Fig. 3. Representative graphs of simultaneous peak vertical ground reaction force (GRFz) and accelerometer data collected during walk (A), trot (B) and canter (C) locomotion. For walk and trot trials, force plate data were collected for both front limbs (red broken line) and hind limbs (green broken line) during the same trial. Beneath the force outputs, the corresponding accelerometer traces are shown. Vertical broken lines indicate the timing of foot on (a) and foot off (b). The red solid line indicates the output from the forelimb accelerometer, and the green solid line the hind limb accelerometer data. Note the precipitous rise in force at foot on and the rapid drop in force at foot off, which allow the accurate determination of foot on and foot off from vertical force data alone. Also note the absence of features in the accelerometer trace during the stance phases, except a minor undulation shortly prior to foot off, corresponding to heel off and foot rotation. The automatic gain control in the telemetry link means that whilst the accelerometer signal amplitude is the same in all three plots, the actual acceleration will differ.