AbstractBackground: ACL injuries is common and can result in long term disability or even have a career ending outcome for the athlete. Women are more exposed to ACL injuries than men are and several factors increase the risk of ACL injuries for women where one is the knee angle velocity. It seems that prevention programs involving plyometric- and strength training has been most effective on altering these risk factors for knee injuries. But many programs involve several exercises which makes it very time consuming. Since the gluteus muscles is our main hip abductor and hip stabilizer it is of great importance for controlling the knee. The ProPrioPlate (PPP) is a device that has been validated and shown to activate the gluteus medius 40% more in a squat compared to a regular bodyweight squat.Purpose: To investigate if a 6 week long training period, 3 sessions/ week, 5minutes/session with the PPP could decrease the mean abduction angular velocity (°/sec) of the knee joint in a Drop jump (DJ) in women with poor knee stabilityMethod: An experimental study design was used. Twelve female athletes with poor knee stability and signs of knee valgus in a drop jump conducted a 6 weeks training program to investigate any changes in abduction angular velocity in a DJ. 3D motion analyzes were performed before and after the training period. Wilcoxon signed ranked test was used to investigate if there were any changes in results between the different test occasions.Results: Median abduction angular velocity of the test performed before the intervention was -34. 34 (min -70. 65 max -11. 53) deg/sec and after the intervention median -34. 22 deg/sec (min -51. 97 max -3. 28). The P value was 0.24 which indicate that there were no statistical significant differences between the three testing occasions. Compliance to the intervention was low, 15%.Conclusion: A 6 weeks training period with the PPP did not decrease the abduction angular velocity. Due to low compliance rate amongst of subjects no conclusion regarding the effect of the device can be made. / Abstrakt:Bakgrund: Svenska ligament registret rapporterar ungefär 5000 främre korsbandsskador (ACL) årligen i Sverige. ACL skador kan resultera i långvarig frånvaro från sporten eller till och med att idrottaren inte längre kan fortsätta sin karriär. Kvinnor är mer utsatta för ACL skador än män och det är flera faktorer som ökar risken för ACL skador hos kvinnor. Forskningen pekar mot att träningsprogram som syftar till att minska risken för knäskador innefattar styrketräning och plyometrisk träning. Många träningsprogram för att minska risken för knäskador innefattar många övningar vilket gör det tidskrävande. ProPrioPlate (PPP) är ett träningsredskap som är validerat och har visats aktivera gluteus medius 40% mer i en knäböj på PPP jämfört med vanliga knäböj.Syftet med denna studie var att undersöka knätabduktionshastighet i ett dropp vertikalhopp innan och efter ett 6 veckors träningsprogram med PPP för kvinnor med bristande knästabilitet.Metod: En exprementell studiedesign har använts. Tjugo frivilliga kvinnliga idrottar med bristande knästabilitet och teckan på valgus vid dropjump genomförde ett 6 veckors träningsprogram för att undersöka om knäabduktionshastighet i ett dropp vertikalhopp förändrades efter träningsperioden. 3D analyser på testpersonerna genomfördes innan och efter träningsperioden. Wilcoxons signed ranked test användes för att undersöka skillnader mellan de olika test tillfällena.Resultat: Medianen av abduktionshastigheten före interventionen var -47,88 grader/sek (min -74,76 max -30.16), -34.34 (min -70.65 max -11.53) och efter interventionen -34.22 (min -51.97 max -3.28) grader/sek. P värdet var 0.24 vilket indikerar att det inte fanns någon signifikant skillnad mellan före- och eftertesterna. Följsamheten till träningen hos deltagarna var låg (15%).Slutsats: En 6 veckors träningsperiod med PPP minskade inte abduktionshastigheten i ett DJ. Låg åtföljnad av våra testpersoner till träningsperioden innebar att inga slutsatser gällande PPP kan utgöras.

Dancers spend many years practicing repetitive movements in order for their bodies to gain flexibility, strength and muscle memory. This thesis investigated the biomechanics of a dance student's knee motion during a tendu to the front in first, third, and fifth positions. A dancer will often perform 75 or more tendu closing actions during one technique class - particularly in ballet technique. During a tendu the moving foot moves along the floor but the toes never leave the floor. The tendu is used to strengthen the leg muscles, particularly the quadriceps and gluteal muscles. Flexion/extension, abduction/adduction, and rotation angles of the knees during a traditional flat footed closing were compared to the knee angles during pli#233; and relev#233; closing. These movements were performed by 10 healthy dance students from USF. The dancers' movements were tracked using the VICON Nexus motion analysis system and 27 passive reflective markers placed on bony landmarks. Visual 3D software was used to calculate the knee angles. There were statistically significant the differences between knee angles during the traditional and pli#233; closings and between the relev#233; and pli#233; closings for all positions. There were only 4 conditions in which there was statistical significance between traditional and relev#233; closings. Knee flexion difference between the traditional and relev#233; closings was unanticipated, as the expectation of the tendu movement is to maintain a fully straight knee throughout the full range. This result suggests that the students may be bending the knees to achieve greater outward rotation, particularly in the third and fifth positions. The pli#233; had the largest range of motion (ROM) for all of the angles tested including abduction/adduction in which the subjects used the abduction at the knee to hold the feet in a turned out position. The collected data gives better insight into the biomechanics of the knee movement and will be used as feedback for improving muscular strength and preventing injuries in dancers.

Females suffer anterior cruciate ligament (ACL) injuries at a 2 to 10-fold greater rate compared to male athletes participating in similar sports. Altered movement patterns and inadequate knee stiffness are two interrelated factors that may increase ACL injury risk. Onset of these neuromuscular risk factors may coincide with the rapid adolescent growth that results in the divergence of a multitude of neuromuscular parameters between sexes. The overall purpose of this dissertation was to determine if neuromuscular ACL injury risk factors in female athletes increase following rapid growth and development compared to males. Male and female athletes were tested with three-dimensional motion analysis techniques during a drop vertical jump over two consecutive years to determine if ACL injury risk factors increased. Pubertal females showed a significant longitudinal increase in knee abduction angle compared to post-pubertal females and both male groups. The increase in knee abduction angle appeared to remain consistent, as the post pubertal female cohort had greater overall knee abduction compared to post-pubertal males. Similar results were found with a greater magnitude of knee abduction moment in post-pubertal females compared to males. Males and females increased ankle, knee and hip active stiffness from the first to second year of testing. Ankle and hip stiffness were increased significantly more in the pubertal group compared to post-pubertal. Sex and maturational group differences were found in hip and ankle joint stiffness. Post-pubertal males had significantly greater hip stiffness than the other groups (even when normalized to body mass). This indicates that post-pubertal males utilized a different neuromuscular strategy during landing. Males had a significantly greater increase from year to year in vertical jump height compared to females. Vertical jump height is often related to a measure of whole body power and indicates that males had a significant neuromuscular spurt compared to females. Early puberty appears to be a critical phase related to the divergence of increased ACL injury risk factors. Injury prevention programs that focus on neuromuscular training may be beneficial to help address the development of ACL injury risk factors that occur in female athletes during maturation.

Study Design: Methodological study. Objectives: To examine the agreement and validity of using observational risk screening guidelines to evaluate ACL injury risk factors. Background: Post-pubescent females have an increased risk of anterior cruciate ligament (ACL) injury compared with their male counterparts partly due to their high-risk landing and cutting strategies. There are currently no scientifically-tested methods to screen for these high risk strategies in the clinic or on the field. Methods and Measures: Three physiotherapists used observational risk screening guidelines to rate the neuromuscular characteristics of 40 adolescent female soccer players. Drop jumps were rated as high risk or low risk based on the degree of knee abduction. Side hops and side cuts were rated on the degree of lower limb 'reaching'. Ratings were evaluated for intrarater and interrater agreement using kappa coefficients. 3D motion analysis was used as a gold standard for determining the validity of ratings. Results: Acceptable intrarater and interrater agreement (k≥0.61) were attained for the drop jump and the side hop, with kappa coefficients ranging from 0.64 to 0.94. Acceptable sensitivity (≥0.80) was attained for the side hop and the side cut, with values ranging from 0.88 to 1.00. Acceptable specificity (≥0.50) was attained for the drop jump, with values ranging from 0.64 to 0.72. Conclusion: Observational risk screening is a practical and cost-effective method of screening for ACL injury risk. Based on levels of agreement and sensitivity, the side hop appears to be a suitable screening task. Agreement was acceptable for the drop jump but its validity needs further investigation.

Study Design: Methodological study. Objectives: To examine the agreement and validity of using observational risk screening guidelines to evaluate ACL injury risk factors. Background: Post-pubescent females have an increased risk of anterior cruciate ligament (ACL) injury compared with their male counterparts partly due to their high-risk landing and cutting strategies. There are currently no scientifically-tested methods to screen for these high risk strategies in the clinic or on the field. Methods and Measures: Three physiotherapists used observational risk screening guidelines to rate the neuromuscular characteristics of 40 adolescent female soccer players. Drop jumps were rated as high risk or low risk based on the degree of knee abduction. Side hops and side cuts were rated on the degree of lower limb 'reaching'. Ratings were evaluated for intrarater and interrater agreement using kappa coefficients. 3D motion analysis was used as a gold standard for determining the validity of ratings. Results: Acceptable intrarater and interrater agreement (k≥0.61) were attained for the drop jump and the side hop, with kappa coefficients ranging from 0.64 to 0.94. Acceptable sensitivity (≥0.80) was attained for the side hop and the side cut, with values ranging from 0.88 to 1.00. Acceptable specificity (≥0.50) was attained for the drop jump, with values ranging from 0.64 to 0.72. Conclusion: Observational risk screening is a practical and cost-effective method of screening for ACL injury risk. Based on levels of agreement and sensitivity, the side hop appears to be a suitable screening task. Agreement was acceptable for the drop jump but its validity needs further investigation.

Study Design: Methodological study. Objectives: To examine the agreement and validity of using observational risk screening guidelines to evaluate ACL injury risk factors. Background: Post-pubescent females have an increased risk of anterior cruciate ligament (ACL) injury compared with their male counterparts partly due to their high-risk landing and cutting strategies. There are currently no scientifically-tested methods to screen for these high risk strategies in the clinic or on the field. Methods and Measures: Three physiotherapists used observational risk screening guidelines to rate the neuromuscular characteristics of 40 adolescent female soccer players. Drop jumps were rated as high risk or low risk based on the degree of knee abduction. Side hops and side cuts were rated on the degree of lower limb 'reaching'. Ratings were evaluated for intrarater and interrater agreement using kappa coefficients. 3D motion analysis was used as a gold standard for determining the validity of ratings. Results: Acceptable intrarater and interrater agreement (k≥0.61) were attained for the drop jump and the side hop, with kappa coefficients ranging from 0.64 to 0.94. Acceptable sensitivity (≥0.80) was attained for the side hop and the side cut, with values ranging from 0.88 to 1.00. Acceptable specificity (≥0.50) was attained for the drop jump, with values ranging from 0.64 to 0.72. Conclusion: Observational risk screening is a practical and cost-effective method of screening for ACL injury risk. Based on levels of agreement and sensitivity, the side hop appears to be a suitable screening task. Agreement was acceptable for the drop jump but its validity needs further investigation. / Medicine, Faculty of / Graduate

Running is known to provide important health benefits. However, the incidence of injury among runners is high, particularly among novice runners, which discourages long term participation in the sport. The knee is the most commonly injured joint in novice runners. In general, aberrant frontal and transverse plane kinematics are associated with the development of knee injuries in runners. It was unknown whether the high rate of knee injury in novice runners was due to abnormal kinematics. Further, it was unclear whether these risk factors for injury could be improved. This dissertation includes four studies investigating kinematics in novice runners, how they change with training and evaluation of a running assessment. The first study compared frontal and transverse plane kinematics of female novice and experienced runners. Novice runners displayed more knee kinematics associated with injury than experienced runners, which may contribute to their higher risk of injury. The second study investigated the effects of two different training programs on kinematics of novice runners: one program consisted of 8 weeks of walking followed by 8 weeks of running, the other consisted of 8 weeks of strength/plyometric training followed by 8 weeks of running. Results demonstrated that training produced small changes in kinematics, however all types of training produced a mix of beneficial and detrimental effects. Participants who completed the study displayed better knee kinematics 8 than those who dropped out, which may have influenced their ability to complete the program. The third study sought to investigate changes in coordination of the hip and ankle joints, and their contributions to knee joint angles thought to contribute to injury. Results demonstrated that both the hip and the ankle may influence changes in knee kinematics, however the relative motion of the hip and the ankle appears to remain stable with training. In the final study, we investigated the reliability and validity of the Running Readiness Scale (RRS), as a low cost assessment of kinematics related to injury in runners. The RRS demonstrated good inter and intra rater reliability. Further, the RRS appeared to effectively discriminate between runners according to knee abduction, but not knee internal rotation.

Background: The incidence of anterior cruciate ligament (ACL) –injury is 3-5 times greater in female athletes compared to male athletes. This may be partially attributed to lower levels of hamstring-quadriceps co-contraction in females with subsequent knee kinematics that increases risk of ACL-injury. Finding training methods that improves co-contraction and increases knee stability is important. Objectives: To evaluate the effects of a new device on hamstring-quadriceps co-contraction and to investigate if training with the device can alter knee kinematics in female athletes. Study design: Controlled experimental study design with repeated measures. Method: Twenty soccer and floor ball athletes were measured with electromyography (EMG) for hamstring-quadriceps co-contraction while performing squats with and without the device. Thirteen athletes also underwent three-dimensional kinematic analyses, measuring knee abduction angles (at initial ground contact and peak angle) during a drop jump, before and after a six week intervention period with the device. Friedman’s test and Wilcoxon signed rank test was used to assess differences and effect sizes (ES) were calculated. Results: Co-contraction was consistently larger on the device (medial side: p<0.001, ES=0.88; lateral side: p<0.001, ES=0.80) and the ratio of medial-to-lateral co-contraction increased (p=0.001, ES=0.79). In the kinematic analysis low adherence rates amongst our subjects meant that the effects of the device on kinematics could not be measured. Conclusion: Performing squats with the new training device stimulates increased hamstring-quadriceps co-contraction and increases the ratio of medial-to-lateral co-contraction. The effects of the device on knee kinematics have yet to be determined.

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