<p>The purpose of this longitudinal study was to determine whether a non-monotonic pattern characterizes the development of postural control in children from age 5 to 8 years, as suggested by previous cross-sectional studies. Postural control was considered in terms of control strategy and its variability operationalized by mean and standard deviation of Centre of Pressure velocity (COPvel); and of effectiveness and its variability operationalized by mean and standard deviation of COP anteroposterior excursion (YS). Periods of significant variability were used to indicate behavioural transitions. Seventeen, healthy children (9 males, 8 females) aged 5 to 6 years (61.5 - 75 months) were tested at 3 to 4 month intervals until age 8 years (83 - 97 months) in eyes-open quiet stance (OS) on a force platform for 30 seconds in each of 10 trials. Data were reorganized into 6 developmental categories based on adjacent test dates prior to (-2, -1) and after (+1, +2, +3) a subject's trial with the lowest COPvel. Developmental category is proposed to represent level of sensorimotor integrative skill. A 1-way MANCOVA revealed a significant effect ( p <.0001) for developmental category with covariance due to height, weight and actual age removed. Post-hoc 1-way ANCOVAs showed a significant effect (p<.OOO1) on measures of strategy. However differences in COPvel (type of strategy used) and differences in its variability (denoting a transition between types of strategies) were not always coincident. Performance outcome (yS) changed linearly across categories. From a consideration of the results it was concluded that a non-monotonic change in control strategy describes the development of quiet stance equilibrium. A transition, marked by variability of COPvel occurs from a primarily open-loop to incorporation of open- and close-loop components of control. Honing of strategy used precedes and follows transitions. Constriction of velocity and excursion may typify the early stages of bi-modal strategy use suggesting instability in realworld situations at this stage. Linear change in effective excursion regardless of strategy employed in unchallenged as may decrease the utility of this measure in assessing stability status in children. Developmental categories describe affiliation with the strategy employed and may represent differentiable levels of sensorimotor integrative skill. As such, they may be more useful in assessing progression of equilibrium control than consecutive age in years.</p> / Master of Science (MSc)

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Recent studies have demonstrated that increases in dynamic strength after weight-training in healthy subjects were associated with reductions in heart rate (HR) and arterial blood pressure (ABP) during formal lifting of identical absolute loads (McCartney et al., 1989; Sale et al., 1990). This study investigated whether the effect could be transferred to strength-related activities of daily living in healthy older men. The effects of 10 weeks (30 sessions) of progressive dynamic weightlifting training on HR and ABP in 10 weight-trained (wttrain) subjects were compared with 5 control subjects. Before and after training intra-brachial artery pressure and HR were monitored continuously during: 10 repetitions of single-arm curl (SAC) and single-arm military press (SAMP) at 70 % of initial 1 repetition maximum (1 RM); 12 repetitions of single- (SLP) and double-leg press (DLP) exercise at 80% of initial 1 RM; 10 mins treadmill walking at 2.5 mph, carrying 20 and 30 pound loads between mins 4-6 and 8-10 respectively (T-10); 4 mins of treadmill walking at 3.0 mph up an incline of 8% (T-4); 12 flights of stairclimbing at 60 steps/min on a Stairmaster 6000 Ergometer (STR). In the wttrain group the 1 RM in SAC, SAMP, SLP and DLP increased overall by 61 (p < 0.007), 30 (p < 0.001), 27 (p<0.001) and 27 per cent (p < 0.001), respectively. After training the mean maximal systolic blood pressure (SBP), diastolic blood pressure (DBP), mean arterial pressure (MAP), heart rate (HR), and rate-pressure product (RPP; 10^3) values in all 4 weightlifting exercises were lower. The decreases were only significant however, for the DBP in the SAC (144.0 ± 14.9 to 110.0 ± 5.2 Torr; p < 0.001), SAMP (151.0 ± 5.9 to 144.0 ± 5.4 Torr; p < 0.007), the MAP for the DLP ( 154.0 ± 5.0 to 147.0 ±5.0 Torr; p < 0.021) and RPP for the SAC (22.7 ± 2.2 to 19.1 ± 1.4; p < 0.041). The same respective measurements in the control group were either unchanged or higher. After training, there were overall reductions in the SBP (p < 0.05, mins 8-10), DBP , MAP and RPP (P < 0.05, mins 1-4) responses during T-10 with consistently higher values found in the control group. Similar, but nonsignificant patterns emerged for T-4. In contrast, there was little or no reduction in any of the measured parameters during stairclimbing. It was concluded that improved strength in older subjects results in an attenuated HR and ABP response during weightlifting, and there is a modest transfer of this effect to certain activities of daily living which involve the trained muscles. / Thesis / Master of Science (MSc)

Children with cerebral palsy (CP) have a higher than normal O2 uptake (VO2) during walking. While various interventions are used to improve locomotion, little is known about their effect on the metabolic and cardiopulmonary cost of walking. We therefore assessed the effects of one popular intervention, hinged ankle foot orthoses (AFO), on cardiopulmonary and metabolic variables during 2 min of steady state treadmill walking at three speeds: 3 kph, comfortable walking speed (CWS) and fast walking speed (FWS). We also assessed the effect of these braces on comfortable and maximum ground walking speed and on gross motor abilities using the Gross Motor Function Measure. Ten children with spastic diplegic CP (9.01 years ± 2.10) who habitually used hinged AFO participated. Not all children could walk at all speeds on the treadmill however, and some cardiopulmonary and metabolic data on three children were missing due to equipment failure. We performed an ANOVA on data for children who walked at 3 kph and CWS (n=8 for heart rate (HR); n=9 for pulmonary ventilation and metabolic variables) and a t-test on data at FWS (n=9 for HR, n=8 for pulmonary ventilation and metabolic variables). When children wore AFO, absolute VO2 was reduced by 4.6% at 3 kph and by 4.1% at FWS, and absolute VO2 per metre walked by 4.6% and 4.4% at the same speeds, respectively. Adjusting VO2 for body mass, or for resting VO2 or calculating energy expenditure in kJ, revealed the same pattern. Pulmonary ventilation was lower with AFO on by 7.17%, but only at 3 kph. AFO did not affect gross motor abilities. Nor did it affect HR, or the respiratory exchange ratio at any speed, nor any physiologic variable at CWS. We suggest the lower O2 cost may reflect an increase in stability and a corresponding decrease in coactivation of lower limb antagonistic muscles. / Thesis / Master of Science (MSc)

Due to the detrimental effects of ride vibrations on occupants and increasing safety concerns, improvement in vehicle dynamic characteristics has become a key focus of researchers. Typically, ride and handling problems have been dealt with independently. There is a dearth of vehicle models capable of capturing occupant biodynamics and its implication on vehicle ride and handling. Also in general, the objective of conventional control systems has been to attenuate vertical dynamic response of the sprung mass of a vehicle. Feedback control based algorithms are predominantly used in active/semi-active suspensions that ignore the biodynamics of occupants. In the current work, a new 50 degree-of-freedom (DOF) combined nonlinear multi-occupant vehicle model is developed using the lumped parameter modelling (LPM) approach. The current model provides a platform for performing a combined study of ride, handling and occupant biodynamics. The model is capable of simulating the combined effect of sitting occupancies, road inputs and driving maneuvers on biodynamic responses. It is analyzed using MATLAB/SIMULINK functionalities and validated by independently correlating the computed responses with existing experimental results. A study is performed on ride behavior of a vehicle-occupant system under two different transient road inputs. In addition, the effect of road roughness on vehicle ride is also studied. Random road profiles are generated from road roughness spectrum given in the ISO 8608:1995 manual. Insights are developed into the ride dynamics of a vehicle traversing over roads of classes A, B, C and D at given test velocities. The effect of sitting occupancies and vehicle velocities on lateral dynamics is also studied. Results underscore the need for considering sitting occupancies while analyzing vehicle dynamics and also highlight the potential of the current model. Furthermore, a Moore-Penrose Pseudoinverse based feed-forward controller is developed and implemented in an independently acting semi-active seat suspension system. Feasibility of feed-forward control in primary suspensions is also investigated. Finally, issues of stability, performance and limitation of the controller are discussed.