ABSTRACT THE EFFECTS OF CLOSED KINETIC CHAIN AND OPEN KINETIC CHAIN EXERCISE ON HIP MUSCULATURE STRENGTH AND TIMING IN FEMALES. by Kelsi Julen Wood

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1 ABSTRACT THE EFFECTS OF CLOSED KINETIC CHAIN AND OPEN KINETIC CHAIN EXERCISE ON HIP MUSCULATURE STRENGTH AND TIMING IN FEMALES by Kelsi Julen Wood The purpose of this study was to determine the effect of open and closed kinetic chain exercise on hip strength and muscle activation patterns in physically active females. Thirty physically active females between the ages of were recruited from the Oxford, Ohio area. Participants were randomly assigned to the control group (Q) (n=10), open kinetic chain training group (O) (n=10), or the closed kinetic chain training group (n=10) (C). All participants underwent a pretest and posttest separated by an 8-week intervention period. Pre and posttests consisted of a neuromuscular assessment (electromyography) and a strength assessment. During the intervention period, group Q maintained normal physical activity levels, group O underwent open kinetic chain exercise training, and group C underwent closed kinetic chain exercise training. The results indicated that the interventions had little or no effect on the gluteal/quadriceps ratio or muscle activation timing. The interventions had a limited effect on peak torque. Both groups O and C experienced an increase in concentric hip internal and external hip rotation peak torque, compared to group Q. Group C experienced an increase in eccentric hip flexion and eccentric hip external rotation, compared to group Q. There were no differences between the intervention groups. i

2 THE EFFECTS OF CLOSED KINETIC CHAIN AND OPEN KINETIC CHAIN EXERCISE ON HIP MUSCULATURE STRENGTH AND TIMING IN FEMALES A Thesis Submitted to the Faculty of Miami University In partial fulfillment of the requirements for the degree of Master of Science Department of Kinesiology and Health by Kelsi Julen Wood Miami University Oxford, OH 2016 Advisor William Berg, PhD Reader Mark Walsh, PhD Reader Eric Brooks, PhD ii

3 Table of Contents Chapter 1: Introduction 1 Patellofemoral Pain Syndrome 1 Patella Maltracking 1 Causes of Patellofemoral Maltracking 2 Therapeutic Interventions 4 Purpose and Hypothesis 6 Chapter 2: Methods 7 Participants 7 Apparatus 8 Procedures 8 Measurements 15 Dependent Variables 16 Interventions 16 Experimental Design and Statistical Analysis 30 Cahpter 3: Results 30 Peak Torque 30 Quadriceps to Gluteal Ratio 45 Timing 50 Chapter 4: Discussion 59 References 63 Appendix A 68 ii

4 List of Tables Tables 1 Mean Participant Demographics 8 2 Open Kinetic Chain exercises weeks Open Kinetic Chain Exercises weeks Open Kinetic Chain Exercises weeks Closed Kinetic Chain Exercises week Closed Kinetic Chain Exercises week Closed Kinetic Chain Exercises week Mean (SD) percent change in peak torque between pre-test and 31 post-test 9 Mean (SD) percent change in quadriceps to gluteal ratio between 45 pre-test and post-test 10 Mean (SD) change in muscle activation time relative to foot 50 contact between pre-test and post-test for the drop jump 11 Mean (SD) change in muscle activation time relative to foot 53 contact between pre-test and post-test for ascending stairs 12 Mean (SD) change in muscle activation time relative to foot 56 contact between pre-test and post-test for descending stairs iii

5 List of Figures 1 Test position for MVIC of right quadriceps 9 2 Test position for MVIC of right gluteus medius 10 3 Test position for MVIC of right gluteus maximus 10 4 Placement of reflective markers 11 5 Starting position for double leg squat 12 6 Double leg squat to 90 degrees 12 7 Starting position for single leg squat 12 8 Single leg squat at 45 degrees 12 9 Ready position for drop jump Landing of drop jump Ascending stairs Descending stairs Mean percent change in concentric knee extension peak torque Mean percent change in eccentric knee extension peak torque Mean percent change in concentric knee flexion peak torque Mean percent change in eccentric knee flexion peak torque Mean percent change in concentric hip extension peak torque Mean percent change in eccentric hip extension peak torque Mean percent change in concentric hip flexion peak torque Mean percent change in eccentric hip flexion peak torque Mean percent change in concentric hip abduction peak torque Mean percent change in eccentric hip abduction peak torque Mean percent change in concenric hip adduction peak torque Mean percent change in eccentric hip adduction peak torque Mean percent change in concentric hip internal rotation peak torque Mean percent change in eccentric hip internal rotation peak torque Mean percent change in concentric hip external rotation peak torque Mean percent change in eccentric hip external rotation peak torque Mean pecent change in total torque Mean percent change in total concentric torque 44 iv

6 31 Mean percent change in total eccentric torque Mean percent change in quadriceps to gluteal ratio for single leg squats Mean percent change in quadriceps to gluteal ratio for double leg squats Mean percent change in quadriceps to gluteal ratio for drop jump Mean percent change in quadriceps to gluteal ratio for ascending stairs Mean percent change in quadriceps to gluteal ratio for descending stairs Mean change in activation time of the vastus medialis oblique 51 relative to foot contact for the drop jump 38 Mean change in activation time of the vastus lateralis relative to foot 51 contact for the drop jump 39 Mean change in activation time of the gluteus medius relative to foot 52 contact for the drop jump 40 Mean change in activation time of the gluteus maximus relative to foot 52 contact for the drop jump 41 Mean change in activation time of the vastus medialis oblique 54 relative to foot contact for ascending stairs 42 Mean change in activation time of the vastus lateralis relative to foot 54 contact for ascending stairs 43 Mean change in activation time of the gluteus medius relative to foot 55 contact for ascending stairs 44 Mean change in activation time of the gluteus maximus relative to foot 55 contact for ascending stairs 45 Mean change in activation time of the vastus medialis oblique relative 57 to foot contact for descending stairs 46 Mean change in activation time of the vastus lateralis relative to foot 57 contact for descending stairs 47 Mean change in activation time of the gluteus medius relative to foot 58 contact for descending stairs 48 Mean change in activation time of the gluteus maximus relative to foot 58 contact for descending stairs v

7 Introduction Knee pain/injury is one of the most common reasons for which individuals seek sports medicine and physical therapy services (Jacobs et al., 2008; Kannus, Aho, Jarvinen & Nittymaki, 1987; Taunton et al., 2003). There are many acute and overuse conditions that can cause knee pain such as osteoarthritis, bursitis, cartilage tear, and ligament strain/tear. The most common type of overuse knee pain is patellofemeral pain syndrome (PFP) (Boiling et al., 2009; Powers, 2003). Patellofemeral Pain Syndrome PFP can be defined as anterior knee pain involving the patella and retinaculum that excludes other intraarticular and peripatellar pathology (Powers, 2003, 2010). PFP causes pain to the anterior knee or behind the patella which worsens with activities like ascending and descending stairs, squating, jumping and running. PFP results from abnormal stresses on the patellofemoral joint (Bolgla, Malone, Umberger & Uhl, 2008; Powers, 2003, 2010; Souza, Draper, Fredericson & Powers, 2009). The patellofemoral joint consists of where the patella meets the femur (thigh bone). The patella tracks in the trochlear groove between the lateral and medial condyles of the femur. Anything that causes the patella to maltrack in the trochlear grove can lead to PFP. Patella Maltracking Maltracking of the patella involves any medial or lateral displacement, tilting, and/or rotation of the patella while performing activities involving knee flexion. Normal arthrokinematics of the patellofemoral joint consist of the patella gliding within the center of the trochlear groove; however, in patients with tracking issues, gliding within the trochlear groove does not occur properly. When maltracking occurs, the patella can apply an excessive amount of stress to either side of the knee depending on the direction it maltracks. There are many different causes of maltracking, including muscular impairment, biomechanical dysfunction, and postural malalignment (Alfonso, 2011). 1

8 Causes of Patella Maltracking Weak Vastis Medialis Oblique One cause for patella maltracking is weakness in the vastis medialis oblique (VMO) muscle. The VMO attaches to the medial side of the patella, so when it is weak it can allow lateral rotation and/or tilting which effects the way the patella tracks in the trochlear groove. Lateral displacement of the patella can cause irritation of the cartilage on the back of the patella and increase the load placed on lateral structures of the knee such as the lateral retinaculum. Tight Illiotibial Band and Hamstrings Another muscular dysfunction that can affect the tracking of the patellofemoral joint is stiffness of the illiotibial band (IT band). The IT band is fibrous tissue that attaches to the iliac crest via the tensor fascia lata. Fibers of the IT band insert on the lateral epicondyle of the femur, lateral side of the patella and tibia, and produce hip flexion, abduction, and internal rotation. If the IT band is stiff (i.e., excessive tension), it can pull the patella laterally causing it to track outside of the center of the trochlear groove, and leading to cartilage irritation and/or lesions resulting in PFP. Research by Waryasz and McDermott (2008) found that tight IT bands are a positive risk factor for developing PFP. In the same study, other positive risk factors for PFP included hamstring and/or gastrocnemius tightness. With hamstrings being the main knee flexor, when they are excessively tight they pull the tibia posteriorly, which can cause excessive pressure on/or tearing of the patella cartilage and disrupting patellofemoral joint mechanics. This same posterior pressure is seen with gastrocnemius tightness, which can also lead to foot pronation (Juhn, 1999). Foot Pronation Foot pronation, also known as flat feet, is a mixture of dorsiflexion, eversion and abduction of the ankle joint (Juhn, 1999). Pronation causes a decrease in the medial arch in the bottom of the foot, which leads to compensation higher up the anatomical chain. Pronation causes the tibia or femur to rotate, ultimately altering the movement of the patella on the femur. 2

9 This causes the patella to laterally maltrack in the trochlear groove, irritating the cartilage, while also allowing the knee to fall medially creating greater stress to medial structures of the knee. Molgarrd, Rathleff and Simonsen (2011) found a greater foot pronation in high school students with PFP than those without PFP. Valgus Angulation of the Knee Knee pain and injury are found to be relatively common among physically active females fifteen to thirty years of age (Baldon et al., 2012; Boling et al., 2010). Anatomically, females are built differently from males, which make females more prone to knee injuries (Powers, 2003, 2010). The difference in the quadriceps angle (Q angle) is an example of that. The Q angle is the angle from a line starting at the anterior superior iliac spine (ASIS) down to the patella, and another line drawn from the tibial tuberosity through the patella (Bolgla et al., 2008; Powers, 2003, 2010). An increase in the Q angle can result in greater valgus force (i.e., lateral pressure applied to the knee) and increasing the force from the quadriceps and patella tendon by pulling the patella laterally, causing PFP (Powers, 2010). This angle is typically found to be larger in females than males, due to women having wider hips and weaker hip musculature (Powers, 2010). There are two potential risks to the knee when the Q angle increases. First, the increase in Q angle causes irritation to the patella cartilage due to its lateral maltracking. Second, a valgus movement of the knee can cause an excessive load on medial structures such as the medial collateral ligament, medial retinaculum, along with the anterior cruciate ligament. Chen et al. (2008) found that excessive Q angle was pronounced in females with PFP. Femoral Rotation, Hip Musculature Strength and Activation Research on the cause of patella maltracking has investigated more proximal structures, specifically the hip musculature and its effect on internal rotation of the femur. An increase in internal femoral rotation can be caused by weak abductors and external rotators of the hip, like the gluteus medius and gluteus maximus. If these muscles are weak, and not doing their job as external rotators, the femur can internally rotate and place stress on medial structures at the knee. Internal rotation of the femur results in lateral maltracking of the patella, causing irritation to the cartilage and increasing the likelihood of developing PFP. 3

10 Recent research has shown a difference in activation of overall electromyography (EMG) activity in hip abductors, extensors, and external rotators in patients with knee pain compared to those without (Blogla et al., 2008; Boiling et al., 2009; Nakawaga et al., 2001; Souza et al., 2013). Balden et al. (2009) investigated the difference in hip strength between females who had PFP and those who did not. Their results showed that the PFP group displayed lower mean hip abduction and adduction torque when compared to the control group. Along with a decrease in hip strength, people with PFP have demonstrated a delayed onset and shorter duration of hip musculature during activities like ascending and descending stairs. A study done by Cowen, Cossley and Bennell (2009) looked at the difference between gluteus medius, vastus medialis oblique, and vastus lateralis activation between those with PFP and those without. Results indicated that the PFP sufferers displayed a delay in activation of the gluteus medius relative to heel strike during ascending stairs. Similar research, done by Brindle, Mattacola and McCory (2003), also showed delayed activation of the gluteus medius relative to toe contact with the stair, and shorter gluteus medius contraction duration in patients with anterior knee pain while both ascending and descending stairs. This research has sparked an interest in improved interventions for patients with PFP. Therapeutic Intervention Interventions for PFP differ depending on the reason for patella maltraking. Strengthening the VMO With VMO weakness being a common cause of patella maltracking, treatments of PFP have focused on strengthening the VMO. Currently, both closed kinetic chain (CKC) and open kinetic chain (OKC) exercises are used for prevention and treatment of knee injuries. OKC exercise involves movement in one segment of the extremity without movement of the other segments of the extremity. The distal segment is free to move, and resistance is usually applied to the distal segment (Fitzgerald, 1997). For example, exercises like straight leg raises, short arc quads, and long arc quads could be utilized to strengthen the quadriceps under non weight bearing conditions. In CKC exercise, movement in one segment of the extremity is only possible 4

11 with movement of other segments of the extremity. CKC exercises are typically weight bearing, and the distal segment is usually fixed to a supporting surface (Fitzgerald, 1997). An example of a CKC quad strengthening exercises would be squats, using multiple segments of your body under weight bearing conditions. In addition, techniques such as moving the patella properly into the trochlear groove with bracing, taping, and soft tissue mobilization are also utilized (Powers 2003). Bracing and taping are done by applying force from the lateral side of the patella, moving it medially too stay within the trochlear groove. Both strengthening and bracing allows the patella to stay in the groove during movement without altering the patellafemoral mechanics. Research by Neptune, Wright, and Bogert (2000) found that increasing strength of the VMO, along with bracing, reduced average patellofemoral joint load when three-dimensional lower extremity musculoskeletal models were placed in running simulations. Research by Elias, Kilambi, Goerke, and Cosgarea (2009), also found that strengthening the VMO can reduce pressure to the lateral cartilage of the patella. Stretching Tight Tissues Stiffness of the IT band, hamstring, or gastrocnemius muscles are treated by stretching while at the same time strengthening other structures like the VMO. Manual stretching (done by another person), self-stretching, and myofascial release techniques are used frequently to help stretch and elongate tight muscles and tissues. Decreasing the stiffness of these structures allow for the patella to correctly relocate to the center of the trochlear groove, alleviating PFP. Research by Douciette and Goble (1992) demonstrated a decrease in pain after activity in patients with PFP when flexibility of the IT band had increased. Correcting Foot Pronation PFP patients with excessive foot pronation can typically be treated with foot orthotics. When placed in shoes, orthotics create an arch in the bottom of the foot, preventing the foot from collapsing, decreasing rotation of the tibia or femur, and allowing the patella to glide within the trochlear groove properly. Research in patients with PFP and excessive foot pronation found an improvement in PFP when custom-fitted orthotics were used (Johnston & Gross, 2004). Eng and Pierrynowski (1993) investigated the effects of foot orthotics in two groups of patients with PFP. 5

12 The control group received an exercise program consisting of quadriceps and hamstring strengthening and stretching, and the other group participated in the same exercise program along with wearing foot orthotics that decreased foot pronation. Results showed that both groups had decreased pain, but the group with the orthotics showed a greater decrease in pain than the control group. Similar research done by Collins et al. (2008) and Sutlive et al. (2004) also found orthotics to be beneficial to those with PFP. Strengthening Hip Musculature Knee pain and injury in females has been associated with weakness and decreased activation in hip musculature (abductors, extensors, and external rotators) (Souza et al., 2013). It has been shown that lack of hip strength and delayed onset timing of hip musculature can produce a valgus angle in the knee, which over time can put abnormal stresses on the knee joint, causing PFP and other knee injuries. Traditionally, prevention and treatment of PFP, and knee pathology in general, has not focused on hip musculature. However, it has been suggested that improving hip strength and muscle activation patterns might alleviate knee pain and reduce the likelihood of knee injury (Souza et al., 2013). Consequently, strengthening hip musculature, specifically the gluteus medius (GMed) and gluteus maximus (GMax), would likely result in a greater contribution of the gluteal muscles relative to the quadriceps muscle. Both OKC and CKC exercise are used to treat PFP and rehabilitate knee injuries in general. However, research on the relative effectiveness of each type of exercise has been limited and equivocal (Bankhtiary, 2007; Herrington and Al-Sherhi., 2007; Steine, Brosky, Reinking, Nyland and Mason, 1996). The newly understood relationship between knee pain/injury and hip strength and muscle activation patterns in females suggests that closed kinetic chain exercise may be more effective, given its presumed ability to involve proximal locations like the hip. Purpose and Hypothesis The purpose of this study was to determine the effect of OKC and CKC exercise on hip strength and muscle activation patterns in physically active females. This study was performed using healthy physically active females due to PFP being more prevalent in that population (Baldon et al., 2012; Boling et al., 2010). We wanted to investigate the effects of OKC and CKC 6

13 interventions on healthy subjects before testing on patients with PFP or any general knee pain. Testing on healthy individuals was essential before testing on patients with pain because if the interventions were not successful on healthy individuals it would not be necessary to try on patients with knee pain. The study randomly assigned participants to three different groups; OKC exercise intervention (O), CKC exercise intervention (C), and control (Q). Each group was put through pre and posttests that included EMG recording of bilateral VMO, vastus lateralis (VL), GMed, and GMax during double leg squats, single leg squats, drop jump, and ascending and descending stairs. In addition, strength assessments of the dominant leg VMO, VL, GMed, and GMax were performed both concentrically and eccentrically. During the 8 weeks between pre and posttest, the control group maintained their normal activity levels, while the intervention groups trained with their designated exercises three times a week. We hypothesized that the CKC exercise would be more beneficial at improving strength, increasing gluteal contribution, and prompting earlier onset of muscle activation during the drop jump and ascending and descending stairs. Methods Participants Thirty physically active females between the ages of were recruited from the Oxford, Ohio area to participate in this research study. To be able to participate, participants had to be moderately physically active according to American College of Sports Medicine (ACSM, 2010) guidelines, and be free from lower extremity injuries, peripheral neuropathy, or recent lower extremity surgery. The study was approved by Miami University s Institutional Review Board and all participants provided informed consent. Participants were randomly assigned to the control group (n=10), open kinetic chain training group (n=10), or the closed kinetic chain training group (n=10) prior to arrival at the pretest. Each participant was compensated a total of $ for the time and effort devoted to the study. Participant demographics are presented in Table 1. 7

14 Table 1. Mean Participant Demographics Open Kinetic Closed Kinetic Control Chain Chain Age (yrs) 21± ± ±2.83 Height (cm) ± ± ±1.41 Weight (kg) 61.22± ± ±8.99 Body mass index (kg/m 2 ) Number of Physical Activity Sessions a 4± ± ±1.62 Week Most Prevalent Types of Physical Activity Cardio* and Resistance training Cardio* and Resistance training Cardio* and Resistance training *Cardio consisted of track or treadmill running and using an elliptical. Apparatus Muscle activation was recorded using wireless EMG (Myosystem 2400, Noraxon, USA). Video recording was done using two stationary JVC GR-DVL9800 cameras and digitized using SIMI Reality Motion software. Strength testing was done on the Humac NORM isokinetic dynamometer. For both exercise interventions, a multitude of tools were utilized throughout the eight week interventions including level 2-5 therabands, a dowel rod, airex pad, BOSU ball, swiss balls, adjustable ankle weights, and a treatment table. Procedures Pretest Upon arrival at the laboratory, participants were read the informed consent form aloud before agreeing to participate, and then completed medical history and physical activity questionnaires (Appendix A). After recording participant height and weight, EMG electrodes were placed on the right and left VMO, VL, GMed, and GMax. The skin was shaved and cleaned 8

15 with alcohol before electrode placement. Before beginning testing, participants did a five minute warm up walk on the treadmill at 3.5 mph. The pretest lasted minutes. Maximum Voluntary Isometric Contraction Once the warm up was complete, each participant was asked to perform 5 second maximum voluntary isometric contractions (MVIC) of the VMO, VL, GMed, and GMax bilaterally. MVIC testing of the VMO and VL was performed using a maxed out leg extension machine (see Figure 1). The first trial was a practice trial performed at 50% maximum effort, and trials 2 and 3 were performed at 100% maximum effort with 30 seconds of rest in between trials. Trials 2 and 3 were recorded using EMG; and the peak value method of finding MVIC values was used. The highest mean amplitude value for a 1000 ms window was located for each channel, and used for channel normalization relative to 100% of MVIC. To obtain the MVIC for the bilateral GMed, participants were side-lying on the isokinetic dynamometer pushing up against a strap that was placed 5 centimeters above the midline of the knee (see Figure 2). Lastly, to obtain MVIC for bilateral GMax, participants were asked to lay prone on the isokinetic dynamometer with their knee bent to 90 degrees and with a strap secured 5 centimeters proximal to the joint line of the knee. Participants pushed their foot straight up towards the ceiling in hip extension (see Figure 3). Figure 1. Test position for MVIC of right quadricep 9

16 Figure 2. Test position for MVIC of right gluteus medius Figure 3. Test position for MVIC of right gluteus maximus Video Markers After MVIC data was collected, participants were brought to the testing area where reflective markers were placed bilaterally on the patella, tibial tuberosity, and anterior superior iliac spine (see Figure 4). 10

17 Figure 4. Placement of reflective markers Movement tasks Participants performed several tasks including a double leg squat, single leg squat, drop jump, and ascending and descending stairs while EMG and video were recorded. Each task was demonstrated for the participant and then practiced by the participant until they felt comfortable doing the activity. Two video cameras were set up to capture the each task. Camera one was placed 10 feet in front of the participant during the single leg squats, double leg squats, drop jump, and descending stairs. Camera two was placed 3 feet behind the top of the steps to capture the front of the participant during ascending steps. During the double leg squat, participants were asked to cross their arms over their chest and, in one fluid motion, squat until the tops of their thighs were parallel to the floor, and then return to the starting position (see Figures 5 and 6). Participants were asked to perform 5 discrete trials with 30 seconds of rest in between each. 11

18 Figure 5. Starting position for double leg squat Figure 6. Double leg squat to 90 degrees Single leg squats were performed on both legs alternating between right and left on each trial. Participants crossed their arms over their chest and in one fluid motion, squated to approximately 45 degrees of knee flexion, and then returned to starting position (see Figures 7 and 8). Participants were asked to perform 5 discrete trials on each leg with 30 seconds of rest in between each. Figure 7. Starting position for single leg squat Figure 8. Single leg squat at 45 degrees 12

19 The drop jump was performed from a 32 cm tall box where participants were asked to begin with their big toes over the edge of the box, and elbows bent to ninety degrees by their sides. They were asked to drop from the box, not jump, by leading with their dominant foot and landing softly with both feet at the same time in a squat and hold that position until released (see Figures 9 and 10). Participants were asked to perform 5 discrete trials with 30 seconds of rest in between each. Figure 9. Ready position for drop jump Figure 10. Landing of drop jump Lastly, participants were asked to ascend and descend a flight of five steps at their natural walking pace. When ascending, participants started one foot length away from the first riser and ascended the stairs starting with their right foot while keeping elbows bent to 90 degrees (see Figure 11). Participants were asked to perform 5 discrete trials alternating between ascending and descending with 30 seconds of rest in between each. 13

20 Figure 11. Ascending stairs When descending stairs, participants started with their toes at the edge of the top step and then descended the stairs starting with their left foot while keeping elbows bent at ninety degrees (see Figure 12). Participants continued walking to a point three meters from the last step. Participants were asked to perform 5 discrete trials alternating between ascending and descending with 30 seconds of rest in between each. Figure 12. Descending stairs 14

21 Strength Assessment Using the isokinetic dynamometer, participants performed knee flexion/extension, hip flexion/extension, hip abduction/adduction, and hip internal/external rotation both concentrically and eccentrically on their dominant leg only. Trial 1 was a practice trial performed at 50% maximum effort, trials 2 and 3 were performed at 100% maximum effort, each separated by 60 seconds of rest. Each trial consisted of three consecutive repetitions performed at 60 degrees per second. Peak torque was recorded for each max effort trial. Measurement EMG The EMG (Telemyo 2400, Noraxon, USA) signal was recorded with 12bit resolution at a bandwidth of Hz, and amplified 1,000x. All trials were sampled at 1,500 Hz as well as rectified and smoothed using a 10Hz lowpass Butterworth filter. The EMG data were analyzed using Myoresearch v2.02 software. EMG activity of the VMO, VL, GMax, and GMed were recorded. For double and single leg squats, the EMG integrals for the complete action were analyzed. For the drop jump, the EMG integrals were analyzed from the time the participant made contact with the ground to the time where no more downward motion was made. For ascending and descending stairs, the EMG integrals were analyzed from the time the participant made contact to the third riser to the time there was no contact with the third riser. To determine activation time of each muscle relative to foot contact in the drop jump and ascending and descending stairs, the rectified EMG signals were visually inspected. This technique for detecting onset of muscle activity has been shown to be reliable (Hodges and Bui 1996). Foot contact was detected by pressure sensitive mats placed in the landing area of the drop jump and on the third stair step. Foot contact with the pressure sensitive mat was automatically marked on the EMG record. Muscle activation time was compute as the time difference between muscle onset and foot contact. 15

22 Strength Peak torque was recorded in newton-meters for each maximum effort trial on the isokinetic dynamometer. Post test All pretest activities were repeated for the post test. All pretest dynamometer settings were reproduced in the posttest. Dependent Variables Peak Torque The percentage change in peak torque between pretest and post test was computed for each muscle in both concentric and eccentric knee flexion/extension, hip flexion/extension, hip abduction/adduction, and hip internal/external rotation. Quadriceps to gluteal ratio The ratio that was investigated was the contribution of the gluteal muscles (GMed & GMax) relative to the contribution of the quadriceps muscles (VMO & VL). The percentage change in quadriceps to gluteal ratio was computed for each of the five movement tasks; double leg squats, single leg squats, drop jump, ascending and descending stairs. If the value is positive the gluteal muscles were more active in the post test, if the value is negative the quadriceps were more active in the post test. Muscle Activation Time Change in absolute muscle activation time relative to foot contact was computed for three of the movement tasks; drop jump, ascending stairs, and descending stairs. For the drop jump the activation time was relative to the time the foot made contact with the ground. For ascending and descending stairs, the activation time was relative to the time the foot made contact with the third step. Interventions Both training interventions were executed in three sessions a week for eight weeks. There could be no more than three sessions in four consecutive days, allowing for adequate rest 16

23 between sessions. Each session lasted 30 to 60 minutes. Each participant had two trainers/monitors that were trained by a licensed physical therapist and certified athletic trainer. The trainers/monitors were taught and then tested on how to facilitate proper technique of exercises and how to appropriately progress exercise intensity and duration. Exercises were progressed accordingly if participants displayed appropriate form and acceptable fatigue. Our average percentage of intervention compliance rate was 99.58% in group O and 100% in group C. Group O exercises and progressions for weeks one and two are found in Table 2. Group O exercises and progressions for weeks three through five are found in Table 3. Group O exercises and progressions for weeks six through eight are found in Table 4. Table 2. Open Kinetic Chain exercises weeks 1-2 Exercise Diagram Progressions Short arc quad -with bolster under knee, participant will straighten their leg and then control it back down to starting position 10 lbs, 3 sets of lbs, 3 sets of lbs, 3 sets of lbs, 3 sets of lbs, 3 sets of lbs, 3 sets of 15 Long arc quad -sitting on the edge of the table, participant will straighten their leg and then control it back down to starting position 7 lbs, 3 sets of 10 7 lbs, 3 sets of 15 8 lbs, 3 sets of 10 8 lbs, 3 sets of 15 9 lbs, 3 sets of 10 9 lbs, 3 sets of 15 17

24 Hamstring curl -sitting on the edge of the table with theraband around ankle, participant will bend leg to 90 degrees and then control it back to starting position. Level 3 theraband, 3 sets of 10 Level 3, 3 sets of 15 Level 4, 3 sets of 10 Level 4, 3 sets of 15 Level 5, 3 sets of 10 Level 5, 3 sets of 15 Hip internal rotation -sitting on the edge of the table with theraband around ankle, participant will move their foot laterally and then control it back to starting position. Level 2 theraband, 3 sets of 10 Level 2, 3 sets of 15 Level 3, 3 sets of 10 Level 3, 3 sets of 15 Level 4, 3 sets of 10 Level 4, 3 sets of 15 Hip external rotation - sitting on the edge of the table with theraband around ankle, participant will move their foot medially and then control it back to starting position. Level 2 theraband, 3 sets of 10 Level 2, 3 sets of 15 Level 3, 3 sets of 10 Level 3, 3 sets of 15 Level 4, 3 sets of 10 Level 4, 3 sets of 15 18

25 Table 3. Open Kinetic Chain exercises weeks 3-5 Exercise Diagram Progressions Straight leg raise: flexion -while laying on back and leg straight, participant will lift leg even with bent knee and control it back down to starting position. Side-lying hip abduction -side-lying with leg straight, participant will lift top leg towards ceiling and control it back down to starting position. Side-lying hip adduction -side-lying with leg straight, participant will lift bottom leg towards ceiling and control it back down to starting position. 3 lbs, 3 sets of 15 4 lbs, 3 sets of 15 5 lbs, 3 sets of 15 6 lbs, 3 sets of 15 7 lbs, 3 sets of 15 8 lbs, 3 sets of 15 9 lbs, 3 sets of lbs, 3 sets of lbs, 3 sets of 15 No weight, 3 sets of 10 No weight 3 sets of 15 1 lb, 3 sets of 10 1 lb, 3 sets of 15 2 lbs, 3 sets of 10 2 lbs, 3 sets of 15 3 lbs, 3 sets of 10 3 lbs, 3 sets of 15 4 lbs, 3 sets of 10 2 lbs, 3 sets of 10 2 lbs, 3 sets of 15 3 lbs, 3 sets of 10 3 lbs, 3 sets of 15 4 lbs, 3 sets of 10 4 lbs, 3 sets of 15 5 lbs, 3 sets of 10 5 lbs, 3 sets of 15 6 lbs, 3 sets of 10 19

26 Straight leg raise: extension -while laying on stomach with leg straight, participant will lift leg towards ceiling and control it back down to starting position. Hip extension with knee flexion -while laying on stomach with knee bent, participant will lift leg towards ceiling and control it back down to starting position. No weight, 3 sets of 15 2 lbs, 3 sets of 10 2 lbs, 3 sets of 15 3 lbs, 3 sets of 10 3 lbs, 3 sets of 15 4 lbs, 3 sets of 10 4 lbs, 3 sets of 15 5 lbs, 3 sets of 10 5 lbs, 3 sets of 15 No weight, 3 sets of 10 No weight, 3 sets of 15 2 lbs, 3 sets of 10 2 lbs, 3 sets of 15 3 lbs, 3 sets of 10 3 lbs, 3 sets of 15 4 lbs, 3 sets of 10 4 lbs, 3 sets of 15 5 lbs, 3 sets of 10 Table 4. Open Kinetic Chain exercises weeks 6-8 Exercise Diagram Progressions Prone hamstring curls -while laying on stomach with theraband around ankle, participant will bend knee up towards body and control it back down to starting position. Level 2 theraband, 3 sets of 10 Level 2 theraband, 3 sets of 15 Level 3 theraband, 3 sets of 10 Level 3 theraband, 3 sets of 15 Level 4 theraband, 3 sets of 10 Level 4 theraband, 3 sets of 15 Level 5 theraband, 3 sets of 10 Level 5 theraband, 3 sets of 15 Level 5 theraband, 4 sets of 15 20

27 Clamshells -while side-lying and legs bent to 70 degrees, participant will keep heels together while separating knees. Frogger -while laying on stomach with knees separated about 15 inches and ankles pressed together, participant will move heels straight up to the ceiling and control it back down to starting position. Quadruped hip extension with knee extension -while on all fours, participant will move leg backwards until it is straight and even with body and control it back down to starting position. Quadruped hip extension with knee flexion -while on all fours, participant will keep knee bent and push heel towards ceiling and Level 2 theraband, 3 sets of 10 Level 2 theraband, 3 sets of 15 Level 3 theraband, 3 sets of 10 Level 3 theraband, 3 sets of 15 Level 4 theraband, 3 sets of 10 Level 4 theraband, 3 sets of 15 Level 5 theraband, 3 sets of 10 Level 5 theraband, 3 sets of 15 Level 5 theraband, 4 sets of 15 No weight, 3 sets of 10 No weight, 3 sets of 15 2 lbs, 3 sets of 10 reps 2 lbs, 3 sets of 15 reps 3 lbs, 3 sets of 10 reps 3 lbs, 3 sets of 15 reps 4 lbs, 3 sets of 10 reps 4 lbs, 3 sets of 15 reps No weight, on edge of plinth from 90degrees hip flexion to 10 degrees hip extension, 3 sets of 10 No weight, 3 sets of 10 No weight, 3 sets of 15 2 lbs, 3 sets of 10 reps 2 lbs, 3 sets of 15 reps 3 lbs, 3 sets of 10 reps 3 lbs, 3 sets of 15 reps 4 lbs, 3 sets of 10 reps 4 lbs, 3 sets of 15 reps 5 lbs, 3 sets of 10 reps No weight, 3 sets of 10 No weight, 3 sets of 15 2 lbs, 3 sets of 10 reps 2 lbs, 3 sets of 15 reps 3 lbs, 3 sets of 10 reps 3 lbs, 3 sets of 15 reps 4 lbs, 3 sets of 10 reps 4 lbs, 3 sets of 15 reps 21

28 control it back down to starting position. 5 lbs, 3 sets of 10 reps Group C exercises and progressions for weeks one and two are found in Table 5. Group C exercises and progressions for weeks three through five are found in Table 6. Group C exercises and progressions for weeks six through eight ae found in Table 7. Table 5. Closed Kinetic Chain exercises weeks 1-2 Exercise Diagram Progressions Double leg squat with band -standing with feet hip width apart, participants will bend hips and knees as if they were to sit down in a chair. Side stepping -standing with feet hip width apart, slight bend in knees and theraband around knees, participants will step sideways. Squatting to 45 degrees knee flexion. Level 2 theraband, 3 sets of 10 Squatting to 90 degrees knee flexion. Level 2 theraband, 3 sets of 10 Level 2 theraband, 3 sets of 15 Level 3 theraband, 3 sets of 10 Level 3 theraband, 3 sets of 15 Level 4 theraband, 3 sets of 10 Level 2 theraband, 20ftx2 Level 2 theraband, 20ftx4 Level 3 theraband, 20ftx4 Level 4 theraband, 20ftx4 Level 5 theraband, 20ftx4 Level 5 theraband, 20ftx6 22

29 Double leg balance with band on unstable surface -standing with feet hip width apart and slight bend in knees, participants stand on unstable surface. Double leg bridge with band -while in hook-lying position, participant will lift hips off the table and control it back down to starting position. Level 2 theraband, 30secs x4 Level 2 30secs x4 with ball toss in center of gravity (COG) Level 2 30secs x4 with ball toss outside COG No band, Single leg balance on bosu 30 secs x4 bilaterally No band, single leg balance on bosu 30 secs x4 bilaterally with ball toss in COG No band, single balance on bosu 30secs x4 bilaterally with ball toss outside COG Level 2 theraband, 3 sets of 10 Level 2 theraband, 3 sets of 15 Level 3 theraband, 3 sets of 10 Level 3 theraband, 3 sets of 15 Level 4 theraband, 3 sets of 10 Level 4 theraband, 3 sets of 15 Double leg Romanian dead lift -standing with feet hip width apart and slight bend in knees, participants apply pressure into the front of their thighs with dowel rod while bending at the hips until about 90 degrees and control it back up to starting position. No weight, 3 sets of 10 No weight, 3 sets of 15 5lbs on bar, 3 sets of 10 5lbs on bar, 3 sets of 15 10lbs on bar, 3 sets of 10 10lbs on bar, 3 sets of 15 23

30 Table 6. Closed Kinetic Chain exercises weeks 3-5 Exercise Diagram Progressions Single leg bridge -while in hook-lying position, participant will straighten on leg to be even with bent knee and then lift hips off the table and control it back down to starting position. Single leg balance with single arm row -while standing on one leg and holding the theraband in same side hand, participant will pull band towards body while keeping elbow bent to 90 degress. 3 sets of 10 bilaterally 3 sets of 15 bilaterally 6 inch block under planted foot, 3 sets of 10 6 inch block under planted foot, 3 sets of 15 8 inch block under planted foot, 3 sets of 10 8 inch block under plated foot, 3 sets of 15 BOSU under planted foot, round side up, 3 sets of 10 BOSU under planted foot, round side up, 3 sets of 15 Swissball under planted foot, 3 sets of 10 Level 3 theraband, same side, 3 sets of 10 Level 3 theraband, same side, 3 sets of 15 Level 3 theraband, opposite side, 3 sets of 15 Level 4 theraband, opposite side, 3 stes of 10 Level 4 theraband, opposite side, 3 sets of 15 Level 5 theraband, opposite side, 3 sets of 10 Level 5 theraband, opposite side, 3 sets of 15 Blue airex under planted foot, opposite side, 3 sets of 10 Blue 24

31 airex under planted foot, opposite side, 3 sets of 15 Single leg balance with isometric hip abduction at wall -while standing on one leg the opposite leg is bent to 90 degrees with a ball placed in between that knee and the wall, the participant pushes into the ball. Single leg balance with hip external rotation -standing next to where the theraband is anchored the participant will stand on the leg closest to anchor, with the theraband in opposite hand and elbow bent to 90 degrees, participant will rotate away from stance leg. 10 second hold 10 x each leg 10 second hold 15 x each leg 10 second hold 20 x each leg 10 second hold 25 x each leg 10 second hold 30 x each leg 15 second hold 10 x each leg 15 second hold 15 x each leg 15 second hold 20 x each leg 15 second hold 25 x each leg Level 2 theraband with 3 second pause, 3 sets of 10 Level 2 theraband with 3 second pause, 3 sets of 15 Level 3 theraband with 3 second pause, 3 sets of 10 Level 3 theraband with 3 second pause, 3 sets of 15 Level 4 theraband with 3 second pause, 3 sets of 10 Level 4 theraband with 3 second pause, 3 sets of 10 Level 5 theraband with 3 second pause, 3 sets of 10 25

32 Level 5 theraband with 3 second pause, 3 sets of 15 Level 5 theraband with 5 second pause, 3 sets of 15 Single leg balance with hip hike -standing on the edge of a step, participant will lower outside leg to the floor without bending the leg on the step. No weight with 3 second pause at top, 3 sets of 15 2 lbs with 3 second pause at top, 3 sets of 10 2 lbs with 3 second pause at top, 3 sets of 15 3 lbs with 3 second pause at top, 3 sets of 10 3 lbs with 3 second pause at top, 3 sets of 15 4 lbs with 3 second pause at top, 3 sets of 10 4 lbs with 3 second pause at top, 3 sets of 15 5 lbs with 3 second pause at top, 3 sets of 10 5 lbs with 3 second pause at top, 3 sets of 15 26

33 Table 7. Closed Kinetic Chain exercises weeks 6-8 Exercise Diagram Progressions Single leg Romanian deadlift with band -standing on one leg with knee slightly bent, participants apply pressure into the front of their thigh with dowel rod while bending at the hips until about 90 degrees and control it back up to starting position. All sets will be performed while theraband is pulling participants knee medially. No weight 3 sets of 10 No weight 3 sets of 15 Holding 3 lb weights in both hands, 3 sets of 10 Holding 3lb weights in both hands, 3 sets of 15 Holding 5 lb weights in both hands, 3 sets of 10 Holding 5 lb weights in both hands, 3 sets of 15 Holding 7 lb weights in both hands, 3 sets of 10 Holding 7 lb weights in both hands, 3 sets of 15 Holding 10 lb weights in both hands, 3 sets of 10 27

34 Single leg balance with band and ball toss -standing on one leg with a theraband pulling their leg in a valgus position, participants must resist the band and maintain balance. Single leg squat with band -standing on one leg with a theraband pulling their leg in a valgus position, participants must resist the band and squat as if they were to sit down in a chair. All sets will be performed while theraband is pulling participants knee medially. 30 seconds 4x, with ball toss On ground with Level 2 theraband, 45 seconds 4 times On ground with Level 3 theraband, 30 seconds 4 times On ground with Level 3 theraband, 45 seconds 4 times On airex pad with LEVEL 2 theraband, 30 seconds 4 times On airexpad with LEVEL 2 theraband, 45 seconds 4 times On airex pad with Level 3 theraband, 30 seconds 4 times On airex pad with Level 3 theraband, 45 seconds 4 times On airex pad with Level 4 theraband, 30 seconds 4 times All sets will be performed while theraband is pulling participants knee medially. Chair with airex pad Level 2 theraband, 3 sets of 15 reps Chair without airex pad Level 2 theraband 3, sets of 10 reps Chair without airex pad Level 2 theraband, 3 sets of 15 reps Chair with airex pad Level 3 theraband, 3 sets of 10 reps Chair with airex pad Level 3 theraband, 3 sets of 15 reps Chair without airex pad Level 3 theraband, 3 sets of 10 reps Chair without airex pad Level 3 theraband, 3 sets of 15 reps 28

35 Chair with airex pad Level 4 theraband, 3 sets of 10 reps Stair descent with band -standing on edge of the step with a theraband pulling their leg in a valgus position, participants must resist the band and take a forward step down to the ground. All sets will be performed while theraband is pulling participants knee medially. Level 2 theraband, 4 inch step, 3 sets of 10 reps Level 2 theraband, 4 inch step, 3 sets of 15 reps Level 2 theraband, 6 inch step, 3 sets of 10 reps Level 2 theraband, 6 inch step, 3 sets of 15 reps Level 2 theraband, 8 inch step, 3 sets of 10 reps Level 2 theraband, 8 inch step, 3 sets of 15 reps Level 3 theraband, 4 inch step, 3 sets of 10 reps Level 3 theraband, 4 inch step, 3 sets of 15 reps Level 3 theraband, 6 inch step, 3 sets of 10 reps 29

36 Lunge with band -participant will perform lunges while resisted a theraband that will be pulling the front leg into a valgus position. All sets will be performed while theraband is pulling participants knee medially. Level 2 theraband, 3 sets of 10 Level 2 theraband, 3 sets of 15 reps Level 3 theraband, 3 sets of 10 reps Level 3 theraband, 3 sets of 15 reps Level 4 theraband, 3 sets of 10 reps Level 4 theraband, 3 sets of 15 reps Level 2 theraband, lead leg on airex pad, 3 sets of 10 reps Level 2 theraband, lead leg on airex pad, 3 sets of 15 reps Level 3 theraband, lead leg on airex pad, 3 sets of 10 reps Experimental Design and Statistical Analysis The experiment utilized a between group randomized design. One-way ANOVAs were used to analyze the mean values of the dependent variables for the three groups. An alpha level of.05 was used for the one-way ANOVAs. If differences were found among the three groups, follow up comparisons were performed using t-tests with the alpha level adjusted to.017 using the Bonferroni procedure. Results Peak Torque The mean (and SD) percent change in peak torque appear in Table 8. Table 8. Mean (SD) percent change in peak torque between pre-test and post-test. 30

37 Action Open Kinetic Chain Group Knee Extension Concentric (73.38) Knee Extension Eccentric (55.36) Knee Flexion Concentric (47.4) Knee Flexion - Eccentric (63.59) Hip Extension Concentric (35.92) Hip Extension Eccentric (22.74) Hip Flexion Concentric (29.01) *Hip Flexion Eccentric (56.77) Hip Abduction Concentric (44.06) Hip Abduction Eccentric (45.02) Hip Adduction Concentric (133.96) Hip Adduction Eccentric (78.99) *Hip Internal Rotation Concentric (23) Hip Internal Rotation Eccentric (28.9) Closed Kinetic Chain Group (29.04) 9.88 (20.18) (29.05) (44.44) (30.93) (23.02) (25.49) (30.45) (57.4) 13.9 (29.61) 88.5 (168.88) 21.5 (37.38) (40.5) 9.3 (24.9) Control Group (30.91).87 (22.13) (22.69) (38.33) -1.3 (34.34) (23.13) 1.4 (33.96) (22.22) 6.51 (41.2) 4.5 (20.46) 26.9 (77.36) 4.7 (20.59) -4.1 (13.55) -8.8 (19.6) 31

38 Percent change *Hip External Rotation Concentric (38.92) *Hip External Rotation Eccentric (44.13) Total (41.5) Total-Concentric 31.3 (40.5) Total-Eccentric 18.7 (43.66) * = significant ANOVA Knee Extension (27.25) (15.37) (25.8) 32.3 (37.6) 17.1 (16.35) (12.61) -7.7 (14.98) 2.14 (17.2) 5.36 (25.7) -1.0 (14.75) Figure 13 displays the mean percent change in concentric knee extension peak torque. A one-way ANOVA did not detect a significant difference among the three groups in the percent change in concentric knee extension peak torque, F(2,27)=0.297, p=0.74. Figure 14 displays the mean percent change in eccentric knee extension peak torque. A one-way ANOVA did not detect a significant difference among the three groups in the percent change in eccentric knee extension peak torque, F(2,27)=0.630, p= Concentric Knee Extension Torque Open Closed Control Group Figure 13. Mean percent change in concentric knee extension peak torque. 32