AN EMG OPTIMIZATION MODEL OF THE KINETIC DEMANDS ON THE LOWER BACK DURING ASYMMETRICAL GAIT AND LOAD CARRIAGE

Gait asymmetries are associated with a high incidence of lower back pain (LBP). Although there are several causes of gait asymmetry (i.e. amputation, injury, or deformities), lower back kinetic demands have not been quantified and suitably compared due to experimental limitations in these clinical populations. Further, the impact of gait asymmetry on lower back demands during carrying tasks has not been established. This dissertation addressed these issues by artificially and safely inducing gait asymmetry in healthy able-bodied participants during walking and carrying tasks. LBP risk was assessed by L5/S1 vertebral joint force levels estimated with an OpenSim musculoskeletal model of the lower back adapted to incorporate participant-specific responses using an EMG optimization approach. The model was evaluated systematically for force estimate efficacy and sensitivity to input parameters prior to gait asymmetry assessments. Twelve participants performed walking and carrying tasks on a treadmill at individually scaled speeds while kinematics, external kinetics, and muscle activities (EMG) were recorded. Walking conditions consisted of unperturbed symmetrical gait, and asymmetrical gait induced by perturbing the right leg with a 2.54 cm shoe leveler, ~1 kg ankle weight, combined weight and shoe leveler, or a clinical walking boot that restricted ankle joint motion and added mass. Load carrying was performed while holding 7.5% and 15% bodyweight dumbbells in one or two hands during symmetric gait and asymmetric gait induced by the walking boot. The perturbations were successful in producing different degrees of gait asymmetry. However, L5/S1 joint forces were not significantly different between conditions despite unique spatiotemporal asymmetries. This indicates that LBP in those with gait asymmetry may not be due solely to level planar walking. During carrying tasks, gait asymmetry induced by the walking boot increased some metrics of lower back loading. Further, carrying a load in the hand contralateral to the walking boot produced larger forces than when carried on the same side. These results emphasize the importance of evaluating specific sources of gait asymmetry during daily activities other than walking when assessing LBP risk and would encourage more inclusive ergonomic carrying guidelines

EFFECTS OF BACKPACK TYPE ON KINEMATICS OF THE LOWER BACK DURING WALKING AND JOGGING

Heavy backpacks have been suggested to have a pathogenic role in experience of low back pain among children. We have conducted a repeated-measure study to investigate the backpack-induced changes in lumbo-pelvic coordination of forty gender-balanced college age students when they walked and jogged on a treadmill with two different types of backpacks: normal and ergonomically modified. The backpack-induced changes in lumbo-pelvic coordination were larger when carrying an ergonomically modified vs. a normal backpack as well as when jogging versus walking. The larger changes in lumbo-pelvic coordination when carrying an ergonomically modified backpack were likely due to kinematic restraints imposed by rigidity and enhanced attachments devised in the backpack for increased comfort. Given the role of lower back biomechanics in low back pain, the effects of such larger mechanical abnormalities in the lower back when carrying an ergonomically-modified backpack on risk of low back pain among children requires further investigation

The effect of backpack load on trunk kinematics of imitated pathological gait: a case study

Background: It is well documented that loaded backpacks affect the biomechanics of gait in both children and adults. Minimal information is available with regard to the effects of backpacks on the biomechanics of gait in individuals with clinical gait abnormalities, such as those seen in cerebral palsy. Healthy, non-clinical populations can be taught how to ‘imitate’ typical gait abnormalities in order to study various experimental interventions without enlisting clinical patients. The objective of this study was to determine the acute effect of backpack load on kinematics of the trunk during typical and imitated pathological gait. Methods: COVID 19 restrictions precluded the use of multiple subjects as originally planned, therefore in response to those limitations only one healthy female (25 yrs) performed two trials each of 4 gait styles (typical, crouch, toe, and jump gait), under unloaded and backpack-loaded conditions. Trials were recorded and digitized using a 12-camera motion analysis system. The loaded conditions utilized a student backpack weighted at 20% of the participant’s body weight (11.8 kg) using various sized small weights. Kinematics of the trunk including mean lateral trunk tilt, mean trunk inclination and mean anterior-posterior pelvic tilt, along with select spatio-temporal variables, were compared across loading conditions and among each gait type. Results: The kinematic variables of trunk tilt and pelvic tilt were exaggerated under the loaded conditions across pathological gait patterns. Double support time increased while single support time decreased. Significance: This case-study investigation was conducted as a hypothesis-generating study for kinematic variables of the trunk under load in populations exhibiting the studied gait patterns. The findings warrant further research in reference to load carriage parameters. Electromyographic testing may be beneficial to add to the current test battery in order to capture additional compensatory muscle actions that may contribute to overall dynamic motor control of the participant. Future research should contribute to better informed carriage practices for individuals with pathological gait patterns seen in cerebral palsy and toe walking

Lot- und Profiländerung der Wirbelsäule durch das Tragen eines Schulranzens bei 11- bis 14-jährigen Kindern

Es liegen zum Teil widersprüchliche Aussagen der Studien zur Auswirkung einer Belastung durch einen Schulranzen auf die Wirbelsäule vor. Bei den wenigen vorhanden Studien fand eine Betrachtung der Fragestellung mit unterschiedlichen Methoden und verschiedenen Gewichtsbelastungen statt. Auf Grund der differenten Herangehensweisen der Studien, die zu dem Thema Auswirkungen des Schulranzens auf die Wirbelsäulenform durchgeführt wurden, ist es das Ziel dieser Studie die Veränderungen der Wirbelsäulenparameter durch das Gewicht eines Schulranzens mittels Rasterstereographie genauer zu untersuchen. Hierbei ist diese Studie eine der ersten Studien, die auf die für die Kinder wenig belastende Möglichkeit der Raststereographie zurückgreift. In der Raststereographie können die Parameter Kyphose- und Lordosewinkel, Lot- und Seitabweichung und Oberflächenrotation gemessen werden. Der Kyphose- und Lordosewinkel spiegeln eine Änderung der Wirbelsäule in der sagittalen Ebene wieder und zeigen, ob es bei einer Gewichtsbelastung zu einer Verstärkung, Abflachung oder einem Gleichbleiben der Rückenform komm

Three dimensional kinetic analysis of asymmetrical lifting

Manual lifting is dynamic in nature and involves asymmetrical loading of the human body. This study investigated kinematic and kinetic characteristics of asymmetrical lifting in three dimensions, and then constructed a 3-D biomechanical force model of the lower back which is capable of quantifying torsional stress on the human spine. Eleven healthy adult male manual workers were recruited as subjects and lifted a 1 Okg load placed at the sagittal plane (0°) and at 30°, 60° and 90° lateral planes to the right, from 150mm and 500mm initial lift heights, respectively, to an 800mm high bench in the sagittal plane. Subjects' spinal motions and the trajectorial movements of the load in three-dimensional space were monitored simultaneously by a Lumbar Motion Monitor and a V-scope Motion Analyzer. Generally, the spinal motion factors increased as a function of increasing task asymmetry and differed (p < 0.05) between the lower (150mm) and higher (500mm) levels in the sagittal plane. In all asymmetrical conditions the motion factors showed a dramatic increase at the 500mm level compared to the increase at the 150mm level. The rates of increase in the horizontal and frontal planes were greater than those in the sagittal plane. Task asymmetry had a significant effect on the spinal kinematic parameters in the frontal plane at the two lift heights, and only at the high level (500mm) in the horizontal plane, with exception of average acceleration . Initial lift height exerted a significant effect on peak velocity and acceleration in both frontal and horizontal planes and on range of motion in the horizontal plane. Kinetic characteristics of the object being lifted in three-dimensions increased with an increase in task asymmetry. The increase was more dramatic in the lateral direction in the horizontal plane. However, motion factors in the vertical direction dominated the full range of the lift, irrespective of task asymmetry and lift height. The kinetic measures differed (p < 0.05) between the lower ( 1 50mm) and the higher (500mm) levels in the vertical direction except for average force. Task asymmetry had a significant effect on dynamic measures in the anterior-posterior direction. Both task asymmetry and lift height had a significant effect on dynamic motion factors in the lateral direction. From insights gained in the empirical study a three-dimensional biomechanical force model of the lower back was constructed based on a mechanism of muscle force re-orientation in the lumbar region. Acknowledging that the lower back is designed to be able to rotate around its longitudinal axis, the proposed model accounts for compression and shear forces and a torsional moment. The model has similar predictability to Schultz and Andersson's (1981) model when the human trunk exerts only a flexion-extension moment in the sagittal plane, but additionally predicts dramatic increases in shear forces, oblique muscle forces and torsional moment under asymmetrical lifting conditions which the Schultz-Andersson model does not. The increase rates in these forces and moment are not linearly related over task asymmetric angle

Effects of quadriceps strength asymmetry, ageing and external loading on stair negotiation

Ageing is associated with reduced stability and increased risk of falls. One risk factor for falls is sarcopenia: age-related muscle loss. Exaggeration of age-related muscle loss in one limb over the other results in strength asymmetry. This asymmetry typically increases with age and previous research has identified negative impact on gait and stability. This thesis develops to, firstly, identify a reliable method to assess strength asymmetry levels (chapter 5), then investigate the effects of quadriceps strength asymmetry on the biomechanics of stair negotiation in a young population (chapter 6) and “symmetrical” and “asymmetrical” older adults (chapter 7), before, finally, studying the effects of external loading (chapter 8). In the first study, within- and between-day testing of isometric maximal voluntary contractions of the quadriceps identified this method as a reliable method to assess strength levels in both legs, and the percentage asymmetry between legs. Consequent studies used this method to analyse the effect of age (young adults versus older adults), asymmetry (15%) and load carriage (unloaded versus 5% body weight bilaterally versus 10% body weight unilaterally) on a range of kinetic and kinematics variables during stair ascent and descent. The young healthy population (8.8±8.5% asymmetry) demonstrated only two significant differences in biomechanical variables between the stronger and weaker leg out of 60 variables measured. This was possibly as a result of type I error as absolute differences in mean values were negligible. Older adults (16.6±14.2% asymmetry) demonstrated detrimental effects of ageing regardless of asymmetry level, suggesting the overall loss of quadriceps strength due to age seems to play a key role. Results demonstrated greater effects on centre of mass and centre of pressure inclination angles and knees angles, rather than contact time and ground reaction force, suggesting the loss of strength can be controlled for to a greater extent in contact time and force. Under additional demands of external loading, effects of group (i.e., age and asymmetry) were typically not found and significant effects were instead a result of loading, primarily during unilateral load carriage. Greater ground reaction force and lateral inclination towards the load was demonstrated when stepping on the leg ipsilateral to the load. Overall, while the impact of strength asymmetry was minimal, this thesis highlights the important impact of age-related loss of muscle strength on stability during stair negotiation. Furthermore, the findings suggest splitting loads bilaterally when under the additional demands of loading.N/

An investigation into the importance of off-horse exercise on riding position of horse riders

In equestrian science, anecdotal evidence suggests that certain fitness parameters are beneficial for riding position. Studies have investigated the demands of riding; however, there is no objective data linking the general fitness of riders to its effects on riding position. This research set out to investigate the perceived importance of off-horse exercise on riding position, the impact that certain fitness parameters have and the effectiveness of a specifically tailored exercise programme. Nearly 90% of respondents stated they believed off-horse exercise to impact on their riding position, with dressage, leisure and older riders to be most likely to participate. The average fitness of riders including aerobic capacity, core stability, balance, flexibility and posture was then researched regarding the effect these might have on riding position. In a cross sectional study the relationship with riding position and pressure distribution, looking at the laterality of the seat, were explored. With the exception of cardiovascular fitness these were then tested for transferability of skill in an intervention trial. A mechanical horse and video analysis were used for analysis and the TekScan pressure mat recorded pressure distribution. Aerobic capacity was found to have no impact on riding position in this study and hip flexibility was assumed to have the greatest impact on riding position. After the intervention, the range of motion of the angles was decreased suggesting a more stable and quiet seat due to increased core stability. In line with other research asymmetries in the rider were found in pressure distribution, which were significantly decreased post intervention (trot and canter). No improvements in medio-lateral symmetry were found. Transferability of skill in riding position can be explained with the high similarity of standing posture and riding position. Overall horse rider specific training regimes can be recommended for improvement of riding position, but combination with riding instruction is suggested

Watch your step! Towards predicting osteoarthritis onset based on side-to-side imbalances

Osteoarthritis (OA) is a debilitating disease characterized by the erosion of articular cartilage at the extremity of bones. OA contributes to economic burdens, pain, and abnormal locomotion to accommodate for loss of protective cartilage. Since there is no cure for OA, mitigating disease onset can relieve the lives of millions of people who are at higher risk of OA such as females and overweight people.The progressive disappearance of protective cartilage leads to bone-on-bone contact at the joints, which is aggravated by higher-than-normal joint contact forces. Although OA can affect any joint, the primary weight-bearing joints of the lower body, i.e. hip, knee, and ankle, suffer the most impairment. Thus, investigating walking behavior can aid in detecting abnormal locomotion that may lead to OA.The objectives of this study were (1) to investigate a simple mechanical model’s ability to accurately reproduce measured gait kinetics and (2) to propose and evaluate novel parameters to supplement current noninvasive clinical tools for gait analysis.For a total of forty healthy subjects, kinematic and kinetic parameters were optimized for 300 consecutive steps to fit experimental vertical ground reaction force data measured during treadmill walking. Using an existing inverted spring-loaded pendulum with a spring-loaded ankle, we assessed the variations in leg and ankle stiffnesses during gait. We quantified bilateral lower limb symmetry, gait regularity, and gait variability based on the optimized stiffness values, which highlighted gait disparities between males and females, and between different body mass index categories.Our results confirmed that all subjects exhibited a certain amount of side-to-side asymmetry, irregularity, and variability in their leg and ankle stiffnesses during walking. Furthermore, large inter-subject variability indicated that our simple model could detect idiosyncratic gait patterns and therefore estimate potential imbalances in gait patterns. Future studies to test these walking assessments with accelerations as input parameters, which are easier to measure in a clinical setting, can improve current screenings for OA

Wearables for Movement Analysis in Healthcare

Quantitative movement analysis is widely used in clinical practice and research to investigate movement disorders objectively and in a complete way. Conventionally, body segment kinematic and kinetic parameters are measured in gait laboratories using marker-based optoelectronic systems, force plates, and electromyographic systems. Although movement analyses are considered accurate, the availability of specific laboratories, high costs, and dependency on trained users sometimes limit its use in clinical practice. A variety of compact wearable sensors are available today and have allowed researchers and clinicians to pursue applications in which individuals are monitored in their homes and in community settings within different fields of study, such movement analysis. Wearable sensors may thus contribute to the implementation of quantitative movement analyses even during out-patient use to reduce evaluation times and to provide objective, quantifiable data on the patients’ capabilities, unobtrusively and continuously, for clinical purposes