A critical review of studies related to the modelling of the human locomotor system is given. Kinematic and dynamic modelling and analysis of the pelvis-leg apparatus as an ensemble of four rigid body segments are described. Experiments were performed on two patients with custom-made instrumented massive proximal femoral prostheses implanted after tumour resection. Telemetered axial forces transmitted along the prostheses, together with kinematic, force plate and electromyographic data, were recorded synchronously during level walking, single and double leg stance, and isometric tests of the hip muscles. A sagittal plane model of the locomotor system, with an anatomical model of the knee joint, was developed from an existing model and used for a comparative study of methods for the calculation of the internal forces. A three-dimensional computer graphics-based animated model of the locomotor system was developed, with the hip as a ball-and-socket joint, the knee as a parallel spatial mechanism and the ankle as a two-hinge complex. Thirty-four muscles or muscle groups were included. A method for the determination of the orientation of multi-joint systems from surface markers was developed to take account of measurement errors including skin movement artefacts. Both the 2D and 3D models of the locomotor system were evaluated and validated quantitatively with the telemetered femoral axial forces. It is concluded that (a) a significant part of the bending moments along limbs are transmitted by a combination of tensile forces in muscles and compressive forces in bones so that moments transmitted by the bones are much less than the limb moments, (b) bi-articular muscles play a major role in modulating forces in bones, (c) appropriate simulation of muscle forces is important in experimental or theoretical studies of load transmission along bones, (d) computer graphics-based modelling and animation are important tools in bridging the gap between clinical users and biomechanists.

M.Tech. (Chiropractic) / Problem Statement: Ankle sprains are one of the most common acute injuries treated by physicians (Pellow & Brantingham, 2001). Most ankle sprains involve the lateral ankle ligaments, with the anterior tibiotalar ligament being the most commonly affected in injuries involving plantarflexion and inversion. These injuries often result in restriction of movements that will limit gait (Crosbie, Green, Refshauge, 1999). Even in the event of injury to one ankle, the sensorimotor and postural deficits can be bilateral due to central processing of motor control information (Munna et. al., 2010, Monaghan et. al., 2006). The primary aim of a chiropractic adjustment is to increase joint range of motion (Fryer, Mudge, McLaughlin, 2002) and to correct local joint dysfunction (Pellow & Brantingham, 2001). No prior research has been done using the Zebris FDM-system to analyze changes in gait after ankle adjustment. Method: Sixty participants between the age of 15 and 45 years were recruited. The participants were asked to sign a consent form after which a thorough case history, full physical exam and foot and ankle regional examination were performed. Participants were included in the study if they were of the correct age, had a chronic history of minor ankle sprain and had palpable motion restrictions of ankle joint range of motion. Participants were excluded if they had a history of severe ankle injury or ankle surgery, had any contraindications to chiropractic adjustment or were currently undergoing any other treatment that could interfere with the study, including the use of certain medications. Each participant underwent a gait assessment before and after they received a chiropractic adjustment to the restricted ankle joint. Procedure: Objective measurements were obtained using the Zebris FDM-system before and after participants received one chiropractic adjustment using a long axis distraction technique. The Zebris FDM-system uses capacitive force sensors arranged on a platform in a high density. The measuring plate allows dynamic force distribution to be analysed during gait. The length of the Zebris platform allowed successive footfalls to be captured and measurements taken during three full gait cycles were used in the analysis. All data was processed using the WinFDM program to produce a gait report (Zebris Medical GmbH, 2008) Results: A statistically significant change was seen in the single support line on the non-adjusted side. Changes were measured in the other gait parameters although they were not statistically significant. Conclusion: This study has shown that chiropractic adjustment of the ankle joint has an effect on the path of centre of pressure and foot rotation during gait. It also helps clinicians to see that the adjustment has a bilateral effect. Future studies will be able to determine whether this is a positive or a negative outcome as the limits of normal and pathological gait using these parameters have not yet been set. Chiropractors can treat patients with a history of chronic ankle sprain more effectively if they have a better understanding of residual motion restrictions and movement patterns after acute ankle sprain. A future study including several treatments could be beneficial as clinical chiropractic practice would most likely involve more than one treatment of a patient with a history of ankle sprain. In this way the lasting and accumulative effects of chiropractic adjustment could be measured.

Patients with lower limbs problems are an increasing population in the US and many of them require surgery and its subsequent post-op Physical Therapy (PT). For all these patients, tracking their progress and evolution towards full recovery is very important. To assess the patients and track their progress, patients are usually required to perform very specific tests administered by a physical therapist. These tests either require very expensive equipment or rather require the subjective experience of the physical therapist who administer them. One of these tests is the Functional Gait Assessment (FGA) test, perhaps the most widely adopted one for gait assessment. This thesis presents a system for Clinical Gait Assessment using exclusively the sensors embedded in today’s smartphones. The system processes the raw sensor data to perform the FGA test and calculate additional metrics, capable of identifying problems in the human gait. The system is therefore objective, as it is based on measurements; cheap, as it only requires a smartphone; mobile, as it can be used pretty much anywhere; and self-care, as it does not need the presence of a physical therapist. The system was designed and tested on the Android OS with the phone attached to the back of the user using a belt or elastic band. It includes a new step detection algorithm with a mean absolute error of ±1 and algorithms to detect the deviation from a straight path with an accuracy of 90%, 80%, 35%, and 30% for each of the required deviation levels of the FGA test. Additionally, the system includes autocorrelation and DTW metrics, which provide additional information to detect different impediments of the user gait.

No description available.

The aim of this study was to determine the combined effects of high-heeled shoes and load carriage on gait and posture adaptation. Furthermore, the adaptation of gait and posture to the combined two conditions was examined by a comparison of the measured parameters between experienced and novice groups. 30 participants underwent a quantitative measurement of temporospatial, kinematic, and kinetic parameters of hip, knee, and ankle on both loaded and unloaded limbs using 3D motion analysis. Double support time and stride length increased during high-heeled gait and the magnitude of alteration was greater with a load. Increased plantarflexion was main cause of raised heel. Ankle plantarflexor moment increased with high-heeled but decreased with load carriage. As a result, plantarflexor moment diminished, in addition knee extensor moment exaggerated further. Hip extensor moment increased with heel height but not with load weight, however, hip angle was affected only by the load.

With the popularity of outdoor activities like hiking, the demands of certain types of employment, or being a student, an individual’s ability to carry a load is an important mobility consideration. By understanding the changes to an individual’s gait when supporting a backpack load, an individual’s ability to carry heavy loads for prolonged periods could be improved. Most biomechanical studies have examined the changes in able-bodied gait when carrying a load. However, research is lacking on the effect of backpack loads on amputee gait patterns. This project examined the effects of a backpack load on the gait patterns of unilateral transtibial amputees. Ten participants performed walking trials on four surfaces (level ground, uneven ground, walking up an incline, and walking down an incline), without a pack and with a pack. A total of 40 trials were collected per subject, with 10 trials collected on each surface. Three-dimensional motion data were collected with an eight-camera Vicon Motion Analysis system to describe limb motion as well as compare kinematic outcomes between tasks and conditions. Force platform data were collected during the level ground trials and used to calculate kinetic measures for both limbs. With the addition of the pack changes were seen on each surface, with different changes occurring to each limb. The ramp up surface created the most changes when comparing the two conditions. The only change seen across all four surfaces was a decrease in ankle dorsiflexion before push-off on the prosthetic limb. The two next most common changes were increases in knee and hip flexion during weight-acceptance.

Background: Declines in gait velocity, stride length, cadence, and postural stability are common with advancing age and have further been linked to heightened fall risk and functional decline. Physical activity can slow or prevent such gait declines in older adults. In young adults, Nordic walking (NW) training has been shown to increase stride length and gait speed, yet has demonstrated inconsistent findings regarding joint loading, with reports of both increases and decreases in this respect. Further, research of this facet has very minimally been examined as it pertains to older adults. Purpose: The aim of the present study was to determine both the initial effect, and the prolonged effect following an 8-week intervention, of Nordic walking (NW) on older adult gait performance and postural alignment and stability. Methods: Gait and postural alignment and stability during NW and conventional walking were assessed and compared following an 8-week NW program (2x/week) in 12 healthy older adults (age: 68 ± 6.8 years; 8 female, 4 male). Participants performed six 5m walking trials, 3 with poles and 3 without, followed by two 6 Minute Walk Test (6MWT) trials, one with poles (WP) and the other without (NP). Gait characteristics and trunk measures in the sagittal and frontal planes were quantified using a 6 inertial sensor accelerometry system (APDM, Oregon, USA) as well as an eight camera 3-dimensional motion capture system (Vicon, Oxford, UK) with 2 force platforms (Kistler, Winterthur, Switzerland) embedded within. All variables were assessed using two-way repeated measures ANOVAs to compare NW to conventional walking and before and after the intervention. Results: When comparing walking WP to NP at initial pre-testing, significantly longer stride length, slower gait speed, and increased double support time were found to coincide with decreases in power generation and absorption at the hip and knee WP. However, following prolonged practice, a longer stride length, faster gait speed, and increased power generation at pre-swing at the hip and power absorption during loading and terminal swing about the knee were found WP post-intervention. Conclusions: An initial 8-week training period is necessary for novice NW in order to develop technique and to restore gait and postural alignment to more “normal” standards following training. Additionally, since the acquisition of the skill requires proper allocation of attention between two tasks: walking and pole manipulation, NW should be done so in a relatively safe environment, free of distraction and obstacles. Finally, with frail elderly, a longer acquisition period may be necessary since facilitation of movement must first occur.

At an early age, i.e., up to about 1-2 years, humans learn to walk and subsequently develop a robust and flexible gait. This is learned by repetitively taking similar steps and the experience is stored in the muscle/reflexive memory. Over the last 30 years, a variety of humanoid bipedal robots have been developed to copy the human gait. However, walking/locomotion is still a relatively difficult control problem due to its complex hybrid nature because of non-smooth dynamics. Although, simple walking comprises of single support in which one leg swings forward, then it impacts with ground for a brief double support phase and further transition of the other support leg to start a new swing. The steps are repeated again and again in a similar manner for walking over an even surface. As the swinging leg strikes the ground, it is a non-linear impact which poses a challenge since it causes non-zero initial state errors for each step which depend on the error in the gait at last moment for previous step. The usual bipedal control relies on complex techniques based on inverse kinematics, ZMP (Zero-Moment Pole) and COP (Centre Of Pressure) to generate the required control inputs for the joints. However, a basic cognitive assumption is that walking is a relatively simple task which can be learned and the biological systems have achieved it by simple repetitions. This has been over-looked in these control techniques. In the past, ILC has been proposed to solve the repetitive learning problems. The Iterative Learning Controller learns to generate the desired set of input signals to compensate for the output tracking errors in a sequential manner such that in the initial iterations, the signals values at earlier time indices have faster rate than the later ones. So, at the last time index the convergence is achieved after all the earlier ones. ILC learns/adapts the joint control for repetitive gaits. In this thesis it has been proposed to be used as a muscle memory where control signals are learnt for a repetitive batch. Thus, ILC equates to “learning a sequence of action by muscles”. Due to the transfer of state error in a cyclic manner from the end of a previous step/repetition to the recent step/repetition, the convergence has to be established in joint control and state space. Similar is the case of continuous walking where the ground impacts transfer part of the error in the gait to the start of a new step representing an impacting Cyclic ILC scenario. Hence, the ILC problem is changed from finite to an infinite horizon. The second problem occurs with the non-constant length of the iteration due to change in step size. The two scenarios have been considered: Firstly, when the control input is updated using ILC with identical initial conditions at the start of each repetition. Secondly, control input update under varying initial conditions leading to Cyclic ILC. The batch to batch evolution of control inputs at each sample time within a batch is formulated. The sequential convergence of control input generated by ILC algorithms has been investigated. The exact relationship for the rate of convergence of the control input has been formulated down to the sample-time level. This provides deeper insight about the ILC algorithms and hence exact factors affecting the convergence could be established. Limits of the learning process have been clearly demonstrated as well. Although, simpler D-ILC converges for zero initial error but for cyclic non-zero initial errors, it has offset error which corresponds to the initial state error. With proportional part, the PD-ILC algorithm has eliminated the offset error which has been illustrated for a damped pendulum and further implemented to bipedal locomotion. For reasons of energy efficiency, passive dynamics has been chosen for the compass gait model of the biped. The walking problem for the compass gait robot has been solved using the modified PD-ILC which utilizes the acceleration error term as well. The steady gait has been achieved for the compass gait robot on flat surface which has been verified by the phase portraits.

The objective of this thesis is to develop and validate a computational framework based on mathematical models for the motion prediction and dynamic stability quantification of human walking, which can differentiate the dynamic stability of human walking with different mechanical properties of the leg. Firstly, a large measurement database of human walking motion was created. It contains walking measurement data of 8 subjects on 3 self-selected walking speeds, which 10 trials were recorded at each walking speed. The motion of whole-body centre of mass and the leg were calculated from the kinetic-kinematic measurement data. The fundamentals of leg property have been presented, and the parameters of leg property were extracted from the measurement data of human walking where the effects of walking speed and condition of foot-ground contact were investigated. Three different leg property definitions comprising linear axial elastic leg property, nonlinear axial elastic leg property and linear axial-tangential elastic leg property were used to extracted leg property parameters. The concept of posture-dependent leg property has been proposed, and the leg property parameters were extracted from the measurement data of human walking motion where the effects of walking speed and condition of foot-ground contact were also investigated. The compliant leg model with axial elastic property (CAE) was used for the dynamic stability analysis of human walking with linear and nonlinear axial elastic leg property. The compliant leg model with axial and tangential elastic property (CATE) was used for that with linear axial-tangential elastic leg property. The posture - dependent elastic leg model (PDE) was used for that with posture-dependent leg property. It was found that, with linear axial elastic leg property, the global stability of human walking improves with the bigger touchdown contact angle. The average leg property obtained from the measurement data of all participants allows the maximum global stability of human walking. With nonlinear axial elastic leg property, the global stability decreases with the stronger nonlinearity of leg stiffness. The incorporation of the tangential elasticity improves the global stability and shifts the stable walking velocity close to that of human walking at self-selected low speed (1.1-1.25 m/s).By the PDE model, the human walking motions were better predicted than by the CATE model. The effective range of walking prediction was enlarged to 1.12 – 1.8 m/s. However, represented by PDE model, only 1-2 walking steps can be achieved. In addition, the profiles of mechanical energies represented by the PDE model are different from that of the orbital stable walking represented by CATE model. Finally, the minimal requirements of the human walking measurements and the flexibility of simple walking models with deliberate leg property definitions allow the computational framework to be applicable in the dynamic stability analysis of the walking motion with a wide variety of mechanical property of the leg.

Understanding why fish move the way in which they do has applications far outside of biology. Biological propulsion has undergone millions of years of refinement, far outpacing the capabilities of anything created by man. Research in the areas of unsteady/biological propulsion has been increasing in the last several decades with advances in technology. Researchers are currently conducting experiments using pitching and heaving airfoils, mechanized fish, and numerical fish. However, the surrogate propulsors that are being used in experiments are driven analytically, whereas in this study, a method has been developed to exactly follow the motion of swimming fish. The research described in this thesis couples the image analysis of swimming fish with computational fluid dynamics to accurately simulate a virtual fish. Videos of two separate fish swimming modes were analyzed. The two swimming modes are termed `free-stream swimming' and the `Kármán gait'. Free-stream swimming is how fish swim in a section of water that is free of disturbances, while Kármán gait swimming is how fish swim in the presence of a vortex street. Each swimming mode was paired with two simulation configurations, one that is free of obstructions, and one that contains a vortex street generating D-section cylinder. Data about the efficiency of swimming, power output, and thrust production were calculated during the simulations. The results showed that the most efficient mode of swimming was the Kármán gait in the presence of a Kármán vortex street. Evidence corroborating this has been found in the literature. The second most efficient means of swimming was found to be free-stream swimming in the absence of obstructions. The other two configurations, which are not observed in experiments, performed very poorly in regard to swimming efficiency.