Stair locomotion is an important but challenging functional activity for people with lower limb pathology. This study aimed to investigate the bilateral changes in force-bearing on lower limbs during stair locomotion in patients with unilateral ACL deficiency. The ground reaction forces (GRF) were collected from three force platforms: One at ground level in front of a 5-step stair and two on the first two steps respectively. Parameters in vertical and anterior-posterior GRF were extracted and compared between the ACL-deficient (ACLD) and control groups. The ACLD group showed significantly slower stepping cadences in both stair ascent and stepping down to the ground (p < 0.05). The vertical GRF in the ACLD group demonstrated smaller peak forces but larger minimum forces between the two peaks than those in the control group during both stair ascent and descent. Significantly reduced anterior propulsive forces and push-off rates in the late stance were also found in both limbs of the ACLD group (p < 0.05). The slower cadences and reduced force-bearing on the affected limb suggested a protective strategy was adopted. However, the anterior loading parameters in the early stance on the unaffected limb demonstrated different adaptations with significantly larger magnitudes during stair ascent but reduced magnitudes during stair descent (p < 0.05). Similar results were also found in the weight- transferring strategies between legs in consecutive steps with a significantly larger percentage of lift-up forces but a smaller percentage of impact forces on the leading unaffected limb. The results of this study indicated a cautious force-bearing strategy and bilateral adaptation were apparent in the patients with unilateral ACL deficiency. This information may provide a safety guideline for the patients and be helpful for a better use of the stair tasks as part of a rehabilitation program.

Students in dancing department routinely perform hours of dancing every day. Extreme ankle posture can subject the ankle of the dancers to high stress and can significantly increase the mobility of the ankle. This causes ankle sprain which occurs frequently during daily walking. Measurements of the ground reaction force (GRF) and the center of pressure (CoP) provide useful variables to analyze the walking patterns of dancers, which might help understand the causes of ankle sprain. The aims of this work were (1) to investigate the differences in gait patterns between dancers and non-dancers and (2) to explore the gait characteristics in dancers. Thirteen students in dancing department and twenty age-matched normal healthy subjects were recruited. All subjects were requested to walk along a 10-meter walkway. Results showed that the dancers have greater medial shear force of the GRF, and decreased the CoP velocity during the pre-swing phase, delayed peak-CoP velocity occurrence during the mid-stance, and straighter CoP trajectory through the forefoot at push off. The intense and demanding dancing activities change the walking pattern of dancers, which may lead to higher chance of getting ankle sprain.

The aim of the present study was to quantify the inter-day reliability of force platform data from horses at the trot. The subjects were ten horses judged to be sound on the basis of clinical evaluation and similarity of ground reaction force peaks of left and right limbs. The same handler trotted horses in hand for four consecutive days over a force platform at their natural and comfortable velocity between 2.70 and 3.60 m s−1. For each horse, velocity was controlled in a range of±0.15 m s−1. Five contacts per limb were recorded on each day. Custom-written code in MATLAB was used to smooth the data and time-normalize to 101 data points. The agreement boundary was used to determine the reliability of seven force variables. Stance duration, peak vertical force and vertical impulse were the most reliable variables (<10% variability in the mean), while peak braking and propulsive forces and impulses had larger variation across the three days (>20% variability in the mean). Variables with low variability may require fewer animals, trials and days to obtain accurate data while maintaining adequate statistical power. These results may act both as a reference when studying variability in lame horses and as a guide for planning future equine kinetic studies.

Upon encountering a wet or contaminated floor, people often modify their gait and posture to prevent themselves from slipping. This study was conducted to investigate the modification of gait patterns in healthy young adults as they approached and stepped on a slippery floor. Ten females and twelve males were instructed to walk at two different pacer speeds, 90 and 120steps/min, guided by a metronome, on a walkway with two forceplates placed at the center. During the step immediately prior to stepping on a forceplate with or without slippery disturbance, temporo-spatial parameters, selected kinematic parameters, and foot-floor reaction forces were evaluated in each cadence. The results showed that modifications of gait patterns for slip perturbation included shorter step length, increases of flexion angles of hip and knee joints,increases of plantarflexion angles of ankle joint with flattened foot, and decreases of the forward and backward groundreaction forces. However, it was found that such modifications for slip perturbation did not seem to efficiently prevent people from falling.

Foot areas of a wide range of kangaroos, wallabies and rat-kangaroos were measured from fresh material and museum specimens. The areas of the plantar pads scaled according to the predictions of geometric similarity. The terminal claw areas of digits IV and V scaled with a lower than predicted exponent, reflecting functional demands of different species. The pressure that these marsupials exert on the ground during quiet standing is proportional to (body weight)0.35, and is considerably lower than those exerted by ungulates. Hopping kangaroos exert pressures proportional to (body weight)0.37. The pressures exerted by medium and large macropods are comparable to those of galloping ungulates. The findings support the commonly held belief that introduced grazing animals may cause greater mechanical disruption of the soil surface, leading to increased rates of soil erosion, than Australia's indigenous grazing fauna.