Our purpose was to evaluate effects of cadence manipulation on plantar loading during running. Participants (n=38) ran on a treadmill at their preferred speed in 3 conditions: preferred, 5% increased, and 5% decreased while measured using in-shoe sensors. Data (contact time [CT], peak force [PF], force time integral [FTI], pressure time integral [PTI] and peak pressure [PP]) were recorded for 30 right footfalls. Multivariate analysis was performed to detect differences in loading between cadences in the total foot and 4 plantar regions. Differences in plantar loading occurred between cadence conditions. Total foot CT and PF were lower with a faster cadence, but no total foot PP differences were observed. Faster cadence reduced CT, pressure and force variables in both the heel and metatarsal regions. Increasing cadence did not elevate metatarsal loads; rather, total foot and all regions were reduced when healthy runners increased their cadence. If a 5% increase in cadence from preferred were maintained over each mile run the impulse at the heel would be reduced by an estimated 565 body weightss (BWs) and the metatarsals 140-170 BWs per mile run despite the increased steps taken. Increasing cadence may benefit overuse injuries associated with elevated plantar loading.

Introduction: Irish dance has evolved to become more athletically demanding, thus making the art form very hard on dancers' bodies. Irish dancers must land from difficult moves without letting their knees bend or heels touch the ground, causing large amounts of force to be absorbed by the body. Past studies have found dancers landing with a range of 4.5–6 times body weight, potentially causing high amounts of overuse injury. The majority of injuries incurred by Irish dancers are due to overuse (79.6%). The landings that occur in Irish dance have been minimally evaluated in current literature. Obtaining values of vertical ground reaction forces (GRFs) produced by Irish dancers will assist in understanding the causes of overuse injuries, fill significant gaps in the current literature, and identify which Irish dance moves should be used less frequently to possibly reduce the chance for overuse injury. Purpose: To determine vertical GRFs produced by female Irish dancers in hard and soft shoes during common movements. The purpose of this study was to determine peak force, rise rate of force, and impulse in selected Irish hard shoe and soft shoe dance movements. Materials and Methods: Sixteen female Irish dancers between 14 and 25 years of age were recruited from the 3 highest competitive levels. Each performed a warm-up, reviewed 8 common Irish dance moves, and then performed each move 3 times upon a force plate. Four moves each were performed in soft and hard shoes. GRFs were measured using a 3-dimensional force plate running at 1000 Hz. Peak force, rise rate, and vertical impulse were all calculated. It was hypothesized that the 8 moves would produce different GRFs. Results: Peak forces normalized by each dancer's body weight were significantly different across moves (F = 65.4, p < 0.01; F = 65.0, p < 0.01; and F = 67.4, p < 0.01 respectively). Years of experience was not correlated with peak force, rise rate, or impulse (p < 0.40). Conclusion: There is a large range in peak forces created by Irish dancers. Moves that have high average peak forces may have a higher risk in causing overuse injuries. All dancers should take care to limit the use of these moves in their choreography to prevent such injury.

Background: Achilles tendinopathy is a common clinical syndrome of chronic Achilles tendon pain combined with thickening of the tendon and impaired tendon function. Tendinopathy is often, but not always, induced by mechanical overload, and is frequently accompanied by abnormalities at the tissue level, such as hypercellularity and angiogenesis, in which case the condition is called tendinosis. In tendinosis, there are no signs of intratendinous inflammation, but occasionally increased apoptosis is observed. Tendinosis is often hard to treat and its pathogenesis is still not clear. Recently, a new hypothesis has gained support, suggesting a biochemical model based on the presence of a non-neuronal production of classically neuronal signal substances by the primary tendon cells (tenocytes) in tendinosis. The possible functional importance of these signal substances in tendons is unknown and needs to be studied. In particular, the neuropeptide substance P (SP) and catecholamines are of interest in this regard, since these substances have been found to be up-regulated in tendinosis. As both SP and catecholamines are known to exert effects in other tissues resulting in changes similar to those characteristic of tendinosis, it is possible that they have a role in tendinosis development. It is furthermore unknown what elicits the increased intratendinous neuropeptide production in tendinosis, but given that tendon overload is a prominent riskfactor, it is possible that mechanical stimuli are involved. The hypothesis of this thesis work was that intratendinous production of SP is up-regulated in response to load of Achilles tendons/tenocytes, and thatstimulation of the preferred SP receptor, the neurokinin-1 receptor (NK-1 R), aswell as stimulation of the catecholamine α2 adrenoreceptors, contribute to the hypercellularity seen in tendinosis, via increased proliferation and/or decreased apoptosis, and that SP stimulates tendon angiogenesis. The purpose of the studies was to test this hypothesis. To achieve this, two model systems were used: One in vivo (rabbit Achilles tendon overload model of tendinosis) and one in vitro (human primary Achilles tendon cell culture model). Results: In the rabbit Achilles tendon tissue, SP and NK-1 R expression was extensive in the blood vessel walls, but also to some extent seen in the tenocytes. Quantification of endogenously produced SP in vivo confirmed intratendinous production of the peptide. The production of SP by human tendon cells in vitro was furthermore demonstrated. The catecholamine synthesizing enzyme tyrosine hydroxylase (TH), as well as the α2A adrenoreceptor (α2A AR), were detected in the tenocytes, both in vivo in the rabbit tissue and in vitro in the human tendon cells. As a response to mechanical loading in the in vivo model, the intratendinous levels of SP increased, and this elevation was found to precede distinct tendinosis changes. The in vitro model demonstrated the same response to load, i.e. an increased SP expression, but in this case also a decrease in the NK-1 R expression. In the in vivo model, exogenously administered SP, as well as clonidine (an α2 AR agonist), accelerated tenocyte hypercellularity, an effect that was not seen when administrating a specific α2A AR antagonist. Exogenous administration of SP also resulted in intratendinous angiogenesis and paratendinous inflammation. In the in vitro model, both SP and clonidine had proliferative effects on the human tenocytes, specifically mediated via NK-1R and α2A AR, respectively; both of which in turn involved activation/phosphorylation of the extracellular signal-regulated kinases 1 and 2 (ERK1/2). Exogenously administered SP, in Anti-Fas induced apoptosis of the tenocytes in vitro, confirmed SP to have an anti-apoptotic effect on these cells. This effect was specifically mediated via NK-1 R and the known anti-apoptotic Akt pathway. Conclusions: In summary, this thesis concludes that stimulation of NK-1 R and α2A AR on tenocytes, both in vitro and in vivo, mediates significant cell signalling effects leading to processes known to occur in tendinosis, including hypercellularity. The pathological role of the hypercellularity in tendinosis is still unclear, but it is likely to affect collagen metabolism/turnover and arrangement, and thereby indirectly tendon biomechanical function. Additional evidence is here provided showing that SP not only causes tenocyte proliferation, but also contributes to anti-apoptotic events. Furthermore, it was concluded that SP may be involved in the development of tendinosis, since its production is increased in response to load, preceding tendinosis, and since SP accelerates tendinosis changes, through some mechanistic pathways here delineated. These findings suggest that inhibition of SP, and possibly also catecholamines, could be beneficial in the reconstitution/normalization of tendon structure in tendinosis.

Sammanfattning Syfte: Syftet med den här studien var att undersöka den upplevda effekten av upprepad behandling med kinesiotejp under 2 veckor, sett till smärta och besvär hos idrottare med medialt tibiasyndrom (MTS). Frågeställningarna som ställdes var: vilken effekt har behandling med kinesiotejp på smärta vid MTS samt vilken effekt har behandling med kinesiotejp på besvär och symtom vid medialt MTS? Metod: Femton personer med diagnosen MTS deltog i studien (10 kvinnor och 5 män). Samtliga deltagare var aktiva inom friidrott alternativt löpning. Deltagarna skattade sin smärta i båda benen, men endast ett ben tejpades. En lottning utfördes för att fastställa vilket ben som skulle behandlas med kinesiotejp. De med smärta i enbart ett ben tejpades på det benet som var symtomgivande. Deltagarna tejpades vid 2 tillfällen, de tejpades vid det första mötet och tejpen fick sedan sitta kvar i 6 dagar. Den sjätte dagen tog deltagarna själva bort tejpen och dagen efter utfördes samma tejpning igen. Sex dagar senare togs tejpen bort och efter 2 veckor utan tejp skickades en uppföljningsenkät ut. Deltagarna skattade upplevd smärta och besvär i båda benen på en visuell analog skala (VAS) vid första mötet och en uppföljning av smärta och besvär gjordes efter 1, 2 och 4 veckor. De fick också uppge upplevd symtomförändring efter 1, 2 och 4 veckor. Resultat: Upplevd smärta och besvär mätt på VAS-skalan visade ingen signifikant förändring över tid mellan det tejpade benet och det otejpade benet. Vid första uppföljning upplevde dock 12 av 15 (80 %) en symtomförbättring i sitt tejpade ben, medan 2 av 12 (16,7 %) upplevde en förbättring i sitt otejpade ben (p&lt;0,05). En tendens till upplevd förbättring fanns vid uppföljning vid vecka 2: 9 av 15 (60 %) upplevde en förbättring på sitt tejpade ben medan 3 av 12 (25 %) upplevde en förbättring på sitt otejpade ben (p=0,57). Slutsats: Resultatet i denna studie visade att behandling med kinesiotejp kunde minska upplevda symtom hos idrottare med MTS den första veckan efter applicering. En tendens till minskning av upplevda symtom kunde även ses vid uppföljning efter 2 veckor med behandling av kinesiotejp. Ingen ytterligare effekt kunde ses efter borttagning av tejpen. Denna omedelbara effekt visar att kinesiotejp kan vara en möjlig behandlingsmetod för idrottare med MTS. Nyckelord: medialt tibiasyndrom, MTS, kinesiotejp, idrottare, överbelastningsskada / Abstract Aim: The purpose of this study was to examine the perceived effect of repeated treatment with kinesiotape during 2 weeks, in terms of pain and symptoms in athletes with medial tibial stress syndrome (MTSS). The research questions were: what effect does treatment with kinesiotape has in pain of MTSS and what effect does treatment with kinesiotape has in pains and symptoms of MTSS? Method: Fifteen people diagnosed with MTSS participated in the study (10 women and 5 men). All participants were track- and-field athletes or runners. The participants estimated their pain in both legs, but only one leg was taped. A lottery was conducted to determine which leg was to be treated with kinesiotape. Those with pain in only one leg were taped to the leg that was symptomatic. Participants were taped on 2 occasions, they were taped in the first meeting and the tape was then left for 6 days. On the sixth day the participants took the tape off and the following day they were taped again. Six days later, the tape was removed and after 2 weeks without tape a follow-up survey was sent. Participants estimated perceived pain and symptoms in both legs on a visual analogue scale (VAS) at the first meeting and follow-ups of pain and symptoms were made after 1, 2 and 4 weeks. They also estimated perceived change in symptoms after 1, 2 and 4 weeks. Results: Perceived pain and symptoms as measured on VAS revealed no significant change over time between the taped leg and the non-taped leg. At the first follow-up however, 12 of 15 (80%) experienced an improvement in symptoms in the taped leg, while 2 of 12 (16.7%) experienced improvement in their non-taped legs (p&lt;0.05). A tendency to perceived improvement was found at follow-up in week 2: 9 of 15 (60%) experienced an improvement in their taped legs while, 3 of 12 (25%) experienced an improvement in their non-taped leg (p=0.57). Conclusions: The result of this study showed that treatment with kinesiotape decreased perceived symptoms in athletes with MTSS in the first week after application. A trend for reduction of perceived symptoms could also be seen at follow-up after 2 weeks of treatment with kinesiotape. No further effect was seen after removal of the tape. This immediate effect showed that kinesiotape may be a possible treatment for athletes with MTSS. Key words: medial tibial syndrome, MTSS, athletes, overuse injury.

Bakgrund: Axelskador är vanligt förekommande inom idrott. Det finns ett tydligt samband mellan axelskador och idrotter som innefattar hand- och armrörelser ovanför huvudhöjd, som till exempel handboll. Axellederna utsätts för såväl hård fysisk kontakt som hög belastning vid repetitiva kaströrelser vilket ställer stora krav på axelledens strukturer. Prevalensen av aktuell eller tidigare axelskada rapporteras vara mellan 58 till 75 % hos spelarna. Syfte: Syftet med studien var att undersöka hur ett preventivt träningsprogram riktat mot riskfaktorer för skada i axelleden, utfört under åtta veckor i slutskedet av tävlingssäsong, påverkade prevalensen av överbelastningsskador i axelleden hos elithandbollsspelare i Sverige. Hur påverkas prevalensen av överbelastningskador och av allvarliga överbelastningsskador i axelleden under åtta veckor med samtidigt genomförande av ett preventivt träningsprogram för axelleden på elithandbollsspelare i Sverige? Metod: Studien var av kvasi-experimentell design vilken bestod av sex mättillfällen under åtta veckor. Nio elithandbollslag aktiva i Mellansverige rekryterades, varav 110 av 162 tillgängliga spelare inkluderades vid studiestart. Exkludering under och efter studieperioden gjorde att analysen utfördes på ett färre antal spelare. Lagen delades in i interventions- (n = 48) eller kontrollgrupp (n = 32) genom stratifierat urval, medelålder (± SD) 22.0 (3.3) respektive 21.9 (4.0). Interventionsgruppen tilldelades ett preventivt träningsprogram bestående av tre övningar i syfte att förbättra riskfaktorer för axelskador hos ”overhead athletes”. Kontrollgruppen tilldelades ingen intervention. Träningsprogrammet utvärderades genom att analysera prevalensen av överbelastningsskada och allvarlig överbelastningsskada i axelleden mätt med en modifierad version av The Oslo Sports Trauma Research Centre Overuse Injury Questionnaire. Resultat: Totalt 455 överbelastningssymtom rapporterades hos 42 spelare (53 %) varav 95 symtom var allvarliga hos 18 spelare (23 %). Prevalensen av överbelastningsskada minskade för både interventions- och kontrollgruppen från 42 % (95 % CI 28-56 %) till 25 % (95 % CI 13-37 %) respektive 53 % (95 % CI 36-70 %) till 31 % (95 % CI 15-47 %). Prevalensen av allvarliga överbelastningsskador minskade för både interventions- och kontrollgruppen från 15 % (95 % CI 5-25 %) till 6 % (95 % CI -1-13 %) respektive 19 % (95 % CI 5-32 %) till 13 % (95 % CI 1-24 %). Det fanns ingen signifikant skillnad mellan grupperna gällande prevalensen efter åtta veckors intervention. Allvarlighetspoängen minskade genomgående med en signifikant skillnad (p = 0.001) över tid för båda grupperna där kontrollgruppen förbättrades något mer. Det fanns en tendens till skillnad mellan grupperna (p = 0.064) gällande allvarlighetspoäng. Slutsats: Resultaten av denna studie visar på att prevalensen av allvarlig överbelastningsskada i axelleden hos elithandbollsspelare i Sverige möjligtvis kan reduceras till viss del genom utförande av ett preventivt träningsprogram två eller fler gånger per vecka under åtta veckor. Prevalensen av allvarliga symtom för överbelastningsskada minskade till ett något lägre värde för interventionsgruppen. Skillnaden för prevalens av överbelastningsskada inom interventionsgruppen, undergrupperade på antal utförda förebyggande träningspass, var signifikant (p = 0.044). Allvarlighetspoängen minskade i båda grupperna under studien. Det fanns en tendens till signifikant skillnad mellan grupperna (p = 0,.064), där kontrollgruppen förbättrades något mer trots ett högre värde vid mätning vecka 8. Axelskada och dysfunktioner hos ”overhead athletes” kan orsakas av olika faktorer vilket innebär att även riskfaktorerna bakom var och en av dessa tillstånd kan variera. Det är därför viktigt att upplysa om att träningsprogrammets påverkan på individnivå kan se annorlunda ut jämfört med resultatet på gruppnivå i den större populationen. / Background: Shoulder injuries are common in sport. In particular there is a clear relationship between shoulder injuries and sports that includes hand- and arm movements over the head, for example handball. In handball, the shoulder joints are exposed to hard physical contact as well as high loads during repetitive throwing which puts high demands on the structures inside and surrounding the shoulder joint. The prevalence of current or previous shoulder injuries is reported to be between 58 to 75 % in studies of handball players. Aim: The purpose of this study was to investigate how a preventive training program aimed at risk factors for shoulder injuries in the shoulder joint, performed during eight weeks in the final stage of competitive season, affected the prevalence of overuse injuries in the shoulder joint for elite handball players in Sweden.  How is the prevalence of overuse injuries and severe overuse injuries in the shoulder joints of elite Swedish handball players affected by the implementation of an eight-week preventive training program? Method: The study was of a quasi-experimental design which consisted of six measurements taken during eight weeks. Nine elite handball teams active in the middle regions of Sweden were recruited, from which 110 of the 162 available players were included. Exclusions during and after the study period reduced the number of players. The teams were divided into an intervention (n = 48) or control group (n = 32) through stratified sampling, with mean age (± SD) 22.0 (3.3) and 21.9 (4.0), respectively. The intervention group was assigned a preventive exercise program consisting of three exercises with the purpose of improving riskfactors for shoulder injuries for overhead athletes. The control group was not assigned any intervention. The training program was evaluated by analyzing the prevalence of overuse and severe overuse symptoms in the shoulder measured with a modified version of The Oslo Sports Trauma Research Centre Overuse Injury Questionnaire. Results: A total of 455 overuse symptoms were reported by 42 players (53 %) of which 95 symptoms in 18 players (23 %) were severe. The prevalence of overuse injuries decreased in both the intervention and the control group from 42 % (95 % CI 28-56 %) to 25 % (95 % CI 13-37 %) and 53 % (95 % CI 36-70 %) to 31 % (95 % CI 15-47 %), respectively. The prevalence of severe overuse injuries decreased in both the intervention and the control group from 15 % (95 % CI 5-25 %) to 6 % (95 % CI -1-13 %) and 19 % (95 % CI 5-32 %) to 13 % (95 % CI 1-24 %), respectively. There was no significant difference between the groups regarding prevalence after the intervention of eight weeks. Severity score consistently decreased with a significant difference over time (p = 0.001) for both groups, with a slightly greater improvement in the control group. There was a tendency towarda difference between the groups (p = 0.064) regarding the severity score. Conclusions: The results of this study show that the prevalence of severe overuse injuries in the shoulder joint of elite handball players in Sweden might be reduced to some extent by performing a preventive exercise program two or more times per week for eight weeks. The prevalence of severe symptoms of overload injury decreased to a slightly lower value for the intervention group. The difference of prevalence of overuse injuries within the intervention group, stratified by the number of executed preventive exercise programs (&lt;2 and ≥2), was significant (p = 0.044). Severity score decreased in both groups during the study. However, there was a tendency to a significant difference between the groups (p = 0.064), where the control group improved slightly more in spite of a higher value when measured at week 8. Shoulder injury and dysfunctions of overhead athletes can be caused by various factors, which means that the riskfactors for each of these conditions may vary. It is therefore important to highlight that the effects of a training program may be different at the individual level compared with the results at group level.

This thesis includes four papers based on three different prospective cohort studies on injury characteristics in men’s professional football. The same general methodology was used in all papers. Time-loss injuries and player individual exposure was registered for match and training separately. The general aim was to investigate potential internal and external risk factors for injury, with a focus on age, playing position, time in professional football, playing surface (artificial turf and natural grass), changes between surfaces and climate; and to evaluate the study methodology. Paper I was based on data collected between 2001 and 2010 from 26 top professional clubs in Europe; the UCL injury study. In total, 6140 injuries and 797 389 hours of exposure were registered. A decreased general injury rate was observed for newcomers compared with established players (hazard ratio (HR), 0.77; 95% CI 0.61-0.99). Using goalkeepers as a reference, all outfield playing positions had significantly higher age-adjusted injury rates. Using players aged ≤ 21 years as a reference, the overall adjusted injury rate increased with age, with a peak injury rate among players aged 29 to 30  years (HR, 1.44; 95% CI, 1.24-1.68). Paper II and Paper III are based on data collected during two consecutive seasons, 2010 and 2011, in the Swedish and Norwegian male first leagues. In total, 2186 injuries and 367 490 hours of football exposure were recorded. No statistically significant differences were found in acute injury rates on artificial turf (AT) compared with natural grass (NG) during match play (rate ratio, 0.98, 99% CI 0.79-1.22) or training (rate ratio 1.14, 99% CI 0.86-1.50) when analysing at the individual player level. However, when analysing at the club level, clubs with AT installed at their home arena had a significantly higher acute training injury rate (rate ratio 1.31, 99% CI 1.04-1.63) and overuse injury rate (rate ratio 1.38, 99% CI 1.14-1.65) compared to clubs with NG installed at their home venue. No association was found between frequent surface shifts and subsequent overuse injury risk (risk ratio 1.01, 95% CI 0.91-1.12). Analyses on the total cohort showed no difference in injury rates between clubs in the two climate zones (total rate ratio 1.01, 95% CI 0.92-1.10). Data included in Paper IV were collected during two consecutive seasons 2008 and 2009. During this period, two Norwegian elite football clubs were concurrently included in two research groups’ surveillance systems. The capture rate for match injuries was similar between the two audits, while the capture rate for training injuries was slightly higher with individual-based exposure recording. The inter-rater agreement in injury variable categorisations was in most aspects very high.

As a common source of long-term pain and physical disability, overuse injuries, such as chronic tendinopathies, severely impact a patient’s quality of life. Caused by repetitive trauma, chronic tendinopathies affect hundreds of millions of people each year. The exact pathogenic mechanism in developing this musculoskeletal injury is still largely unknown, making clinical recommendations on the best course of treatment highly debatable. Nonetheless, advancements in biotechnology have made autologous blood products, specifically the use of platelet rich plasma injections, an increasingly popular method in the orthopedic field. Studies have shown that the concentrated platelet sample harbors a number of bioactive mediators. Once activated and injected at the site of injury, these growth factors and cytokines augment the natural healing process in tendinopathic cases. With limited reported complications, many clinicians believe that platelet rich plasma therapy is a safe and accessible treatment option for patients diagnosed with chronic tendinopathy. As such, the primary purpose of this paper is to determine the efficacy of platelet rich plasma injections in treating chronic tendinopathies. This literature review determined that current published studies and research on the effectiveness of PRP injections have produced contradictory results. Due to its autologous characteristic, platelet concentration differs significantly from patient to patient, contributing to high variability in terms of its effectiveness between patients. However, with low long-term costs and fast recovery, PRP injections are a promising, non-surgical intervention for treating chronic tendinopathies. Several patient-centered clinical studies have reported significant improvements in range of motion and pain management when compared to traditional injection treatments. These effects are maximized when administered under ultrasound guidance or when used in conjunction with a strict eccentric exercise program. Nonetheless, continued research is needed to determine optimal injection standards so that clinical recommendations can be further developed and supported.

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