Analysis of the backpack loading efects on the human gait

Gait is a simple activity of daily life and one of the main abilities of the human being. Often during leisure, labour and sports activities, loads are carried over (e.g. backpack) during gait. These circumstantial loads can generate instability and increase biomechanicalstress over the human tissues and systems, especially on the locomotor, balance and postural regulation systems. According to Wearing (2006), subjects that carry a transitory or intermittent load will be able to find relatively efficient solutions to compensate its effects.info:eu-repo/semantics/publishedVersio

Optimisation of performance in the triple jump using computer simulation

While experimental studies can provide information on what athletes are doing, they are not suited to determining what they should be doing in order to improve their performance. The aim of this study was to develop a realistic computer simulation model of triple jumping in order to investigate optimum technique. A 13-segment subject-specific torque-driven computer simulation model of triple jumping was developed, with wobbling masses within the shank, thigh, and torso. Torque generators were situated at each hip, shoulder, knee, ankle, and ball joint. Kinetic and kinematic data were collected from a triple jump using a force plate and a Vicon motion analysis system. Strength characteristics were measured using an isovelocity dynamometer from which torque-angle and torque-angular velocity relationships were calculated. Segmental inertia parameters were calculated from anthropometric measurements. Viscoelastic parameters were obtained by matching an angle-driven model to performance data for each phase, and a common set for the three contact phases was determined. The torque-driven model was matched to performance data for each phase individually by varying torque generator activation timings using a genetic algorithm. The matching produced a close agreement between simulation and performance, with differences of 3.8%, 2.7%, and 3.1% for the hop, step, and jump phases respectively. The model showed good correspondence with performance data, demonstrating sufficient complexity for subsequent optimisation of performance. Each phase was optimised for jump distance with penalties for excessive angular momentum at take-off. Optimisation of each phase produced an increase in jump distance from the matched simulations of 3.3%, 11.1%, and 8.2% for the hop, step, and jump respectively. The optimised technique showed a symmetrical shoulder flexion consistent with that employed by elite performers. The effects of increasing strength and neglecting angular momentum constraints were then investigated. Increasing strength was shown to improve performance, and angular momentum constraints were proven to be necessary in order to reproduce realistic performances

Optimisation of performance in the triple jump using computer simulation

While experimental studies can provide information on what athletes are doing, they are not suited to determining what they should be doing in order to improve their performance. The aim of this study was to develop a realistic computer simulation model of triple jumping in order to investigate optimum technique. A 13-segment subject-specific torque-driven computer simulation model of triple jumping was developed, with wobbling masses within the shank, thigh, and torso. Torque generators were situated at each hip, shoulder, knee, ankle, and ball joint. Kinetic and kinematic data were collected from a triple jump using a force plate and a Vicon motion analysis system. Strength characteristics were measured using an isovelocity dynamometer from which torque-angle and torque-angular velocity relationships were calculated. Segmental inertia parameters were calculated from anthropometric measurements. Viscoelastic parameters were obtained by matching an angle-driven model to performance data for each phase, and a common set for the three contact phases was determined. The torque-driven model was matched to performance data for each phase individually by varying torque generator activation timings using a genetic algorithm. The matching produced a close agreement between simulation and performance, with differences of 3.8%, 2.7%, and 3.1% for the hop, step, and jump phases respectively. The model showed good correspondence with performance data, demonstrating sufficient complexity for subsequent optimisation of performance. Each phase was optimised for jump distance with penalties for excessive angular momentum at take-off. Optimisation of each phase produced an increase in jump distance from the matched simulations of 3.3%, 11.1%, and 8.2% for the hop, step, and jump respectively. The optimised technique showed a symmetrical shoulder flexion consistent with that employed by elite performers. The effects of increasing strength and neglecting angular momentum constraints were then investigated. Increasing strength was shown to improve performance, and angular momentum constraints were proven to be necessary in order to reproduce realistic performances.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Applied Biomechanics: Sport Performance and Injury Prevention

This Special Issue had, as its main objective, the compilation of biomechanical studies on sports performance and its relationship with musculoskeletal injuries. It is a collection of research on eight different sports (soccer, volleyball, swimming, cycling, skiing, golf, athletics, and hockey) considering injuries in general and specific injuries such as hamstring muscle injury, anterior cruciate ligament of the knee, and pain of the pubic symphysis. Additionally, it is noteworthy that most of the studies considered both men and women. Classical biomechanical tools have been used, such as 2D and 3D motion analysis, force platforms, and electromyography

Influence of muscle-tendon unit structure, function, and menstrual cycle phase in dancers’ physical performance

Flexibility and jump are crucial capabilities for dancers but reaching good performance in both is a challenge. Given that muscle-tendon stiffness (SMTU) might affect both these capabilities and that muscle structure and concentration of female hormones across the menstrual cycle may affect SMTU, this thesis aimed to determine the factors that might affect SMTU and, therefore, physical performance in female dancers, especially through the menstrual cycle. A piece of equipment to measure and train flexibility in highly flexible participants was developed and validated. Then, fifteen young adult dance students under oral contraception, eleven dance students without contraception and twenty non-dancers without contraception completed several laboratory-based tests. Participants underwent semitendinosus and rectus femoris ultrasound imaging, flexibility and vertical jump tests including electromyography, kinematics, and pain mixed-method assessment. Participants also provided serum/saliva samples on test days, including ovulatory, follicular and luteal phases. An intervention involving stretching the most flexible limb allowed evaluation of limb asymmetries and impact on function. Results showed no statistical structural and functional differences between dancers and non-dancers. Asymmetries in flexibility, but SMTU, between limbs, were found for all groups. Those asymmetries appear to not influence jump performance. Four-series of passive constant torque stretch was not sufficient to cause or increase any asymmetry or to affect SMTU. Stretching did not change jump height, muscle activation and kinematics of vertical jumps. Dancers presented irregular menstrual cycle with the change in hormone across the phases being associated with changes in key outcome variables. Thus, oestrogen and relaxin appear to be positively correlated to muscle laxity while progesterone is positively correlated to SMTU. This thesis’ results will provide data for the development of training strategies to improve performance and potentially decrease injuries in dancers. Additionally, contributing to research on hormonal factors in female performance and, therefore, women’s health

Relation of muscular contractions to mechanical deformation in the human tibia during different locomotive activities

As one of the major hard tissue in humans and most vertebrates, the skeleton, generally referring to bone, provides the essential frame to support the body and to thus permit locomotion. Considering the functional requirements of bones across different species, e.g. from rats to dinosaurs, or during different growth periods, e.g. from embryo to old age, it is not difficult to conceive that bones adapt to the experienced mechanical environment. In fact, mechanically regulated bone modeling and remodeling is one of the major means to maintain regular bone metabolism. The findings on the bone adaptation to the mechanical environment have been well theorized by Julius Wolff in 1890s [1] as ‘Wolff’s law’ and refined later by Harold Frost as ‘mechanostat’ [2-4]. Evidence from numerous animal studies in the past revealed the adaptation process of the bones to the well-defined artificial mechanical environment and suggested certain relationship between the adaptation in relation to the types of loading, e.g. loading amplitude, loading cycle, loading frequency and so on [5-8]. Conversely, bone degradation was generally observed during disuse, e.g. prolonged bed rest [9], or in the microgravity environment during space flight [10]. Indeed, the best way to further our understanding in this adaptation process is to quantitatively study the mechanical loading on bone during daily locomotor activities. However, this is still rather challenging due to technical difficulties. More importantly, the mechanical load on bones can vary greatly across individuals or species, as the variance between the body size, locomotor pattern and speed

The effect of joint compliance within rigid whole-body computer simulations of impacts

In high impact human activities, much of the impact shock wave is dissipated through internal body structures, preventing excessive accelerations from reaching vital organs. Mechanisms responsible for this attenuation, including lower limb joint compression and spinal compression have been neglected in existing whole-body simulation models. Accelerometer data on one male subject during drop landings and drop jumps from four heights revealed that peak resultant acceleration tended to decrease with increasing height in the body. Power spectra contained two major components, corresponding to the active voluntary movement (2 Hz 14 Hz) and the impact shock wave (16 Hz 26 Hz). Transfer functions demonstrated progressive attenuation from the MTP joint towards the C6 vertebra within the 16 Hz 26 Hz component. This observed attenuation within the spine and lower-limb joint structures was considered within a rigid body, nine-segment planar torque-driven computer simulation model of drop jumping. Joints at the ankle, knee, hip, shoulder, and mid-trunk were modelled as non-linear spring-dampers. Wobbling masses were included at the shank, thigh, and trunk, with subject-specific biarticular torque generators for ankle plantar flexion, and knee and hip flexion and extension. The overall root mean square difference in kinetic and kinematic time-histories between the model and experimental drop jump performance was 3.7%, including ground reaction force root mean square differences of 5.1%. All viscoelastic displacements were within realistic bounds determined experimentally or from the literature. For an equivalent rigid model representative of traditional frictionless pin joint simulation models but with realistic wobbling mass and foot-ground compliance, the overall kinetic and kinematic difference was 11.0%, including ground reaction force root mean square differences of 12.1%. Thus, the incorporation of viscoelastic elements at key joints enables accurate replication of experimentally recorded ground reaction forces within realistic whole-body kinematics and removes the previous need for excessively compliant wobbling masses and/or foot-ground interfaces. This is also necessary in cases where shock wave transmission within the simulation model must be non-instantaneous