Characterization and validation of a split belt treadmill for measuring hindlimb ground-reaction forces in able-bodied and spinalized felines

Abstract

BACKGROUND The measurement of ground reaction forces (GRFs) in animals trained to locomote on a treadmill after spinal cord injury (SCI) could prove valuable for evaluating training outcomes; however, quantitative measures of the GRFs in spinal felines are limited. NEW METHOD A split belt treadmill was designed and constructed to measure the GRFs of feline hindlimbs during stepping. The treadmill consists of two independent treadmill assemblies, each mounted on a force plate. The design allows measurements of the vertical (Fz), fore-aft (Fy) and mediolateral (Fx) ground-reaction forces for both hindlimbs while the forelimbs are resting on a platform. RESULTS Static and dynamic noise tests revealed little to no noise at frequencies below 6 Hz. Validation of the force plate measurements with a hand-held force sensor force showed good agreement between the two force readings. Peak normalized (to body mass) vertical GRFs for intact cats were 4.89±0.85N/Kg for the left hindlimb and 4.79±0.97N/Kg for the right. In comparison, trained spinalized cats peak normalized vertical GRFs were 2.20±0.94N/Kg for the left hindlimb and 2.85±0.99N/Kg for the right. COMPARISON WITH OTHER EXISTING METHODS Previous methods of measuring GRFs used stationary single force plates or treadmill mounted to single force plate. Using independent treadmills for each hindlimb allows measurement of the individual hindlimb’s GRFs in spinalized cats following body-weight supported treadmill training. CONCLUSIONS The split belt force treadmill enables the simultaneous recording of ground-reaction forces for both hindlimbs in cats prior to spinalization, and following spinalization and body-weight-supported treadmill training (BWST).

A rodent brain-machine interface paradigm to study the impact of paraplegia on BMI performance

“…GRF, inclinometer and accelerometer sensor data were acquired using LabVIEW software (1000 s/s), which was filtered offline using a 2 nd order Butterworth zero-phase low-pass filter (inclinometer used a 20 Hz cutoff; load cells and accelerometer used a 200 Hz cutoff). Load cell cut-off frequencies are similar to commercial software used in animal research settings (Dimiskovski et al, 2017) and power spectral analyses revealed that a majority of sensor data signals fell below 1 Hz and 25 Hz for the inclinometer and accelerometer/load cells respectively. All sensor data were normalized to a period found in the 200 ms time window prior to tilt start for each trial.…”

Intrathecal Delivery of BDNF Into the Lumbar Cistern Re-Engages Locomotor Stepping After Spinal Cord Injury

“…Kinematic analysis shows similar gait recovery with BDNF or treadmill training in spinalized cats. The analysis of the GRFs also showed results similar to trained animals in terms of weight support [20] and superior to non-treated animals. The BDNF treated cats were capable of performing some full weight-bearing stepping during locomotion at medium speed (0.4 m/s).…”

“…Ground reaction forces (GRFs) were collected in six cats (two Controls and four BDNFs) during locomotion trials 5 weeks post-transection using an instrumented split belt treadmill where each belt motor assembly (left and right) was mounted on a Kistler force plate (Kistler Instrument Corp., Winterhur, SUI) [20]. The vertical components of the GRFs (Fz) were evaluated during locomotion at 0.4 m/s to estimate the animals' ability to weight support.…”

“…A linear mixed model with average peak vertical force per trial as the dependent variable and group (BDNF or Control), side (left or right) and the group*side interaction as factors (with side and trial as repeated measure variables and cat as the grouping variable) was used to evaluate the effects of group on the peak vertical GRF. According to results on able-bodied cats showing that the hindlimbs support about 40% of the body weight during locomotion [21], [22], the vertical force necessary for full weight support is about 4 N/kg (normalized to the animal's mass) [20].…”

Constraints on Stance-Phase Force Production during Overground Walking in Persons with Chronic Incomplete Spinal Cord Injury

“…Spinally injured cats have shown altered limb loading that contributes to a 55% reduction in vertical ground reaction forces (GRFs) compared with intact felines. 8 Similar reductions are also evident in hindlimb propulsive and braking forces in rats after spinal injury, 9 resulting in limited locomotion. 10 A paucity of studies, however, has explored the impact of iSCI on force production during overground walking in humans.…”