Lower Extremity Strength and Mechanics During Jumping in Women With Patellofemoral Pain

Context: Lower extremity (LE) weakness might be associated with altered mechanics during weight bearing in subjects with patellofemoral pain syndrome (PFPS). Objective: To analyze LE strength, mechanics, and the association between these variables among women with and without PFPS during a simulated athletic task. Design: Case control. Setting: Motion-analysis laboratory. Subjects: 20 women with PFPS and 20 healthy women. Main Outcome Measures: Peak isometric lateral trunk-flexion, hipabduction, hip external-rotation, knee-flexion, and knee-extension strength, as well as hip- and knee-joint excursions and angular impulses during single-leg jumps. Results: PFPS subjects produced less hip-abduction, hip external-rotation, and trunk lateral- flexion force than the control group. The PFPS group also demonstrated greater hipadduction excursion and hip-abduction impulses. The association between the strength measurements and LE mechanics was low. Conclusions: Women with PFPS demonstrate specific weaknesses and altered LE mechanics. Weakness is not, however, highly correlated with observed differences in mechanics. ABSTRACT FROM AUTHO

Varied response to mirror gait retraining of gluteus medius control, hip kinematics, pain, and function in 2 female runners with patellofemoral pain.

STUDY DESIGN: Case report. BACKGROUND: The underlying mechanism of the changes in running mechanics after gait retraining is presently unknown. This case report assesses changes in muscle coordination and kinematics during treadmill running and step ascent in 2 female runners with patellofemoral pain after mirror gait retraining. CASE DESCRIPTION: Two female runners with chronic patellofemoral pain underwent 8 sessions of mirror gait retraining during treadmill running. Subjective measures and hip abductor strength were recorded at baseline and after the retraining phase. Changes in hip mechanics and electromyography data of the gluteus medius during treadmill running and step ascent were also assessed. OUTCOMES: Both runners reported improvements in pain and function that were maintained for at least 3 months. During running, peak contralateral pelvic drop (baseline-postretraining difference: runner 1, 2.6° less; runner 2, 1.7° less) and peak hip adduction (baseline-postretraining difference: runner 1, 5.2° less; runner 2, 6.3° less) were reduced after retraining. Kinematic reductions accompanied earlier activation of the gluteus medius relative to foot strike (baseline-postretraining difference: runner 1, 12.6 milliseconds earlier; runner 2, 37.3 milliseconds earlier) and longer duration of gluteus medius activity (runner 1, 55.8 milliseconds longer; runner 2, 44.4 milliseconds longer). Runner 1 transferred reduced contralateral pelvic drop to step ascent, whereas runner 2 did not (contralateral pelvic drop baseline-postretraining difference: runner 1, 3.6° less; runner 2, 1.5° more; hip adduction baseline-postretraining difference: runner 1, 3.0° less; runner 2, 0.5° more). Both runners demonstrated earlier onset of gluteus medius activity during step ascent (baseline-postretraining difference: runner 1, 48.0 milliseconds earlier; runner 2, 28.3 milliseconds earlier), but only runner 1 demonstrated longer activation duration (runner 1, 25.0 milliseconds longer; runner 2, 69.4 milliseconds shorter). DISCUSSION: While changes in hip mechanics and gluteus medius activity during running were consistent with those noted during step ascent for runner 1, runner 2 failed to demonstrate similar consistency between the tasks. Earlier onset and longer duration of gluteus medius activity may have been necessary to alter step mechanics for runner 2. LEVEL OF EVIDENCE: Therapy, level 4. NOTE: This is a non-final version of an article published in final form in Willy, R. W., & Davis, I. S. (2013). Varied response to mirror gait retraining of gluteus medius control, hip kinematics, pain, and function in 2 female runners with patellofemoral pain. The Journal of Orthopaedic and Sports Physical Therapy, 43(12), 864-874. doi:10.2519/jospt.2013.451

Are mechanics different between male and female runners with patellofemoral pain?

INTRODUCTION: Patellofemoral pain (PFP) has often been attributed to abnormal hip and knee mechanics in females. To date, there have been few investigations of the hip and knee mechanics of males with PFP. The purpose of this study was to compare the lower extremity mechanics and alignment of male runners with PFP with healthy male runners and female runners with PFP. We hypothesized that males with PFP would move with greater varus knee mechanics compared with male controls and compared with females with PFP. Furthermore, it was hypothesized that males with PFP would demonstrate greater varus alignment. METHODS: A gait and single-leg squat analysis was conducted on each group (18 runners per group). Measurement of each runner's tibial mechanical axis was also recorded. Motion data were processed using Visual 3D (C-Motion, Bethesda, MD). ANOVAs were used to analyze the data. RESULTS: Males with PFP ran and squatted in greater peak knee adduction and demonstrated greater peak knee external adduction moment compared with healthy male controls. In addition, males with PFP ran and squatted with less peak hip adduction and greater peak knee adduction compared with females with PFP. The static measure of mechanical axis of the tibial was not different between groups. However, a post hoc analysis revealed that males with PFP ran with greater peak tibial segmental adduction. CONCLUSION: Males with PFP demonstrated different mechanics during running and during a single-leg squat compared with females with PFP and with healthy males. Based upon the results of this study, therapies for PFP may need to be sex specific. NOTE: This is a non-final version of an article published in final form in Medicine & Science in Sports & Exercise 44, no. 11 (Nov 2012): 2165-2171

The Last Mile in Analyzing Wellbeing and Poverty : Indices of Social Development

__Abstract__ Development practitioners worldwide increasingly recognize the importance of informal institutions - such as norms of cooperation, non-discrimination, or the role of community oversight in the management of investment activities – in affecting well-being, poverty, and even economic growth. There has been little empirical analysis that tests these relationships at the international level. This is largely due to data limitations: few reliable, globally-representative data sources exist that can provide a basis for cross-country comparison of social norms and practice, social trust and community engagement

The Effect of a Hip Strengthening Program on Mechanics during Running and Single Leg Squatting

STUDY DESIGN: Block randomized controlled trial. OBJECTIVES: To investigate whether a strengthening and movement education program, targeting the hip abductors and hip external rotators, alters hip mechanics during running and during a single-leg squat. BACKGROUND: Abnormal movement patterns during running and single-leg squatting have been associated with a number of running-related injuries in females. Therapeutic interventions for these aberrant movement patterns typically include hip strengthening. While these strengthening programs have been shown to improve symptoms, it is unknown if the underlying mechanics during functional movements is altered. METHODS: Twenty healthy females with excessive hip adduction during running, as determined by instrumented gait analysis, were recruited. The runners were matched by age and running distance, and randomized to either a training group or a control group. The training group completed a hip strengthening and movement education program 3 times per week for 6 weeks in addition to single-leg squat training with neuromuscular reeducation consisting of mirror and verbal feedback on proper mechanics. The control group did not receive an intervention but maintained the current running distance. Using a handheld dynamometer and standard motion capture procedures, hip strength and running and single-leg squat mechanics were compared before and after the strengthening and movement education program. RESULTS: While hip abductor and external rotation strength increased significantly (P<.005) in the training group, there were no significant changes in hip or knee mechanics during running. However, during the single-leg squat, hip adduction, hip internal rotation, and contralateral pelvic drop all decreased significantly (P = .006, P = .006, and P = .02, respectively). The control group exhibited no changes in hip strength, nor in the single-leg squat or running mechanics at the conclusion of the 6-week study. CONCLUSION: A training program that included hip strengthening and movement training specific to single-leg squatting did not alter running mechanics but did improve single-leg squat mechanics. These results suggest that hip strengthening and movement training, when not specific to running, do not alter abnormal running mechanics. LEVEL OF EVIDENCE: Therapy, level 2b. NOTE: This is not the final published version. The final version was published in the Journal of Orthopaedic and Sports Physical Therapy. 2011 Sep; 41(9): 625-32. doi: 10.2519/jospt.2011.347

ESTABLISHING TRAINING PARAMETERS FOR A DEEP NEURAL NETWORK TO ASSESS 2D, FRONTAL PLANE KINEMATICS

The purpose of this study was to establish the optimal training parameters to assess frontal plane, 2D kinematics using DeepLabCut. DeepLabCut is an open-source platform that allows the user to train neural networks for customized feature detection in 2D videos. Deep neural networks were trained using frontal plane videos from 41 participants who completed single- and double-leg drop landings. Networks were trained with an increasing number of training iterations (25-250k) and training frames (200-800). Our results indicate that a minimum of 175k training iterations and 400 training frames were adequate for stable network performance (training/test errors= 2.8/3.7 pixels)

Differences In Mechanics Between First And Second Drop Vertical Jump Landings

A drop jump and landing, followed by another maximal jump and landing, has been used when assessing injury risk utilizing the Landing Error Scoring System (LESS). Vertical ground reaction force (vGRF) and knee excursion are also commonly analyzed during a drop vertical jump. Previous studies have assessed initial drop vertical jump landing mechanics without assessing the second landing from the subsequent vertical jump. Additionally, analyzing landing mechanics based on subject jump height has not been examined for either landing 1 (L1) or landing (L2). The purpose of this study was to investigate whether there was a difference in LESS scores, vGRF, and knee excursion between the first and second landings of the drop vertical jump in all subjects and when divided into subgroups based on jump height.https://dune.une.edu/pt_studrrposter/1004/thumbnail.jp

Transition to forefoot strike reduces load rates more effectively than altered cadence

Background Excessive vertical impacts at landing are associated with common running injuries. Two primary gait-retraining interventions aimed at reducing impact forces are transition to forefoot strike (FFS) and increasing cadence (CAD). The objective of this study was to compare the short- and long-term effects of 2 gait-retraining interventions aimed at reducing landing impacts. Methods A total of 39 healthy recreational runners using a rearfoot strike and a CAD of ≤170 steps/min were randomized into CAD or FFS groups. All participants performed 4 weeks of strengthening followed by 8 sessions of gait-retraining using auditory feedback. Vertical average load rates (VALR) and vertical instantaneous load rates were calculated from the vertical ground reaction force curve. Both CAD and foot strike angle were measured using 3-dimensional motion analysis and an instrumented treadmill at baseline and at 1 week, 1 month, and 6 months after retraining. Results Analysis of variance revealed that the FFS group had significant reductions in VALR (49.7%) and vertical instantaneous load rates (41.7%), and changes were maintained long term. Foot strike angle in the FFS group changed from 14.2° dorsiflexion at baseline to 3.4° plantarflexion, with changes maintained long term. The CAD group exhibited significant reduction only in VALR (16%) and only at 6 months. Both groups had significant and similar increases in CAD at all follow-ups (CAD, +7.2% to 173 steps/min; and FFS, +6.1% to 172 steps/min). Conclusion FFS gait-retraining resulted in significantly greater reductions in VALR and similar increases in CAD compared to CAD gait-retraining in the short and long term. CAD gait-retraining resulted in small reductions in VALR at only the 6-month follow-up

Running in standard versus minimalist shoes

The purpose of this study was to determine if running in a minimalist shoe results in a reduction in ground reaction forces and alters kinematics over standard shoe running. The secondary purpose of this study was to determine if within–session accommodation to a novel minimalist shoe occurs. Running in a minimalist shoe appears to, at least in the short–term, increase loading of the lower extremity over standard shoe running. The accommodation period resulted in less favorable landing mechanics in both shoes. These findings bring into question whether minimal shoes will provide enough feedback to induce an alteration that is similar to barefoot running