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Lexington, KY, United States

Crowell H.P.,U.S. Army | Davis I.S.,University of Delaware | Davis I.S.,Drayer Physical Therapy Institute
Clinical Biomechanics | Year: 2011

Background: Tibial stress fractures, which are among the most common running related injuries, have been associated with increased lower extremity loading (i.e., peak positive acceleration of the tibia, vertical force impact peak, and average and instantaneous vertical force loading rates) during initial contact. This study was conducted to evaluate the efficacy of a gait retraining program designed to reduce this loading during running and to assess the short-term persistence of these reductions. Methods: Ten runners (six females and four males) with peak positive tibial acceleration greater than 8 g, measured in an initial screening, participated in the retraining program. During the retraining sessions, subjects ran on a treadmill and received real-time visual feedback from an accelerometer attached to their distal tibias. Tibial acceleration and vertical ground reaction force data were collected from subjects during overground data collection sessions held pre-training, post-training, and at a 1-month follow-up. Findings: Peak positive acceleration of the tibia, vertical force impact peak, and average and instantaneous vertical force loading rates were all reduced immediately following the gait retraining. The decrease in tibial acceleration was nearly 50%. The reductions in vertical force loading rates and vertical force impact peak were approximately 30% and 20%, respectively. These reductions were maintained at the 1-month follow-up. Interpretation: Subjects were able to run with reduced tibial acceleration and vertical force loading immediately following completion of the gait retraining program and at the 1-month follow-up evaluation. This may reduce their risk of stress fractures. © 2010 Elsevier Ltd. Source


Fellin R.E.,University of Delaware | Manal K.,University of Delaware | Davis I.S.,University of Delaware | Davis I.S.,Drayer Physical Therapy Institute
Journal of Applied Biomechanics | Year: 2010

Researchers conduct gait analyses utilizing both overground and treadmill modes of running. Previous studies comparing these modes analyzed discrete variables. Recently, techniques involving quantitative pattern analysis have assessed kinematic curve similarity in gait. Therefore, the purpose of this study was to compare hip, knee and rearfoot 3-D kinematics between overground and treadmill running using quantitative kinematic curve analysis. Twenty runners ran at 3.35 m/s ± 5% during treadmill and overground conditions while right lower extremity kinematics were recorded. Kinematics of the hip, knee and rearfoot at footstrike and peak were compared using intraclass correlation coefficients. Kinematic curves during stance phase were compared using the trend symmetry method within each subject. The overall average trend symmetry was high, 0.94 (1.0 is perfect symmetry) between running modes. The transverse plane and knee frontal plane exhibited lower similarity (0.86-0.90). Other than a 4.5 degree reduction in rearfoot dorsiflexion at footstrike during treadmill running, all differences were ≤1.5 degrees. 17/18 discrete variables exhibited modest correlations (>0.6) and 8/18 exhibited strong correlations (>0.8). In conclusion, overground and treadmill running kinematic curves were generally similar when averaged across subjects. Although some subjects exhibited differences in transverse plane curves, overall, treadmill running was representative of overground running for most subjects. © 2010 Human Kinetics, Inc. Source


Lloyd C.H.,University of Calgary | Stanhope S.J.,University of Delaware | Davis I.S.,University of Delaware | Davis I.S.,Drayer Physical Therapy Institute | Royer T.D.,University of Delaware
Gait and Posture | Year: 2010

Persons with a unilateral, trans-tibial amputation have an increased risk of developing osteoarthritis (OA) in the knee of their intact limb. Between-side strength discrepancies observed in individuals with an amputation may indicate overuse of the intact limb and increased osteoarthritis risk; however, the relationship between lower extremity strength and gait mechanics has not been addressed in previous literature. It was hypothesized that amputee subjects' strength and gait would be more asymmetrical than controls, and that strength asymmetry would positively correlate with gait variable asymmetry and intact side gait variables associated with osteoarthritis risk. Eight persons with unilateral, trans-tibial amputation and eight able-bodied control subjects participated. Three gait variables related to osteoarthritis risk (knee external adduction moment, knee adduction moment load rate, and vertical ground reaction force load rate) were measured bilaterally, along with three strength measures (hip abductors, knee extensors, and knee flexors). Four of the six variables were more asymmetrical in the amputee group than the control group (p< 0.05 and/or effect size greater than 0.70). Knee extension strength asymmetry was significantly related to knee adduction moment load rate asymmetry (rho = 0.714), and knee flexion strength asymmetry was moderately related to the vertical ground reaction force on the intact limb (rho = 0.643). Results suggest that strength asymmetry in unilateral trans-tibial amputees has a moderate relationship with osteoarthritis risk, and may be a useful way to assess gait ability and the need for rehabilitation in this population. © 2010. Source


Dierks T.A.,Indiana University | Davis I.S.,University of Delaware | Davis I.S.,Drayer Physical Therapy Institute | Hamill J.,University of Massachusetts Amherst
Journal of Biomechanics | Year: 2010

Runners rarely run to the point of maximum fatigue or exhaustion. However, no studies have investigated how the level of exertion associated with a typical running session influences running mechanics. The purpose of this study was to investigate the effects that running in an exerted state had on the kinematics and joint timing within the lower extremity of uninjured, recreational runners. Twenty runners performed a prolonged treadmill run at a self-selected pace that best represented each runner's typical training run. The run ended based on heart rate or perceived exertion levels that represented a typical training run. Kinematics and joint timing between the foot, knee, and hip were analyzed at the beginning and end of the run. Increases were primarily observed at the end of the run for the peak angles, excursions, and peak velocities of eversion, tibial internal rotation, and knee internal rotation. No differences were observed for knee flexion, hip internal rotation, or any joint timing relationship. Based on these results, runners demonstrated subtle changes in kinematics in the exerted state, most notably for eversion. However, runners were able to maintain joint timing throughout the leg, which may have been a function of the knee. Thus, uninjured runners normally experience small alterations in kinematics when running with typical levels of exertion. It remains unknown how higher levels of exertion influence kinematics with joint timing and the association with running injuries, or how populations with running injuries respond to typical levels of exertion. © 2010 Elsevier Ltd. Source


Fellin R.E.,University of Delaware | Rose W.C.,University of Delaware | Royer T.D.,University of Delaware | Davis I.S.,University of Delaware | Davis I.S.,Drayer Physical Therapy Institute
Journal of Science and Medicine in Sport | Year: 2010

When analysing gait, the identification of the period of stance is often needed. Forceplates are typically used, but in their absence kinematic data can be employed. Five kinematic methods have been previously described in the literature. However, these methods have not been compared to each other for overground or treadmill running. Therefore, the purpose of this study was to compare these five kinematic methods of identifying the stance phase with vertical ground reaction force data both during overground and treadmill running. We recruited forty recreational runners (20 males) for this study. Twenty runners underwent an instrumented gait analysis during overground running, and twenty were tested during instrumented treadmill running. All runners ran at 3.35. m/s. Each kinematic method was compared with stance identified from the vertical ground reaction force (gold standard) for overground running. This method was then repeated for treadmill running. Two methods were found to be valid and reliable for determining footstrike. These were the time when the distal heel marker reached a minimum vertical position, and when the vertical velocity of this same marker changed from negative to positive. These methods had absolute errors that ranged from 22.4. ms to 24.6. ms for both modes of running. Toe-off was best identified using peak knee extension, with absolute errors of 4.9. ms for overground running and 5.2. ms for treadmill running. Utilising automated kinematic methods of determining stance will aid researchers studying running when forceplates are unavailable. © 2010 Sports Medicine Australia. Source

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