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.

We developed a novel approach that requires subjects to produce and finely tune ground reaction forces (GRFs) while standing. Using this method we were able to identify specific contributions of individual muscles and how these contributions change with the effects of age. One of the aims of this investigation was to determine whether electromyographic data in our findings was due to random muscle activation or representative of a neuromuscular control strategy. Ten healthy young adults (5 male, 5 female) with their dominant foot fixed within a boot mounted to a force platform participated twice in a target matching protocol, requiring subjects to control both the direction and magnitude of GRF along the horizontal plane while maintaining constant inferior-superior loads of 50% body-weight. Subjects were asked to manoeuvre a cursor with their dominant leg to match a series of targets projected on a screen. Targets appeared at random one at-a-time, separated by 30o around a circular trajectory. Subjects applied loads to the force platform in various horizontal directions to move the cursor while also controlling body weight. A successful target match required subjects to maintain 50% body weight and 30% of their peak horizontal load for one second. Electromyography (EMG) of eight muscles that cross the knee joint, ground reaction forces, and kinematic data were recorded for each successful match. EMG was normalized to percent maximum voluntary isometric contractions collected on an isokinetic dynamometer. Each target matching session was separated by two-three days. A random model, single measures intra-class correlation analysed the reliability for both test-retest and intra-day results, in addition to intersubject reliability. We observed moderate to high ICC values (0.60 – 0.993) for most muscles in most directions, indicating low within-subject variance. In addition, moderate to high between-subject reliability was observed in all eight muscle activation profiles, indicating subjects used similar neuromuscular control strategies to achieve the desired GRFs. Our findings support that groups who have undergone the same number of testing sessions can be compared, and that a single testing session is all that is required to compare neuromuscular control strategies used by a group to achieve target locations. The second aim of this investigation was to evaluate age related differences in neuromuscular control about the knee joint using our target match protocol. Thirty-three healthy adults (17 younger 24 years ±2, 16 older 59 years ±5), completed the same protocol evaluated above. The mean magnitude of muscle activity, specificity index, and mean direction of muscle activity were calculated in each target direction. Older adults presented with significantly lower strength in knee flexion and extension, hip abduction, and ankle plantar flexion. Significantly (p<0.25) higher mean activation magnitudes in the rectus femoris, vastus lateralis, vastus medialis, biceps femoris, semitendinosus, medial gastrocnemius, and tensor facia lata were also observed. Intraclass correlations (ICC) magnitudes indicate the percentage of global variance that can be explained by within subject and between trial variability. Muscle activation patterns were found to be similar in all muscles (ICC≤0.82). Similar patterns are supported by non-significant differences in mean direction of activation and muscle activation specificity. These results indicated that healthy older adults utilise different activation magnitudes for stabilising the knee while maintain similar muscle activation synergies in all muscles to younger adults.

We developed a novel approach that requires subjects to produce and finely tune ground reaction forces (GRFs) while standing. Using this method we were able to identify specific contributions of individual muscles and how these contributions change with the effects of age. One of the aims of this investigation was to determine whether electromyographic data in our findings was due to random muscle activation or representative of a neuromuscular control strategy. Ten healthy young adults (5 male, 5 female) with their dominant foot fixed within a boot mounted to a force platform participated twice in a target matching protocol, requiring subjects to control both the direction and magnitude of GRF along the horizontal plane while maintaining constant inferior-superior loads of 50% body-weight. Subjects were asked to manoeuvre a cursor with their dominant leg to match a series of targets projected on a screen. Targets appeared at random one at-a-time, separated by 30o around a circular trajectory. Subjects applied loads to the force platform in various horizontal directions to move the cursor while also controlling body weight. A successful target match required subjects to maintain 50% body weight and 30% of their peak horizontal load for one second. Electromyography (EMG) of eight muscles that cross the knee joint, ground reaction forces, and kinematic data were recorded for each successful match. EMG was normalized to percent maximum voluntary isometric contractions collected on an isokinetic dynamometer. Each target matching session was separated by two-three days. A random model, single measures intra-class correlation analysed the reliability for both test-retest and intra-day results, in addition to intersubject reliability. We observed moderate to high ICC values (0.60 – 0.993) for most muscles in most directions, indicating low within-subject variance. In addition, moderate to high between-subject reliability was observed in all eight muscle activation profiles, indicating subjects used similar neuromuscular control strategies to achieve the desired GRFs. Our findings support that groups who have undergone the same number of testing sessions can be compared, and that a single testing session is all that is required to compare neuromuscular control strategies used by a group to achieve target locations. The second aim of this investigation was to evaluate age related differences in neuromuscular control about the knee joint using our target match protocol. Thirty-three healthy adults (17 younger 24 years ±2, 16 older 59 years ±5), completed the same protocol evaluated above. The mean magnitude of muscle activity, specificity index, and mean direction of muscle activity were calculated in each target direction. Older adults presented with significantly lower strength in knee flexion and extension, hip abduction, and ankle plantar flexion. Significantly (p<0.25) higher mean activation magnitudes in the rectus femoris, vastus lateralis, vastus medialis, biceps femoris, semitendinosus, medial gastrocnemius, and tensor facia lata were also observed. Intraclass correlations (ICC) magnitudes indicate the percentage of global variance that can be explained by within subject and between trial variability. Muscle activation patterns were found to be similar in all muscles (ICC≤0.82). Similar patterns are supported by non-significant differences in mean direction of activation and muscle activation specificity. These results indicated that healthy older adults utilise different activation magnitudes for stabilising the knee while maintain similar muscle activation synergies in all muscles to younger adults.

We developed a novel approach that requires subjects to produce and finely tune ground reaction forces (GRFs) while standing. Using this method we were able to identify specific contributions of individual muscles and how these contributions change with the effects of age. One of the aims of this investigation was to determine whether electromyographic data in our findings was due to random muscle activation or representative of a neuromuscular control strategy. Ten healthy young adults (5 male, 5 female) with their dominant foot fixed within a boot mounted to a force platform participated twice in a target matching protocol, requiring subjects to control both the direction and magnitude of GRF along the horizontal plane while maintaining constant inferior-superior loads of 50% body-weight. Subjects were asked to manoeuvre a cursor with their dominant leg to match a series of targets projected on a screen. Targets appeared at random one at-a-time, separated by 30o around a circular trajectory. Subjects applied loads to the force platform in various horizontal directions to move the cursor while also controlling body weight. A successful target match required subjects to maintain 50% body weight and 30% of their peak horizontal load for one second. Electromyography (EMG) of eight muscles that cross the knee joint, ground reaction forces, and kinematic data were recorded for each successful match. EMG was normalized to percent maximum voluntary isometric contractions collected on an isokinetic dynamometer. Each target matching session was separated by two-three days. A random model, single measures intra-class correlation analysed the reliability for both test-retest and intra-day results, in addition to intersubject reliability. We observed moderate to high ICC values (0.60 – 0.993) for most muscles in most directions, indicating low within-subject variance. In addition, moderate to high between-subject reliability was observed in all eight muscle activation profiles, indicating subjects used similar neuromuscular control strategies to achieve the desired GRFs. Our findings support that groups who have undergone the same number of testing sessions can be compared, and that a single testing session is all that is required to compare neuromuscular control strategies used by a group to achieve target locations. The second aim of this investigation was to evaluate age related differences in neuromuscular control about the knee joint using our target match protocol. Thirty-three healthy adults (17 younger 24 years ±2, 16 older 59 years ±5), completed the same protocol evaluated above. The mean magnitude of muscle activity, specificity index, and mean direction of muscle activity were calculated in each target direction. Older adults presented with significantly lower strength in knee flexion and extension, hip abduction, and ankle plantar flexion. Significantly (p<0.25) higher mean activation magnitudes in the rectus femoris, vastus lateralis, vastus medialis, biceps femoris, semitendinosus, medial gastrocnemius, and tensor facia lata were also observed. Intraclass correlations (ICC) magnitudes indicate the percentage of global variance that can be explained by within subject and between trial variability. Muscle activation patterns were found to be similar in all muscles (ICC≤0.82). Similar patterns are supported by non-significant differences in mean direction of activation and muscle activation specificity. These results indicated that healthy older adults utilise different activation magnitudes for stabilising the knee while maintain similar muscle activation synergies in all muscles to younger adults.

Muscular stabilisation strategies during activities of daily living alter in the presence of knee osteoarthritis (OA). By examining neuromuscular adaptations using our weight-bearing target match protocol, the main objective of this research is to establish sex differences in adaptations of neuromuscular control that are associated with older males and females with and without OA. 66 participants completed the protocol while EMG, ground reaction forces (GRF), and kinematics were recorded. Muscle activation patterns were presented in polar plots with an EMG vector representing normalised muscle activation in twelve directions, each representing a GRF vector scaled to 30% maximal effort. Asymmetry about the polar plot (activation occurring in one direction more than another) was determined and specificity index (SI) and mean direction of activation were calculated when appropriate. Healthy females demonstrated greater rectus femoris (RF) mean muscle magnitude (XEMG) (p=0.067) and less biceps femoris (BF) XEMG than healthy males (p=0.084) and females with OA (p=0.041), and males and females with OA demonstrated greater RF XEMG than healthy controls of the same sex (p=0.016, 0.072, respectively). Females with OA had significantly greater medial gastrocnemius XEMG than healthy females (p=0.031) and males with OA (p=0.020). Females with OA have less specificity in all muscles compared to males with OA and OA participants generally had less specificity compared to healthy controls of the same sex. Healthy males had the largest SI for lateral gastrocnemius with an asymmetrical activation pattern contrasting the more symmetrical activation pattern of all other groups. In conclusion, we suggest OA-affected adults and healthy females use a quadriceps dominant strategy to stabilise the joint, and that this strategy may be a compensatory mechanism for reduced quadriceps function. We suggest RF, BF, MG, and LG should be targeted for prophylactic intervention as they displayed altered activation strategies in participants with OA and healthy females.

Despite the well-researched impact of ACL injuries, both acutely and longitudinally, and even though adolescent females have the highest risk of sustaining an ACL injury, there is surprisingly very little biomechanical research conducted on adolescent populations after an ACL rupture has taken place. The increasing rates of ACL injuries and re-injury among adolescents demonstrates a need for improved rehabilitation and return-to-activity (RTA) guidelines that are age/maturity- and sex-appropriate. To accomplish this, the first step is to describe this population alongside a non-injured activity-, maturity- and sex-matched population. Therefore, the overall purpose of this Doctoral thesis was to provide evidence to support the creation of return-to-activity guidelines for adolescent patients with ACL injuries. The findings of this thesis, briefly outlined below, can directly contribute to improving clinical and rehabilitation management of ACL injuries among adolescent males and females. First, a systematic review was performed to synthesize sex differences in muscle activation patterns in movements associated with ACL injuries in both adult and adolescent populations. Ultimately, 30 articles were included in the review with a wide range of inconsistent findings. In brief, females demonstrated higher pre- and post-landing activation of the quadriceps and lower activation of the hamstrings in 15 of 27 studies. Females also had higher quadriceps-to-hamstring co-contraction ratios during pre- and post-landing phases compared to their male counterparts in 4 of 9 studies. What's more concerning was the identification of only five research articles that evaluated muscle activations in adolescent or younger cohorts, further emphasising the importance of addressing this gap in literature. The second article of this thesis explored metrics used to evaluate knee joint function that are often a part of rehabilitation guidelines, such as limb symmetry indices (LSI) during single limb hopping and strength tasks. To date, no evidence exists to support or refute the use of these measures in an adolescent population. Therefore, we sought to investigate LSIs and knee joint function among adolescent males and females with and without ACL-injuries during single-limb assessments. A total of 141 participants were recruited and evaluated during a series of maximum voluntary tasks; isometric knee extension and flexion, and single-limb hopping tasks (anterior-hops, lateral-hops, 6m timed-hops, cross-hops, and triple-hops). In brief, females and males with ACL injuries had lower performance metrics compared to their matched controls, however, the differences were not the same within each sex. Females displayed deficits in all tasks, whereas males with and without ACL injuries were only different in the anterior-hop, triple-hop, and knee extension tasks. The final two articles of this thesis are complimentary as they both explored knee stabilisation strategies during countermovement jumps (CMJs) and side-cutting tasks. However, Article 3 included only adolescent males and females without ACL injuries to identify the influence of sex and limb-dominance on knee stabilisation strategies, whereas Article 4 included the same uninjured cohorts but compared with matched groups of males and females with ACL injuries. In both studies, surface electromyography and full-body kinematics were captured during CMJs and side-cutting. Knee stabilisation strategies were evaluated using co-activation indices (CIs), full muscle waveforms, knee joint flexion stiffness (KJFS) and knee joint sagittal and frontal excursions (KJSE and KJFE, respectively). In Article 3, sex differences were observed in CIs, with females having higher medial CIs in the non-dominant limb in both CMJs and side-cuts, and higher total CIs in the non-dominant limb during side-cuts. Between-limb differences were present in both sexes. Females had higher total CI in their non-dominant limb in CMJs and higher frontal KJE in their non-dominant limb during the stance phase of side-cuts. Males had higher medial CIs in their dominant limb in CMJs and higher sagittal KJE in their non-dominant limb during the preparatory and landing phases of CMJs. No significant sex or limb differences were identified in individual muscle activations or KJFS. Based on these findings, males and females were treated statistically independent when evaluating the effect of ACL-injury in Article 4. Interestingly, when comparing groups, only one significant effect of injury was observed in knee stability metrics; males with ACL injuries had significantly higher vastus medialis activity during the preparatory phase of the CMJ compared to their uninjured counterparts. There were no other significant differences in either task. Despite the importance of ACL injury prevention in adolescents, the evidence on sex difference in muscle activation patterns in this population is still scarce. The results of this Doctoral thesis indicate that males and females in adolescent populations have differences in knee stabilisation strategies and overall knee joint function. These findings further support the need for additional research considering risk factors such as, age/maturity-, sex-, and limb-dominance. This research will contribute to the tailoring of rehabilitation programs, thus providing an opportunity to improve the success rate of rehabilitation following ACL-injury among adolescents.

Background: Jump height, utilization of the stretch-shortening cycle (SSC) and knee stability is key qualifications and important factors for athletic performance. This is usually practiced with the help of plyometric training. However, plyometric training is considered as an exercise with high-impact that adds stress on the body. Trampoline training is an activity with a growing number of adolescent’s performers, and with the ability to train the same qualities that plyometric training. However, few studies have investigated trampoline trainings effect on jump height, utilization of the SSC and the knee stability in comparison to ordinary plyometric exercises. Aim: The aim of the study was to investigate whether the jump height in a countermovement jump (CMJ) and a squat jump (SJ), the use of SSC and knee stability at landing is different in adolescents who are training using a trampoline and adolescents training using plyometric exercises. Methods: Thirty (n=30) participants, 19 handball players and 11 trampoline practitioners, aged 14-18 years, completed this cross-sectional study. This study involved three tests, a CMJ and a SJ for measuring the jump height and SSCand a double leg drop jump test for measuring the knee stability. Results: The result showed a significant difference in relative jump value between the groups, were the handball group showed a higher value in the CMJ and the SJ compared to the trampoline group. In the utilization of the SSC there were no significant difference between the groups. The result showed that there was a significant difference between the groups knee stability, were the handball group showed a greater knee degrees of varus compared to the trampoline group. Conclusion: Findings from this study suggests that adolescents might benefit from performing plyometric training to achieve a greater jump height and trampoline training to achieve a greater knee stability. Both activities had the same effect on the utilization of theSSC. More studies are needed, including a more homogenous group with larger sample sizes, to support the present results and investigate whether the results are reliable.

Abstract Background: The Gluteus Medius (GM) muscle has an important role in stabilizing the pelvis and controlling the knees during athletic activities. Weakness in the GM can affect performance negatively and increase the risk of lower extremity (LE) injuries. During functional activities different parts of the muscle becomes activated depending on the degree of hip flexion. However, many GM strength exercises only train the GM in one fixed degree of hip flexion. Purpose: The purpose of the present study was to develop and validate a new training device designed to increase the muscle activation of the GM during progressive hip flexion in squats. Methods: The new device was developed to offer resistance training against hip abduction during squats. To be able to validate the new device in activating the GM, 32 female athletes (mean age 20 ± 3) with various athletic backgrounds was included in the study. All subjects performed squats on and off the device while surface electromyographical (SEMG) activity was recorded from GM on both sides of the body. Results: All test subjects were able to perform the squat and to activate the GM. When the squats were performed on the new device the muscle activation in GM was significantly higher compared to bodyweight squats (Z=-4.9, p &lt; 0.001). Correlation tests between a complete sequence of five squats and one selected repetition revealed that activation was consistent throughout the exercise, (right GM: rs = 0.93, p &lt; 0.001, left GM: rp = 0.92, p &lt; 0.001) . No differences in activation were found between the right and left GM when squatting on the device. Conclusion: This study showed that the newly developed training device increased the muscle activity in GM during squats. Moreover, the results showed that squatting on the device activates the left and right side of the body equally and that the GM was activated during the whole exercise, under ongoing hip flexion. This information could be used to develop new training methods with the aim to improve stabilization of the pelvis and lower extremities during functional activities. / Sammanfattning Bakgrund: Gluteus medius (GM) fyller en viktig funktion vid idrottsliga aktiviteter genom att den stabiliserar bäckenet och kontrollerar knäna. Svaghet i GM kan påverka prestationen negativt samt öka risken för skador i de lägre extremiteterna (LE). Vid funktionella aktiviteter aktiveras olika delar av GM beroende på graden av höftflexion. Många styrkeövningar för GM tränar emellertid muskeln i endast en fixerad grad av höft flexion. Syfte: Syftet med den här studien har varit att utveckla samt validera ett nytt träningsredskap, designat för att optimera muskelaktiveringen av GM under höftflexion. Metod: Träningsredskapet utvecklades för att erbjuda motstånd mot abduktion vid knäböj. För att validera redskapets förmåga att aktivera GM inkluderades 32 kvinnliga idrottare (medelålder, 20 ± 3 år) med varierande idrottslig bakgrund. Alla försökspersoner utförde knäböjningar med och utan träningsredskapet samtidigt som elektromyografisk aktivitet mättes i höger och vänster GM. Resultat: Alla försökspersoner kunde utföra knäböjningar och lyckades aktivera GM. Knäböjningar som utfördes på träningsredskapet resulterade i signifikant högre aktivering av GM jämfört med knäböjningar utan redskapet (Z=-4.9, p &lt; 0.001). Korrelations test mellan kompletta sekvenser om fem repetitioner och enstaka repetitioner visade att aktiveringen var konstant under hela övningen, (höger GM: rs = 0.93, p &lt; 0.001, vänster GM: rp = 0.92, p &lt; 0.001). Inga skillnader i aktivering hittades mellan höger och vänster GM vid knäböjningar på redskapet. Slutsats: Studien visade att det utvecklade träningsredskapet ökade aktiveringen av GM vid knäböjningar. Resultaten visade också att denna aktivitet var jämnt fördelad mellan höger och vänster GM samt att aktiveringen var konstant under hela övningen. Resultaten i denna studien kan användas för att utveckla nya träningsmetoder med syfte att förbättra stabiliseringen av bäckenet och de lägre extremiteterna vid funktionella aktiviteter.

Purpose: Adolescents have significantly higher rates of diagnosed anterior cruciate ligament (ACL) injuries compared to adult cohorts. Approximately two-thirds of ACL injuries are non-contact scenarios that occur while performing “high-risk” maneuvers. Less than 50% of adolescents are able to return-to-activity, with females specifically having a lower activity level post-injury (Hewett, Di Stasi, & Myer, 2013; Schmale, Kweon, Larson, & Bompadre, 2014). Identifying the quantitative demand of a task used to assess return-to-activity will help establish its role in evaluating the knee stabilization strategies based on muscular coactivations and biomechanical outputs. Therefore, the aim of this study was to (1) assess the neuromuscular and biomechanical quantitative outputs of the lunge and drop-vertical jump (DVJ) in healthy adolescent male and females athletes and (2) to examine the muscular coactivation strategies of adolescent male and female athletes with and without an ACL injury. Methods: A total of 68 uninjured adolescent male and female athletes between the ages of 10 to-18 were used to identify the quantitative demand of the lunge and DVJ. Neuromuscular and biomechanical quantitative outputs included mean peak knee flexion (PKF), integrated knee excursion (iKEXC) in the sagittal and frontal planes, integrated knee joint power (iJP), and integrated electromyography (EMG) were used to assess the within (task) and between (sex) interactions. An additional 17 male and 37 female adolescents with an ACL injury were included to assess the impact of an ACL injury on the knee stabilization strategies (coactivations) used to maintain dynamic knee joint stability (frontal plane knee excursion). Ethics was approved by the University of Ottawa Research Ethics Board (uOttawa REB H09/17/10) (CHEO REB 17/74X). Results: Quantitative data for uninjured groups indicated that the lunge produced greater peak knee flexion, knee excursion, and quadriceps activation values than the DVJ. Conversely, the DVJ produced greater joint power, biceps femoris, gastrocnemii, and gluteus medius values. As for knee stabilization strategies, during the DVJ female ACL injured groups produced greater symmetry and higher muscular activations between anterior-posterior and medial-lateral muscular coactivations, which resulted in increased stability compared to uninjured female groups. Males with an ACL injury indicated similar knee stabilization strategies however decreased stability compared to males without an ACL injury. Conclusion: Results of this thesis identified differences in quantitative data between the lunge and DVJ, indicating differing demand requirements for each task. Results of the second study indicate that uninjured females use knee stabilization strategies that do not restrict their degrees of freedom through asymmetrical coactivations, while females with an ACL injury have increased coactivations in both anterior-posterior and medial-lateral muscle groups, resulting in increased dynamic knee joint stability as evidenced by reduced frontal plane knee excursion motion. Males, however, failed to show a difference between groups in dynamic knee stability, suggesting that those with an ACL injury compensated in a way to perform the DVJ efficiently and similarly to the uninjured group, while maintaining dynamic knee joint stability. In a clinical setting, these findings may help in understanding the direction of use of the lunge and DVJ tasks in a rehabilitation setting. As well as provide insight into the differing male and female adolescent knee stabilization strategies used to maintain dynamic knee joint stability during functional tasks.

No description available.