Older adults' neuromuscular adaptations to resistence training and effects on challenging gait tasks

Community locomotion is threatened when older individuals are required to negotiate obstacles, which place considerable stress on the musculoskeletal system. The vulnerability of older adults during challenging locomotor tasks is further compromised by age-related strength decline and muscle atrophy. The first study in this investigation determined the relationship between the major muscle groups of the lower body and challenging locomotor tasks commonly found in the community environment of older adults. Twenty-nine females and sixteen males aged between 62 and 88 years old (68.2 ±6.5) were tested for the maximal voluntary contraction (MVC) strength of the knee extensors and 1-RM for the hip extensors, flexors, adductors, abductors, knee extensors and flexors and ankle plantar flexors. Temporal measurements of an obstacle course comprising four gait tasks set at three challenging levels were taken. The relationship between strength and the obstacle course dependent measures was explored using linear regression models. Significant associations (p≤0.05) between all the strength measures and the gait performances were found. The correlation values between strength and obstructed gait (r = 0.356-0.554) and the percentage of the variance explained by strength (R2 = 13%-31%), increased as a function of the challenging levels, especially for the stepping over and on and off conditions. While the difficulty of community older adults to negotiate obstacles cannot be attributed to a single causal pathway, the findings of the first study showed that strength is a critical requirement. That the magnitude of the association increased as a function of the challenging levels, suggests that interventions aimed at improving strength would potentially be effective in helping community older adults to negotiate environmental gait challenges. In view of the findings of the first study, a second investigation determined the effectiveness of a progressive resistance-training program on obstructed gait tasks measured under specific laboratory conditions and on an obstacle course mimicking a number of environmental challenges. The time courses of strength gains and neuromuscular mechanisms underpinning the exercise-induced strength improvements in community-dwelling older adults were also investigated. The obstructed gait conditions included stepping over an obstacle, on and off a raised surface, across an obstacle and foot targeting. Forty-three community-living adults with a mean age of 68 years (control =14 and experimental=29) completed a 24-week progressive resistance training program designed to improve strength and induce hypertrophy in the major muscles of the lower body. Specific laboratory gait kinetics and kinematics and temporal measures taken on the obstacle course were measured. Lean tissue mass and muscle activation of the lower body muscle groups were assessed. The MVC strength of the knee extensors and 1-RM of the hip extension, hip flexion, knee extension, knee flexion and ankle plantar flexion were measured. A 25% increase on the MVC of the knee extensors (p≤0.05) was reported in the training group. Gains ranging between 197% and 285% were recorded for the 1-RM exercises in the trained subjects with significant improvements found throughout the study (p≤0.05). The exercise-induced strength gains were mediated by hypertrophic and neural factors as shown by 8.7% and 27.7% increases (p≤0.05) in lean tissue mass and integrated electromyographic activity, respectively. Strength gains were accompanied by increases in crossing velocity, stride length and reductions in stride duration, stance and swing time for all gait tasks except for the foot targeting condition. Specific kinematic variables associated with safe obstacle traverse such as vertical obstacle heel clearance, limb flexion, horizontal foot placements prior to and at post obstacle crossing and landing velocities resulted in an improved crossing strategy in the experimental subjects. Significant increases in the vertical and anterior-posterior ground reaction forces accompanied the changes in the gait variables. While further long-term prospective studies of falls rates would be needed to confirm the benefits of lower limb enhanced strength, the findings of the present study provide conclusive evidence of significant improvements to gait efficiency associated with a systematic resistance-training program. It appears, however, that enhanced lower body strength has limited effects on gait tasks involving a dynamic balance component. In addition, due to the larger strength-induced increases in voluntary activation of the leg muscle compared to relatively smaller gains in lean tissue mass, neural adaptations appear to play a greater contributing role in explaining strength gains during the current resistance training protocol.

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.

Inspection of drop-weight impact damage in woven CFRP laminates fabricated by different processes

The influence of manufacturing process on the drop-weight impact damage in woven carbon/epoxy laminates was inspected by visual observation, dyepenetrant X-ray technique, and optical microscopy observation. The MTM56/ CF0300 woven quasi-isotropic laminates were fabricated by two processes: the autoclave and the Quickstep processes. Quickstep^TM is a novel composite manufacturing process, which was designed for the out-of-autoclave production of high-quality composite parts at lower cost. It utilizes higher heat conduction of fluid other than gas to transfer heat to components, which results in much shorter cure cycles. The laminates cured by this fast heating process showed different impact failure modes from those cured by the conventional autoclave process. The residual indentation in the top side of the Quickstep-cured laminates had a bigger diameter, but a smaller depth at the same impact energy level. Dye-penetrant X-ray revealed more intense and connected impact damage regions in the autoclave-cured laminates. Optical micrography as a supplementary method showed less severe matrix damage in the quickstep-cured laminates indicating a more ductile property of the resin matrix cured at a faster heating rate.

Using open-ended tasks for teaching, learning and assessment

This article explores the use and development of open- ended tasks in classrooms. Open-ended tasks can be used in teaching situations, for learning about student learning, and for assessment.

Tasks and pedagogies that facilitate mathematical problem solving

This is a report from one aspect of a project seeking to identify teacher actions that support mathematical problem solving. The project developed a planning and teaching model that describes the type of classroom tasks that can facilitate mathematical problem solving, the sequencing of the tasks, the nature of teaching heterogeneous groups, ways of dfferentiating tasks, and particular pedagogies. We report here one teacher's implementation of the
model using a unit of work that he planned and taught. The report provides important insights into the implementation of the theoretically founded model and the responses of students. We found that the model can be used for planning and teaching and for encouraging problem solving. The model has a positive effect on the learning of most students. Specific teachers actions were identified in order to address the needs of the students we are most
keen to support, those experiencing dfficulties.

Comparison of corticomotor excitability during visuomotor dynamic and static tasks

The human central nervous system (CNS) has the ability to modulate its activity during the performance of different movements. Recent evidence, however, suggests that the CNS can also modulate its activity in the same movement but with increased precision during a visuomotor static task. This study aimed to extend on these findings by using transcranial magnetic stimulation (TMS) to measure the CNS during the performance of two visuomotor dynamic tasks. Twelve volunteers participated in this study, performing two separate motor tasks. Study I (“Position Tracking”) involved participants to perform a visuomotor tracking task using a dial potentiometer and matching their response icon to the computer generated tracking icon whilst holding a pincer grip. Study II (“Force Tracking”) involved participants to perform a similar visuomotor tracking task by applying or releasing pressure against a fixed force transducer. Tasks were conducted at two speeds (“slow” being one tracking cycle in 10 s; and “fast” being two tracking cycles in 10 s) and compared to a visuomotor static task at a similar muscle contraction level. Results showed corticospinal changes with significant increases (p = 0.002) in excitability demonstrated during Study I (42.3 ± 16.8%) and Study II (56.3 ± 34.2%) slow speed tasks. Moreover, significant reduction in corticospinal inhibition was also observed during both tracking tasks at slow (59.3 ± 13.7%; p = 0.001) and fast speeds (31.9 ± 12.3%; p = 0.001). The findings may provide information on the underlying physiology during the early stages of motor skill acquisition.

Validation of accelerometer data for measuring impacts during jumping and landing tasks

The purpose of this study was to examine the validity of a commercially-available accelerometer, as used in the field team sports context. Ten adult participants completed two movement tasks: 1) a drop landing task from 30-cm, 40-cm and 50-cm heights [DLAND], and 2) a countermovement jumping task [CMJ]. Peak acceleration values, both smoothed and unsmoothed, occurring in the longitudinal axis [Y] and calculated to produce vector magnitude values [VM], were compared to peak vertical ground reaction force values [VGRF]. All acceleration measures were moderately correlated (r = 0.45 – 0.70), but also significantly higher than weight-adjusted VGRF, for both tasks. Though the raw acceleration measures were mostly above the acceptable limit for error (> 20%), the smoothed data had reduced error margins by comparison, most of which were well below 20%. These results provide some support for the continued use of accelerometer data, particularly when smoothed, to accurately quantify impacts in the field.

From profiles to rich tasks : the situated nature of 'authenticity' in the context of reforming curriculum and assessment practices

Outcome based education that has dominated Australian education in the 1990s is under review in the early years of the twenty first century. The available historical 'texts' produced during the first half of the 1990s, which include the national Statements and Profiles, and the state Curriculum and Standards Frameworks, provide us with documents that we can engage with not simply for 'history's sake', but with an opportunity to, in the words of the feminist author Dorothy Smith, 'displace[s] the analysis from the text as originating in writer or thinker, to the discourse itself as an ongoing intertextual process' bringing into view the social relations in which texts are embedded and which they organise' (1990, p. 161-2). Most Australian states and territories have now commenced significant situated, local curriculum renewal and reform. This renewed interest in curriculum offers insights into the character of recent assessment practices in Australia, recognising the tensions inherent in assessment practices and authentic assessment models. This paper explores, by way of an overview of the broad curriculum and assessment practices adopted in Australia over the past twenty-five years, the situated nature of 'authenticity' in the context of curriculum and assessment practices and how as teacher educators we are responding through our everyday work.

Virtual world security inspection : a software inspection process carried out on popular virtual world environments

 Virtual property theft is a serious problem that exists in virtual worlds. Legitimate users of these worlds invest considerable amounts of time, effort and real-world money into obtaining virtual property, but unfortunately, are becoming victims of theft in high numbers. It is reported that there are over 1 billion registered users of virtual worlds containing virtual property items worth an estimated US$50 billion dollars. The problem of virtual property theft is complex, involving many legal, social and technological issues. The software used to access virtual worlds is of great importance as they form the primary interface to these worlds and as such the primary interface to conduct virtual property theft. The security vulnerabilities of virtual world applications have not, to date, been examined. This study aims to use the process of software inspection to discover security vulnerabilities that may exist within virtual world software – vulnerabilities that enable virtual property theft to occur. Analyzing three well know virtual world applications World of Warcraft, Guild Wars and Entropia Universe, this research utilized security analysis tools and scenario testing with focus on authentication, trading, intruder detection and virtual property recovery. It was discovered that all three examples were susceptible to keylogging, mail and direct trade methods were the most likely method for transferring stolen items, intrusion detection is of critical concern to all VWEs tested, stolen items were unable to be recovered in all cases and lastly occurrences of theft were undetectable in all cases. The results gained in this study present the key problem areas which need to be addressed to improve security and reduce the occurrence of virtual property theft.

Virtual world security inspection

Virtual property theft is a serious problem that exists in virtual worlds. Legitimate users of these worlds invest considerable amounts of time, effort and real-world money into obtaining virtual property, but unfortunately, are becoming victims of theft in high numbers. It is reported that there are over 1 billion registered users of virtual worlds containing virtual property items worth an estimated US$50 billion dollars. The problem of virtual property theft is complex, involving many legal, social and technological issues. The software used to access virtual worlds is of great importance as they form the primary interface to these worlds and as such the primary interface to conduct virtual property theft. The security vulnerabilities of virtual world applications have not, to date, been examined. This study aims to use the process of software inspection to discover security vulnerabilities that may exist within virtual world software – vulnerabilities that enable virtual property theft to occur. Analyzing three well know virtual world applications World of Warcraft, Guild Wars and Entropia Universe, this research utilized security analysis tools and scenario testing with focus on authentication, trading, intruder detection and virtual property recovery. It was discovered that all three examples were susceptible to keylogging, mail and direct trade methods were the most likely method for transferring stolen items, intrusion detection is of critical concern to all VWEs tested, stolen items were unable to be recovered in all cases and lastly occurrences of theft were undetectable in all cases. The results gained in this study present the key problem areas which need to be addressed to improve security and reduce the occurrence of virtual property theft.

Frequency, intensity and duration of physical tasks performed by Australian rural firefighters during bushfire suppression

The current study combined, for the first time, video footage of individual firefighters wearing heart rate monitors and personal GPS units to quantify the frequency, duration and intensity of tasks performed by Australian rural fire crews when. suppressing bushfires. Across the four fireground 'shifts', the firefighters performed 34 distinct fireground tasks. Per shift, the task frequency ranged from once (raking fireline in teams, carrying a quick fill pump) to 103 times {lateral repositioning of a 38-mm charged firehose) .. The tasks lasted between 4 ± 2 s (bowling out 3-8-mm firehose) and 461 ± 387 s (raking fireline in teams). The task intensity~ as measured by average heart rate ranged between 97 ± 16 beats·min-1 (55.7 ± 8.7. %HRmax) and 157 ± 15 beats·min-1 (86.2 ± 10.8 %HRmax)· The tasks were performed a speeds that ranged from 0.12 ± 0.08 m·s-1 (manual hose retraction of 38-mm charged firehose) to 0.79 ± 0.40 m·s-1 (carrying a 38-mm coiled hose). Tasks found to be simultaneously frequent, long and intense (or two of these three) are likely to form the basis for job-specific testing of Australian rural firefighters suppressing bushfires.