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Stephen P. Messier and Mary Ann Brody

This study examined the mechanics of translation and rotation during the conventional and handspring soccer throw-ins. Thirteen male collegiate soccer players were filmed at 100 fps while performing a conventional soccer throw-in for distance. Additionally, two male collegiate and two male youth league soccer players were filmed at 200 fps while performing a handspring throw-in. Analysis of the conventional throw-in revealed that rapid trunk flexion, and shoulder and elbow extension just prior to release appear to make important contributions to the performance variables (initial ball velocity, angle of release, range, angular momentum). Results of the handspring throw-in analysis suggest that the angular momentum generated during the preparatory and ball support phases was transferred to the arms, forearms, and ball during the latter stages of the movement. Although generalization to a larger population is limited, the results of this study suggest that the handspring throw-in technique has the potential to generate greater release velocities and longer throws, thereby enhancing scoring opportunities during throw-in situations.

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Stephen P. Messier, Christopher D. Thompson, and Walter H. Ettinger Jr.

The purpose of this study was to determine the long-term effects of aerobic walking and weight training interventions on gait mechanics and knee pain in older adults with knee osteoarthritis (OA). One hundred three older adults (age ≥60 years) with radio-graphic evidence of knee OA were randomized to one of three treatment groups: aerobic walking, health education control, or weight training. Both exercise intervention groups exercised 3 days · week-1 for 18 months. The aerobic group significantly improved temporal components of gait as well as knee and ankle joint kinematics relative to the health education group across the 18-month intervention. Moreover, the weight training group exhibited significantly greater ankle plantar flexion velocity. Analysis of the ground reaction forces indicated that the aerobic group exhibited significantly greater force relative to the health education group. Finally, both exercise groups exhibited significantly less knee pain than the health education group. The results suggest that long-term aerobic walking and, to a lesser extent, weight training regimens improve walking mechanics in older adults with knee osteoarthritis. These improvements in gait are associated with a reduction in knee pain during activities of daily living.

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C. Mark Woodard, Margaret K. James, and Stephen P. Messier

Our purpose was to compare methods of calculating loading rate to the first peak vertical ground reaction force during walking and provide a rationale for the selection of a loading rate algorithm in the analysis of gait in clinical and research environments. Using vertical ground reaction force data collected from 15 older adults with symptomatic knee osteoarthritis and 15 healthy controls, we: (a) calculated loading rate as the first peak vertical force divided by the time from touchdown until the first peak; (b) calculated loading rate as the slope of the least squares regression line using vertical force and time as the dependent and independent variables, respectively; (c) calculated loading rate over discrete intervals using the Central Difference method; and (d) calculated loading rate using vertical force and lime data representing 20% and 90% of the first peak vertical force. The largest loading rate, which may be of greatest clinical importance, occurred when loading rates were calculated using the fewest number of data points. The Central Difference method appeared to maximize our ability to detect differences between healthy and pathologic cohorts. Finally, there was a strong correlation between methods, suggesting that all four methods are acceptable. However, if maximizing the chances of detecting differences between groups is of primary importance, the Central Difference method appears superior.

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Shannon L. Mihalko, Phillip Cox, Edward Ip, David F. Martin, Paul DeVita, Monica Love, Santiago Saldana, D. Wayne Cannon, Rebecca E. Fellin, Joseph F. Seay, and Stephen P. Messier

Context: While 55 million Americans incorporate running into their exercise routines, up to 65% of runners sustain an overuse injury annually. It has been consistently shown that regular physical activity positively impacts quality of life (QOL), an essential public health indicator; however, the impact of running-related injuries on QOL is unknown. This study seeks to determine whether overuse injury severity impacts QOL in recreational runners, and if self-efficacy mediates this relationship. Design: Community-based prospective cohort study of 300 runners who had been running injury free for at least 5 miles/wk in the past 6 months. Methods: Self-efficacy for running and QOL measures (Short Form-12 Physical Component and Mental Component, Satisfaction with Life, Positive Affect and Negative Affect) were assessed at baseline, time of injury, and follow-up visits. Over 2 years of observation, overuse injuries were diagnosed by an orthopedic surgeon and injured runners were referred to a physical therapist. Results: Injury severity was significantly (P < .01) related with 2 indices of QOL, such that the effect of injury severity was −2.28 units on the Short Form-12 physical component and −0.73 units on positive affect. Self-efficacy accounted for 19% and 48% of the indirect effects on Short Form-12 physical component and positive affect, respectively. Conclusions: Since self-efficacy is a modifiable factor related to decreased QOL, these findings have important clinical implications for rehabilitation interventions.

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Stephen P. Messier, Walter H. Ettinger Jr, Thomas E. Doyle, Timothy Morgan, Margaret K. James, Mary L. O'Toole, and Robert Burns

The purpose of our study was to examine the association between obesity and gait mechanics in older adults with knee osteoarthritis (OA). Subjects were 101 older adults (25 males and 76 females) with knee OA. High-speed video analysis and a force platform were used to record sagittal view lower extremity kinematic data and ground reaction forces. Increased body mass index (BMI) was significantly related to both decreases in walking velocity and knee maximum extension. There were no significant relationships between BMI and any of the hip or ankle kinematic variables. BMI was directly related to vertical force minimum and maximum values, vertical impulse, and loading rate. Increases in braking and propulsive forces were significantly correlated with increased BMI. Maximum medially and laterally directed ground reaction forces were positively correlated with BMI. Our results suggests that, in subjects with knee OA, obesity is associated with an alteration in gait.