Stirrup forces during approach, take-off and landing in horses jumping 70 cm

Stirrups aid the rider to stabilise their lower leg allowing it to be used effectively for communication and in maintaining their position in the saddle. Relatively few studies have investigated stirrup forces and to the best our knowledge no studies have reported stirrup forces in jumping. The aim of the present study was to measure stirrup forces in five showjumping horses ridden by the same professional rider. All horses were in regular training and competition jumping at least 30 cm higher than the fence used for the study. The fence chosen was a 70 cm upright with a pole at the top and a groundline. Right and left stirrup forces were measured using wireless load cells placed between the stirrup leathers and the stirrup. The signals were transmitted and digitised at 100 Hz and synchronised with video from a webcam using an inertial measurement unit. After warming-up, including over jumps, each horse attempted the jump three times from each rein in canter (3 horses left then right rein; 2 horses right then left rein). Mean peak total (sum of left and right) stirrup force for the approach (n=5 strides per horse per jump), take-off and landing phase of the jump was 1,034 +/- 110, 1,042 +/- 284 and 1,447 +/- 256 N (range 905 to 1,815 N), respectively (mean +/- standard deviation). There was no significant difference between right or left mean peak stirrup force during approach or take-off, but mean peak force was consistently higher on the right stirrup during the early phase of landing on either the right or left rein (right: 827 +/- 320 N; left: 615 +/- 336 N; P<0.05). In conclusion, the mean total peak stirrup forces measured in the present study in the same rider jumping five different horses over a 70 cm single upright fence are similar to previous reports of peak stirrup forces in gallop and consistent with observations of asymmetric loading of the saddle and horses' backs by riders.