Background: The most common injuries in new or novice runners include medial tibial stress syndrome and patellofemoral pain syndrome; both overuse injuries. It is known that novice runners use a rearfoot strike pattern 98% of the time while running in traditional running footwear. Furthermore, footwear that is constructed with less cushioning (minimal shoes) and is said to promote forefoot running has increased in popularity. It is still unknown if novice runners convert their strike pattern in minimal shoes or continue to use a rearfoot strike pattern. Consequences of continuing to use a rearfoot strike pattern with less cushioning underfoot include higher vertical loading rates which are directly related to the types of injuries experienced. Aside from the strike pattern in a given shoe, movement stability is an important feature in healthy locomotion. There is a trade-off between being overly stable and being too unstable while running. It is known that the level of experience in running is related to the amount of stride length variability. It is still unknown if altering midsole stiffness has an effect on local dynamic stability while running. Purpose: The primary purpose of this thesis was to compare landing kinematics and kinetics between trained and novice runners in minimal and traditional shoes. The secondary purpose of this thesis was to examine the effect of running experience and midsole construction on local dynamic stability at the ankle, knee and hip. Methods: Twelve trained runners and twelve novice runners were recruited for participation. Four prototypical shoe conditions were tested with midsole geometry and material stiffness being manipulated. This yielded traditional/soft, traditional/hard, minimal/soft and minimal/hard shoe conditions. Participants ran down a 30m indoor runway which was instrumented with force platforms to measure vertical loading rates and motion capture cameras to capture landing kinematics. Participants also ran on a treadmill in each shoe condition to allow for local dynamic stability to be estimated at the ankle, knee and hip in the sagittal plane. Results: Novice runners landed with increased knee extension compared to trained runners. Increasing midsole thickness of the shoes caused an increase in dorsi-flexion of the ankle at heel strike. Manipulating material stiffness did not influence landing kinematics but did influence kinetics. Furthermore, decreasing material stiffness lowered vertical loading rates. Trained runners exhibited increased local dynamic stability (more stable) at the ankle, knee and hip compared to novice runners. Local dynamic stability was not affected by midsole stiffness. Conclusions: Novice runners did not alter their strike pattern in minimally constructed shoes. For this reason, cushioning properties of the shoe dictated vertical loading rates upon the body. Shoe conditions did not alter landing kinematics above the ankle, which is where the between group differences existed as novice runners landed with a more extended knee. Running experience appears to play a role in knee orientation at landing and is unaffected by shoe condition. Local dynamic stability was affected by running experience and does not appear to be related to the shoe condition being worn. Even when kinematics changed across shoe conditions, the stability of the movement did not.

In the long distance running community there is currently controversy as a result of the release of Advanced Footwear Technology (AFT) type of shoes. The AFT shoes with performance enhancing mechanical properties are currently used with great success. All of the current world records in long distance running have been set by athletes wearing the novel type of shoes. The new type of shoes have been shown to reduce energetic cost of running but the exact mechanisms of the reduced energetic cost are still unclear. In the research community several hypotheses of mechanisms and performance enhancing features exist. In this thesis the focus was on investigating the performance enhancing feature, energy return and the effect it has on the biomechanical variables, ground reaction force, joint moments and joint power.  For this thesis five male subelite to elite runners were recruited. The participants ran over two force platforms with a controlled running velocity while motion data was recorded with a marker based motion analysis system. The curves from the contact of the foot with the force platform were analysed with the motion analysis software, Visual 3D and the SPM1D statistical package in Matlab.  The results suggest that energy return properties of AFT shoes do affect lower extremity loading. Significant differences in the biomechanical variables GRF, ankle moment and ankle power were seen between high energy return shoes and low energy return shoes. In addition the number of significantly different intervals show a tendency of a pattern, where shoes share the largest amount of significantly different intervals with shoes that are furthest away on the energy return list. However, shoe #4 did not behave according to the energy return ranking. This means that a sole dependency on energy return characteristics was not found.    The knowledge gained from this thesis does not reduce the controversy surrounding the shoes. It does however establish a base for further research in the area of AFT. From that base, further research could create a solid scientific understanding of the shoes, which can be used to justify regulation changes. Regulations with a solid scientific backing would reduce the controversy. / Inom långdistanslöpning finns det för närvarande en kontrovers till följd av lanseringen av skor av typen Advanced Footwear Technology. Advanced Footwear Technology-skor med prestandaförbättrande mekaniska egenskaper används för närvarande med stor framgång. Alla nuvarande världsrekord i långdistanslöpning har satts av idrottare som bär den nya typen av skor. Det har visat sig att den nya typen av skor minskar den energetiska kostnaden för löpning, men de exakta mekanismerna för den minskade energetiska kostnaden är fortfarande oklara. Inom forskarvärlden finns flera hypoteser om mekanismer och prestationshöjande egenskaper. I den här uppsatsen låg fokus på att undersöka den prestationshöjande egenskapen, energiåtergivning, och vilken effekt den har på de biomekaniska variablerna markreaktionskraft, ledmoment och ledeffekt.  För denna uppsats rekryterades fem manliga subelit- till elitlöpare. Deltagarna sprang över två kraftplattformar med en kontrollerad löphastighet medan rörelsedata registrerades med ett markörbaserat rörelseanalyssystem. Kurvorna från fotens kontakt med kraftplattformen analyserades med rörelseanalys-programmet Visual 3D och statistikpaketet SPM1D i Matlab.  Resultaten tyder på att AFT-skor har egenskaper som ger energiåtergivning och som påverkar belastningen på nedre extremiteterna. Signifikanta skillnader i de biomekaniska variablerna GRF, fotledsmoment och fotledskraft sågs i resultaten. Dessutom visar antalet signifikant olika intervall en tendens till ett mönster, där skor delar det största antalet signifikant olika intervall med skor som ligger längst bort på listan över energiåtergivning. Sko #4 uppförde sig dock inte i enlighet med rangordningen för energiåtergivning. Detta innebär att man inte har funnit något beroende av egenskaperna för energiåtervändning.    Den kunskap som erhållits genom denna uppsats minskar inte kontroverserna kring skorna. Den skapar dock en grund för ytterligare forskning inom området Advanced Footwear Technology. Utifrån denna grund kan ytterligare forskning skapa en solid vetenskaplig förståelse för skorna, som kan användas för att motivera ändringar av regler. Ett regelverk med ett gediget vetenskapligt stöd skulle minska kontroverserna.

Background: In recent years, sudden improvements in long-distance running performance have been suggested to be due to the latest technological innovations in running footwear. However, inter-individual differences appear to be large in the performance enhancing effect these shoes elicit where some runners experience a decline in performance while others improve substantially. The reason for this is not yet fully understood but may be due to differences in anthropometric and neuromuscular characteristics between runners. Aim: The aim of this thesis was to investigate the association between individual anthropometrical and neuromuscular characteristics of runners with changes in running mechanics while wearing these new generation shoes. Method: Eight male endurance runners performed four different testing protocols during one single visit. These consisted of an anthropometrical protocol where measurements of height, weight, leg length and Achilles tendon moment arm length were determined; a jumping protocol where vertical stiffness and eccentric utilization ratio (EUR) were recorded using a force platform; a running protocol where contact time, step length, ankle propulsive power and knee absorption power were measured using a force platform and a 12-camera motion analysis system; and finally a force-velocity protocol where each participant performed calf raises and back squats with incremental loads in a smith machine while barbell velocity was simultaneously recorded. The collected data were then statistically analyzed using Wilcoxon Signed-Rank Test and Spearman’s Rank Correlation Coefficient. Results: Greater peak power in the back squat was associated with a greater reduction in peak knee absorption power (r = -0,905, p = 0,005) and less vertical stiffness during jumping was associated with longer step lengths with the advanced footwear technology (AFT) shoes (r = -0,738, p = 0,046). No associations were found between vertical stiffness during jumping and contact time, EUR with step length and contact time, peak power in the calf raise and Achilles tendon moment arm with peak ankle propulsive power. Conclusion: Runners with less vertical stiffness in the lower limb during jumping exhibited greater step length increase with AFT shoes. This may be due to the spring-like behavior the shoes possess. However, the larger step length increases the demands on lower limb strength and runners with less power in the lower limb may increase their knee absorption power during ground contact, leading to potentially less efficient running mechanics. Those with greater power in the lower limb may, on the other hand, run more efficiently by decreasing their knee absorption power leading to less muscular effort. / Bakgrund: De senaste årens förbättringar inom långdistanslöpning har föreslagits bero på de teknologiska framstegen som gjorts inom löparskokonstruktion. Det verkar emellertid finnas en skillnad i den prestationshöjande effekt som dessa skor framkallar, där vissa löpare upplever en försämring medan andra förbättras avsevärt. Orsaken till detta är fortsatt okänt men kan ha att göra med skillnader i antropometriska och neuromuskulära egenskaper mellan löpare. Syfte: Syftet med denna uppsats var att undersöka sambandet mellan individuella antropometriska och neuromuskulära egenskaper hos löpare med förändringar i löpmekanik som dessa nya generationens skor framkallar.Metod: Åtta manliga långdistanslöpare utförde fyra olika testprotokoll under ett enda besök. Dessa bestod av ett antropometriskt protokoll där längd, vikt, benlängd och momentarmslängd av Akillessenan mättes; ett hopprotokoll där vertikal styvhet och EUR registrerades med hjälp av en kraftplatta; ett löpprotokoll där kontakttid, steglängd, fotledskraft och knäledskraft mättes med hjälp av kraftplattor och ett rörelseanalyssystem med 12 kameror; och slutligen ett kraft-hastighetsprotokoll där varje deltagare utförde tåhävningar och knäböj med stigande belastning i en smith-maskin medan skivstångshastighet samtidigt registrerades. Den insamlade data analyserades därefter med Wilcoxon Signed-Rank Test och Spearman’s Rank Correlation Coefficient. Resultat: Högre peak power i benböj var associerat med en större minskning av maximal knäabsorptions power (r = -0,905, p = 0,005) och mindre vertikal styvhet under vertikalhopp var associerad med längre steglängd med AFT-skorna (r = -0,738, p = 0,046). Inget samband hittades mellan vertikal styvhet under vertikalhopp och kontakttid, EUR med steglängd och kontakttid, maximal power i tåhävningar och hälsenans momentarm med maximal propulsionspower i fotleden. Konklusion: Löpare med mindre vertikal styvhet i de nedre extremiteten under vertikalhopp uppvisade större steglängdsökning med AFT-skor. Detta kan bero på det fjäderliknande beteende skorna har. Den längre steglängden ökar dock kraven på styrkan i den nedre extremiteten och löpare med mindre kraft, har potentiell ökad knäabsorptions power under markkontakt vilket kan resultera i en mindre effektiv löpmekanik. De med bättre kraftutveckling i de nedre extremiteten kan däremot potentiellt springa mer effektivt med dessa nya generationens skor genom en minskning i knäabsorptions power vilket i sin tur leder till mindre muskulär ansträngning.

Dois modelos mecânicos, o pêndulo-invertido e o massa-mola, explicam como os mecanismos pendular e elástico minimizam o dispêndio energético advindo dos músculos durante caminhada e corrida humana. A presente tese testa dois efeitos que, para nosso conhecimento, todavia não possuem respostas conclusivas da literatura, nomeadamente o processo de envelhecimento na mecânica da corrida humana e o efeito da inclinação do terreno na velocidade ótima da caminhada. Para estudar o primeiro efeito, as forças de reação do solo provenientes de uma plataforma de força (4m x 0,50m), foram usadas para a posterior comparação de: i) trabalho mecânico, ii) parâmetros do sistema massa-mola e, iii) assimetrias contatodespregue entre jovens e idosos. Os idosos produzem menos força durante a fase de trabalho mecânico positivo com uma menor oscilação vertical total e oscilação durante a fase aérea. Conseqüentemente a capacidade de armazenar e re-utilizar energia elástica dos tendões é prejudicada contribuindo para o maior dispêndio energético neste grupo quando comparado com jovens.Para o modelo do custo eletromiográfico (EMG) da caminhada humana criou-se duas abordagens: experimental e teórica. Em ambas as abordagens, informações da atividade EMG de dezesseis músculos, sendo 8 posturais e 8 propulsores foram coletadas e analisadas a partir da integral EMG. A abordagem teórica parece ter uma melhor relação com as evidências experimentais sobre a energética da caminhada humana em inclinações. Os principais mecanismos envolvidos na nova hipótese são i) músculos posturais que não realizam trabalho muscular, exercem uma função importante na determinação do dispêndio energético total e ii) a presente hipótese leva em consideração a co-contração de músculos antagonistas no dispêndioenergético total. Mais experimentos são necessários para confirmar o modelo apresentado neste estudo. Além disso, através de estratégias de otimização e predição linear, um modelo teórico foi delineado a fim de determinar parâmetros mecânicos (comprimento de passada e velocidade de progressão) e energéticos da locomoção terrestre em situações onde as informações disponíveis são apenas a massa e uma curva força de reação vertical versus tempo. Os resultados advindos do modelamento correspondem aos parâmetros determinados experimentalmente. Laboratórios que detenham apenas uma plataforma de força, ou nas áreas onde as informações de entrada do atual modelo sejam as únicas informações (e.g. paleontologia, biomecânica forênsica, etc), a predição de variáveis primárias da locomoção podem ser preditas com razoável acurácia. / Two mechanical models, the inverted pendulum and spring-mass, explain how do the pendular and elastic mechanisms minimizing energy expenditure from muscles during human walking and running. Here, we test two effects that, to our knowledge, do not have yet conclusive responses from literature, specifically the ageing effects on mechanics of human running, and the effect of gradient on walking optimal speed. In order to check the former effect, the ground reaction forces came from a force platform (4m x 0.5m) were used for a later comparison: i) mechanical work, ii) spring-mass parameters and, iii) landing-takeoff asymmetries. The old subjects produce less force during positive work resulting in a smaller overall and aerial vertical oscillation of the centre of mass. Consequently, the potential for restore elastic energy from tendons is reduced contributing to greater energy expenditure than in young subjects. In relation to Electromyographical (EMG) Cost of human walking we created two approaches: experimental and theoretical. In both approaches, information from EMG activity of sixteen muscles, eight postural and eight propulsor were collected and analysed. The theoretical approach seems to fit better with the energy expenditure during gradient walking. The main mechanisms involved in this new hypothesis are i) postural muscles that do not perform muscular work, play an important role in the total energy expenditure and ii) the present hypothesis take the co-contraction into account of the antagonist muscles in the total energy expenditure. Further experiments are necessary to confirm this hypothesis. Besides, using optimization and linear prediction procedures, a theoretical model was designed to estimate mechanical parameters (stride length and velocity of progression) and energetic variables of terrestrial locomotion when available information consists only of mass and one vertical ground reaction force versus time.The results from this modelling are similar to experimentally obtained data. Laboratories with just one force platform, or in areas where the present model’s input information be the unique accessible data (e.g. palaeontology, forensic biomechanics, etc) the prime variables of locomotion may be estimated with reasonable accuracy.

Dois modelos mecânicos, o pêndulo-invertido e o massa-mola, explicam como os mecanismos pendular e elástico minimizam o dispêndio energético advindo dos músculos durante caminhada e corrida humana. A presente tese testa dois efeitos que, para nosso conhecimento, todavia não possuem respostas conclusivas da literatura, nomeadamente o processo de envelhecimento na mecânica da corrida humana e o efeito da inclinação do terreno na velocidade ótima da caminhada. Para estudar o primeiro efeito, as forças de reação do solo provenientes de uma plataforma de força (4m x 0,50m), foram usadas para a posterior comparação de: i) trabalho mecânico, ii) parâmetros do sistema massa-mola e, iii) assimetrias contatodespregue entre jovens e idosos. Os idosos produzem menos força durante a fase de trabalho mecânico positivo com uma menor oscilação vertical total e oscilação durante a fase aérea. Conseqüentemente a capacidade de armazenar e re-utilizar energia elástica dos tendões é prejudicada contribuindo para o maior dispêndio energético neste grupo quando comparado com jovens.Para o modelo do custo eletromiográfico (EMG) da caminhada humana criou-se duas abordagens: experimental e teórica. Em ambas as abordagens, informações da atividade EMG de dezesseis músculos, sendo 8 posturais e 8 propulsores foram coletadas e analisadas a partir da integral EMG. A abordagem teórica parece ter uma melhor relação com as evidências experimentais sobre a energética da caminhada humana em inclinações. Os principais mecanismos envolvidos na nova hipótese são i) músculos posturais que não realizam trabalho muscular, exercem uma função importante na determinação do dispêndio energético total e ii) a presente hipótese leva em consideração a co-contração de músculos antagonistas no dispêndioenergético total. Mais experimentos são necessários para confirmar o modelo apresentado neste estudo. Além disso, através de estratégias de otimização e predição linear, um modelo teórico foi delineado a fim de determinar parâmetros mecânicos (comprimento de passada e velocidade de progressão) e energéticos da locomoção terrestre em situações onde as informações disponíveis são apenas a massa e uma curva força de reação vertical versus tempo. Os resultados advindos do modelamento correspondem aos parâmetros determinados experimentalmente. Laboratórios que detenham apenas uma plataforma de força, ou nas áreas onde as informações de entrada do atual modelo sejam as únicas informações (e.g. paleontologia, biomecânica forênsica, etc), a predição de variáveis primárias da locomoção podem ser preditas com razoável acurácia. / Two mechanical models, the inverted pendulum and spring-mass, explain how do the pendular and elastic mechanisms minimizing energy expenditure from muscles during human walking and running. Here, we test two effects that, to our knowledge, do not have yet conclusive responses from literature, specifically the ageing effects on mechanics of human running, and the effect of gradient on walking optimal speed. In order to check the former effect, the ground reaction forces came from a force platform (4m x 0.5m) were used for a later comparison: i) mechanical work, ii) spring-mass parameters and, iii) landing-takeoff asymmetries. The old subjects produce less force during positive work resulting in a smaller overall and aerial vertical oscillation of the centre of mass. Consequently, the potential for restore elastic energy from tendons is reduced contributing to greater energy expenditure than in young subjects. In relation to Electromyographical (EMG) Cost of human walking we created two approaches: experimental and theoretical. In both approaches, information from EMG activity of sixteen muscles, eight postural and eight propulsor were collected and analysed. The theoretical approach seems to fit better with the energy expenditure during gradient walking. The main mechanisms involved in this new hypothesis are i) postural muscles that do not perform muscular work, play an important role in the total energy expenditure and ii) the present hypothesis take the co-contraction into account of the antagonist muscles in the total energy expenditure. Further experiments are necessary to confirm this hypothesis. Besides, using optimization and linear prediction procedures, a theoretical model was designed to estimate mechanical parameters (stride length and velocity of progression) and energetic variables of terrestrial locomotion when available information consists only of mass and one vertical ground reaction force versus time.The results from this modelling are similar to experimentally obtained data. Laboratories with just one force platform, or in areas where the present model’s input information be the unique accessible data (e.g. palaeontology, forensic biomechanics, etc) the prime variables of locomotion may be estimated with reasonable accuracy.

Dois modelos mecânicos, o pêndulo-invertido e o massa-mola, explicam como os mecanismos pendular e elástico minimizam o dispêndio energético advindo dos músculos durante caminhada e corrida humana. A presente tese testa dois efeitos que, para nosso conhecimento, todavia não possuem respostas conclusivas da literatura, nomeadamente o processo de envelhecimento na mecânica da corrida humana e o efeito da inclinação do terreno na velocidade ótima da caminhada. Para estudar o primeiro efeito, as forças de reação do solo provenientes de uma plataforma de força (4m x 0,50m), foram usadas para a posterior comparação de: i) trabalho mecânico, ii) parâmetros do sistema massa-mola e, iii) assimetrias contatodespregue entre jovens e idosos. Os idosos produzem menos força durante a fase de trabalho mecânico positivo com uma menor oscilação vertical total e oscilação durante a fase aérea. Conseqüentemente a capacidade de armazenar e re-utilizar energia elástica dos tendões é prejudicada contribuindo para o maior dispêndio energético neste grupo quando comparado com jovens.Para o modelo do custo eletromiográfico (EMG) da caminhada humana criou-se duas abordagens: experimental e teórica. Em ambas as abordagens, informações da atividade EMG de dezesseis músculos, sendo 8 posturais e 8 propulsores foram coletadas e analisadas a partir da integral EMG. A abordagem teórica parece ter uma melhor relação com as evidências experimentais sobre a energética da caminhada humana em inclinações. Os principais mecanismos envolvidos na nova hipótese são i) músculos posturais que não realizam trabalho muscular, exercem uma função importante na determinação do dispêndio energético total e ii) a presente hipótese leva em consideração a co-contração de músculos antagonistas no dispêndioenergético total. Mais experimentos são necessários para confirmar o modelo apresentado neste estudo. Além disso, através de estratégias de otimização e predição linear, um modelo teórico foi delineado a fim de determinar parâmetros mecânicos (comprimento de passada e velocidade de progressão) e energéticos da locomoção terrestre em situações onde as informações disponíveis são apenas a massa e uma curva força de reação vertical versus tempo. Os resultados advindos do modelamento correspondem aos parâmetros determinados experimentalmente. Laboratórios que detenham apenas uma plataforma de força, ou nas áreas onde as informações de entrada do atual modelo sejam as únicas informações (e.g. paleontologia, biomecânica forênsica, etc), a predição de variáveis primárias da locomoção podem ser preditas com razoável acurácia. / Two mechanical models, the inverted pendulum and spring-mass, explain how do the pendular and elastic mechanisms minimizing energy expenditure from muscles during human walking and running. Here, we test two effects that, to our knowledge, do not have yet conclusive responses from literature, specifically the ageing effects on mechanics of human running, and the effect of gradient on walking optimal speed. In order to check the former effect, the ground reaction forces came from a force platform (4m x 0.5m) were used for a later comparison: i) mechanical work, ii) spring-mass parameters and, iii) landing-takeoff asymmetries. The old subjects produce less force during positive work resulting in a smaller overall and aerial vertical oscillation of the centre of mass. Consequently, the potential for restore elastic energy from tendons is reduced contributing to greater energy expenditure than in young subjects. In relation to Electromyographical (EMG) Cost of human walking we created two approaches: experimental and theoretical. In both approaches, information from EMG activity of sixteen muscles, eight postural and eight propulsor were collected and analysed. The theoretical approach seems to fit better with the energy expenditure during gradient walking. The main mechanisms involved in this new hypothesis are i) postural muscles that do not perform muscular work, play an important role in the total energy expenditure and ii) the present hypothesis take the co-contraction into account of the antagonist muscles in the total energy expenditure. Further experiments are necessary to confirm this hypothesis. Besides, using optimization and linear prediction procedures, a theoretical model was designed to estimate mechanical parameters (stride length and velocity of progression) and energetic variables of terrestrial locomotion when available information consists only of mass and one vertical ground reaction force versus time.The results from this modelling are similar to experimentally obtained data. Laboratories with just one force platform, or in areas where the present model’s input information be the unique accessible data (e.g. palaeontology, forensic biomechanics, etc) the prime variables of locomotion may be estimated with reasonable accuracy.

No description available.