Release Angle Research Articles

External Versus Two Different Internal Foci of Attention in Long-Distance Throwing.

The present study examined the influence of attentional focus on performance during a long-distance throwing task. Twelve participants executed three maximum-effort, long-distance baseball throwing attempts in three focus conditions: internal focus on wrist flexion (wrist internal focus), internal focus on the separation between pelvis and upper torso orientations (torso internal focus), and external focus on the ball path (external focus). Compared with the external focus and torso internal focus conditions, performance was poorer in the wrist internal focus condition. Performances were not different in the torso internal and external focus conditions. In addition, attentional focus affected the release angle of the ball but not its initial velocity. Our results reveal that the body part targeted for internal focus of attention and the forcefulness of the motor activity can be as important to motor performance as whether the attention is internal or external.

Overground-Propulsion Kinematics and Acceleration in Elite Wheelchair Rugby.

Maximal acceleration from standstill has been identified as a key performance indicator in wheelchair rugby; however, the impact of classification and kinematic variables on performance has received limited attention. This study aimed to investigate kinematic variables during maximal acceleration, with level of activity limitation accounted for using sport-classification scores. Based on their sporting classification scores, which reflect combined trunk, arm, and hand function, 25 elite wheelchair rugby players were analyzed in high-, mid-, and low-point groups before completing five 5-m sprints from a stationary position. Inertial measurement units and video analysis were used to monitor key kinematic variables. Significant differences in kinematic variables were evident across the classification groups, particularly for the first stroke-contact angle (1-way ANOVA F2,122 = 51.5, P < .05) and first stroke time (F2,124 = 18.3, P < .05). High-point players used a first stroke-contact angle that was closer to top dead center of the wheel than either other group, while also using a shorter overall stroke time than low-point players. A linear mixed-effects model was used to investigate how kinematic variables influenced performance, with results suggesting that increased release angles (ie, farther around the wheel) and decreased stroke angles resulted in larger peak accelerations. Further investigation revealed that these results are likely influenced by strong relationships for the high-point group, as there was often no clear trend evident for midpoint and low-point groups. Findings show that various propulsion approaches exist across classification groups, with this information potentially informing individual wheelchair setups and training programs.

Experimental study of oblique particle clouds in water

Laboratory experiments were conducted to investigate the dynamics of oblique particle cloud in stagnant water. Previous laboratory studies on vertically downward particle clouds indicated the importance of nozzle diameter do and mass of sand particles in form of an aspect ratio of Lo/do where Lo is the length of occupied sand particle in a pipe. In addition, particle size plays an important role in mixing capability of particle clouds. 30 laboratory experiments were carried out to consider the effects of Lo/do, particle size D50, angle of release θ, and release height H. In order to generalize the outcome of the present study, both particle size and release height were normalized to form Stokes number St and release number η. Three classes of particle size were identified for 0 < St < 1 and a relatively wide range of aspect ratio 0.8 ≤ Lo/do ≤ 40.1 was formed by changing the mass of sand particles. To consider the effects of release angle and release height, four release angles of θ=15°, 30°, 45°, and 60° were chosen and three release numbers of η=8.5, 13.2, and 17 were selected. Trajectories of particle clouds were identified based on the position of cloud front. Empirical formulations were developed to model the path of the frontal head of oblique particle clouds. Using a theoretical approach, the location of particle fall out was estimated within ± 10% accuracy. Variations of the frontal velocity of particle clouds in vertical direction were investigated and an empirical equation was proposed based on dimensional analysis to predict the frontal velocity at different initial conditions. Mixing efficiency of particle clouds was characterized by entrainment coefficient αe. The entrainment coefficients of particle clouds were computed using the theoretical entrainment hypothesis. It was found that the Stokes number can significantly alter the mixing capability of particle clouds. The influence of controlling parameters on particle−particle interactions can be studied by estimating the drag reduction due to particle grouping effects. The averaged drag coefficients Cd of particle clouds were calculated from momentum equation and a semi-empirical model was proposed to estimate the drag reduction of particle clouds. Significant drag reduction occurred in particle clouds in comparison with individual particles.

A BIOMECHANICAL ANALYSIS OF SPIN BOWLING IN CRICKET

The main aim of this study was to evaluating the various relationships of the identified biomechanical variables towards the performance of spin bowling and evaluating the contribution of identified biomechanical variables and construction of predictive model. Five interuniversity level leg-spin bowlers were recruited from LNIPE, India, and their bowling actions were captured by three video cameras, in a field setting. A value of α = 0.05 was used for all tests as the criterion to determine the presence or absence of significance. Pearson’s product moment correlation coefficient (r) was used for evaluating the various relationships of the selected variables towards the performance of spin bowling. Significant relationship was found between the Angle of Release (r = 0.965, P < 0.05), Average Velocity (r = 0.541, P < 0.05), Elbow joint Right (r = -0.392, P < 0.05), Hip Joint left (r = 0.402, P < 0.05), and Shoulder joint left (r = -0.383, P < 0.05). Multiple Linear Regression was used for evaluating the contribution of identified biomechanical variables and construction of predictive model. The regression equation was reliable as the value of R 2 was 0.945. The two variables selected in that regression equation explain 94.5% of the total variability in lateral deviation of ball was good. Since F-value for that regression model was highly significant, the model was reliable. This study provides further understanding of the biomechanical variables are associated with skilled performance in cricket leg-spin bowling, which coaches should consider when training less-skilled performers. Article visualizations:

Direction and Relevance of the Focus of Attention in Dart Throwing With and Without Concurrent Visual Feedback

Many research studies have shown the advantage of directing the focus of attention (FOA) externally as opposed to internally. However, it is not clear how the availability of concurrent visual feedback might impact attentional processes as the FOA is shifted between internal, external, relevant, and irrelevant sources of attention. The current experiment varied the FOA by asking the participants to judge joint angles (internal-relevant), respiration (internal-irrelevant), dart release angle (external-relevant), and tone loudness (external-irrelevant) at dart release in which task-intrinsic concurrent visual feedback was available or not. Spatial errors and trial-to-trial variability in the outcome were reduced when vision was available. Spatial errors were greater during internal judgments compared with external judgments particularly when vision was not available and when making judgments about task-relevant factors. A focus on irrelevant factors generally did not affect performance compared with relevant factors. These findings suggest that availability of concurrent visual feedback modulates focus of attention effects in motor control.

The relevance of body positioning and its training effect on badminton smash

ABSTRACTOne of the dominant skills in badminton is the forehand overhead smash, which consists of 1/5 attacks during games. Empirical evidences show that one has to adjust the body position in relation to the coming shuttlecock to produce a powerful and accurate smash. Therefore, positioning is a fundamental aspect influencing smash quality. Unfortunately, a search of literature has shown that there is a dearth/lack of study on this fundamental aspect. The goals of this study were to determine the influence of positioning and training experience on smash quality in order to discover information that could help learn/acquire the skill. Using 3D motion capture and full-body biomechanical modelling, 14 skilled and 15 novice players were analysed. Results have revealed that the body positioning has direct influence on shuttlecock release angle and clearance height of the offensive player. The results also suggest that, for training the positioning of beginners, one could conduct a self-selected comfort position towards a statically hanged shuttlecock and then step one foot back – a practical reference marker for learning. As one gains experience through repetitive training, improved limbs’ coordination would increase smash quality further. We hope our findings will benefit practitioners for developing effective training programmes for beginners.

Formulation and development of embelin liquisolid systems using quality by design approach

The purpose of the present investigation was to improve dissolution properties of poorly water soluble herbal active ingredient, Embelin (EMB) by formulating liquisolid systems. The new mathematical model was employed for the preparation of the liquisolid systems. Drug loaded liquisolid systems were optimized by utilizing design of experiments (DoE) and principal component analysis (PCA) with carrier-coating ratio (X1) and drug concentration in liquid (X2) as factors. Angle of repose and percentage drug release in 30 min were selected as dependent variables. The liquisolid systems were prepared using Solutol® HS-15 in combination of Synperonic® PE/L61 in ratio of 1:1 as non-volatile liquid, Neusilin US2 as carrier and Aerosil 200 as coating material. The relationship between dependent and independent variables were further explicated through regression analysis and response surface plots. Prepared systems were characterized by Fourier transform infrared spectroscopy, differential scanning calorimetry and powder X-ray diffraction studies. In-vitro dissolution results revealed significant enhancement in drug release properties from the formulations. Physicochemical characterization of liquisolid systems proposed reduction in drug crystallinity which might be ascribed for improvement in dissolution properties. Study demonstrated successful utilization of Solutol® HS-15 in combination of Synperonic® PE/L61 for dissolution enhancement of EMB.

Experiments with a falling rod

We study the motion of a uniform thin rod released from rest, with the bottom end initially in contact with a horizontal surface. Our focus here is the motion of the bottom end as the rod falls. For small angles of release with respect to the horizontal, the rod falls without the bottom end slipping. For larger angles, the slipping direction depends on the static friction coefficient between the rod and the horizontal surface. Small friction coefficients cause the end to slip initially in one direction and then in the other, while for high coefficients, the end slips in one direction only. For intermediate values, depending on the angle of release, both situations can occur. We find the initial slipping direction to depend on a relation between the angle at which the rod slips, and a critical angle at which the frictional force vanishes. Comparison between experimental data and numerical simulations shows good agreement.

Children With Dystonia Can Learn a Novel Motor Skill: Strategies That are Tolerant to High Variability.

Children with dystonia are characterized by highly variable and seemingly uncontrolled movements. An important question for any rehabilitative effort is whether these children can learn and improve their performance. This study compared children with dystonia due to cerebral palsy, typically developing children, and healthy adults in their ability to acquire a novel sensorimotor skill. Using a virtual setup, subjects threw a virtual ball tethered to a post to hit a virtual target. Multiple combinations of release angle and velocity of the arm at ball release could achieve a target hit-the task was redundant and afforded solutions with different sensitivity to variability. Subjects performed 200 trials for two target locations that presented different types of redundancy. We hypothesized that children with dystonia develop strategies that are tolerant to their high variability. Estimating this variability highlighted the insufficiency of traditional outcome measures. Therefore, additional analyses of data distributions and of ball release timing were applied. Results showed that: 1) children with dystonia reduced their performance error despite their high variability; 2) this improvement was brought about by finding error-tolerant solutions; and 3) they generated arm trajectories that created time windows for ball release that were tolerant to timing variability. While reduced in magnitude, the performance improvements in children with dystonia paralleled those in healthy children and adults. These findings demonstrate that children with dystonia are able to adapt their behavior to their high variability, an important basis for any rehabilitative intervention.

Comparison of Shooting Arm Motions in Basketball

A kinematic model is used to analyze basketball shooting arm motions in the vertical plane that produce desired ball release speed, angle and backspin. The release conditions are related to arm motions using general kinematic equations. The paper compares three types of shooting arm motions: pure hand shots, hand-forearm shots, and general shots controlled by hand, forearm and upper arm motions. In pure hand shots, release speed, angle and backspin are severely limited. All hand-forearm shot configurations are able to produce desired release speed, angle and backspin. General shots redundantly provide shooters with any desired ball release speed, angle and backspin, and they are required to suitably control each joint angular velocity and acceleration.

Prediction of patient-specific post-operative outcomes of TAVI procedure: The impact of the positioning strategy on valve performance

Prosthesis positioning in transcatheter aortic valve implantation procedures represents a crucial aspect for procedure success as demonstrated by many recent studies on this topic. Possible complications, device performance, and, consequently, also long-term durability are highly affected by the adopted prosthesis placement strategy. In the present work, we develop a computational finite element model able to predict device-specific and patient-specific replacement procedure outcomes, which may help medical operators to plan and choose the optimal implantation strategy. We focus in particular on the effects of prosthesis implantation depth and release angle. We start from a real clinical case undergoing Corevalve self-expanding device implantation. Our study confirms the crucial role of positioning in determining valve anchoring, replacement failure due to intra or para-valvular regurgitation, and post-operative device deformation.

Relationship Between Hand Contact Angle and Shoulder Loading During Manual Wheelchair Propulsion by Individuals with Paraplegia.

Shoulder loading during manual wheelchair propulsion (WCP) contributes to the development of shoulder pain in individuals with spinal cord injury (SCI). To use regression analysis to investigate the relationships between the hand contact angle (location of the hand on the pushrim at initial contact and release during the push phase of the WCP cycle) with propulsion characteristics, pushrim forces, and shoulder kinetics during WCP in individuals with paraplegia. Biomechanical data were collected from 222 individuals (198 men and 24 women) with paraplegia from SCI during WCP on a stationary ergometer at a self-selected speed. The average age of participants was 34.7 years (±9.3), mean time since SCI was 9.3 years (±6.1), and average body weight was 74.4 kg (±15.9). The majority (n = 127; 56%) of participants had lower level paraplegia (T8 to L5) and 95 (42%) had high paraplegia (T2 to T7). Increased push arc (mean = 75.3°) was associated with greater velocity (R = 0.384, P < .001) and cycle distance (R = 0.658, P < .001) and reduced cadence (R = -0.419, P <.001). Initial contact angle and hand release angles were equally associated with cycle distance and cadence, whereas a more anterior release angle was associated with greater velocity (R = 0.372, P < .001). When controlling for body weight, a more posterior initial contact angle was associated with greater posterior shoulder net joint force (R = 0.229, P = .001) and greater flexor net joint moment (R = 0.204, P = .002), whereas a more anterior hand release angle was significantly associated with increased vertical (R = 0.270, P < .001) and greater lateral (R = .293, P < .001) pushrim forces; greater shoulder net joint forces in all 3 planes - posterior (R = 0.164, P = .015), superior (R = 0.176, P = .009), and medial (R = 0.284, P < .001); and greater external rotator (R = 0.176, P = .009) and adductor (R = 0.259, P = .001) net joint moments. Current clinical practice guidelines recommend using long, smooth strokes during manual WCP to reduce peak shoulder forces and to prevent shoulder pain development. The position of the hand at both initial contact and hand release must be considered in WCP training. It is recommended that participants should reach back to initiate contact with the pushrim to maximize push arc but avoid a more anterior hand position at release, because this could increase shoulder load during the push phase of WCP.

Gender-Based Correlation Profiles Among the Release Factors and Distance Thrown in Paralympic Seated Shot Put.

The purpose of this study was to investigate the relationships among release factors (speed, height, and angle) and distance thrown in Paralympic seated shot put. Forty-eight trials performed by 11 men and 5 women during the 2012 US Paralympic trials in track and field were analyzed. With both genders combined, release speed (r = .95, p < .01) and angle (r = .51, p < .01) showed significant correlations to distance thrown. Release speed (r = .94, p < .01) in men and all release factors (r = .60-.98, p < .02) in women showed significant correlations to distance. Release speed and angle were identified as important predictors of the distance, explaining over 89-96% of the variance in distance thrown. Unlike athletes without disability, seated shot-putters exhibited significant positive speed-angle correlations (combined: r = .37, p < .01; women: r = .57, p = .03). Application of these results should address a focus in training on generating speed through the release point with a consistent release angle.

Reliability of the Achilles tendon tap reflex evoked during stance using a pendulum hammer

The tendon tap reflex (T-reflex) is often evoked in relaxed muscles to assess spinal reflex circuitry. Factors contributing to reflex excitability are modulated to accommodate specific postural demands. Thus, there is a need to be able to assess this reflex in a state where spinal reflex circuitry is engaged in maintaining posture. The aim of this study was to determine whether a pendulum hammer could provide controlled stimuli to the Achilles tendon and evoke reliable muscle responses during normal stance. A second aim was to establish appropriate stimulus parameters for experimental use. Fifteen healthy young adults stood on a forceplate while taps were applied to the Achilles tendon under conditions in which postural sway was constrained (by providing centre of pressure feedback) or unconstrained (no feedback) from an invariant release angle (50°). Twelve participants repeated this testing approximately six months later. Within one experimental session, tap force and T-reflex amplitude were found to be reliable regardless of whether postural sway was constrained (tap force ICC=0.982; T-reflex ICC=0.979) or unconstrained (tap force ICC=0.968; T-reflex ICC=0.964). T-reflex amplitude was also reliable between experimental sessions (constrained ICC=0.894; unconstrained ICC=0.890). When a T-reflex recruitment curve was constructed, optimal mid-range responses were observed using a 50° release angle. These results demonstrate that reliable Achilles T-reflexes can be evoked in standing participants without the need to constrain posture. The pendulum hammer provides a simple method to allow researchers and clinicians to gather information about reflex circuitry in a state where it is involved in postural control.

Formulation and evaluation of clotrimazole transdermal spray

Context: Transdermal spray (TS) of clotrimazole (CTZ) was formulated to improve the drug transport through the skin up to 12 h to achieve the antifungal efficacy.Objective: The aim of present study was to formulate and evaluate antifungal transdermal spray to improve the permeation of clotrimazole across the skin and to decrease the dosing frequency in fungal infection.Materials and methods: Different ratios of ethanol and acetone and various grades of eudragit and ethyl cellulose were evaluated according to six criteria: viscosity, drying time, stickiness, appearance and integrity on skin and water washability. Propylene glycol (PG) and polyethylene glycol 400 (PEG 400) were used in the study as plasticizer and solubilizer. The TS was evaluated for in vitro drug release, spray angle, spray pattern, average weight per dose, pH, drug content, evaporation time, leak test and antifungal efficacy study.Results and discussion: Eudragit E100 and blend of ethanol and acetone (80:20) satisfied the desired criteria. The selection of optimized batch was based on the results of in vitro drug release, spray pattern and spray angle. The optimized batch showed the spray angle <85° and uniform spray pattern. The formulation containing PG showed higher drug release than PEG 400. The inclusion of eutectic mixture consisting of camphor and menthol (1:1) showed improved drug transport through the rat skin and larger mean zone of inhibition indicating the improved antifungal efficacy.Conclusion: The TS of CTZ can be an innovative and promising approach for the topical administration in the fungal diseases.

A movable technological simulation system for kinematic analysis to provide immediate accurate feedback and predict javelin throw distance

The use of information technology (IT) and highly sophisticated devices in learning and evaluating training process is very common in today's sport sciences. The research aimed is a Trying to identify using of the biomechanical simulation system to evaluate physical variables in javelin throw. A new movable biomechanical simulation system to expect the javelin throwing distance and evaluate physical variables was developed, which consisted of a 800g sledge to be accelerated along a rope. The release angle can be adjusted within the range of 26 - 40 degrees. The takeoff height can be likewise adapted to the individual conditions of the athlete. By a laser-steered measure (LAVEG) the velocity of the throw carriage can be determined. 20 sport students were selected. The research proves that only 10 seconds are needed to show the expected distance. This research also recommends using this new movable technological biomechanical simulation system in learning and evaluating training processes.

Limb and Medicine Ball Mass Effects on Seated Single Arm Shot Put Performance

Functional performance tests (FPT) are important tools to assess muscle strength and power before and after injury. In contrast to the lower extremity, there are fewer FPT for the upper extremity. The seated single arm shot put (SSASP) test has the potential to fill the void of upper extremity FPT however, the underlying mechanics have yet to be examined. PURPOSE: To examine the effects of upper extremity dominance, and medicine ball mass on the underlying SSASP projectile mechanics. METHODS: Thirty healthy, college-aged men and women (20.5±1.5yrs; 181.5±6.2cm; 84.7±8.7kg) performed dominant (DOM) and non-dominant (NDOM) SSASP trials using three .114m diameter medicine ball loads (1kg, 2kg, 3kg). Customized touch sensitive gloves, synchronized with kinematic data of the hands, signaled ball release so release height (RH), release angle (RA), and peak anterior (AV) and vertical (VV) velocity could be quantified for each trial. In addition, the horizontal distance (HD) from release to first floor impact was recorded. Statistical analyses included separate limb by mass (RH, RA, HD) and limb by mass by direction (VV, AV) analysis of variance. RESULTS: At each level of ball mass, DOM HD was significantly greater (P<.001, 1kg:10.7%, 2kg:8.4%, 3kg:7.0%) than NDOM. For both DOM (95% CIdiff:.68-1.18m) and NDOM (95% CIdiff:.54-1.07m), the HD decrease between 1kg and 2kg was significantly greater (P<.001) than between 2kg and 3kg. RA (P=.026, η2=.16) and AV (P<.001, η2=.58) decreased linearly with each subsequent ball mass increase, however VV was not significantly altered. Across both VV and AV, DOM was significantly greater than NDOM (P=.001, 95% CIdiff:.16-.57m/s). No significant results for release height were revealed. CONCLUSION: Based on the ball mass effects, it appears the SSASP should be conducted with the 1kg and 2kg medicine balls. We ascribe the peak velocity differences between the limbs to greater muscle strength and power for the DOM limb. Because no other limb differences were revealed for the underlying mechanics, by extension, the greater DOM HD can be attributed to the peak velocity differences. Thus, while these data further support the use of SSASP HD as FPT for the upper extremity, further research directly measuring muscle performance is needed to validate this interpretation.

Modeling and Simulation for Free Fall Bomb Dynamics in Windy Environment

The main goal of aircraft bombing is its success in the destruction of the required target depending on the correct aiming and the correct moment of release. Different conditions, such as air speed, altitude, angle of release and the presence of wind, have a significant effect on the choice of the release moment to ensure target destruction. In this paper, a Six-degree of freedom (6DOF) mathematical model for the free fall bomb is presented describing the motion of the bomb in the three-dimensional space in the presence of stochastic winds. The aerodynamic coefficients for the free fall bomb are calculated through Missile Datcom computer program, however, these coefficients can be calculated either experimentally using the wind tunnel or a flight test; or mathematically through the Computational Fluid Dynamics (CFD). The stochastic wind affecting the trajectory of the bomb is defined by a velocity spectral represented by the Continuous Dryden Spectral. The contribution in this paper is the modeling and evaluation of the free fall bomb flight simulation in the presence of stochastic wind affecting the bomb flight trajectory.

An Investigation into the FertilizerParticle Dynamics Off-the-Disc

<abstract> <bold><sc>Abstract.</sc></bold> The particle size range specifications for two biosolids-derived organomineral fertilizers (OMF) known as OMF₁₀ (10:4:4) and OMF₁₅ (15:4:4) were established. Such specifications will enable field application of OMF with spinning disc systems using conventional tramlines spacing. A theoretical model was developed, which predicts the trajectory of individual fertilizer particles off-the-disc. The drag coefficient (C_d) was estimated for small time steps (10^-6 s) in the trajectory of the particle as a function of the Reynolds number. For the range of initial velocities (20 to 40 m s^-1), release angles (0° to 10°) and particle densities (1000 to 2000 kg m^-3) investigated, the analysis showed that OMF₁₀ and OMF₁₅ need to have particle diameters between 1.10 and 5.80 mm, and between 1.05 and 5.50 mm, respectively, to provide similar spreading performance to urea with particle size range of 1.00 to 5.25 mm in diameter. OMF₁₀ and OMF₁₅ should have 80% (by weight) of particles between 2.65 and 4.30 mm, and between 2.55 and 4.10 mm, respectively. Due to the physical properties of the material, disc designs and settings that enable working at a specified bout width by providing a small upward particle trajectory angle (e.g., 10°) are preferred to high rotational velocities. However, field application of OMF with spinning discs applicators may be restricted to tramlines spaced at a maximum of 24 m; particularly, when some degree of overlapping is required between two adjacent bouts. The performance of granular fertilizers can be predicted based on properties of the material, such as particle density and size range, using the contour plots developed in this study.

Analysis of throw distances of detached objects from horizontal-axis wind turbines

This paper aims at predicting trajectories of the detached fragments from wind turbines, in order to better quantify consequences of wind turbine failures. The trajectories of thrown objects are attained using the solution to equations of motion and rotation, with the external loads and moments obtained using blade element approach. We have extended an earlier work by taking into account dynamic stall and wind variations due to shear, and investigated different scenarios of throw including throw of the entire or a part of blade, as well as throw of accumulated ice on the blade. Trajectories are simulated for modern wind turbines ranging in size from 2 to 20 MW using upscaling laws. Extensive parametric analyses are performed against initial release angle, tip speed ratio, detachment geometry, and blade pitch setting. It is found that, while at tip speeds of about 70 m/s (normal operating conditions), pieces of blade (with weights in the range of approximately 7-16 ton) would be thrown out less than 700 m for the entire range of wind turbines, and turbines operating at the extreme tip speed of 150 m/s may be subject to blade throw of up to 2 km from the turbine. For the ice throw cases, maximum distances of approximately 100 and 600 m are obtained for standstill and normal operating conditions of the wind turbine, respectively, with the ice pieces weighting from 0.4 to 6.5 kg. The simulations can be useful for revision of wind turbine setback standards, especially when combined with risk assessment studies. Copyright © 2015 John Wiley & Sons, Ltd.