Kinematic analysis of the skeleton start

The purpose of this study was to describe the kinematics of the skeleton start and to compare one-foot versus two-foot starting techniques. The first two steps of the start of six national team skeleton athletes were videotaped during competition and analyzed. There were similarities between the kinematics of skeleton starts and sprint starts; however, the results showed that despite similar 50 meter start times there were differences between the one-foot and two-foot groups in knee angles off the block, trunk angle, toe height during recovery, support and flight times, and step length. These results suggest that the one-foot and two-foot starts are unique yet both effective techniques.

Neuromuscular mechanics and hopping training in elderly

Purpose: The present study examined the effects of repetitive hopping training on muscle activation profiles and fascicle–tendon interaction in the elderly.Methods: 20 physically active elderly men were randomly assigned for training (TG) and control groups (CG). TG performed supervised bilateral short contact hopping training with progressively increasing training volume. Measurements were performed before the training period (BEF) as well as after 2 weeks (2 W) and 11 weeks (11 W) of training. During measurements, the gastrocnemius medialis–muscle (GaM) fascicle and its outer Achilles tendon length changes during hopping were examined by ultrasonography together with electromyographic (EMG) activities of calf muscles, kinematics, and kinetics.Results: At 2 W, the ankle joint stiffness was increased by 21.0 ± 19.3 % and contact time decreased by 9.4 ± 7.8 % in TG. Thereafter, from 2–11 W the jumping height increased 56.2 ± 18.1 % in TG. Simultaneously, tendon forces increased 24.3 ± 19.0 % but tendon stiffness did not change. GaM fascicles shifted to shorter operating lengths after training without any changes in their length modifications during the contact phase of hopping. Normalized EMG amplitudes during hopping did not change with training.Conclusions: The present study shows that 11 W of hopping training improves the performance of physically active elderly men. This improvement is achieved with shorter GaM operating lengths and, therefore, increased fascicle stiffness and improved tendon utilization after training. Based on these results, hopping training could be recommended for healthy fit elderly to retain and improve rapid force production capacity. © 2014 Springer-Verlag Berlin Heidelberg

Comfort in Australian offices: beyond the models?

 Thermal comfort models, as we know them today, have been available since the early 1970’s and have been applied to assess the conditioning of our buildings. What we have is a comfort value of an interior environment at a particular location as a result of several measured parameters. What we don’t often consider is how the building contributes to this resulting thermal environment and how occupants respond to its possible changes. The following research considers the climatic and comfort findings from 15 fully air conditioned office buildings between Brisbane and Melbourne Australia during brief seasonal periods of measurement. Initially, each office building
was considered as its own individual project; however the grouping of the results has led to some interesting observations:
Regardless of building type or whether there is a narrow controlled comfort band,
there can be a significant variation in the clothing level of occupants.
There is a greater exterior to interior air temperature correlation than might be expected among fully air-conditioned buildings. The diurnal ranges of interior temperatures (over 24 hours) may be far greater than anticipated. It is realised that fully conditioned buildings are far more variable than perhaps realised and that occupant comfort may relate more to user interaction (CLO value), building construction type (weight) and envelope air tightness. As a result, this investigation raises perhaps more questions than answers as to how we assess thermal comfort in
buildings.

Kinematic and kinetic improvements associated with action observation facilitated learning of the power clean in Australian footballers

This study investigated the effectiveness of action observation (AO) on facilitating learning of the power clean technique (kinematics) compared with traditional strength coaching methods and whether improvements in performance (kinetics) were associated with an improvement in lifting technique. Fifteen subjects (age, 20.9 ± 2.3 years) with no experience in performing the power clean exercise attended 12 training and testing sessions over a 4-week period. Subjects were assigned to 2 matched groups, based on preintervention power clean performance and performed 3 sets of 5 repetitions of the power clean exercise at each training session. Subjects in the traditional coaching group (TC; n = 7) received the standard coaching feedback (verbal cues and physical practice), whereas subjects in the AO group (n = 8) received similar verbal coaching cues and physical practice but also observed a video of a skilled model before performing each set. Kinematic data were collected from video recordings of subjects who were fitted with joint center markings during testing, whereas kinetic data were collected from a weightlifting analyzer attached to the barbell. Subjects were tested before intervention, at the end of weeks 2 and 3, and at after intervention at the end of week 4. Faster improvements (3%) were observed in power clean technique with AO-facilitated learning in the first week and performance improvements (mean peak power of the subject's 15 repetitions) over time were significant (p < 0.001). In addition, performance improvement was significantly associated (R = 0.215) with technique improvements. In conclusion, AO combined with verbal coaching and physical practice of the power clean exercise resulted in significantly faster technique improvements and improvement in performance compared with traditional coaching methods.

Kinematic analysis and workspace determination of hexarot-a novel 6-DOF parallel manipulator with a rotation-symmetric arm system

Parallel mechanisms possess several advantages such as the possibilities for high acceleration and high accuracy positioning of the end effector. However, most of the proposed parallel manipulators suffer from a limited workspace. In this paper, a novel 6-DOF parallel manipulator with coaxial actuated arms is introduced. Since parallel mechanisms have more workspace limitations compared to that of serial mechanisms, determination of the workspace in parallel manipulators is of the utmost importance. For finding position, angular velocity, and acceleration, in this paper, inverse and forward kinematics of the mechanism are studied and after presenting the workspace limitations, workspace analysis of the hexarot manipulator is performed by using MATLAB software. Next, using the obtained cloud of points from simulation, the overall borders of the workspace are illustrated. Finally, it is shown that this manipulator has the important benefits of combining a large positional workspace in relation to its footprint with a sizable range of platform rotations.

Breakdown in central motor control can be attenuated by motor practice and neuro-modulation of the primary motor cortex

The performance of a repetitive index finger flexion–extension task at maximal voluntary rate (MVR) begins to decline just a few seconds into the task and we have previously postulated that this breakdown has a central origin. To test this hypothesis, we have combined two objectives; to determine whether motor practice can lessen the performance deterioration in an MVR task, and whether further gains can be achieved with a transcranial magnetic stimulation (TMS) protocol that increases corticomotor excitability (CME). Eleven right-handed subjects participated in a randomized crossover study design that consisted of a 15-min interventional TMS at I-wave periodicity (ITMS) and single-pulsed Sham intervention prior to six 10-s practice sets of a repetitive finger flexion–extension task at MVR. Motor-evoked potentials (MEPs) were recorded from the first dorsal interosseous muscle. The starting movement rate, and the percentage decline in rate by the end of the MVR were quantitated. Training of the MVR task improved the sustainability of the task by reducing the decline in movement rate. CME increased steadily after each training bout, and this increase was maintained up to 20 min after the last bout. ITMS further increased CME, and was associated with an increase in both the starting rate of the MVR task and its sustainability, when compared to Sham. The results implicate central motor processes in the performance and sustainability of the MVR task, and indicate that MVR kinematics can improve with short-term training and with non-invasive neuro-modulation.

Examining the perception of tenants in sustainable office buildings

Purpose – The purpose of this paper is to address two major challenges faced by sustainable building owners: first, address the gap between an occupant’s expectations of sustainable building outcomes and what the building actually provides and second, overcome the lack of user knowledge about sustainability design and operation for a particular with regards to performance. Design/methodology/approach – This study used a focus group approach to investigate the gap between: user expectations and sustainable building performance. The study surveyed occupants of sustainable office buildings in Melbourne, Australia. Findings – There is no significant relationship between users’ expectations and users’ experience of sustainable building performance and users’ knowledge about sustainability and the building they were worked in. Research limitations/implications – The research was limited to sustainable office buildings. New office buildings seeking to incorporate sustainability which need to focus on the needs of tenants in order to maximise value. Practical implications – There is an urgent need to ensure sustainable office buildings meet the needs of present and future occupiers without compromising short and long-term occupier satisfaction levels with regards to sustainability and operation of the building. Social implications – Increasing the level of sustainability in office buildings has been a major trend over the past decade however the tenants need to be consulted in the post-occupancy phase. Originality/value – Little attention has been given in the property management literature to sustainable office buildings and value drivers. This is an original and innovative study, partly due to the recent developments in sustainable buildings.

Neuromuscular mechanics and hopping training in elderly

Purpose: The present study examined the effects of repetitive hopping training on muscle activation profiles and fascicle–tendon interaction in the elderly. Methods: 20 physically active elderly men were randomly assigned for training (TG) and control groups (CG). TG performed supervised bilateral short contact hopping training with progressively increasing training volume. Measurements were performed before the training period (BEF) as well as after 2 weeks (2 W) and 11 weeks (11 W) of training. During measurements, the gastrocnemius medialis–muscle (GaM) fascicle and its outer Achilles tendon length changes during hopping were examined by ultrasonography together with electromyographic (EMG) activities of calf muscles, kinematics, and kinetics. Results: At 2 W, the ankle joint stiffness was increased by 21.0 ± 19.3 % and contact time decreased by 9.4 ± 7.8 % in TG. Thereafter, from 2–11 W the jumping height increased 56.2 ± 18.1 % in TG. Simultaneously, tendon forces increased 24.3 ± 19.0 % but tendon stiffness did not change. GaM fascicles shifted to shorter operating lengths after training without any changes in their length modifications during the contact phase of hopping. Normalized EMG amplitudes during hopping did not change with training. Conclusions: The present study shows that 11 W of hopping training improves the performance of physically active elderly men. This improvement is achieved with shorter GaM operating lengths and, therefore, increased fascicle stiffness and improved tendon utilization after training. Based on these results, hopping training could be recommended for healthy fit elderly to retain and improve rapid force production capacity.

Touching space: Using motion capture and stereo projection to create a "virtual haptics" of dance

This paper describes the work of a group of artists in Australia who used real-time motion capture and 3D stereo projection to create a large-scale performance environment in which dancers seemed to "touch" the volume. This project re-versions Suzanne Langer's 1950s philosophy of dance as "virtual force" to realize the idea of a "virtual haptics" of dance that extends the dancer's physical agency literally across and through the surrounding spatial volume. The project presents a vision of interactive dance performance that "touches" space by visualizing kinematics as intentionality and agency. In doing so, we suggest the possibility of new kinds of human-computer interfaces that emphasize touch as embodied, nuanced agency that is mediated by the subtle qualities of whole-body movement, in addition to more goal-oriented, task-based gestures such as pointing or clicking. © 2010.

Modulation of corticomotor excitability after maximal or sustainable-rate repetitive finger movement is impaired in Parkinson’s disease and is reversed by levodopa

Objectives: In healthy subjects, fatiguing exercises induce a period of post-exercise corticomotor depression (PECD) that is absent in Parkinson’s disease (PD). Our objective is to determine the time-course of corticomotor excitability changes following a 10-s repetitive index finger flexion–extension task performed at maximal voluntary rate (MVR) and a slower sustainable rate (MSR) in PD patients OFF and ON levodopa.
Methods: In 11 PD patients and 10 healthy age-matched controls, motor evoked potentials (MEPs) were recorded from the extensor indicis proprius (EIP) and first dorsal interosseous (FDI) muscles of the dominant arm immediately after the two tasks and at 2-min intervals for 10 min.
Results: In the OFF condition the PECD was absent in the two test muscles after both the MVR and MSR tasks. In the ON condition finger movement kinematics improved and a period of PECD comparable to that in controls was present after both tasks.
Conclusion: The absence of PECD in PD subjects off medication indicates a persisting increase in corticomotor excitability after non-fatiguing repetitive finger movement that is reversed by levodopa.