences were observed in the shape of the plots of the 5 horses; these differences appear to be directly related with the digital standing conformation. This process was then evaluated of the effect of 4 types of orthopaedic shoes, compared with a standard shoe, on a hard and a soft surface.