Obstacle Crossing in Healthy Young and Older Individuals

Introduction: In the United States, the average population age is rising and will continue to increase in the coming years.With an older population comes increased risk of injury associated with falls. Falls are considered a leading cause of injury and death in older individuals, and many falls are caused by body imbalance or obstacle collision due to a clearly visible stationary object (e.g., rug, chair, branch). Older adults tend to cross obstacles with increased toe clearance in order to prevent tripping, but much of what is known about obstacle crossing in older adults is limited to artificial obstacles that are unique to the laboratory. Currently, there is little data about how older adults cross the varied types of obstacles that are likely encountered during community ambulation. Thus, this study compared measures of obstacle crossing between young and older adults. Methods: Fifteen healthy, older adults (68 ± 6 years) and fifteen healthy, young adults (23 ± 2 years) completed a series of obstructed walking trials within the lab while barefoot. A 3D motion capture system tracked participants while they completed at least ten trials of walking for each obstacle along an 8-meter walkway. Obstacles were presented in a randomized order. Participants were instructed to “walk at a comfortable pace, stepping over the obstacle along the way”. The obstacles were a branch and a parking curb, representing natural obstacles, and a dowel rod, the traditional obstacle in laboratory studies. Vertical and horizontal toe clearance was measured to assess crossing strategies. Results: Older individuals crossed the branch, the curb, and the dowel with increased margins of safety when compared to younger adults, which can be seen through the significantly higher foot clearance, specifically the lead toe clearance (p= .013), and trail toe clearance (p= .001). The curb had a smaller approach and landing distance due to the depth. Regardless of age, the dowel was crossed with a greater margin of safety than the branch and the curb, shown by higher leading and trailing limb toe clearances. The dowel also caused the greatest decrease in gait speed. Discussion: These results show that older individuals increase foot clearance in both the leading and trailing limbs to prevent tripping, supporting the idea that the obstacle is perceived as a greater risk by older individuals. Interestingly, the branch and the curb appear to be less threatening than the dowel rod based on toe clearances. The smaller approach distance and landing distance for the curb, which can be attributed to its depth, suggest step length is maintained across obstacle types, regardless of the increased risk of obstacle contact

Obstacle Crossing in Healthy Young and Older Individuals

Introduction: In the United States, the average population age is rising and will continue to increase in the coming years.With an older population comes increased risk of injury associated with falls. Falls are considered a leading cause of injury and death in older individuals, and many falls are caused by body imbalance or obstacle collision due to a clearly visible stationary object (e.g., rug, chair, branch). Older adults tend to cross obstacles with increased toe clearance in order to prevent tripping, but much of what is known about obstacle crossing in older adults is limited to artificial obstacles that are unique to the laboratory. Currently, there is little data about how older adults cross the varied types of obstacles that are likely encountered during community ambulation. Thus, this study compared measures of obstacle crossing between young and older adults. Methods: Fifteen healthy, older adults (68 ± 6 years) and fifteen healthy, young adults (23 ± 2 years) completed a series of obstructed walking trials within the lab while barefoot. A 3D motion capture system tracked participants while they completed at least ten trials of walking for each obstacle along an 8-meter walkway. Obstacles were presented in a randomized order. Participants were instructed to “walk at a comfortable pace, stepping over the obstacle along the way”. The obstacles were a branch and a parking curb, representing natural obstacles, and a dowel rod, the traditional obstacle in laboratory studies. Vertical and horizontal toe clearance was measured to assess crossing strategies. Results: Older individuals crossed the branch, the curb, and the dowel with increased margins of safety when compared to younger adults, which can be seen through the significantly higher foot clearance, specifically the lead toe clearance (p= .013), and trail toe clearance (p= .001). The curb had a smaller approach and landing distance due to the depth. Regardless of age, the dowel was crossed with a greater margin of safety than the branch and the curb, shown by higher leading and trailing limb toe clearances. The dowel also caused the greatest decrease in gait speed. Discussion: These results show that older individuals increase foot clearance in both the leading and trailing limbs to prevent tripping, supporting the idea that the obstacle is perceived as a greater risk by older individuals. Interestingly, the branch and the curb appear to be less threatening than the dowel rod based on toe clearances. The smaller approach distance and landing distance for the curb, which can be attributed to its depth, suggest step length is maintained across obstacle types, regardless of the increased risk of obstacle contact

Dominant Clonotypes in the Repertoire of Peripheral CD4+ T Cells in Rheumatoid Arthritis

Clonal expansion of T cell specificities in the synovial fluid of patients has been taken as evidence for a local stimulation of T cells. By studying the T cell receptor (TCR) repertoire of CD4 ± T cells in the synovial and peripheral blood compartments of patients with early rheumatoid arthritis (RA), we have identified clonally expanded CD4 + populations. Expanded clonotypes were present in the peripheral blood and the synovial fluid but were not preferentially accumulated in the joint. Dominant single clonotypes could not be isolated from CD4+ cells of HLA-DRB1 *04+ normal individuals. Clonal expansion involved several distinct clonotypes with a preference for Vf633, V1314', and VJ817'CD4+ T cells. A fraction of clonally related T cells expressed IL-2 receptors, indicating recent activation. The frequencies of clonally expanded V/317+CD4+ T cells fluctuated widely over a period of one year. Independent variations in the frequencies of two distinct clonotypes in the same patient indicated that different mechanisms, and not stimulation by a single arthritogenic antigen, were involved in clonal proliferation. These data support the concept that RA patients have a grossly imbalanced TCR repertoire. Clonal expansion may result from intrinsic defects in T cell generation and regulation. The dominance of expanded clonotypes in the periphery emphasizes the systemic nature of RA and suggests that T cell proliferation occurs outside of the joint. (J. Clin. Invest