The purpose of this study was to compare the shoulder resultant joint moment (RJM) during a shoulder internal rotator exercise using elastic resistance employing four different movement strategies and two different starting elastic strains. Methods: Ten subjects aged 27.4 ± 2.6 yr (5 female and 5 male) with no previous shoulder pathology performed four sets of six repetitions of shoulder rotation though 180° using elastic resistance (Thera-Band® elastic band, blue) during two acceleration (medium and low) and two cadence (2s:2s, <1s:1s) strategies at 0% elastic starting strain. The acceleration movement strategies were also performed with starting strain of 30%. A mathematical model using Newtonian mechanics was used to compute the RJM. Elastic band recoil force was measured with a force transducer. Forearm acceleration was determined by a miniature uniaxial accelerometer secured at the wrist. Electrogoniometer data were collected to determine the range of motion (ROM) as well as the angle between the forearm and band which was used to determine elastic moment arm. Paired t-tests were used to identify joint angle specific RJM differences between conditions. Results: Angle specific comparisons revealed that RJM in the moderate acceleration movement strategy was significantly different from RJM in the low acceleration movement strategy through 150° (83%) of range of motion (p<0.05). Shoulder RJM was up to 111% higher in the moderate acceleration strategy (P < 0.01). Angle specific comparisons revealed RJM in the <1:1 cadence strategy was significantly different from RJM in the 2:2 cadence through 108° (60%) of the range of motion (p<0.05). RJM was up to 47% higher in the <1:1 cadence (p<0.01). RJM in the low acceleration strategy was significantly greater with 30% elastic start strain relative to 0% elastic start strain through 180º of angular excursion (p<0.001). The pattern and magnitude of neuromuscular loading was significantly different in higher acceleration movement strategies (moderate acceleration and fast cadence). Conclusions: These findings indicate that differential limb acceleration as a result of movement strategy significantly affects shoulder load during elastic resistance exercise. The pattern and magnitude of load was different in each movement strategy and could result in differential neuromuscular adaptation through training. Clinicians and exercise professionals should consider movement strategy/acceleration as an important factor when prescribing elastic resistance exercise for safety and efficacy. / October 2006

The purpose of this study was to compare the shoulder resultant joint moment (RJM) during a shoulder internal rotator exercise using elastic resistance employing four different movement strategies and two different starting elastic strains. Methods: Ten subjects aged 27.4 ± 2.6 yr (5 female and 5 male) with no previous shoulder pathology performed four sets of six repetitions of shoulder rotation though 180° using elastic resistance (Thera-Band® elastic band, blue) during two acceleration (medium and low) and two cadence (2s:2s, <1s:1s) strategies at 0% elastic starting strain. The acceleration movement strategies were also performed with starting strain of 30%. A mathematical model using Newtonian mechanics was used to compute the RJM. Elastic band recoil force was measured with a force transducer. Forearm acceleration was determined by a miniature uniaxial accelerometer secured at the wrist. Electrogoniometer data were collected to determine the range of motion (ROM) as well as the angle between the forearm and band which was used to determine elastic moment arm. Paired t-tests were used to identify joint angle specific RJM differences between conditions. Results: Angle specific comparisons revealed that RJM in the moderate acceleration movement strategy was significantly different from RJM in the low acceleration movement strategy through 150° (83%) of range of motion (p<0.05). Shoulder RJM was up to 111% higher in the moderate acceleration strategy (P < 0.01). Angle specific comparisons revealed RJM in the <1:1 cadence strategy was significantly different from RJM in the 2:2 cadence through 108° (60%) of the range of motion (p<0.05). RJM was up to 47% higher in the <1:1 cadence (p<0.01). RJM in the low acceleration strategy was significantly greater with 30% elastic start strain relative to 0% elastic start strain through 180º of angular excursion (p<0.001). The pattern and magnitude of neuromuscular loading was significantly different in higher acceleration movement strategies (moderate acceleration and fast cadence). Conclusions: These findings indicate that differential limb acceleration as a result of movement strategy significantly affects shoulder load during elastic resistance exercise. The pattern and magnitude of load was different in each movement strategy and could result in differential neuromuscular adaptation through training. Clinicians and exercise professionals should consider movement strategy/acceleration as an important factor when prescribing elastic resistance exercise for safety and efficacy.

The purpose of this study was to compare the shoulder resultant joint moment (RJM) during a shoulder internal rotator exercise using elastic resistance employing four different movement strategies and two different starting elastic strains. Methods: Ten subjects aged 27.4 ± 2.6 yr (5 female and 5 male) with no previous shoulder pathology performed four sets of six repetitions of shoulder rotation though 180° using elastic resistance (Thera-Band® elastic band, blue) during two acceleration (medium and low) and two cadence (2s:2s, <1s:1s) strategies at 0% elastic starting strain. The acceleration movement strategies were also performed with starting strain of 30%. A mathematical model using Newtonian mechanics was used to compute the RJM. Elastic band recoil force was measured with a force transducer. Forearm acceleration was determined by a miniature uniaxial accelerometer secured at the wrist. Electrogoniometer data were collected to determine the range of motion (ROM) as well as the angle between the forearm and band which was used to determine elastic moment arm. Paired t-tests were used to identify joint angle specific RJM differences between conditions. Results: Angle specific comparisons revealed that RJM in the moderate acceleration movement strategy was significantly different from RJM in the low acceleration movement strategy through 150° (83%) of range of motion (p<0.05). Shoulder RJM was up to 111% higher in the moderate acceleration strategy (P < 0.01). Angle specific comparisons revealed RJM in the <1:1 cadence strategy was significantly different from RJM in the 2:2 cadence through 108° (60%) of the range of motion (p<0.05). RJM was up to 47% higher in the <1:1 cadence (p<0.01). RJM in the low acceleration strategy was significantly greater with 30% elastic start strain relative to 0% elastic start strain through 180º of angular excursion (p<0.001). The pattern and magnitude of neuromuscular loading was significantly different in higher acceleration movement strategies (moderate acceleration and fast cadence). Conclusions: These findings indicate that differential limb acceleration as a result of movement strategy significantly affects shoulder load during elastic resistance exercise. The pattern and magnitude of load was different in each movement strategy and could result in differential neuromuscular adaptation through training. Clinicians and exercise professionals should consider movement strategy/acceleration as an important factor when prescribing elastic resistance exercise for safety and efficacy.

The purpose of this study was to compare joint moments during the active peak vertical ground reaction force (PVGRF) when running in three conditions. Twenty-five subjects, sixteen male and nine female, were measured using 3-dimensional motion analysis while running barefoot, in Vibram FiveFingers® (VF®) minimalist running shoes and in traditional running shoes at a 7-minute-mile pace (3.84 m/s). Joint moment differences were calculated and compared using a mixed model analysis of variance. Results showed the VF® was effective at mimicking both the kinetic and kinematic attributes of barefoot running. The only significant difference found when comparing barefoot and VF® running was in the ankle angle (p < .005). All other variables in the lower extremity were the same for the two conditions. Though the subjects in our study had no previous experience with VF® (or barefoot) running they were able to closely mimic barefoot running upon initial running trials. Joint moments at the ankle were higher for barefoot and VF® running (p < .001) when compared with shod running. This may potentially lead to a greater risk of injury at the ankle joint when running barefoot or in VF®. The hip joint moments were only different when comparing the barefoot condition to the shod condition (p=.002), with the barefoot condition higher than shod running. The knee joint moment was smaller during the VF® and barefoot conditions when compared with shod running (p < .001) and may lead to a decrease in injury rates at the knee. Though a reduction in moments of the lower extremity may lead to a decrease of injury at the corresponding joint, it is important to consider the adaptations that take place as a result of varying stresses. According to Wolff's law, bone and surrounding tissue will adapt to the loads it is placed under. Taking this into consideration, it is important to remember that lower moments may lead to weaker bones and surrounding tissues and without compensation for these reduced loads, injury rates may remain the same over time.

The objective of the proposed study was to perform three-dimensional (3D) inverse dynamics analysis to determine lower extremity (ankle, knee and hip) joint moments on previously collected slip perturbation experimental data. In addition, the aging effect on the joint moment generation in both normal walking and reactive-recovery conditions was examined. Dataset collected during previous slip and fall experiments, which were conducted in a typical gait analysis setting, were analyzed in current study. All the participants were subjected to the screening criteria, which defined the successful reactive-recovery (i.e. non-fall trials) based on slip distance, sliding heel velocity, whole body COM velocity, and motion pictures. Nine young and nine old healthy participants, who were identified possessing representative trials, were involved as participants in current study. A local coordinate system was constructed on each joint and each segment of the lower extremity based on available landmarks using the Gram-Schmidt orthogonalization algorithm. 3D inverse dynamics was implemented to obtained lower extremity joint moments. Magnitude and timing of obtained joint moment patterns during stance phase were subjected to one and two-way analysis of covariance (ANCOVA) with walking velocity as covariate. The aging effect and gait condition effect were evaluated. Increases in peak joint moment, peak joint power, and joint moment generation ratio were detected in successful reactive-recovery. Distinct age-related joint moment generation strategy was observed through findings of peak joint moment ratio and joint moment generation rate. The elderly, who were able to reactive recover, were found to be as rapid as their younger counterparts in terms of initiating and developing reactive joint moment. It was concluded that ankle joint was critical in balance recovery while hip joint assumed the major responsibility of balance maintenance of upper body during successful reactive-recovery. Increased demand on muscle strength during balance recovery lead to the distinct joint moment generation strategy adopted by the elderly, and confirmed the necessity of lower extremity strength training. In addition, implementation of 3D joint moment analysis was justified in current study and was suggested in future slip and fall researches. / Master of Science

Ce travail doctoral a pour objectif de mettre en place des méthodes permettant de quantifier les efforts subits par le nageur avec palme, lors de la pratique de 3 activités (Natation, Randonnée Aquatique et Body-Board). Pour ce faire, un modèle utilisant des procédures de dynamique inverse a été mis en place. Dans la première phase de cette étude, la cinématique tridimensionnelle des 3 segments du membre inférieur gauche a été analysée. Il en résulte 3 cinématiques fondamentalement différentes. Avec un modèle type Bottum-Up, la mesure d’efforts distaux est nécessaire. Un robot palmeur a donc été développé, afin de reproduire la cinématique du pied pour chacune des ces pratiques et ainsi permettre une mesure fiable des forces et moments au centre articulaire de la cheville. Ainsi, nous avons quantifié via le modèle, les moments au genou et à la hanche. Ainsi, via le robot nous pouvons quantifier l’effet d’un design de palme sur les efforts subit par l’utilisateur à la cheville, et s’assurer par le modèle que les efforts ne sont pas répercutés sur le genou ou la hanche. En plus de cette étude biomécanique, une analyse de l’activité musculaire a été réalisée sur les principaux muscles moteurs du membre inférieur, pour différentes cinématiques et différents designs de palme. Les résultats nous ont prouvé que le design de la palme a un effet non uniforme sur l’ensemble des muscles, et que pour chacune des pratiques, les demandes musculaires ne sont pas similaires. / The present work had in objective to develop some methods to quantify the joint torque endured by a fin swimmer during is activity for 3 sports (Swimming, Snorkeling, Body-Board). In this way, a model using inverse dynamic methods has been done. During the first step of this study, the 3D kinematic of each activity was mad on the 3 segments of the lower limbs, and this allows defining 3 specifics motions. For a Bottom-Up model, a forces measurement on distal segment is needed to make the calculation. So, a swimming fin robot has been develop to reproduce the foot kinematics for each activity and measure all forces and torques on the ankle joint. By this way, with all this inputs, by the model we can quantify the demands on knee and hip. With this robot, we measure the effect of design modification on muscular request on the joint ankle, and by the model we assure torques are not postpone on knee or hip. In addition to this biomechanical study, a muscular activities study has been realise on the main muscle, and this for different kinematics and different fin blade shapes. The results acknowledge that the fin designs differentiate the effect on specific muscles, and that for each activity the muscular requests are not the same.

The obesity is a dysfunction that is increasingly concerned with its indexes in Brazil and in the world. Population research has registered an alarming increase in the incidence of obesity in Brazil, some surveys indicate that more than 50% of the population is overweight. Obesity is a chronic and interrelated disease directly or indirectly with other pathological situations. Clinically, obesity is associated with numerous health problems. Excess weight is also associated with orthopedic problems due to overload in the musculoskeletal system, is an important contributor to the development of knee varus / valgus in children and associated with increased risk of osteoarthritis of the knee. Overweight and obese children tend to remain obese in adulthood and are more likely to develop comorbidities at earlier ages. For the biomechanical analysis it is necessary to describe and calculate the forces that produce the movement. The moment of strength characterizes the sum of the forces of muscles, tendons, ligaments and bones that are acting internally to counter external forces acting on our body. The objective of this study was to analyze the articular moments in lower limbs of obese children during walking at different speeds. The study group consisted of 16 individuals, aged 8 to 10 years, male and / or female, volunteers, Being divided into two subgroups: overweight group and normal weight group. To evaluate the average speed, Cefise brand photocells were used, the fast speed was established as 30% above the average value of the selected auto speed. For gait evaluation, the VICON three-dimensional cinemetry system (model 624, Oxford, UK) was used with the VICON NEXUS 1.8.5 software. This system consists of seven infrared cameras (MX cameras) that operated at a frequency of acquisition of 200 Hz, recognizing in real time the reflective markers of 14 mm of diameter positioned in the subject, using the model in. For the acquisition of the kinetic data, two AMTI OR6-6-2000 force platforms (Advanced Mechanical Technologies, Inc.) were used, with a sampling rate of 200 Hz. The kinetic data were collected synchronously to the kinematic data for the calculation Of the resulting articular moments. The results revealed that individuals walking at rapid speed showed a significant increase in hip flexion, knee extension and abduction moment peaks and dorsiflexion. It is concluded that walking speed interferes in the joint mechanics, specifically in the articular moments, of the lower limbs of children. It was observed that walking at a rapid rate increases joint moments and with increasing peaks of joint moments, there may be an increase in joint load, and a higher risk of injury in overweight children. / A obesidade é uma disfunção que preocupa cada vez mais pelos seus índices no Brasil e no mundo. As pesquisas populacionais têm registrado um alarmante aumento na incidência de obesidade no Brasil, alguns levantamentos apontam que mais de 50% da população está acima do peso. A obesidade é uma doença crônica e inter-relacionada direta ou indiretamente com outras situações patológicas. Clinicamente, a obesidade está associada a inúmeros problemas de saúde. O excesso d peso também está associado com problemas ortopédicos devido à sobrecarga no sistema musculoesquelético, é um importante contribuinte para o desenvolvimento de varo/valgo de joelho em crianças e associada ao aumento do risco de osteoartrite do joelho. As crianças com sobrepeso e obesidade tendem a permanecer obesos na idade adulta e são mais propensas a desenvolver em idades mais precoces as comorbidades. Para a análise biomecânica são necessários a descrição e o cálculo das forças que produzem o movimento. O momento de força caracteriza o somatório das forças dos músculos, tendões, ligamentos e ossos que estão agindo internamente para opor as forças externas que agem sobre o nosso corpo. O objetivo deste estudo foi analisar os momentos articulares em membros inferiores de crianças obesas durante a marcha em diferentes velocidades O grupo estudado foi composto por 16 indivíduos, com idade de 8 a 10 anos de idade, dos sexos masculino e/ou feminino, voluntários, sendo dividido em dois subgrupos: grupo excesso de peso e grupo peso normal. Para avaliar a velocidade média foram utilizadas fotocélulas da marca Cefise, a velocidade rápida foi estabelecida como 30% acima do valor da média da velocidade auto selecionada. Para a avaliação da marcha, foi utilizado o sistema de cinemetria tridimensional VICON (modelo 624, Oxford, Reino Unido), com o software VICON NEXUS 1.8.5. Este sistema é constituído de sete câmeras infravermelho (MX câmeras) que operaram a uma frequência de aquisição de 200 Hz, reconhecendo em tempo real os marcadores reflexivos de 14 mm de diametro posicionados no sujeito, utilizando o modelo pulg in gait. Para a aquisição dos dados cinéticos, foram utilizadas duas plataformas de força AMTI OR6-6-2000 (Advanced Mechanical Technologies, Inc.), com taxa de amostragem de 200 Hz. Os dados cinéticos foram coletados de forma sincronizada aos dados cinemáticos para o cálculo dos momentos articulares resultantes. Os resultados revelaram que os indivíduos quando caminharam em velocidade rápida apresentaram significativo aumento dos picos de momento de flexão de quadril, extensão e abdução do joelho e dorsiflexão. Conclui-se que a velocidade de caminhada interfere na mecânica articular, especificamente nos momentos articulares, do membro inferior de crianças. Constatou-se que caminhar em velocidade rápida aumenta os momentos articulares e com o aumento dos picos de momentos articulares, pode haver um aumento de carga nas articulações, e maior risco de lesões em crianças com excesso de peso.

Ankle sprains are one of the most common injuries within athletics in the United States with approximately one-million student athletes experiencing ankle sprains each year. Studies argue excessive or rapid ankle inversion occurring from jump landings may cause ankle sprains. Also, the effect of limb dominance on risk of ankle sprain is not well documented. The aim of this study was to determine if there is an affect of leg dominance on landing mechanism of the ankle joint that predisposes either ankle joint to greater risk of ankle sprain. Twelve recreationally active subjects were recruited and completed four maximal vertical jumps. Ground reaction force, marker position data and maximal vertical jump height were collected using two Bertec Force plates, a 10-camera motion capture system, and a Vertec Vertical Jump Trainer, respectively. Cortex and Visual3D software programs were used to process the motion capture data and to calculate peak vertical ground reaction forces(vGRF), loading rate, and ankle joint moments. There were no statistically significant differences in ankle joint moment or loading rate between limbs, but peak vGRF were significantly higher (p < 0.05) in the non-dominant ankle. The results suggest the non-dominant ankle displays higher injury potential, as the non-dominant leg accumulates a larger peak landing force.

Introduction: Asymmetric gait is prevalent among older adults as well as in people with gait pathologies (e.g., Parkinson’s disease, following a stroke) and has been linked to a higher risk of falls. While a certain level of gait asymmetry is present in healthy young adults, the simulation of larger asymmetry in this population provides information about efficient strategies to regulate dynamic stability. Research investigating gait asymmetry has described spatiotemporal and kinematic strategies. However, limited information is available regarding changes in gait kinetics. Research objectives: This thesis aims to determine the gait control strategies utilized by young adults to regulate simulated gait asymmetry combined with different arm movement amplitude. We hypothesized that the hip joint would be the most affected by different arm swing conditions and asymmetric gait. We also hypothesized that asymmetric gait and active arm swing would lead to increased variability in the lower-limb movements. Methods: Fifteen healthy young adults (23.4±2.8 years, 7 Females) walked with three arm swing conditions (held, normal, and active) during symmetric and asymmetric walking conditions. The CAREN-extended System (Motek Medical, Amsterdam, NL) was used for data collection. Outcome measures included step length and width mean and variability (meanSD), vertical ground reaction forces, and lower-limb joint moment impulse mean and variability (meanSD) in the sagittal and frontal planes. Results: When comparing arm swing conditions, the active arm swing led to an increase in step width variability, vertical ground reaction forces, hip and knee variability in the sagittal plane, ankle abduction moment for the fast leg, as well as in knee variability in the frontal plane. As for gait symmetry, the asymmetric condition led to increased step width for the fast and slow legs and increased vertical ground reaction forces for the slow leg. The asymmetric condition further prompted adjustments in the frontal and sagittal planes, particularly at the ankle and hip joints during the braking phase, and in the knee joint during the propulsion phase phases when compared to the symmetric walking condition. Conclusion: Findings suggest that participants increased hip activity to control the effect of arm motion on the trunk to minimize adaptations in the lower-limb joints. The asymmetry condition demonstrated that participants searched for flexible lower-limb strategies aimed at minimizing bilateral differences between the fast and slow legs during asymmetric walking.

No description available.