Determination of peak vertical ground reaction force from duty factor in the horse (Equus caballus)

Abstract

Measurement of peak vertical ground reaction force (GRFz) from multiple limbs simultaneously during highspeed, over-ground locomotion would enhance our understanding of the locomotor mechanics of cursorial animals. Here, we evaluate the accuracy of predicting peak GRFz from duty factor (the proportion of the stride for which the limb is in contact with the ground). Footmounted uniaxial accelerometers, combined with UHF FM telemetry, are shown to be practical and accurate for the field measurement of stride timing variables, including duty factor. Direct comparison with the force plate produces a mean error of 2.3·ms and 3.5·ms for the timing of foot on and foot off, respectively, across all gaits. Predictions of peak GRFz from duty factor show mean errors (with positive values indicating an overestimate) of 0.8±0.04·N·kg -1 (13%; N=42; mean ± S.E.M.) at walk, -0.3±0.06·N·kg -1 (3%; N=75) at trot, -2.3±0.27·N·kg -1 (16%; N=18) for the non-lead limb at canter and +2.1±0.7·N·kg -1 (19%; N=9) for the lead limb at canter. The substantial over-and underestimate seen at canter, in the lead and non-lead limbs, respectively, is attributed to the different functions performed by the two limbs in the asymmetrical gaits. The difference in load experienced by the lead and non-lead limbs decreased with increasing speed.

Accuracy and precision of gait events derived from motion capture in horses during walk and trot

“…A study by Witte et al (2004) utilises hoof-mounted accelerometers to obtain timings for front limb hoof-on and hoof-off in walk and trot compared to force plates. The average force plate derived stance phase duration for walk was 753.4 ms. Our motion capture-derived algorithms are more accurate to detect hoof-off in the front limbs with À 0.2 ms (measurement error; ME: 0.03%) compared to the hoof-mounted accelerometers with a mean error of 3.6 ms (ME: 0.48%).…”

“…For algorithm B (hoof-on only), A and E, the distal dorsal marker on the hoof was used because it is closer to the pivot point of the hoof during break-over (Witte et al, 2004). Method C and D used the lateral hoof marker.…”

“…Reproducible and uniform segmentation into spatial and temporal characteristics (Lord et al, 2013) with force plates is considered the reference standard to detect timing of hoof-contact (Olsen et al, 2012;Sutherland, 2002;Witte et al, 2004).…”

The three-dimensional locomotor dynamics of African (Loxodonta africana) and Asian (Elephas maximus) elephants reveal a smooth gait transition at moderate speed

“…Foot touchdowns and lift-offs for the two right limbs were determined by measuring foot acceleration using two uni-axis accelerometers (ADXL150, Analogue Devices, Norwood, MA, USA; Witte et al 2004). The accelerometers were mounted on the dorsal side of the toenail of each middle toe using melted glue, with their sensitive axis along the proximal-distal direction.…”

Is a standalone inertial measurement unit accurate and precise enough for quantification of movement symmetry in the horse?

“…In multi-sensor systems with synchronized sensors (Warner et al, 2010, Starke et al, 2012a,c, Pfau et al, 2012, the sacral sensor can be used to segment all sensor data (Starke et al, 2012b). If thoracic limb hoof contact is required, IMUs located on the distal limb (Olsen et al, 2012) or hoof mounted accelerometers or gyroscopes (Witte et al, 2004, Keegan et al 2005 provide precise results.…”