Objective: This study examined the impact of two common sizes of ballast on gait biomechanics. The terrain was designed to simulate a railroad work setting to investigate the variation in gait kinetics and muscle activation while walking. Background: Research and epidemiology suggest a potential link between walking surface characteristics and injury. However, few studies have investigated the impact of ballast surfaces, which is a surface of interest in the railroad and construction industries, on gait dynamics. Method: For this study, 20 healthy adult men walked along three distinct pathways (no ballast [NB], walking ballast [WB], and mainline ballast [MB]). WB and MB consisted of rock with an average size of 0.75 to 1 in. and 1.25 to 1.5 in., respectively. Full-body motion, ground reaction forces, and electromyographic (EMG) signals from lower extremity muscles were collected, and three dimensional joint moments were calculated. Parameters of interest were moment trajectories and ranges, EMG activity, and temporal gait measures. Results: Joint-specific differences indicate significant variations between surface conditions. Joint moment ranges were generally smaller for MB and WB compared with NB. EMG activity, in particular, co-contraction levels, was found to be significantly greater on ballast compared with NB. Temporal gait parameters were significantly different for MB than for either WB or NB. Conclusion: Walking on ballast increases muscle activation to control the moments of the lower extremity joints. Application: The results suggest that ballast has an effect on muscles and joints; thus, the findings provide insight to improve and develop new work practices and methods for injury prevention.

Joint kinetics and muscle activity while walking on ballast.

Background. Methods of measuring lower extremity function is limited for those with partial weight bearing (PWB) status in early phases of a lower extremity rehabilitation program. Objectives. The purpose of this study was to measure intra-rater reliability of two lower extremity PWB performance measures using an incline exercise apparatus and to evaluate the concurrent validity and responsiveness to change of these two measures. Methods. Thirty-seven adult patients with lower extremity injuries were measured on two PWB measures (PWB20 and PWB30) of lower extremity performance as well as several common measures of LE function. After initial testing, subjects were asked to return for retesting, following four to six weeks of rehabilitation intervention. Reliability of the data from the measures was tested using intraclass correlation coefficients (ICC); validity was based on bivariate correlations of the measures. The minimal detectable change (MDC) value and limb symmetry index (LSI) were used to study the responsiveness of the PWB measures. Results. The ICC for the PWB20 and PWB30 were 0.95 and 0.98, respectively. The bivariate correlations of the PWB20 with stair climbing and walking speed were greater than those of the PWB30. Correlations ranged from r = 0.49 to 0.72 between the PWB measures and the functional measures. For most patients, their change in score between initial testing and follow-up exceeded the MDC; the LSI improved for all patients. Conclusion. Using the incline apparatus yielded reliable PWB data. In addition, performance on the PWB measures correlated fairly well with common measures of function.

Reliability and Validity of a Partial Weight Bearing Measure of Lower Extremity Performance

Study Design: A pre and post-test measure of six randomized lower extremity (LE) functional performance tests. Objectives: To determine whether valid inferences about LE performance could be obtained using a sliding incline apparatus. Background: Current functional tests require patients to bear full weight on their lower extremities, and are not indicated for acute recovery states that require a partial-weight bearing (PWB) status. Measuring LE performance early in the rehabilitation process is essential in determining an accurate prognosis. Two LE performance tests were designed to measure functional performance of individuals with PWB status using a commercially available sliding incline apparatus. Methods and Measures: Patients 18 years of age or older with LE dysfunction (n=21) participated. Diagnosis included: knee joint pathology, ACL reconstruction, TKA, patellofemoral dysfunction, and tibial plateau fractures. The PWB tests were preformed on a commercially available sliding incline apparatus. Subjects completed the following tests in a randomized order: a one-legged PWB 30 repetition squat test, one-legged PWB 20 second squat test, time to ascend stairs, time to descend stairs, distance of a onelegged hop, and walking speed. Subjects completed a pre-test initially and a post-test three to four weeks following treatment. Data Analysis: Two-way ANOVA was used to compare the rate of improvement between the uninjured and injured LE for each of the single legged tests (i.e., the two PWB tests and the hop test); paired t-tests were used to test for improvement on the stair climbing tests and the walking test. It was expected that the injured LE would improve at

Diana K. Hansen

Papers

Abduction/adduction moment at the knee in stair climbing and level walking