Effects of approach velocity and foot-target characteristics on the visual regulation of step length

Two questions emerge from the literature concerning the perceptual-motor processes underlying the visual regulation of step length. The first concerns the effects of velocity on the onset of visual control (VCO), when visual regulation of step length begins during goal-directed locomotion. The second concerns the effects of different obstacles such as a target or raised surface on step length regulation. In two separate experiments, participants (Experiment 1 & 2: n=12, 6 female, 6 male) walked, jogged, or sprinted towards an obstacle along a 10 m walkway, consisting of two marker-strips with alternating black and white 0.50 m markings. Each experiment consisted of three targeting or obstacle tasks with the requirement to both negotiate and continue moving (run-through) through the target. Five trials were conducted for each task and approach speed, with trials block randomised between the six participants of each gender. One 50 Hz video camera panned and filmed each trial from an elevated position, adjacent to the walkway. Video footage was digitized to deduce the gait characteristics. Results for the targeting tasks indicate a linear relationship between approach velocity and accuracy of final foot placement (r=0.89). When foot placement was highly constrained by the obstacle step length shortened during the entire approach. VCO was found to occur at an earlier tau-margin for lower approach velocities for both experiments, indicating that the optical variable ‘tau' is affected by approach velocity. A three-phase kinematic profile was found for all tasks, except for the take-off board condition when sprinting. Further research is needed to determine whether this velocity affect on VCO is due to ‘whole-body' approach velocity or whether it is a function of the differences between gait modes.

Foot-targeting in reaching and grasping

Foot positioning was investigated when right-handed (Experiment One) and left handed adults (Experiment Two) stopped walking to grasp a stationary 70 mm ball at shoulder height. In both experiments centroid location formed by the toe and heel coordinates relative to the object was highly consistent within a target-location condition, demonstrating a foot-targeting phenomenon. Centroid location in the anterior-posterior direction was uninfluenced by grasping hand but the centroid shifted right for left hand grasps and left for right hand grasps. With the target either centrally located or on the same side as the dominant hand, foot positioning brought the grasping hand closer to the target in the medial-lateral direction. When the target object was aligned with the shoulder opposite the dominant hand both groups adopted foot positions to the left of the target. Thus, neither group adopted optimal foot position when the target was located opposite their dominant hand. Foot orientation angle relative to the target was also influenced by choice of grasping hand. Collectively, the findings demonstrate a close association between grasping hand and foot position when approaching to reach and grasp an object but also suggest that foot-dominance may influence medial-lateral centroid location.

Re-emerging conflict in the Solomon Islands? The underlying causes and triggers of the riots of April 2006

The recent tensions in Honiara, the capital of the Solomon Islands, in April 2006 provide a clear warning that despite the presence of the Regional Assistance Mission in the Solomon Islands, led by the Australian government, many of the issues that led to prolonged conflict in 1998 have not yet been adequately addressed. This piece of research examines the root causes of continued conflict as experienced by the people themselves, and the triggers for the sudden explosion of violence in April 2006. It offers insights into the successes and failures of the international presence in the Solomon Islands, as well as presenting local opinions on the likelihood of further conflict. Based on the findings some suggestions are made regarding the targeting of programs, and the adaptations that may need to be made in the approach adopted by the international community.

Measuring food access in Melbourne: access to healthy and fast foods by car, bus and foot in an urban municipality in Melbourne

Access to healthy food can be an important determinant of a healthy diet. This paper describes the assessment of access to healthy and unhealthy foods using a GIS accessibility programme in a large outer municipality of Melbourne. Access to a major supermarket was used as a proxy for access to a healthy diet and fast food outlet as proxy for access to unhealthy food. Our results indicated that most (>80%) residents lived within an 8–10 min car journey of a major supermarket i.e. have good access to a healthy diet. However, more advantaged areas had closer access to supermarkets, conversely less advantaged areas had closer access to fast food outlets. These findings have application for urban planners, public health practitioners and policy makers.

Foot mucus is a good source for non-destructive genetic sampling in polyplacophora

A non-destructive method for collecting samples for DNA analysis from the mucus of molluscs was successfully adapted for use with the genus Ischnochiton. DNA was extracted using a Chelex-based method and the COI subunit of the mtDNA was amplified and sequenced. Sequences from the mucus were crosschecked against sequences from the foot tissue of the same animal and were found to be identical. This method provides a non-destructive way of carrying out larger studies of the genetics of rare organisms and may be of general use for genetic-based field studies of molluscs.

Obesity and pronated foot type may increase the risk of chronic plantar heel pain : a matched case-control study

Background : Chronic plantar heel pain (CPHP) is one of the most common musculoskeletal disorders of the foot, yet its aetiology is poorly understood. The purpose of this study was to examine the association between CPHP and a number of commonly hypothesised causative factors.

Methods : Eighty participants with CPHP (33 males, 47 females, mean age 52.3 years, S.D. 11.7) were matched by age (± 2 years) and sex to 80 control participants (33 males, 47 females, mean age 51.9 years, S.D. 11.8). The two groups were then compared on body mass index (BMI), foot posture as measured by the Foot Posture Index (FPI), ankle dorsiflexion range of motion (ROM) as measured by the Dorsiflexion Lunge Test, occupational lower limb stress using the Occupational Rating Scale and calf endurance using the Standing Heel Rise Test.

Results : Univariate analysis demonstrated that the CPHP group had significantly greater BMI (29.8 ± 5.4 kg/m2 vs. 27.5 ± 4.9 kg/m2; P < 0.01), a more pronated foot posture (FPI score 2.4 ± 3.3 vs. 1.1 ± 2.3; P < 0.01) and greater ankle dorsiflexion ROM (45.1 ± 7.1° vs. 40.5 ± 6.6°; P < 0.01) than the control group. No difference was identified between the groups for calf endurance or time spent sitting, standing, walking on uneven ground, squatting, climbing or lifting. Multivariate logistic regression revealed that those with CPHP were more likely to be obese (BMI ≥ 30 kg/m2) (OR 2.9, 95% CI 1.4 – 6.1, P < 0.01) and to have a pronated foot posture (FPI ≥ 4) (OR 3.7, 95% CI 1.6 – 8.7, P < 0.01).

Conclusion : Obesity and pronated foot posture are associated with CPHP and may be risk factors for the development of the condition. Decreased ankle dorsiflexion, calf endurance and occupational lower limb stress may not play a role in CPHP.

Foot complications in Type 2 diabetes : an Australian population-based study

Aims To determine the prevalence and risk factors for neuropathy and peripheral vascular disease (PVD) in the Australian diabetic population and identify those at high risk of foot ulceration.

Methods The Australian Diabetes Obesity and Lifestyle study included 11 247 adults aged ≥ 25 years in 42 randomly selected areas of Australia. Neuropathy and PVD were assessed in participants identified as having diabetes (based on self report and oral glucose tolerance test), impaired fasting glucose, impaired glucose tolerance and in a random sample with normal glucose tolerance (total n = 2436).

Results The prevalence of peripheral neuropathy was 13.1% in those with known diabetes (KDM) and 7.1% in those with newly diagnosed (NDM). The prevalence of PVD was 13.9% in KDM and 6.9% in NDM. Of those with diabetes, 19.6% were at risk of foot ulceration. Independent risk factors for peripheral neuropathy were diabetes duration (odds ratio (95% CI) 1.73 (1.33–2.28) per 10 years), height (1.42 (1.08–1.88) per 10 cm), age (2.57 (1.94–3.40) per 10 years) and uric acid (1.59 (1.21–2.09) per 0.1 mmol/l). Risk factors for PVD were diabetes duration (1.64 (1.25–2.16) per 10 years), age (2.45 (1.86–3.22) per 10 years), smoking (2.07 (1.00–4.28)), uric acid (1.03 (1.00–1.06) per 0.1 mmol/l) and urinary albumin/creatinine ratio (1.11 (1.01–1.21) per 1 mg/mmol).

Conclusions The prevalence of neuropathy and PVD was lower in this population than has been reported in other populations. This may reflect differences in sampling methods between community and hospital-based populations. Nevertheless, a substantial proportion of the diabetic population had risk factors for foot ulceration.

Information-based regulation of high-velocity foot-targeting tasks

Judging time-to-contact with a target is an important criterion for avoiding harm in everyday walking and running tasks, and maximizing performance in high-velocity sporting tasks. The information-based regulation of step length and duration during target-directed locomotion was examined in relation to gait mode, approach velocity, target task, expertise, and sporting performance during a series of four experiments. The first three experiments examined novice performers (Each n=12, 6 males, 6 females), whilst the last experiment examined expert gymnasts (n=5). Two reference strips with alternating 50cm black and white intervals were placed on either side of the approach strip for all of the experiments. One 50Hz-panning video camera filmed the approach from an elevated position. In Experiment 4, two stationary 250Hz cameras filmed the post-flight performance of the gymnastic vaults and, in addition, two qualified judges provided a performance score for each vaulting trial. The panning video footage in each experiment was digitized to deduce the gait characteristics. In Experiment 4, the high-speed video footage was analyzed three-dimensionally to obtain the performance measures such as post-flight height. The utilization of visual stimulus in target-directed locomotion is affected by the observer's state of motion as characterized by the mode of locomotion and also often the speed of locomotion. In addition, experience plays an important role in the capacity of the observer to utilize visual stimulus to control the muscular action of locomotion when either maintaining or adjusting the step mechanics. The characteristics of the terrain and the target also affect the observer's movement. Visual regulation of step length decreases at higher approach speeds in novice performers, where as expert performers are capable of increasing visual regulation at higher approach speeds. Conservatism in final foot placement by female participants accounts for the observed increase in distance from the critical boundary of the obstacle relative to toe placement. Behavioural effects of gender thus affect the control of final foot placement in obstacle-directed locomotion. The visual control of braking in target-directed locomotion is described by a tau-dot of-0.54. When tau-dot is below -0.54 a hard collision with the obstacle will occur, however, when tau-dot is above -0.54, a soft collision with the target will occur. It is suggested that the tau-dot margin defining the control of braking reveals the braking capacity of the system. In the target-directed locomotion examined a tau-dot greater than -0.70 would possibly exceed the braking capacity of the system, thus, leading to injury if performed. The approach towards the take-off board and vaulting horse in gymnastics is an example of target-directed locomotion in sport. Increased visual regulation of the timing and length of each step is a requirement for a fast running approach, a fundamental building block for the execution of complex vaults in gymnastics. The successful performance of complex vaults in gymnastics leads towards a higher judge's score. Future research suggestions include an investigation of visual regulation of step length in curved target-directed locomotion.

Development and evaluation of an ELISA for the detection and 3D antibodies to foot and mouth disease virus

A group specific ELISA (enzyme-linked immunosorbent assay) was developed to detect virus infection associated antibodies in the serum of animals infected with any serotype of foot and mouth disease virus. The assay was developed from non-infectious sources, and is therefore suitable for use in countries where FMDV is exotic.