The effect of feedback training on the Landing Error Scoring System

Transcription

1 The University of Toledo The University of Toledo Digital Repository Theses and Dissertations 2012 The effect of feedback training on the Landing Error Scoring System Sara C. Doebel The University of Toledo Follow this and additional works at: Recommended Citation Doebel, Sara C., "The effect of feedback training on the Landing Error Scoring System" (2012). Theses and Dissertations This Thesis is brought to you for free and open access by The University of Toledo Digital Repository. It has been accepted for inclusion in Theses and Dissertations by an authorized administrator of The University of Toledo Digital Repository. For more information, please see the repository's About page.

2 A Thesis entitled The Effect of Feedback Training on the Landing Error Scoring System by Sara C. Doebel, ATC Submitted to the Graduate Faculty as partial fulfillment of the requirements for the Master of Science Degree in Exercise Science Dr. Phillip Gribble, Committee Chair Dr. Brian Pietrosimone, Committee Member Dr. Kate Pfile, Committee Member Dr. Patricia R. Komuniecki, Dean College of Graduate Studies The University of Toledo May 2012

3 Copyright 2012, Sara C. Doebel, ATC This document is copyrighted material. Under copyright law, no parts of this document may be reproduced without the expressed permission of the author.

4 An Abstract of The Effect of Feedback Training on the Landing Error Scoring System by Sara C. Doebel, ATC Submitted to the Graduate Faculty as partial fulfillment of the requirements for the Master of Science Degree in Exercise Science The University of Toledo May 2012 Context: Suboptimal lower extremity biomechanics during jump-landing may lead to various lower extremity joint injuries. Verbal feedback has been used previously to positively alter landing biomechanics, yet the use of technology in an effort to allow for the participant to make real-time biomechanical adjustments during landing has not been evaluated. Objective: Determine the immediate effects of real-time feedback (RTF) and traditional feedback (TF) on Landing Error Scoring System (LESS) scores compared to a control condition, that performed jump-landing without any feedback. Design: Single blinded, randomized controlled trial. Setting: Research laboratory. Participants: Twentyeight physically active female participants with no history of lower extremity injury volunteered and were randomized into 3 groups (RTF: n=9, age=20.0±1.4yrs, height=163.98±5.7cm, mass=65.4±9.5kg; TF: n=10, age=20.5±1.3yrs, height=166.12±6.4cm, mass=62.6±7.2kg; Control: n=9, age=21.0±2.1yrs, height=163.16±6.6cm, weight=64.8±17.8kg). Interventions: All participants completed three sets of six jump-landing trials (18 total) off a 30cm box. Participants in the RTF and TF groups were additionally provided standardized verbal feedback instructions from a single clinician after each set. In addition to verbal feedback, participants in the RTF iii

5 group were equipped with retroreflective markers positioned on the lower extremity. Using Cortex software and 3-dimentional Motion Analysis, markers on the middle of the patella and the dorsum of the great toe of the right limb were highlighted in color, and connected with a segment line. RTF participants were able to visualize their 3- dimensional model on a 107cm monitor, and were instructed to align the highlighted knee-foot segment with a stationary vertical reference line in the frontal plane during landing. Control participants received no feedback while performing the 18 box jumps. Main Outcome Measures: All participants performed the LESS testing protocol at baseline and immediately following the intervention consisting of a forward jump off a 30cm box transitioning into a maximal vertical jump. Trials were recorded in the frontal and sagittal planes using two-dimensional video and evaluated with the LESS scoring criteria by two blinded independent assessors. Delta scores from baseline were calculated for all three groups. Independent t-tests and effect sizes (Cohen s d) were performed to assess change scores in the LESS for specific comparisons (TF v. control; RTF v. control). Alpha was set at p<0.05 a priori. Results: While not statistically significant, LESS scores decreased following RTF (-1.33±1.5) and TF(-1.10±2.4), while the control group remained unchanged. (0.00±1.2; F 2,25 =1.39, P=0.27). However, a strong effect size indicated the RTF was more effective than the Control group (d = -0.97; -1.90, 0.05); while a moderate effect size supported the differences between the TF and Control groups (d = -0.56; -1.46, 0.38). Conclusion: RTF decreased LESS score and had a strong effect for immediately improving LESS score compared to the control.tf showed significantly decreased LESS scores compared to the control. Further study is warranted iv

6 to determine the clinical impact of the addition of RTF in making biomechanical corrections during landing. v

7 Acknowledgements I would first like to thank my advisor Dr. Phillip Gribble for providing direction and offering his assistance throughout the entire development of this research project. I also need to thank Hayley Ericksen, my doctoral advisor. Her guidance and involvement in the writing process, data collection and statistical analysis, helped make this process less intimidating and much more fun. Thank you for all of the time and effort you put into to helping me complete this project. I d like to thank my committee members, Dr. Brian Pietrosimone and Dr. Kate Pfile, for their assistance in the writing process. Another big thank you goes to my fellow data collection partners, Adam Lepley and Allison Strouse. I appreciate the many hours spent collecting LESS footage. Finally, I need to thank my family for encouraging me and supporting me in all my endeavors. Go Rockets! Blast off! vi

8 Table of Contents Abstract... iii-v Acknowledgements... vi Table of Contents... vii-viii List of Tables... ix List of Figures...x List of Abbreviations... xi 1 Introduction Background Problem Statement Purpose Statement Significance of Study Hypothesis Limitations Literature Review ACL Injury Poor Jump-Landing Technique Landing Error Scoring System Proper Jump-Landing Technique...12 vii

9 2.5 Feedback Summary Methodology Participants Instrumentation Independent Variables Dependent Variables Procedures Landing Error Scoring System (LESS) Interventions Real-Time Feedback Intervention Traditional Feedback Intervention Control Group Statistical Analysis Results Discussion Limitations Future Research Conclusion...36 References...37 A Appendix...42 viii

10 List of Tables 3.1 Participant Demographics Group Demographics Pre and Post LESS Scores Average Change of LESS Scores by Group Between Group Less Score Change...31 ix

11 List of Figures 3-6 LESS Setup...26 A-1 LESS Score Sheet...42 A-2 LESS Item Description...44 A-3 Real-time feedback individual subject LESS scores...47 A-4 Traditional feedback individual subject LESS scores...48 A-5 Control group individual subject LESS scores...49 x

12 List of Abbreviations ACL...Anterior cruciate ligament Combo...Combination feedback EP...Expert provided feedback GRF...Ground reaction force IC...Initial contact LESS...Landing Error Scoring System RTF...Real-time feedback SA...Self-analysis feedback TF...Traditional feedback xi

13 Chapter 1 Introduction 1.1 Background Jumping and landing are common tasks performed during athletics. In a sport such as volleyball, athletes perform in excess of 60 maximal jumps per hour of game play. 1 These athletes could be at risk for jump-landing injuries if they are landing with poor biomechanics. Landing with excessive knee valgus or with limited knee or hip flexion can place stress on muscles, ligaments and bones surrounding a lower extremity joint 2-4 and place the athlete at greater risk for injury. More than 70% of anterior cruciate ligament (ACL) injuries are sport related and a majority of these are caused by noncontact mechanisms, such as landing from a jump. 5-9 Previous research leads us to believe that poor biomechanical landing patterns are associated with increased knee injury risk. 2,3,10-14 Identifying athletes with poor jump-landing technique may be difficult for some clinicians and will often go unnoticed unless it results in injury. 15 Correcting these poor jump-landing techniques can prove to be a difficult task which may take time. In order to prospectively screen participants who may possess these faulty landing mechanics, it may be necessary to examine their movement patterns across multiple planes of motion The

14 Landing Error Scoring System (LESS) is a tool used for assessing jump-landing biomechanics in a clinical setting. 16 This system was developed as an assessment tool, which compares to the gold standard motion analysis systems, but is more cost effective, practical and time effective in large-scale mass screenings to identify potentially detrimental landing patterns. 16 The LESS has been demonstrated to be a valid and reliable tool used for identification of an athlete s poor jump landing mechanics, 16 but identification is just the first step. Educating the athlete on how to properly land and making corrections to these identified faults could be challenging. Feedback is an intervention that has been shown to make positive changes in jump landing biomechanics which may lead to a reduction in injury risk. 3,6,15,17,18 Previous literature has categorized feedback in several ways including augmented, 1,3,15,18 sensory, 15,18 self, 3,19 expert 3,19 and combination. 3,6,15,18,19 For this study, feedback will be defined by three categories: expert provided (EP), self-analysis (SA) and combination (combo). Expert feedback is feedback provided through verbal correction, verbal instruction or visual demonstration from an expert. 19 Self-analysis feedback is feedback conducted through video tape or self analysis of previous jumps and combo feedback utilizes a combination of both EP and SA feedback. 19 In previous studies, in which feedback was given by an expert in several ways, was defined as traditional feedback. Traditional feedback has previously been demonstrated to be effective at improving jump-landing and includes an expert instructing a participant to land softer or providing participants with a checklist for proper landing. 3,6 2

15 Regardless of the type of feedback used, the effectiveness of the intervention depends on the accuracy of feedback. 3,18 Whether it s a person, computer or the participant themselves giving the feedback, the information needs to be correct in order for the athlete to benefit and make a positive change. 18 The frequency of the feedback and whether or not it is combined with another technique, such as strength training or plyometric training, could also alter the effectiveness of the feedback. 18 There is a need to determine which feedback method or methods are most effective at improving jump-landing biomechanics. There are many variations in the method of delivery and type of feedback which can be used. One or more EP feedback techniques such as watching an expert, verbal advice given from an expert, or a checklist on how to properly complete a jump landing task, could be combined with one or more forms of SA feedback, such as using past jump landing experiences or assessing themselves through videotape of their own previous jumps. There is limited research on how frequent feedback should be conducted and how much time in between feedback sessions is appropriate for greatest retention. More information needs to be obtained about each type of feedback in order to implement the most successful intervention to address poor jump-landing biomechanics. Previous studies have used self-analysis feedback conducted through video tape in which the participant is able to evaluate errors of their own jump landing trial and are able to make changes for the next trial. 3,6,15 One concept of feedback that has yet to be studied is real-time feedback (RTF). Real-time feedback allows participants to view markers representing their own anatomical landmarks in real-time. This allows 3

16 participants to make adjustments to their landing at that moment in time, rather than receiving the feedback after completion of the task. 1.2 Problem Statement Lower extremity injuries are occurring as a result of poor jump-landing mechanics. 3,5-7,15,18,20,21 Athletes, especially females, are landing with multiple biomechanical errors including; small knee flexion, excessive knee valgus and decreased hip flexion angles. 5,7,20,22 These deficits are not usually identified or improved until after injury occurs. Identification and correction of poor jump-landing biomechanics through the LESS prior to participation, could help prevent future injury when landing from a jump. Feedback has been shown to improve jump-landing mechanics and is slowly being implemented into injury prevention programs. However, it is unknown if real-time video feedback is effective at improving jump-landing biomechanics. 1.3 Purpose Statement The purpose of this study is to determine the immediate effect of a real-time feedback intervention versus a traditional feedback intervention and a control (no feedback) intervention on the scoring of the LESS in females. Traditional feedback has already been shown to be an effective mechanism for improving jump landing mechanics, 3 however, to our knowledge, the immediate effects of real-time feedback is yet to be determined. By using the LESS, which has previously been shown to be an effective clinical tool, this study will determine whether or not a single feedback session will produce immediate improvements in females jump-landing biomechanics. 4

17 1.4 Significance of Study This study will be a significant endeavor to investigate the effectiveness of a realtime feedback intervention as a means to improve jump-landing mechanics. By understanding the effects of this type of feedback, other clinicians will be able to use this information in the clinical setting as well as the research laboratory. Moreover, success of this project will provide insight into the effect of a real-time feedback intervention and could provide information to be implemented in long-term studies. Long-term studies will be the ultimate test for the effectiveness of feedback; however the question of whether or not the feedback can make positive changes initially must first be addressed. This study will also be beneficial to other clinicians looking to study feedback responses and we feel will contribute positively to this body of knowledge. 1.5 Hypothesis H1- Those undergoing a real-time feedback intervention will have improved postintervention LESS scores when compared to traditional feedback and no feedback control groups. H2- Those undergoing the traditional feedback will have improved postintervention LESS scores when compared to the control group. H3- Those in the no feedback control group will not show any improvement in post-intervention LESS scores. 1.6 Limitations One limitation in this study is using the LESS which uses a box drop jumplanding task. A sport specific task would be more ideal; however the box drop jump- 5

18 landing provides a standardized way to effectively evaluate groups of people for comparison. Another foreseen limitation to this study is during the pre-intervention testing, as part of the LESS jump-landing task, the participant will complete a rebound jump after the initial landing. This rebound jump, however, will not be completed during the intervention period; instead the participants will simply jump from a box and stick the landing. Due to this difference in landing task it may be difficult for participants to apply the feedback and make biomechanical changes during a different landing task. This study was also being limited to only female participants. Previous research has shown that females are more at risk of tearing their ACL due to poor jump-landing mechanics. 20 Therefore, in order to increase the external application of the results of this preliminary study, only females are being used as participants. Furthermore, this study is limited by the fact that only a single session of feedback is being evaluated. Initial improvement from a single session of feedback is crucial, but feedback will only be beneficial if long-term results can be seen. However, it is important to determine if the RTF is more effective, or equally effective, as a traditional feedback intervention in improving jump landing mechanics. Once this knowledge is gained, future research should aim to show the long term effects of different feedback mechanisms. 6

19 Chapter 2 Literature Review 2.1 ACL Injury Anterior cruciate ligament (ACL) injuries are a common occurrence in athletics. One in 3000 people per year in the general population in the United States sustain this injury, 23 with females having a 4-6 fold increased risk compared to their male counterparts participating in the same sports at similar levels As many as 80% of ACL injuries are caused by non-contact mechanisms, such as during the landing phase of a jump. 5-9 The increased female risk, coupled with the increase in female sports participation, has fueled further investigation into this topic. 27 Through this increase in interest, both intrinsic and extrinsic injury factors have been investigated. Of the extrinsic factors, lower extremity biomechanics have been found to be the most compelling to account for the gender differences in injury rate. 28,29,30,31,32 Lower extremity biomechanics may also be most easily modifiable when compared to intrinsic factors such as a smaller cross-sectional area of the ACL in females, 28 a narrow intercondylar notch 33,34 and hormonal differences 35 between genders. Previous research has shown positive alterations in lower extremity biomechanics with the implementation of appropriate interventions, such as feedback 14,36 7

20 2.2 Poor Jump Landing Technique It has been reported that during a four hour volleyball practice each member of the USA national volleyball team may perform 300 to 500 spikes. 37 Each of those spikes requires jumping and landing and landing with poor mechanics could be placing athletes at an increased risk for injury. It has been found that non-contact jumping injuries often occur immediately after initial foot contact with the knee positioned in small flexion angles. 20 Landing with small knee flexion angles has been found to cause ground reaction forces to be higher. 38 The estimated average knee flexion angle when ACL injury occurs is 21 degrees. 7 At this point in the knee range of motion, quadriceps contractions are generating significant anterior tibial shear force which can facilitate high load on the ACL, 16 placing potential strain on the ligament. Knee flexion angle is not the only concern during non-contact ACL injuries. It has been found that an increase in knee valgus angle also increases the risk of a non-contact ACL injury during jump-landing activities. 39 Findings from a 2010 study 39 show that females typically land with seven to thirteen degrees of valgus at the knee, while males typically land with three to eight degrees. Higher peak knee valgus angles have been found to be associated with increased activity of the lateral thigh musculature. 40 According to Palmieri-Smith et al 40, this could be due to a weakness in the medial thigh musculature, shown through their findings of increased muscle activity in the medial thigh musculature in participants with a low knee valgus angle. 40 Yet another factor contributing to an increase in injury risk during a jump landing task is an increase in ground reaction force (GRF). Ground reaction forces can be 8

21 described as forces experienced from initial contact with the ground, 41 such as that experienced during a jump-landing task. Investigations analyzing vertical GRF found a possible correlation between increased vertical GRF and increased lower extremity injury risk 15,42-44 According to a study by Podraza, 41 higher GRF were found when athletes landed in an extended knee position. Combined previous research 23,45-48 indicates that on average women may have altered neuromuscular control strategies which frequently bring their lower extremity into a potentially injurious position. 28 A study by Chappell et al 28 found female recreational athletes to have altered lower extremity motion patterns which tend to increase proximal anterior tibial shear force during athletic tasks. This increase in anterior tibial shear force places an increased load on the ACL. Identification of athletes displaying poor lower extremity mechanics during a jump landing task may be difficult; however there are clinical assessment tools which have been developed to assist clinicians with this task. 2.3 Landing Error Scoring System The Landing Error Scoring System (LESS) is an inexpensive clinical assessment tool which was developed as an injury-risk-factor-screening tool. 16 The tool is used to identify individuals with poor jump-landing technique who may be at risk for non-contact ACL injuries. 21 The LESS uses two standard video cameras set up in the frontal and sagittal planes to detect potentially detrimental movement patterns during a jump landing task. 16 During the test, participants perform a drop vertical jump off a 30 cm standard plyometric box, land on both feet and upon landing, rebound vertically for maximal height. 16 After the trials are complete, an investigator records all errors, from both the 9

22 frontal and sagittal views, on a standard LESS scoring sheet (Figure 1). The initial contact (IC) phase maximal and knee flexion phase are used for scoring purposes. The LESS measures 17 different aspects of jump-landing, which allows for a very detailed assessment. 16 These aspects were selected based on the influence of a kinematic and kinetic study which assessed the relationship of these movement patterns to ACL injury. 21 Measurements evaluated in the sagittal view include hip, trunk and knee flexion at IC, ankle plantar-flexion at IC, knee flexion displacement, sagittal plane joint displacement, and trunk and hip flexion at maximal knee flexion. 16 Measurements evaluated in the frontal view include: overall impression, foot contact symmetry, stance width, foot position at IC, knee valgus at IC, knee valgus displacement and lateral trunk flexion at IC. 16 Participants are awarded one point, which is considered an error, if he or she does not adequately fulfill the criteria. 16 If the task is completed correctly, no point is awarded. 16 Based on the LESS score, participants can be placed into one of four quartiles, excellent, good, moderate or poor jump landing technique, with a higher LESS score indicating poor technique when landing from a jump. 16 A LESS score which is 4 indicates excellent jump-landing technique; a score ranging from >4 to 5 is considered good; moderate is considered a LESS score ranging from >5 to 6 and poor is considered a LESS score which is >6 points. 16 There are four sets of items which are addressed when formulating a score on the LESS. (Table 1) One set of items evaluated with the LESS during a jump land is lower extremity and trunk positioning at the time of initial contact (items 1-6). 16 To receive a 10

23 perfect score (no errors) on these items a participant must land with: 1.The hips flexed, 2. The trunk flexed and at the midline of the body, 3. Knee flexion greater than 30 degrees, 4. Their knees over their midfoot, 5. Land toe to heel. 16 A second set of items addresses errors in the positioning of the feet at initial contact (items 9-11) and at the time when the entire foot is in contact with the ground (items 7-8). 16 In this case, if the toes are pointing out more or less than 30 degrees or if the stance width is wider or narrower than the width of the shoulder, an error is recorded. An error is also recorded if the landing is not symmetrical at foot contact. The third set of items evaluates lower extremity and trunk movements between initial contact with the ground and the moment of maximum knee flexion angle (items12-15). 16 To be error free, at the time of maximal knee flexion a participants trunk must be in front of the hips, hips flexed greater than at initial contact and the knees must be inside the great toe. Knee flexion displacement also must be greater than 30 degrees. The fourth set of items (items 16-17) are global items which address overall sagittal plane movement and the rater s general impression of the landing quality. 16 In this case the rater is assessing if the participant displays a soft or a stiff landing and provides a score accordingly. 16 The 17 items included for scoring in the LESS make it more comprehensive than previous clinical assessments because of its complete assessment of multiplanar biomechanics. 16 Another beneficial aspect of the LESS is that the jumps are video recorded. This allows the assessor more time to accurately assess and score the jumps. A trained rater requires three to four minutes to score three jump-landing trials. 21 The 11

24 amount of time used to formulate the LESS score is the only difference between a novice and expert rater. Interrater reliability has been shown to be excellent when comparing a novice and an expert at scoring the LESS (ICC=0.085 and p<0.001) and intrarater reliability has also shown to be excellent (ICC-0.91 and SEM=0.42). 22 When comparing subjective expert-rater scores and objective three-dimensional motion-analysis instrumentation values, agreement was found to be moderate to excellent (74-100%) Proper Jump Landing Technique Once poor landing technique is identified with help of the LESS, steps can be taken to make positive changes in movement patterns in an effort to decrease lower extremity injury risk. Research has investigated the exact movement patterns of the hip, knee and ankle during injury, as well as the timing of the injuries. 22,49 From this data, 50,51 conclusions have been made on what biomechanical factors contribute to proper jumplanding technique. Proper jump-landing technique includes landing with increased knee and hip flexion, decreased knee valgus angle, as well as decreased knee and hip internal rotation. 5,16,20 Other factors important in landing to decrease injury risk include landing toes to heal, landing symmetrically and landing with feet shoulder width apart. 16 Knee Flexion Ninety degrees of maximal knee flexion during a jump-landing is ideal to aid in absorption of landing forces. 41 Knee flexion displacement, described as maximal knee flexion minus knee flexion at initial contact, should be greater than 30 degrees when landing from a jump. 16 With an increased knee flexion at landing, muscles are in a more advantageous position to absorb kinetic energy, thereby reducing reaction forces

25 McNitt-Gray 53 found that participants who flexed their knees while landing also had lower ground reaction forces. It is important for the knee to move through a large range of motion when landing, allowing for muscles to absorb excess energy, instead of joints. 53 It has also been proposed that a lack of absorption of ground reaction forces at landing may be a factor in ACL injury. 22 Hip/Trunk Flexion Hip flexion is another important factor in absorbing ground reaction forces during a jump-landing. A more upright position amplifies ground reaction forces which increases the load transmitted to the knee and increases anterior shear force at the knee joint. 41 To aid in the absorption of forces produced when landing from a jump, it is suggested that the hips be flexed during landing. 53 For scoring the LESS 16, hip flexion at maximum knee flexion angle should be greater than at contact. The trunk should also be in front of the hips at maximum knee flexion. 16 These standards were set based on previous research that identified landing with no hip or trunk displacement as a strain acting on the lower extremity, specifically increasing ACL injury risk. 21,54,55 Knee Valgus/Varus According to the LESS 16, subjects should be landing with their knees over their midfoot, which will aid in keeping the knee in a neutral position. It is important to achieve this position because knee valgus and varus has been found to be associated with non-contact ACL injuries from jump-landing. 39,40 Hewett et al 27, also concluded that women who displayed increased knee valgus angle during a drop-landing task were at an 13

26 increased risk of sustaining an ACL injury. Landing with the knee over the midfoot will help avoid an excessive valgus or varus knee position upon landing. Knee and Hip IR/ER When landing from a jump, the knee should be in a neutral position, and avoid going into internal rotation (IR). 50 Internal rotation of the tibia has been has been found to be associated with a dramatic increase in strain on the ACL. 50 Females also tend to land with approximately nine degrees of hip IR. 4 A proper jump-landing should include limited hip IR 16, because an increase in hip IR has been found to be associated with increased knee valgus, which may put the ACL in a potentially injurious position. 4 Landing on Toes It has been suggested that when landing from a jump, an athlete should land softly on his/her toes, then quickly rock back to their heels. 38 In a study which reviewed 29 ACL tears, during the injury mechanism all of the subjects landed on their hindfoot or entire foot flat. 22 With flat foot or hind foot at initial ground contact, it has been shown that the calf musculature may not be able to adequately absorb GRF, resulting in the forces being transmitted directly to the knee. 22 These excess forces can produce great strain on the ligaments of the knee, specifically the ACL. Other Factors Landing with feet shoulder width 16 apart provides a solid base to assist in control and balance when landing from the jump. A balanced landing decreases unnecessary torque which could be placed on the body, specifically in the knee. 56 Other factors contributing to a proper jump-landing include landing with feet evenly and landing on 14

27 both feet at the same time, with toes facing forward. 16 This will help reduce tibial rotation, which when coupled with valgus forces, could place excessive strain on the ACL. 16 As shown above, there are many different factors which play a role in the achievement of proper technique when landing from a jump. For this reason, it may be difficult for an athlete to complete a proper jump-landing without appropriate instruction. An intervention may be needed to give the athlete more insight into proper landing technique. Feedback is an intervention which can be useful in educating an athlete in how to properly land from a jump. Feedback can be implemented in multiple ways and has been found to be effective at improving jump landing mechanics. 3,6,15,17, Feedback Feedback is described as a modality used to prompt an individual to correct potentially harmful biomechanics. 19 There are several different ways in which the literature has defined or categorized feedback including sensory 15,18, augmented 1,3,15,18, self 3,19, expert 3,19 and combination. 3,6,15,18,19 Each feedback study that has been published has defined feedback in different ways. A recent systematic review 19 in review for publication has defined feedback into three different categories: expert provided (EP), self-analysis (SA) and combination (combo). Expert feedback is feedback provided through verbal correction, verbal instruction or visual demonstration from an expert. 19 Through EP feedback, an expert in jump-landing mechanics provides the participant with information on how to make improves to their mechanics during an athletic task. The expert giving the feedback must have sufficient knowledge on how to deliver the proper 15

28 feedback in order for this type of feedback to be most effective. Previous research has shown the effectiveness of various feedback mechanisms in reducing GRF, increasing knee and hip flexion and hip abduction during a jump landing task. 3,6,15,17,18 Herman et al 6 found decreased GRF, increased knee flexion, hip flexion and hip abduction after subjects received combination feedback. Onate et al 3 found significantly increased knee flexion displacement and GRF after EP, SA and combo feedback. Self-analysis feedback is feedback conducted through video tape or analysis of the participant s own previous jumps. 19 Participants are often given pointers for what to look for or how to make biomechanics changes through a check list for landing. When SA feedback is employed, the participant must know which errors they are looking for and how to make improvements in their jump landing task. For example, a subject could be asked to view a video tape of their previous jumps, or be asked to use their experience with their previous jumps to make changes to their landing on their next jumps. 3,15 Another type of SA feedback which is yet to be studied extensively is real-time feedback (RTF). Real-time feedback uses visual input where the participant is able to see markers on specific anatomical landmarks of the lower extremity moving in real-time as they perform a jump landing task. This type of feedback allows participants to make immediate changes as they are performing the task, as opposed to before or after the task is completed. Real-time audio feedback has also been found to be successful in a study by Munro et al 57 which showed an increase in knee flexion angle during jump-landing by wearing a knee sleeve that gave instant, audible feedback concerning knee flexion angle. 16

29 This sleeve was found to be a valid and reliable feedback device to teach athletes to increase their knee flexion during jump-landing training. 57 Combo feedback utilizes a combination of both EP and SA feedback. 19 An example of combination feedback consist of a subject watching themselves land from a jump through videotape or watching an expert model demonstrating a proper jumplanding. 6 Combo feedback could also be completed by giving subjects a checklist for landing 3,6, to aid in their evaluation of their technique, while also having the participant view themself completing a jump-landing task through videotape. EP, SA and combo feedback have been used in recent studies and have been shown to make improvements in certain aspects of jump-landing mechanics, such as ground reaction force, knee flexion, hip flexion and hip abduction. 3,6,15,17,18 Regardless of the type of feedback administered, the effectiveness of feedback depends on the accuracy, whether or not the feedback includes information about performance error, 18 the frequency of the feedback and the amount of time available for the subject to process the feedback. 18 The difficulty of the motor skill being performed also plays a role in the effectiveness of feedback. 18 If the subject can complete the task without difficulty before feedback, there may be little room for improvement making feedback seem unsuccessful. If a more complex task is being performed, feedback may be more effective. If feedback is being delivered with a more complex task, the feedback may be more effective because the difficult task may have more aspects upon which a subject could improve. Therefore it is possible for greater success with a feedback intervention using a more challenging task because of the greater room for improvement. 17

30 Expert Provided Feedback Expert provided feedback is feedback given through verbal correction, verbal instruction or visual demonstration. 19 Examples of EP feedback include instruction on increasing knee flexion during landing, an expert demonstrating how to properly land from a jump, or an expert providing a checklist of how properly land from a jump. Expert provided feedback via verbal instruction has been shown to significantly increase knee angle at initial contact. 17 In a study by Cowling 17, one group of participants were told to land with their knees bending, while another group was told to turn on the muscles at the back of your thigh on earlier and more before landing. The results of this study showed significant increases in knee flexion for both of these types of EP feedback. This example demonstrates two different ways EP feedback can be delivered to produce similar results. In another study by Prapavessis 18, EP feedback significantly lowered ground reaction forces in participants after receiving verbal instruction from an expert to land more softly. Self-Analysis Feedback It is suggested that because learning is a problem solving process; the more involved the individual is in analyzing his or her own performance, the greater the learning value. 58 SA feedback is a type of feedback which allows for an individual to be more involved in the analysis of their own performance. This can be accomplished through videotape self-analysis, in which participants are shown videotape of their own previous jumps and are given feedback on how to make changes based on what they observe. Another way SA feedback is administered is by participant being instructed to 18

31 use the experience of their first jump to land in a manner that would minimize the stress of their next landing. With SA feedback, subjects are able to analyze the task to be completed and are able to make changes to future tasks on their own accord. Onate et al 3 supports the need for individualized videotaping using a SA feedback model to enhance jump-landing. 3 A recent systematic review 19 submitted for publication found interesting differences in SA feedback which used videotape self-analysis versus SA feedback which did not use videotape. The studies included in this review which allowed subjects to watch videotape of their previous jumps before completing their next jumps showed greater reductions in GRF compared to studies without the use of videotape self-analysis. 19 Self-analysis feedback allows for participants to be more involved in the feedback process which may allow for greater improvements in jump landing mechanics. However, this type of feedback may not be as successful unless the participant is given additional information on what to look for when analyzing videotape of their previous jumps. Real-time feedback (RTF) is another type of SA feedback. RTF utilizes 3D motion analysis cameras to allow participants to view markers placed on certain anatomical landmarks on a video monitor. Specifically, markers are placed on the participant s patella and great toe and are connected by vertical line. Participants are instructed to line the red line (patella to great toe) up with the blue (vertical) reference line when landing from a jump. The intent of RTF is to limit excessive movement at the knee in the frontal plane during landing. To our knowledge, RTF has not been extensively studied as a type of feedback to improve jump-landing technique. 19

32 Combination Feedback Combination feedback provides additional information to the participants through both EP and SA feedback. Combo feedback could include a combination of an expert demonstrating the proper landing mechanics, an expert giving verbal feedback to the participant, the participant viewing previous jump-landing trials and/or the participant being instructed to use their experience in their previous jumps to make alterations in an attempt to make changes to their landing mechanics. Several studies have been published regarding the ability of combination feedback to improve jump-landing kinematics. 3,6,15 Results from a study by Onate et al 15 found that participants were able to significantly lower ground reaction forces immediately and oneweek following a feedback intervention which included watching videotape of themselves perform a jump-landing task and being given expert advice about their jumplanding. 15 In a similar study 3, participants who viewed themselves performing a jumplanding task, also watched an expert perform a jump-landing task and were critiqued by an expert about their jump-landing technique, significantly improved their maximum knee flexion angle and knee flexion angle at initial contact. This same combination feedback protocol showed improved knee and hip kinematics during a stop-jump-task in another investigation. 6 One combo protocol which has yet to be studied is the use of realtime feedback in combination with an expert checklist for proper landing. Using the expert checklist has been shown to be a successful tool for improving jump-landing when combined with video-tape self-analysis. 3,6,15 More success may be seen if a participant is given information on how to make changes to better their landing mechanics before 20

33 performing the task and are also able to make corrections in real-time. Of the three types of feedback, EP, SA and combo, Ericksen et al., 19 found combo feedback to be most effective in reducing GRF during jump landing. Combo feedback provides a greater amount of information to the subject regarding their performance in a jump landing task. This increased amount of information may provide a subject with more options in utilizing information which is most helpful to the individual. By combining both expert instruction and videotape analysis, the subject is given an opportunity to hear what needs to be done correctly, but also allows for active involvement in evaluating the mistakes and corrections of their own jump landing trials Summary Jumping and landing is a common task performed during many different athletic activities. Altered or poor landing mechanics, such as excessive knee valgus, can lead to increased lower extremity injury risk. 20,22 Identification of athletes with poor landing mechanics may be achieved by using the LESS, which has been shown to be a valid and reliable clinical tool used to asses jump-landing mechanics. 21 After identification of potentially detrimental landing mechanics with help of the LESS, feedback is an effective modality which can be used to make positive changes in jump-landing mechanics and possibly reduce injury risk. Feedback is a practical way to help alter biomechanics during a jump-landing task and there are many ways feedback can be implemented as an intervention for improving landing mechanics. There is a need to educate athletes, especially females, in how to properly land from a jump to prevent lower extremity 21

34 injuries. However, more research is needed on real-time feedback, to determine its effectiveness in improving jump-landing mechanics. 22

35 Chapter 3 Methodology 3.1 Participants Twenty-eight (20.79±1.57 yrs; ±6.11cm; 64.36±11.43 kg), (Table 3.1) healthy females were recruited from the University of Toledo for this study. The participants were recreationally active, as defined as participating in exercise for at least three times a week for 30 minutes. Participants had no self-reported history of lower extremity fracture or orthopedic surgery and were free of any other lower extremity ligamentous injury within the last six months. Table 3.1: Participant Demographics Mean±SD N (total) 28 Age ± 1.57 Height (cm) ± 6.11 Mass (kg) ± Table 3.2: Group Demographics N (total) Age Height (cm) Mass (kg) Real-Time FB ± ± ±9.5 Traditional FB ± ± ±7.2 Control Group ± ± ±17.8 Mean±SD 23

36 3.2 Instrumentation Camera System for Landing Error Scoring System (LESS) Two standard digital video cameras (Sony Cyper-Shot DSC-HX9/HX9V, San Diego, CA) were set up 136 inches from two AMTI forceplates (Advanced Mechanical Technology Inc., Watertown, MA), one in the frontal plane and one in the sagittal plane. Both of the cameras were used to record video data of the participants while performing the jump landing task and were later used for formulation of the LESS score. Digital Motion Capture System A 12-camera Eagle Digital motion capture system (Motion Analysis Corporation, Santa Rosa, CA) was used with a sampling rate 120Hz for administration of the real-time feedback intervention. 3.3 Independent Variables 1. Feedback intervention a. Real-time feedback (RTF) b. Traditional feedback (TF) c. Control (No feedback) 2. Time a. Pre-intervention b. Post-intervention 3.4 Dependent Variable 1. LESS score (as measured by the LESS scoring checklist) 24

37 3.5 Procedures All participants reported to the biomechanics laboratory for a single testing session. After reading and signing a university approved informed consent form subjects were instructed on the LESS jump-landing task and were prepared for pre-intervention testing. After three successful pre-intervention jumps, subjects were randomized into one of three groups: RTF, TF, or control by concealed allocation and completed the associated intervention. Following the intervention, or no intervention for the control group, the participants completed three post-intervention jumps. Assessors of the LESS were blinded to which intervention the participant received. 3.6 Landing Error Scoring System (LESS) Two video cameras were set up 136 inches away from the force plate, one in a frontal view and one in a sagittal view. (Figure 3-6) The subjects were asked to jump off of a 30 cm box to a horizontal distance equal to 50% of the subject s height away from the force plate. Upon landing on the force plate, the participants immediately rebounded for maximal vertical jump. During explanation of the jump-landing task, emphasis was placed on jumping as high as possible during the rebound, but no other feedback or coaching was provided unless the participant was not properly completing the task, which was assessed by a clinician with experience using the LESS. After instruction on how to complete the task, participants were given as many practice trials as needed for familiarization with the task. Three successful pre-intervention jumps were recorded with the criteria for a successful jump as follows: 1. Jumping off of both feet from the box, 2. 25

38 Jumping forward but not vertically to reach the force plate, 3. Landing with the entire foot of both limbs on the force plate, 4. Completing the task in a fluid motion. Of the three pre-intervention jumps, the jump with the most errors on the LESS was used for statistical analysis. The same procedure was completed for assessing the three post-intervention jumps. Frontal plane camera set 48 inches from lens to floor Jump Box 30cm high 50% 136 height Force inches plate inches Sagittal plane camera set 48 inches from lens to floor Figure 3-6: LESS Setup 26

39 3.7 Interventions Subjects were randomized into one of three groups, RTF, TF, or a control (no intervention) group. During both feedback interventions, participants jumped off a 30 cm high box to a distance of 50% of their height and landed on the force plate, sticking the landing. A clinician with expertise in proper jump-landing and feedback administered the interventions Real-Time Feedback Intervention Following the pre-intervention jumps, the participants in the RTF intervention group were shown a PowerPoint presentation with words and pictures explaining proper landing mechanics. The slides were read aloud to the participants and included the following instructions: 1. Landing with both feet at the same time, 2. Landing in a neutral knee valgus/varus position (not knocked kneed or bow legged), 3. Landing with feet shoulder-width apart, 4. Landing on your toes rolling back to your heels, 5. Landing with increased bending in your knees and hips. In addition to the this feedback, the subjects in the RTF group were prepped with a 40 marker set-up including bilateral AC joint, ASIS, PSIS, greater trochanter, four marker thigh cluster, patella, medial and lateral knee femoral condyles, four marker shank cluster, calcaneus, medial maleoulous, lateral maleoulous, and great toe. One marker was also placed on the sacrum and one on the inferior angle of the right scapula. The subjects were then given the following instructions: 27

40 o You will now be able to see markers representing your knee and toe on the screen in real-time. o Start with your toe marker in line with the reference line and then line your knee marker up with the reference line. This is the way the markers should end up when you land. o This time when you jump we want you to watch the video monitor focusing on keeping the red line in line with the blue reference line when you land from your jump. o This time when you jump we want you to stick the landing (no rebound jump) while trying to keep the red line in line with the blue reference line. The participants in the RTF group completed three sets of six jumps, sticking the landing. Feedback was given via the PowerPoint presentation after each set of jumps. Participants were allowed time to rest before completing three post-intervention jumps in the same manner in which the pre-intervention jumps were performed. All pre- and postintervention jumps were recorded 2-dimensionally from the frontal and sagittal plane for data analysis Traditional Feedback Intervention Following the pre-intervention jumps, the participants in the TF intervention were shown the same PowerPoint with words and pictures explaining proper landing mechanics as the RTF group. The slides were read aloud to the participants and included the same instructions as previously described. The participants in the TF group completed 28

41 three sets of six jumps, sticking the landing. Feedback was given via the PowerPoint presentation after the completion of each set of jumps Control Group Subjects in the control intervention received no form of feedback. Instead, the subjects rested quietly for 10 minutes before undergoing the same post-intervention measurements. 3.8 Statistical Analysis A one-way ANOVA was used to determine differences between groups (RTF, TF, control) in change in LESS score (post-intervention minus pre-intervention). Statistical significance was set at p<0.05. Tukey s post hoc test was applied when statistical significance was found. SPSS 17.0 (IBM, Inc.; Chicago, IL) was used to perform the statistical analyses. Standardized effect sizes (Cohen s d) and 95% confidence intervals (CI) were calculated using pre-intervention and post-intervention values for each group. 29

42 Chapter 4 Results Pre- and post-test scores for the three groups are presented in Table 4.1. The prepost change scores are presented in Table 4.2. While not statistically significant, LESS scores decreased following RTF (-1.33±1.5) and TF(-1.10±2.4), while the control group remained unchanged. (0.00±1.2; F 2,25 =1.39, P=0.27) (Table 4.2). However, a strong effect size indicated the RTF was more effective than the Control group (d = -0.97; -1.90, 0.05); while a moderate effect size supported the differences between the TF and Control groups (d = -0.56; -1.46, 0.38) (Table 4.3). Table 4.1: Pre and Post LESS Scores (# of errors±sd) Pre-intervention Post-intervention Real-Time Feedback 5.89± ±1.12 Traditional Feedback 5.70± ±2.46 Control Group 6.56± ±

43 Table 4.2: Average Change of LESS Scores by Group Group mean±sd Real-Time Feedback -1.10±2.42 Traditional Feedback -1.33±1.50 Control Group 0.00±1.22 Table 4.3: Between Group Comparison of Pre-Post LESS Score Change (F 2,25 =5.548, p=0.01). Tukey post-hoc results are presented. p-value Effect Size (d) and 95%CI Real-Time FB vs. Control (-2.64, -0.03) Traditional FB vs. Control (-2.88, -0.34) Traditional FB vs. Real-Time FB (-1.00, 1.55) 31

44 Chapter 5 Discussion The purpose of this study was to determine the immediate effects of real-time feedback (RTF) compared to traditional feedback (TF) and a control group on dynamic stability as measured with the LESS. The LESS was used as a pre-intervention and postintervention grading tool that is clinically applicable. It was hypothesized that 1) participants in the RTF intervention group would have improved LESS scores preintervention vs. post-intervention when compared to TF and control groups, 2) participants in the TF group would have improved LESS scores pre-intervention vs. postintervention when compared to the control group and 3) participants in the control group receiving no feedback would not show any improvement pre-intervention vs. postintervention. Both the real-time and traditional feedback groups presented with a statistically significant pre-post change in LESS scores compared to the control group who received no feedback, which partially supports our hypotheses. To our knowledge, this is the first time RTF has been used in a controlled investigation. Real-time feedback is an innovative intervention as it allows participants to make instantaneous changes to their mechanics versus making changes after the task is completed. This may improve the carryover of 32

45 feedback training to more realistic athletic tasks, as RTF enables the participant to make on the spot changes necessary for adapting to athletic situations. When comparing effects of RTF and TF, there was no statistical difference found in changes in LESS score, which did not support our hypothesis. However, both real-time feedback and traditional feedback made very similar statistically significant improvements in their LESS scores when compared to the control group. This finding was not consistent with our hypothesis that LESS change scores in the RTF group would be statistically different than LESS change scores in the TF group. Both of the intervention groups were given the PowerPoint showing desirable landing mechanics, while the RTF group was given an intervention focusing on improving knee valgus. The LESS as a clinical tool has a possible 17 errors that are taken into consideration when calculating the total score. One of those 17 errors is knee valgus, which was a major point of emphasis in the RTF intervention. It is possible that the RTF did create an improvement in knee valgus; however, this potential change in isolation would not be enough to significantly impact the total LESS score. Therefore, individual or small groups of changes or improvements from one feedback protocol are not likely to create group differences, which may explain why our two intervention groups did not differ. In the future, it may be useful to consider specific errors/characteristics of the landing task to examine further the effectiveness of different feedback interventions. Previous studies that have used feedback interventions, such as self-analysis feedback, which lets the participant be involved in the analysis of their jump-landing, have found success with this intervention in improving knee flexion angles and 33

46 displacement and decreasing ground reaction force. 3,15 This study also let participants assess their jump-landing through RTF and overall improvement in jump-landing mechanics was found. Similarly, studies that have used a checklist for landing, 3,6,15 which is comparable to the PowerPoint used in this study, found improvement in jump-landing mechanics and decreased ground reaction force. The control group showed no statistically significant pre-post change in LESS change scores. This is consistent with what was hypothesized and the reviewed literature has found similar findings. Cowling et al. 17 and Onate et al., 3 both also found no significant change in their control groups after receiving a feedback intervention. This shows subjects will not improve their jump-landing technique by simply performing more repetitions. Rather, it appears that subjects need feedback about the quality of the landing if they wish to improve. Long-term studies should be performed with real-time feedback to determine if permanent positive changes in jump-landing can be made. Studies should also focus on translating these positive changes into practice or game like situations. 5.1 Limitations Some limitations of this study should be noted. This study was limited by small group sizes, which could have limited our ability to detect stronger statistical differences for our comparisons. Also, the participants were all females in this study. However, previous studies have shown that females are more at risk of ACL tears due to poor landing mechanics, 20 which we felt necessitated the exclusive inclusion of women in this preliminary study in order to increase external application of the results. This study is 34

47 limited by the fact that subjects only went through one session of feedback. However, it was important to determine if RTF could immediately improve jump-landing before progressing to long-term studies. We were able to detect immediate changes in the LESS, but the question still remains whether or not these changes can be retained over time. Future studies should investigate the effect of RTF intervention over time. The LESS has been found to be both valid and reliable for assessing gross motion during dynamic jump landing 59 but the LESS may not be sensitive enough to detect smaller biomechanical changes. However, the LESS is a very clinically relevant tool and can be used easily in the field. 16 Three dimensional motion analysis testing would help to determine specific effects of a RTF intervention on joint angles or moments. For this study, three pre-intervention tests and three post-intervention tests were performed. It should be noted that it was possible for some participants in the intervention groups to score very well on two of the post-intervention jumps excellent ( 4 errors), and also have one poor ( 6 errors) LESS score (A-3 and A-4). However, since one poor jump-landing can lead to injury, the worst LESS score of the three jumps was used for comparison and reflection of this one or two jump post-intervention LESS score improvement is not reflected in the data. Also, just by viewing the post-intervention LESS scores, it is unclear whether knee valgus improved, which was the target of the real-time intervention, or if other components of the LESS improved. 5.2 Future Research Our study demonstrated that RTF does improve jump-landing, but RTF using 3-D motion cameras may not be easily performed in a clinical setting. The future of RTF 35

48 should include a more clinically applicable form of the feedback. Further research needs to be conducted with multiple feedback sessions to see if further improvement in jumplanding can be found using RTF. Long-term studies also needs to be conducted to determine if subjects continue to land properly weeks or months after receiving the RTF intervention. 5.3 Conclusion RTF and TF both significantly improved LESS scores when compared to the control group and were shown to be effective intervention modalities in immediately improving overall jump-landing during a one time feedback session. There were no statistically significant difference observed between RTF and TF. Feedback may be an effective intervention to address poor jump landing mechanics. Further research is needed to investigate the long term and lasting effects of the modality. 36

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54 Appendix A A-1: Landing Error Scoring System Score Sheet Item Correct Error Sagittal View Evaluated at IC Knee Flexion: >30 degrees Yes No-1 Hip Flexion: Hips are flexed Yes No-1 Trunk Flexion: Trunk is flexed on hips Yes No-1 Ankle Plantar Flexion: Toes to heel Yes No-1 Evaluated between IC and moment of MKF Knee Flexion Displacement: > than 45 degrees Yes No-1 Trunk Flexion: Greater than at contact Yes No-1 Hip Flexion: Greater than at contact Yes No-1 Overall Sagittal plane joint displacement Soft Avg-1, Stiff Frontal View Evaluated at IC Lateral Trunk Flexion: Trunk flexed to left or right No Yes-1 Knee Valgus: Knees over the midfoot Yes No-1 Initial Foot Contact: Symmetric Yes No-1 Evaluated at Entire Foot Contact w/ Ground Foot Position: Toes pointing out >30 degrees No Yes-1 Foot Position: Toes pointing out <30 degrees No Yes-1 Stance Width: Less than shoulder width No Yes-1 Stance Width: Greater than shoulder width No Yes-1 Evaluated between IC and moment of MKF Knee Valgus Displacement: Knees inside of large toe No Yes-1 42

55 Overall Overall Impression Excellent Avg-1. Poor-2 Total *Zero points are awarded for an item being performed correctly. *IC=Initial Contact *MKF=Maximum Knee Flexion 43

56 A-2: LESS Item Operational Definitions Landing Error Scoring System Descriptions LESS Item Operational Definition Camera View 1. Knee Flexion angle at IC 2. Hip Flexion angle at IC 3. Trunk Flexion angle at IC 4. Ankle PF angle at IC 5. Knee Valgus angle at IC 6. Lateral Trunk Flexion at IC 7. Stance width-wide 8. Stance width- At the time point of initial contact, if the knee of the test leg is flexed more than 30 degrees, score YES. If the knee is not flexed more than 30 degrees, score NO At the time point of initial contact, if the thigh of the test leg is in line with the trunk then the hips are not flexed and score NO. If the thigh of the test leg I flexed on the trunk, score YES. At the time point of initial contact, if the trunk is vertical or extended on the hips, score NO. If the trunk is flexed on the hips, score YES If the foot of the test leg lands toe to heel, score YES. Of the foot of the test leg lands heel to toe or with a flat foot, score NO. At the time point of initial contact, draw a line straight down from the center of the patella. If the line goes through the midfoot, score NO. If the line is medial to the midfoot, score YES. At the time point of initial contact, if the midline of the trunk is flexed to the left or the right side of the body, score YES. If the trunk is not flexed to the left or right side of the body, score NO. Once the entire foot is in contact with the ground, draw a line down from the tip of the shoulders. If the line on the side of the test leg is inside the foot of the test leg then greater than shoulder width (wide), score YES. If the test foot is internally or externally rotated, grade the stance width based on heel placement. Once the entire foot is in contact with the ground, draw a line down from the tip of the shoulders. If 44 LESS Score Sagittal Y=0 N=1 Sagittal Y=0 N=1 Sagittal Y=0 N=1 Sagittal Y=0 N=1 Frontal Y=1 N=0 Frontal Y=1 N=0 Frontal Y=1 N=0 Frontal Y=1 N=0

57 Narrow 9. Foot position- Toe in 10. Foot position-toe Out 11. Symmetric initial foot contact 12. Knee Flexion Displacement 13. Hip flexion at max knee flexion 14. Trunk Flexion at max knee flexion 15. Knee Valgus Displacement the line on the side of the test leg is outside the foot of the test leg then greater than shoulder width (narrow), score YES. If the test foot is internally or externally rotated, grade the stance width based on heel placement. If the foot of the test leg is internally rotated more than 30 degrees between the time period of initial contact and max knee flexion, then score YES. If the foot is not internally rotated more than 30 degrees between the time period of initial contact to max knee flexion, score NO. If the foot of the test leg is externally rotated more than 30 degrees between the time period of initial contact and max knee flexion, then score YES. If the foot is not externally rotated more than 30 degrees between the time period of initial contact to max knee flexion, score NO. If one foot lands before the other or if one foot lands heel to toe and the other lands toe to heel, score NO. If the feet land symmetrically, score YES. If the knee of the test leg flexes more than 45 degrees from initial contact to max knee flexion, score YES. If the knee of the test leg does not flex more than 45 degrees, score NO If the thigh of the test leg flexes more on the trunk from initial contact to max knee flexion angle, score YES. If the trunk flexes more from the point of initial contact to max knee flexion, score YES. If the trunk does not flex more, score NO At the point of max knee valgus on the test leg, draw a line straight down from the center of the patella. If the line runs through the great toe or is Frontal Y=1 N=0 Frontal Y=1 N=0 Frontal Y=0 N=1 Sagittal Y=0 N=1 Sagittal Y=0 N=1 Sagittal Y=0 N=1 Frontal Y=1 N=0 45

58 16. Joint Displacement 17. Overall Impression medial to the great toe, score YES. If the line is lateral to the great toe, score NO Watch the sagittal plane motion at the hips and knees from initial contact to max knee flexion angle. If the subject goes through large displacement of the trunk, hips, and knees then score SOFT. If the subject goes through some trunk, hip, and knee displacement but not a large amount, then AVERAGE. If the subject if any trunk, hip, and knee goes through very little, displacement, then STIFF. Score EXCELLENT if the subject displays a soft landing and no frontal plane motion at the knee, Score POOR if the subject displays a stiff landing and large knee. All other landings, frontal plane motion at the score AVERAGE Sagittal Sagittal/Fro ntal Soft=0 Avg=1 Stiff=2 Ex.=0 Avg=1 Poor= 2 46

59 A-3: Real-time feedback individual subject LESS scores 47

60 A-4: Traditional feedback individual subject LESS scores 48

61 A-5: Control group individual subject LESS scores 49