Abstrakt Introduktion/bakgrund: I Sverige finns idag tre alpina riksidrottsgymnasier (RIG). Bland alpina idrottare är främre korsbandsruptur en vanlig skada. Rehabiliteringen är ofta lång och krävande där fysioterapeuten har en viktig roll i en lyckad rehabilitering för återgång till idrott. Syftet: Syftet med denna studie var att kartlägga förekomsten av ACLR och fysioterapeutiska insatser i rehabiliteringen hos elever på alpina RIG i Sverige. Metod: En webbenkät skickades ut till alla elever via lärare på de tre alpina riksidrottsgymnasierna. Resultat: Totalt besvarade 24 elever på enkäten. Av dessa hade 29% en främre korsbandsruptur och majoriteten av dessa elever upplevde att dem fick ett adekvat stöd av fysioterapeuten i sin rehabilitering. Drygt hälften av eleverna svarade att det fanns tillgång till fysioterapeut på skolan. Konklusion: Frekvensen av ACLR är hög hos elever på alpina RIG i Sverige. Studier med fler deltagare behövs för att kunna få ett mer omfattande resultat att dra slutsatser ifrån men författarna anser att resultatet belyser fysioterapeutens betydande roll både i rehabilitering och skade-preventiva åtgärder för elever på alpina RIG.

Anterior cruciate ligament (ACL) injuries are common orthopaedic injuries among athletes who participate in sports that involve cutting and changing directions. Many of these adolescent athletes intend to return to sports (RTS), and therefore undergo ACL reconstruction (ACLR). These athletes exhibit unfavorable landing biomechanics from muscle atrophy and asymmetrical neuromuscular control post-ACLR, putting them at a higher risk of re-injury. Thus, rehabilitation following ACLR is important to improve kinetic and kinematic outcomes and reduce re-injury risk. Biofeedback during rehabilitation is thought to be one way to potentially restore neuromuscular control deficits of athletes recovering from ACLR. Therefore, understanding the effectiveness of a biofeedback intervention on factors associated with re-injury among post-ACLR patients is essential in successful RTS. The purpose of this study is to analyze the effect of a 6-week biofeedback intervention on eccentric knee joint power (ECCKP), limb stiffness, and limb stiffness symmetry (using normalized symmetry index, NSI), in addition to secondary lower extremity outcomes that are associated with these metrics, during landing among patients following ACLR. This study used data collected from an ACL-Biofeedback Trial (ClinicalTrials.gov: AR069865) where participants were randomized into a biofeedback (BF) or control group (C). The BF group received visual and tactile feedback during a series of controlled squats while the C group participated in several online and in-person educational sessions. Participants completed 10 stop-jump tasks before (pre), after (post), and 6 weeks after (ret) the intervention. Kinetic, kinematic, and ground reaction forces (GRF) were collected from embedded force plates and 3D motion capture. Partaking in a biofeedback intervention did not improve ECCKP, limb stiffness, or limb stiffness NSI compared to controls. A group-by-time interaction was found for hip excursion (p=0.035), and a main effect of time was found for ECCKP, with this variable increasing by 18.5% from pre to ret (p=0.001). In addition, when considering surgical versus non-surgical limbs, this cohort exhibited interlimb asymmetries in stiffness, peak resultant GRF (rGRF), and time to reach peak rGRF (p<0.009). Further, a group-by-limb interaction (p=0.005) and a 7.1% reduction in peak rGRF were found from post to ret (p=0.02). Participants in this study also exhibited limb stiffness asymmetry greater than 10%, which supports existing literature that observed interlimb asymmetries in athletes following ACLR around the typical RTS time (9-12 months post-ACLR). The results from this analysis demonstrated that the current biofeedback intervention was inadequate in improving ECCKP, limb stiffness, and limb stiffness NSI, but additional biofeedback studies with larger sample sizes that investigate task dependencies are needed to better understand the effectiveness of biofeedback interventions. / Master of Science / Anterior cruciate ligament (ACL) injuries are common orthopaedic injuries among athletes who participate in sports that involve cutting and changing directions. Many of these adolescent athletes intend to return to their pre-injury level, therefore undergo a surgical procedure called ACL reconstruction (ACLR). However, following this procedure, athletes display unsafe and stiff landing patterns due to muscle weakness and asymmetrical neuromuscular, or mind-body, control post-ACLR, which increases their risk of re-injury once they return to sport (RTS) following recovery. Rehabilitation for patients following ACLR is of the utmost importance in improving unsafe movement patterns to reduce the risk of re-injury. Biofeedback training refers to receiving external signals that can be processed and transferred to the muscles in the body. This technique aims to restore the neuromuscular deficits of athletes following ACLR and could potentially be helpful during ACLR rehabilitation. Therefore, understanding the effectiveness of a biofeedback intervention on outcomes associated with an increased risk of re-injury in patients following ACLR is important to safely RTS. The purpose of this study is to determine the effect of a 6-week biofeedback intervention on the ability of the knee to absorb impact forces (quantified as eccentric knee joint power, ECCKP), limb stiffness, and limb stiffness symmetry (measured with normalized symmetry index, NSI), along with secondary outcomes related to these variables, among patients following ACLR. This study used data collected from an ACL-Biofeedback Trial (ClinicalTrials.gov: AR069865) where participants were randomized into a biofeedback (BF) or control group (C). The BF group received visual and resisted feedback during a series of controlled squats while the C group participated in several online and in-person educational sessions. Participants completed 10 stop-jump tasks before and after the intervention, and biomechanical data was obtained. The biofeedback intervention did not result in an improved ability for the knee to absorb impact from landing, and it was not able to decrease limb stiffness or limb stiffness asymmetry. It was able to improve hip excursion, which allows for a favorable, less upright posture when landing. ECCKP improved for both groups, indicating that the biofeedback did not add extra benefit to the participant's rehabilitation outside of the study. Asymmetries were observed between the surgical and non-surgical limbs in limb stiffness, peak GRF, and the time it takes to reach this peak GRF. This sample exhibited limb stiffness asymmetry greater than the recommended 10% threshold, raising concern for when these athletes RTS. The results from this analysis demonstrated that the current biofeedback intervention was inadequate in improving ECCKP, limb stiffness, and limb stiffness NSI, but biofeedback in ACLR rehabilitation can still be efficacious in improving hip biomechanics and overall neuromuscular control but may be task-dependent and call for a larger sample size.

This master’s thesis deals with integrating simulations using Agilents Electronic Design Automation tool ADS with customized Matlab scripts, for solving complex analog and digital radio architectures. In particular, it addresses predistortion, realized in the digital domain, of power amplifiers, modeled in the analog domain. The former is implemented in Matlab while the latter is implemented in ADS. Two versions of integrating the two systems have been tested: 1) Iterative approach on sample basis and 2) Scheduled batch solution by matrix inversion. The concept has been tested on two different PA configurations: 1) a standard class-AB PA and 2) a Doherty PA architecture. Evaluation has also been done on ADS ability to correctly simulate memory effects in PAs and on the actual DPD-algorithms ability to compensate for these memory effects.  An integrated simulation environment for ADS and Matlab was successfully established within the work of this thesis. Matlab scripts, used in predistortion algorithms in the digital domain, could interact directly with component-based PA models, in an enclosed simulation system.  The simulation results show that sample basis method is the most accurate, fast and reliable method to linearize a PA. The PA1 proved to be easier than the DPA to linearize, except for when being close to saturation where better IMD-suppression was achieved with the DPA.  ADS is clearly able to simulate memory effects in the analog domain. At low gain-levels the applied compensating memory-algorithms showed a great improvement to the linearization of the output signal of the PA. At higher gain-levels though, the compensation for memory effects lost their efficiency because the non-linearity of the PA became too significant.

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The continual increase in anterior cruciate ligament (ACL) injuries in sports makes it the most common ligament injury and leads the athlete down a difficult road with reconstruction surgery (ACLR) and months of rehabilitation. Specifically, females are at a greater risk of both primary and secondary ACL injuries compared to males. The purpose of this research was to understand the differences in movement and loading variability between ACLR and healthy athletes during unilateral and bilateral landings while utilizing limb symmetry to understand between group differences. It was hypothesized that females with an ACLR would have greater variability compared to males with an ACLR and healthy female athletes. 40 ACLR and 67 healthy athletes were asked to complete seven stop jumps and 25 ACLR and 30 healthy athletes completed seven single hop trials to assess intra-subject variability. The stop jump task utilized embedded force plates and motion capture technology while the single hop task used loadsol® in-shoe force sensors. The measures studied with the stop jump included posterior and vertical ground reaction force (GRF), knee/hip abduction/adduction angles, and loading rate. The single hop measures included peak force, loading rate, and impulse. To assess variability and limb symmetry, coefficient of variation (CV) and the limb symmetry index (LSI) were calculated for each of outcome measure. A linear mixed effects model was completed in JMP (SAS Institute Inc., Cary, NC) with p<0.05 to see the effects of group, sex, and limb. During the stop jump task, the ACLR athletes showed higher variability for both posterior GRF (p<0.001), posterior GRF LSI (p<0.001), and loading rate (p=0.027) compared to controls. Females with an ACLR had higher variability in vertical GRF (p<0.001) and vertical GRF symmetry (p=0.029) compared to HC females. Additionally, females with an ACLR had higher variability in the vertical GRF (p=0.033) when compared to males with an ACLR. Knee abduction angle (p=0.024) showed males with an ACLR to have higher variability compared to females with an ACLR. For the single hop task, there was a significant difference between sex for loading rate (p<0.001), loading rate LSI (p=0.004), impulse (p=0.006), and impulse LSI (p=0.001) with males producing a higher mean CV compared to females in all measures regardless of group. Overall, these results support the hypothesis that group and sex differences exist and that females with an ACLR will have higher variability and asymmetrical movements than male ACLR patients and healthy females during bilateral landings, which could lead to increased injury risk. In unilateral landings, the results suggest that females are landing with less variability compared to males. With increased variability on the surgical limb of an athlete with an ACLR, it is likely that the athlete will have a more successful return to sport as they can react and adapt to changes in landing during sports. Future work should report reinjury rates to investigate the potential role of movement variability in injury risk and potentially determine variability thresholds for injury risk. The evaluation of bilateral and unilateral landings revealed the need to include both landing tasks in return to sport testing as well as a limb symmetry metric to understand an athlete's functional readiness to react to changing conditions during sports related movement. / Master of Science / Anterior cruciate ligament (ACL) injuries continue to rise in all sports and result in athletes having to undergo reconstruction surgery (ACLR) and months of rehabilitation if they want to compete at a high level again. Specifically, females have a greater risk of suffering both a primary and secondary ACL injury compared to males. Movement differences have been previously researched in hopes of decreasing injury risk. Variability, or the differences between one trial to the next, is a way to visualize the athlete's ability to adapt following injury. The ideal level of adaptability is still unclear as too much variability can be seen as unstable while too little can be seen as unforgiving. The purpose of this project was to better understand movement and loading variability between ACLR and healthy athletes during one legged (unilateral) and two legged (bilateral) landings. Differences between limbs were analyzed to understand whether one leg was favored over the other. Every participant completed seven stop jump trials which required them to run forward, jump off one leg and landing with two legs followed by a maximum vertical jump; another different group completed a series of seven single leg hop tasks during which they started on one-leg and jumped forward as far as they could while maintaining their balance. The measures studied with the stop jump included peak vertical and posterior force, frontal plane knee and hip angles, and loading rate. The single hop measures included peak force, loading rate, and impulse. The loading rate is defined as the ratio of peak force divided by the time it takes the athlete to reach peak force following initial contact. Impulse is the area under the force time curve and provides insight into the athlete's ability to dissipate load. The force data from each trial performed were collected using force plate technology and loadsol® shoe inserts. Variability was calculated using the coefficient of variation (CV) which is the ratio between the standard deviation and the mean value across the trails. The limb symmetry index (LSI) was calculated as the ratio between the surgical/non-dominant and the non-surgical/dominant limbs. During a stop jump, female patients with an ACLR showed greater variability in peak force and force LSI revealing asymmetric landing compared to healthy females. Additionally, females with an ACLR had greater variability compared to males with an ACLR in peak force. The ACLR group had greater variability in posterior force, posterior force symmetry, and loading rate compared to the athletes in the healthy group. During a single hop, males had higher greater variability in loading rate, loading rate limb difference, impulse, and impulse limb difference compared to females. These results suggest that all females have a more unstable and asymmetrical landing compared to all males during bilateral landing. However, during a unilateral landing, females had a less forgiving landing compared to males, which could also indicate an increased injury risk. Future work should investigate reinjury rates to determine whether variability impacts injury risk and if differences in injury risk between males and females are associated with differences in variability.

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