A systematic review of the effect of ageing and falls history on minimum foot clearance characteristics during level walking.

Minimum foot clearance (MFC) is the minimum vertical distance between the lowest point of the foot of the swing leg and the walking surface during the swing phase of the gait cycle. MFC is a gait variable that is linked to the mechanism of a trip because reduced MFC for a given step during walking increases the susceptibility to tripping on an unseen obstacle or due to undetected changes in surface height. Given that tripping is a common cause of falls in older persons, this review was undertaken to determine whether ageing and/or history of falls in older adults influences MFC characteristics during level walking. Studies that assessed MFC characteristics including measures of central tendency (mean and/or median), variability (linear and non-linear measures) and shape (skewness, kurtosis) of the MFC distribution were included in the review. The final yield from a search of seven electronic research databases was 12 unique articles that met all the inclusion criteria. Ageing does not appear to alter measures of central tendency or shape of the MFC distribution. However greater MFC variability was observed in older compared to younger adults and older fallers compared to older non-fallers in the majority of studies. Greater MFC variability may contribute to increased risk of trips and associated falls in older compared to young adults and older fallers compared to older non-fallers.

Ageing effects on knee and ankle joint angles at key events and phases of the gait cycle.

The objective of this research was to determine whether joint angles at critical gait events and during major energy generation/absorption phases of the gait cycle would reliably discriminate age-related degeneration during unobstructed walking. The gaits of 24 healthy adults (12 young and 12 elderly) were analysed using the PEAK Motus motion analysis system. The elderly participants showed significantly greater single (60.3% versus 62.3%, p < 0.01) and double ( p < 0.05) support times, reduced knee flexion (47.7 degrees versus 43.0 degrees , p < 0.05) and ankle plantarflexion (16.8 degrees compared to 3.3 degrees , p = 0.053) at toe off, reduced knee flexion during push-off and reduced ankle dorsiflexion (16.8 degrees compared to 22.0 degrees , p < 0.05) during the swing phase. The plantarflexing ankle joint motion during the stance to swing phase transition (A2) for the young group (31.3 degrees ) was about twice ( p < 0.05) that of the elderly (16.9 degrees ). Reduced knee extension range of motion suggests that the elderly favoured a flexed-knee gait to assist in weight acceptance. Reduced dorsiflexion by the elderly in the swing phase implies greater risk of toe contact with obstacles. Overall, the results suggest that joint angle measures at critical events/phases in the gait cycle provide a useful indication of age-related degeneration in the control of lower limb trajectories during unobstructed walking.

Neural network-based prediction of missing key features in vertical GRF-time recordings.

Ground reaction force (GRF) time recordings are frequently corrupted due to faulty stepping on a force platform during gait, and this results in the loss of valuable data and the need for additional data acquisition. This paper proposes a new approach based on artificial neural networks for the estimation of lost key gait parameters using the available features of an affected GRF-time trace. GRF-time plots were recorded using a force platform during normal walking of 14 young and 13 elderly individuals. Back-propagation neural network models were developed using features extracted from 466 vertical GRF-time characteristics that would be unaffected as inputs, and the likely affected gait features (e.g. stance time (ST), push-off force, (Fmax2) and push-off time (Tmax2)) as output. Performance of the models in predicting ST, Fmax2 and Tmax2 were tested using data from 30 new gait trials. The neural network model predicted the missing STs with 96.5% (+/-2.6%) accuracy (r>0.9). Accuracy of the ST prediction deteriorated when push-off force/time data were unavailable for the prediction model. Fmax2 and its time were reconstructed with an accuracy of 95.7% (+/-2.8%) and 97.6% (+/-1.7%) respectively. These results suggest that an artificial neural network may be applied to estimate missing ST, Fmax2 or Tmax2 information using features from an affected vertical GRF-time plot, and the method shows good promise for reconstructing gait forces from a corrupted force-time trace.

Gait characteristics of young and older individuals negotiating a raised surface: implications for the prevention of falls.

BACKGROUND: Falls in older individuals are a major public health issue because of the financial cost of surgery and re habilitation and the human cost of associated pain and disability. Older individuals are most likely to fall when negotiating an obstacle or obstruction during locomotion. This research was aimed at investigating lower limb motion while a subject negotiated a raised surface. METHODS: The gait of six healthy young (Y) women (mean age 23.1 years) and six healthy older (O) women (mean age 67.6 years) were analyzed with a PEAK motion analyzer and a dual-force-platform system during unobstructed walking and when the subjects were stepping on and off a raised surface of 15 cm. The effect of age on foot clearance and force platform variables was analyzed. RESULTS: During stepping on, the young women cleared the step by the lead foot by a significantly greater margin than the older subjects did (Y = 10.6 cm, O = 9.1 cm; p < .05) but trail-foot clearance was not significantly different (Y 9.4 cm, O = 8.8 cm). Foot clearance in stepping off was low compared with that of ascent, and the older individuals had a significantly higher lead (Y = 1.5 cm, O = 3.3 cm, p < .05) and trail (Y = 1.0 cm, O = 2.1 cm) vertical clearance. Older individuals positioned both the lead and the trail foot relatively farther from the step edge on ascending a raised surface, respectively, Y = 87% and O = 93% of the step cycle and Y = 29% and O = 34%. Foot placement in descent was qualitatively similar for the two groups. The force and the impulse data under the lead and the trail feet confirm modulations consistent with the foot clearance data. CONCLUSION: In negotiating a raised surface older individuals appear to use a nonoptimal foot placement strategy in which, compared with that of young subjects, the trail foot is placed a long way from the edge of the step. The older subjects allowed very little correction time and little latitude in foot placement beyond the edge of the step, suggesting that the approach to the obstacle may be a critical determinant of safety.

A method for the reconstruction of ground reaction force-time characteristics during gait from force platform recordings of simultaneous foot falls.

This paper proposes a method for the reconstruction of foot-ground reaction forces from force platform recordings of two consecutive footfalls. The reconstruction algorithm uses zero-derivative criterion (inflection point) to detect contralateral foot contacts and subtracts contralateral forces from the combined force-time curve in order to reconstruct force-time data. Experimental results suggest that the method can be applied to separate accurately foot-specific gait forces from corrupted force-time data as a result of incorrect stepping on a force platform.

Microcomputer-based system for clinical gait studies.

A microcomputer-based gait recording system is described which can be used to analyse gait routinely in the clinical environment. Foot-ground reaction forces are acquired and processed and the resultant force vector is superimposed on the television image of the subject in real time. A TV-computer interface quantifies the position of reflective markers attached to the joint centres of the lower limb, and moment values, stick-figure diagrams, and joint angle changes can also be displayed shortly after data collection. The system has routine clinical applications in orthotics and prosthetics and is also a valuable tool in teaching the biomechanics of human movement.

A microcomputer-based video vector system for clinical gait analysis.

A microcomputer-based video vector system has been developed to display the resultant ground reaction force vector on a television image of the subject in real-time. For each television field the force platform signals are acquired and processed and the resultant force vector superimposed on the video image of the walking subject. The force platform results are stored on disc and the composite video signals recorded on video tape for further analysis. The system is easy to set up and use and the results can be readily interpreted. The external moments produced at the joint centers by the ground reaction forces can be observed visually and, if required, quantification of the external moments can be achieved following data collection. The spatial resolution of the system is 0.342% vertically and 0.156% horizontally. The force vector visualization technique has routine applications in orthotics and prosthetics. It is also a useful technique for the teaching of biomechanics.

Instrumentation used in clinical gait studies: a review.

This paper reviews the currently available instrumentation used for gait studies and discusses the clinical suitability of the various methods of recording gait parameters. Most of the presently available motion analysis systems appear to be more suited to research than to the routine clinical situation. However the video vector visualization technique appears to be the most useful clinically since it produces a real time display, is simple to operate and interpretation of the data is easier than other systems available. Some further development of the video vector visualization system is necessary to improve its accuracy and to produce quantitative information.