Introduction

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/43992/1/10439_2006_Article_BF02371447.pd

Mobility impairment in the elderly: Challenges for biomechanics research

The problems of mobility impairment in the elderly constitute new and major challenges for biomechanics research. This paper outlines what some of the important problems are, discusses the relevance of biomechanics research to these problems, and reviews some of the current state of knowledge about factors related to the biomechanics of mobility impairments in the elderly. The population of old adults is growing rapidly and the incidence of mobility impairments in old adults is high. Mobility impairment biomechanics research is needed to make the assessments of impairments more precise, to design therapeutic programs that are more effective and to learn more about how mobility impairments can be prevented.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/30086/1/0000457.pd

Stepping Responses of Young and Old Adults to Postural Disturbances: Kinematics

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/111171/1/j.1532-5415.1994.tb04972.x.pd

Do Neural Factors Underlie Age Differences in Rapid Ankle Torque Development?

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/111232/1/j.1532-5415.1996.tb03737.x.pd

Biomechanics of reactions to impending falls

Responses of 11 young adult males, initially standing, to support surface forward accelerations of 0.18 g were investigated. In response to the impending falls this stimulus initiated, body segment motions and myoelectric activities in six muscles were measured. These measurements were then input to 9 or 12 segment whole body biomechanical models and the reaction joint torques needed to produce the motions were calculated.Mean relative joint rotations were as large as 92.8[deg] and calculated relative joint angular accelerations as large as 29.7 rad s-2. Mean myoelectric signal latencies in the six muscles monitored ranged from 135 ms at the ankles to 176 ms at the shoulders with intermediate values at intermediate joints. Mean values of calculated maximum joint torques ranged to 70 Nm at the ankles, 82 Nm at the knees, 73 Nm at the hips, and 19 Nm at the shoulders.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/27580/1/0000624.pd

Biomechanical analyses of rising from a chair

Quantification of the biomechanical factors that underlie the inability to rise from a chair can help explain why this disability occurs and can aid in the design of chairs and of therapeutic intervention programs. Experimental data collected earlier from 17 young adult and two groups of elderly subjects, 23 healthy and 11 impaired, rising from a standard chair under controlled conditions were analyzed using a planar biomechanical model. The joint torque strength requirements and the location of the floor reaction force at liftoff from the seat in the different groups and under several conditions were calculated. Analyses were also made of how body configurations and the use of hand force affect these joint torques and reaction locations.In all three groups, the required torques at liftoff were modest compared to literature data on voluntary strengths. Among the three groups rising with the use of hands, at the time of liftoff from the seat, the impaired old subjects, on an average, placed the reaction force the most anterior, the healthy old subjects placed it intermediately and the young subjects placed it the least anterior, within the foot support area. Moreover, the results suggest that, at liftoff, all subjects placed more importance on locating the floor reaction force to achieve acceptable postural stability than on diminishing the magnitudes of the needed joint muscle strengths.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/29713/1/0000047.pd

A model for studies of the deformable rib cage

An earlier model for the study of rib cage mechanics was modified so that rib deformity in scoliosis could be better represented. The rigid ribs of that model were replaced by five-segment deformable rits. Literature data on cadaver rib mechanical behavior were used to assign stiffnesses to the new individual model ribs so that experimental and model rib deflections agreed. Shear and tension/compression stiffnesses had little effect on individual rib deformation, but bending stiffnesses had a major effect. Level-to-level differences in mechanical behavior could be explained almost exclusively by level to level differences in the rib shape. The model ribs were then assembled into a whole rib cage. Computer simulations of whole rib cage behaviors, both in vivo and in vitro, showed a reasonable agreement with the measured behaviors.The model was used to study rib cage mechanics in two scolioses, one with a 43[deg] and the other with a 70[deg] Cobb angle. Scoliotic rib cage deformities were quantified by parameters measuring the rib cage lateral offset, rib cage axial rotation, rib cage volume and rib distortion. Rib distortion was quantified both in best-fit and simulated computer tomography (CT) scan planes. Model rib distortion was much smaller in best-fit planes than in CT planes. The total rib cage volume changed little in the presence of the scolioses, but it became asymmetrically distributed.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/30087/1/0000458.pd

Age effects on strategies used to avoid obstacles

Chen et al.1 found that the rates of success which 24 healthy younger and 24 healthy older adults achieved in not stepping on fixed and suddenly appearing virtual obstacles was adversely affected by reducing their available response time. This paper reports the gait strategies used by those 48 subjects in avoiding the obstacles and the factors associated with falls by four of the subjects. Differences among gait parameters were analysed with respect to age, gender, available response time, and avoidance strategy. Both short- and long-step strategies were used to avoid stepping on the obstacles, but age differences in strategy choice were not significant. The short-step strategy was used more often with shorter available response times. To avoid a fized obstacle gait was seldom adjusted more than two steps before reaching it; the older adults, however, adjusted their stepping pattern one step earlier than did the younger adults. As the available response time was shortened, the results suggest that older adults had more difficulty than did younger adults in employing the long-step strategy. Although the short-step strategy is easier to employ at short available response times, it becomes a highly risky strategy when combined with a fast walking speed and resulted in actual falls. The results show that in both young and old healthy adults, tripping does not necessarily originate from contacts with a physical obstacle; it can be self initiated.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/31348/1/0000258.pd

Relaxation phenomenon in lumbar trunk muscles during lateral bending

This paper reports myoelectric activity measurements in the lumbar trunk muscles when subjects performed tasks involving various degrees of lateral bending. Biomechanical model analyses were made to estimate the tensions in the lumbar trunk muscles required to perform those tasks. The tensions and the activity measurements were compared to see if a muscle relaxation phenomenon occurred. A relaxation phenomenon in the erector spinae muscles was observed to occur in quiet standing in a laterally-bent position of the trunk, qualitatively similar to the flexion-relaxation phenomenon reported by Schultz et al. in 198513. However, no relaxation was observed to occur in the lateral oblique abdominal muscles in laterally-bent postures of the trunk.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/27189/1/0000192.pd

Biomechanical factors in the progression of idiopathic scoliosis

Idiopathic scoliosis is present when, in upright positions of the trunk, the spine curves to the side for unknown reasons. This paper reviews evidence concerning some biomechanical factors that might underlie the progression of such curves. The review concentrates on studies conducted in our laboratories. Arguments are made, based on biomechanical analyses and experiments, that progression occurs because of defects in the postural control system of the spine.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/43994/1/10439_2006_Article_BF02371453.pd