A rotating ring-disk electrode (RRDE) has been used to study heterogeneous catalytic reactions involving an immobilized enzyme. Glucose oxidase (E.C. 1.1.3.4.) has been immobilized by covalent attachment to a variety of disk electrode supports resulting in the rotating ring-disk enzyme electrode (RRDEE). Covalent attachment to graphitic oxide, platinum and carbon paste has been achieved using the bifunctional reagents glutaraldehyde or 1-ethyl-3(3-dimethyl amino-propyl)-carbodiimide. By varying the electrode rotation speed, the effects of external substrate mass transport on the rate of enzymatic catalysis have been investigated. Extremely small diffusion boundary layers (ca. 10-25 μm) at the disk catalytic support, under conditions of well defined and reproducible hydrodynamics, facilitate this investigation. The rate enzymatic catalysis is evaluated by spectrophotometrically monitoring the formation of the product H₂O₂ in the bulk solution. Peroxide may also be conveniently monitored amperometrically at the concentric platinum ring giving a steady-state response proportional to the substrate concentration. It is assumed that the enzyme obeys Michaelis-Menten kinetics. The intrinsic value of the heterogeneous apparent Michaelis-Menten constant (K'(m)) has been determined from Lineweaver-Burk plots for both methods of product detection. Catalysis limited rates are observed only when the electrode rotation speed is high (ω ≥ 1600 rpm) as established from linear Lineweaver-Burk plots and by calculating characteristic dimensionless parameters relating the ratio of the rate of catalysis to substrate mass transfer (e.g. the Damkoehler number and reaction velocity parameter). A careful characterization of the "immobilized enzyme layer" was necessary to evaluate the RRDEE as a viable model for these investigations. The specific activity of the immobilized enzyme was measured and related to the disk supports, immobilization procedures, and subsequent enzyme loading. Specific activities range from Whereas the effects of external mass transfer resistances may be eliminated at high rotation speeds, any internal or intra-enzyme layer resistances may not. Using chronoamperometric techniques for several disk electroactive species, it was shown that the the effect diffusion coefficients of small molecules within the enzyme layer are approximately 25 - 50% of the bulk solution value. K'(m) determined from the ring amperometric measurements was found to be slightly larger than values determined from the bulk solution detection of product and was attributed to the interenzyme diffusion of product. This, however, was shown not to interfere with product detection under conditions of catalysis limited rates.

No description available.

The purpose of the study was to compare the differences in the kinematics of the instep kick movement in different kick directions in a soccer penalty kick. The significant aspects of the joint movements that influence the kick directions were determined. Eleven female soccer athletes performed the instep kick in two different directions (left and right posts) on an outdoor field. The kinematic data measured from kick techniques were collected using three standard video cameras and a high speed camera (80Hz). All the data was analyzed by paired t-test. There are several variables that are significantly different between the two kick directions. There are only three variables that can predict kick direction significantly: support foot orientation, distance from support heel to the ball center and approach angle. The support foot may be the most useful cue for goalkeepers to predict the ball direction. Other cues may be less helpful because they are difficult to interpret or too subtle to be detected.

No description available.

No description available.

No description available.

The purpose of the study was to compare the differences in the kinematics of the instep kick movement in different kick directions in a soccer penalty kick. The significant aspects of the joint movements that influence the kick directions were determined. Eleven female soccer athletes performed the instep kick in two different directions (left and right posts) on an outdoor field. The kinematic data measured from kick techniques were collected using three standard video cameras and a high speed camera (80Hz). All the data was analyzed by paired t-test. There are several variables that are significantly different between the two kick directions. There are only three variables that can predict kick direction significantly: support foot orientation, distance from support heel to the ball center and approach angle. The support foot may be the most useful cue for goalkeepers to predict the ball direction. Other cues may be less helpful because they are difficult to interpret or too subtle to be detected.

A thorough understanding of typical shoulder motion is desirable for both clinicians and shoulder researchers. With this knowledge, comparisons between normal and special populations (e.g. athletic, working, elderly, injured) are enabled and injury mechanisms for heightened or diminished performance may be identified. The purpose of this study was to generate a robust quantification of typical shoulder kinematic profiles during dynamic humeral elevation in six vertical movement planes, and to determine the influence of humeral movement plane, movement phase, gender, and humeral elevation angle on typical scapulothoracic (ST), glenohumeral (GH), acromioclavicular (AC), and sternoclavicular (SC) kinematics. Upper limb kinematic data were collected on 15 males and 14 females as they elevated and lowered their right humerus in six vertical movement planes with elbows fully extended. A total of 60 shoulder kinematic profiles were generated for both raising and lowering motion phases. Trial-to-trial repeatability of the measured rotations, as indicated by intra-class correlation coefficient was found to be moderate (0.658) to high (0.999). Overall, as the humerus was elevated, scapulothoracic (ST) upward rotation, ST posterior tilt, sternoclavicular (SC) elevation, SC retraction, acromioclavicular (AC) elevation and glenohumeral (GH) elevation all increased. However, ST protraction/retraction, GH internal/external rotation, GH anterior/posterior plane of elevation, and AC protraction/retraction responses were less consistent. There was a main effect of humeral movement plane and elevation angle (p < 0.001) identified for all measured joint rotations. A significant phase main effect was not found for right glenohumeral +anterior/-posterior plane of elevation (GAP), glenohumeral +medial/-lateral elevation (GLE), and acromioclavicular protraction/retraction (APR). At least one significant interaction of the main effects, including that of gender, was present for all rotations. The typical shoulder kinematic profiles provided in this investigation is the largest to date of its kind obtained using skin-mounted shoulder tracking techniques. Clinical scientists will find the profiles useful because they provide motion trends that can be compared to profiles from other segments of the population, including patients with specific shoulder injuries. This work supports the more ambitious future clinical goal of being able to identify people who are at risk for developing shoulder pathologies in clinical settings in a non-invasive manner.

Thesis (PhD)--University of South Australia, 2003.

The ability to perform well during the sprint start and early acceleration phases of sprint running is critical. Many forms of training interventions are utilised to give a sprinter a competitive edge over their opponents in these particular phases. Despite this fact, there has been limited research on the technical and power type training strategies appropriate to improve sprint kinematics and the associated sprint performance in the sprint start and early acceleration phases. PURPOSE: To determine the best sprint start and early acceleration phase kinematic determinants, investigate the effect that load has on the kinematics of the sprint start and early acceleration performance and to determine how various physical characteristics may influence both resisted and unresisted sprint running. METHODS: Ten male track sprinters (mean ± SD: age 20 ± 3 years; height 1.82 ± 0.06 m; weight 76.7 ± 7.9 kg; 100 m personal best: 10.87 + 0.36 s {10.37 - 11.42 s}) attended two testing sessions. The first session required the athletes to sprint twelve 10 m sprints from a block start under unresisted and resisted (10% & 20% body mass) sled conditions. The second session required each athlete to complete an anthropometric assessment (height, mass, 3 bone lengths, 2 bone widths) and a variety of vertical (squat jump, countermovement jump, continuous straight legged jump) and horizontal (single leg hop for distance, single leg triple hop for distance) jump tests (3 trials each). Centre of gravity, joint and segment kinematics were calculated from 2D analysis utilising a kinematic analysis system (Ariel Performance Analysis System, U.S.A.). Means and standard deviations are presented for kinematic and performance measures. Pearson's product-moment correlation coefficients were employed to establish relationships between sprint start (block) performance variables and 10 m sprint performance. A linear regression analysis was used to quantify the relationships between the dependent variables (start performance and 10 m sprint time) and selected kinematic independent variables. ANOVA's with repeated measures were used to determine if there was a significant interaction between the kinematics under the various loaded conditions. A stepwise multiple regression and linear regression analysis were used for the prediction of unresisted and resisted sprint times from anthropometrical and functional performance measures. RESULTS: Mean horizontal block acceleration was identified as the start performance variable with the strongest relationship to 10 m sprint time. The most significant kinematic predictors of mean horizontal block acceleration were a large horizontal block velocity, short start time, and low thigh angle of the front block leg with respect to the horizontal at block takeoff. Sprint time over 10 m was best predicted by a large mean horizontal block acceleration (sprint start performance), increased angle of the front arm shoulder at step takeoff, and increased angle of front upper arm at step takeoff. Sprint start kinematics significantly altered as a result of resisted sled towing were start time (increase) and push-off angle from the blocks (decrease). Step length, stance time and propulsion time significantly increased, whereas flight time and flight distance significantly decreased under loaded conditions. A load of 20% body mass was revealed to be the better training load to utilise during resisted sled sprinting, especially for athletes who performed faster than 2.10 s for a 10 m sprint from a block start. The countermovement jump exercise was a strong predictor of both 10 m and 100 m sprint time. The continuous straight legged jump test was revealed to be a good predictor of resisted sprints over 10m.CONCLUSION: Consideration should be given to the technical training aspects of sprint start performance and forceful arm movements during step takeoff for improving sprint start and early acceleration sprint performance from starting blocks. These technical training aspects should also be supplemented with resisted sled towing with a load of 20% body mass and countermovement jump training to improve sprint ability.