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

Improving the validity of shod human footstrike modelling with dynamic loading conditions determined from biomechanical motion capture trials

This thesis presents and evaluates a number of finite element footstrike models developed to allow the performance of prospective athletic footwear designs to be evaluated in a virtual environment. Successful implementation of such models would reduce the industry’s traditional reliance on physical prototyping and therefore reduce the time and associated costs required to develop a product. All boundary conditions defined in each of the footstrike models reported were directly determined from biomechanical motion capture trials to ensure that the loading applied was representative of shod human running. Similarly, the results obtained with each model were compared to digitised high speed video footage of experimental trials and validated against biomechanical measures such as foot segment kinematics, ground reaction force and centre of pressure location. A simple model loaded with triaxial force profiles determined from the analysis of plantar pressure data was found to be capable of applying highly representative load magnitudes but the distribution of applied loading was found to be less accurate. Greater success at emulating the deformation that occurs in the footwear during an entire running footstrike was achieved with models employing kinematic foot segment boundary conditions although this approach was found to be highly sensitive to the initial orientation of the foot and footwear components, thus limiting the predictive capacity of such a methodology. A subsequent model was therefore developed to utilise exclusively kinetic load conditions determined from an inverse dynamic analysis of an experimental trial and demonstrated the greatest predictive capacity of all reported models. This was because the kinematics of the foot were allowed to adapt to the footwear conditions defined in the analysis with this approach. Finally, the reported finite element footstrike models were integrated with automated product optimisation techniques. A topology optimisation approach was first utilised to generate lightweight midsole components optimised for subject‐specific loading conditions whilst a similar shape optimisation methodology was subsequently used to refine the geometry of a novel footwear design in order to minimise the peak material strains predicted

Muscle activation patterns in shoulder impingement patients

Introduction: Shoulder impingement is one of the most common presentations of shoulder joint problems 1. It appears to be caused by a reduction in the sub-acromial space as the humerus abducts between 60o -120o – the 'painful arc'. Structures between the humeral head and the acromion are thus pinched causing pain and further pathology 2. Shoulder muscle activity can influence this joint space but it is unclear whether this is a cause or effect in impingement patients. This study aimed to observe muscle activation patterns in normal and impingement shoulder patients and determine if there were any significant differences. Method: 19 adult subjects were asked to perform shoulder abduction in their symptomatic arm and non-symptomatic. 10 of these subjects (age 47.9 ± 11.2) were screened for shoulder impingement, and 9 subjects (age 38.9 ± 14.3) had no history of shoulder pathology. Surface EMG was used to collect data for 6 shoulder muscles (Upper, middle and lower trapezius, serratus anterior, infraspinatus, middle deltoids) which was then filtered and fully rectified. Subjects performed 3 smooth unilateral abduction movements at a cadence of 16 beats of a metronome set at 60bpm, and the mean of their results was recorded. T-tests were used to indicate any statistical significance in the data sets. Significance was set at P<0.05. Results: There was a significant difference in muscle activation with serratus anterior in particular showing a very low level of activation throughout the range when compared to normal shoulder activation patterns (<30%). Middle deltoid recruitment was significantly reduced between 60-90o in the impingement group (30:58%).Trends were noted in other muscles with upper trapezius and infraspinatus activating more rapidly and erratically (63:25%; 60:27% respectively), and lower trapezius with less recruitment (13:30%) in the patient group, although these did not quite reach significance. Conclusion: There appears to be some interesting alterations in muscle recruitment patterns in impingement shoulder patients when compared against their own unaffected shoulders and the control group. In particular changes in scapula control (serratus anterior and trapezius) and lateral rotation (infraspinatus), which have direct influence on the sub-acromial space, should be noted. It is still not clear whether these alterations are causative or reactionary, but this finding gives a clear indication to the importance of addressing muscle reeducation as part of a rehabilitation programme in shoulder impingement patients