Dynamics of running on a centrifugal track
AbstractThe centrifugal track is a basin-shaped track characterised by a platform with a parabolic section. The model analysed in this technical note is characterized by five circular lanes with an increasing radius (from 2.59 to 3.37 m) and inclination (from 34° to 60°). The athlete has to run on a selected lane while changing direction at every support phase to maintain a circular trajectory. This gives rise to a centripetal acceleration of the centre of mass that, added to gravity, results in an overweight of the runner. E ach lane is associated with a corresponding running speed that allows the athlete to run perpe...
Source: Sports Engineering - March 13, 2017 Category: Sports Medicine Source Type: research
High-resolution friction measurements of cross-country ski bases on snow
AbstractParticipants in the sport of snow skiing devote considerable effort to reduce sliding friction of the ski. A large industry is devoted to providing products and ski preparation methods with claims of improved ski performance, sometimes at considerable expense. Despite this attention to the topic, there are very little data available to skiers that quantify the effect these products and methods have on reducing ski friction. Determining the coefficient of friction of a ski on snow presents a significant technical challenge. Our approach has been to develop a tribometer incorporating a series of proximity sensors to ...
Source: Sports Engineering - March 2, 2017 Category: Sports Medicine Source Type: research
Characterisation of ball degradation events in professional tennis
AbstractTennis balls are acknowledged to degrade with use and are replaced at regular intervals during professional matches to maintain consistency and uniformity in performance, such that the game is not adversely affected. Balls are subject to the international tennis federation ’s (ITF) ball approval process, which includes a degradation test to ensure a minimum standard of performance. The aim of this investigation was to establish if the ITF degradation test can assess ball longevity and rate of degradation and determine if there is a need for a new degradation test th at is more representative of in-play conditions...
Source: Sports Engineering - February 13, 2017 Category: Sports Medicine Source Type: research
An analytical model for flat-ski friction in steady horizontal gliding
AbstractThis paper addresses sliding friction of a ski during steady horizontal gliding on snow. A simple mathematical theory accounting for both dry and wet friction is developed. The water film evolution along a ski is calculated with a lumped-element thermal model. An analytical solution is obtained for the ski friction force. Representative calculation results are demonstrated for a range of ski velocity, contact surface area fraction, snow temperature, and ski aspect ratio. (Source: Sports Engineering)
Source: Sports Engineering - February 12, 2017 Category: Sports Medicine Source Type: research
Ice hockey skate starts: a comparison of high and low calibre skaters
AbstractThe forward skating start is a fundamental skill for ice hockey players, yet extremely challenging given the low traction of the ice surface. The technique for maximum skating acceleration of the body is not well understood. The aim of this study was to evaluate kinematic ice hockey skating start movement technique in relation to a skater ’s skill level. A 10-camera motion capture system placed on the ice surface recorded “hybrid-V” skate start movement patterns of high and low calibre male ice hockey players (n = 7, 8, respectively). Participants’ lower body kinematics and estimated body centre of mass (...
Source: Sports Engineering - February 10, 2017 Category: Sports Medicine Source Type: research
Rate-activated strapping for improved retention of protective eyewear during impact
In this study, a rate-activated eyewear retention system is studied and compared to a conventional elastic retention system. The rate-activated behavior of the retention system is due to an enclosed shear-thickening fluid, a high solids-loading colloid that undergoes a rapid increase in viscosity above a critical shearing rate. Tensile testing shows that the force required to elongate this retention system is over 10 times higher when stretched at 100 mm/s, compared to 1 mm/s. A women’s lacrosse goggle mounted to an anthropomorphic test dummy head is used as a model system to compare retention system response. Goggles...
Source: Sports Engineering - February 1, 2017 Category: Sports Medicine Source Type: research
Evaluation of wireless bat swing speed sensors
AbstractBatter swing speed is an important parameter in understanding the performance of baseball and softball players. A number of swing speed sensors have recently been introduced and are commercially available. The aim of this study was to compare three wireless swing sensors with high speed video. Swing speed from high speed video was measured by differentiating the position coordinates of tracking markers on the bat barrel. On average, the wireless bat swing sensors reported speeds 8% slower than that found from video tracking. The agreement was better at low swing speeds, suggesting that the current generation of wir...
Source: Sports Engineering - January 31, 2017 Category: Sports Medicine Source Type: research
The round-wheel compound bow model revisited: a new extension
AbstractAn extended offset-eccentric model of an archery twin-round-wheel compound bow is derived. Varying some parameters of the model, the respective effects on the calculated force –draw curve are considered. Two static quality coefficients for the compound bow are introduced. It was found that the twin-round-wheel compound bow can be designed to be more energetic with the help of the model. For a bow with some modifications 18.5% increment of energy was calculated. Also a t heoretical limit for the force–draw curve of the compound bow is concluded. (Source: Sports Engineering)
Source: Sports Engineering - January 27, 2017 Category: Sports Medicine Source Type: research
Forward acceleration of the centre of mass during ski skating calculated from force and motion capture data
AbstractThe purpose of this paper was to present and evaluate a methodology to determine the contribution of bilateral leg and pole thrusts to forward acceleration of the centre of mass (COM) of cross-country skiers from multi-dimensional ground reaction forces and motion capture data. Nine highly skilled cross-country (XC) skiers performed leg skating and V2-alternate skating (V2A) under constant environmental conditions on snow, while ground reaction forces measured from ski bindings and poles and 3D motion with high-speed cameras were captured. COM acceleration determined from 3D motion analyses served as a reference an...
Source: Sports Engineering - December 19, 2016 Category: Sports Medicine Source Type: research
Kinematic analyses of seated throwing activities with and without an assistive pole
This study aimed to identify and compare performance-related kinematic variables associated with both seated throwing techniques. Twenty-nine non-disabled males (21.9 ± 2.6 years) performed 12 maximal throws using a 1-kg ball in two conditions (no-pole and pole). Automatic 3D-kinematic tracking (150 Hz) and temporal data were acquired. There was no significant difference between ball speeds at the point of release between conditions (no-pole = 12.8 ± 1 .6 m/s vs. pole = 12.9 ± 1.5 m/s). There were four kinematic variables that were strongly correlated with ball speed when throwing with or without an assis...
Source: Sports Engineering - December 9, 2016 Category: Sports Medicine Source Type: research
Simulation to clarify the effect of paddling motion on the hull behavior of a single kayak in a sprint race
The objective of this study was to investigate the effect of the paddling motion on the hull behavior by numerical simulation. A dynamic simulation model of a paddler, paddle and hull in a single kayak, which was previously developed, was used for the simulation. One standard paddling motion and three modified motions were prepared for the simulation. Three modified motions were created based on suggestions by coaches of the Japan Olympic team. These motions were thought to be often seen in paddlers of lower skill level and, therefore, empirically considered to be typically bad motions. From the simulation results, the fol...
Source: Sports Engineering - December 7, 2016 Category: Sports Medicine Source Type: research
The effect of acceleration signal processing for head impact numeric simulations
AbstractBrain injury research in sport employs a variety of physical models equipped with accelerometers. These acceleration signals are commonly processed using filters. The purpose of this research was to determine the effect of applying filters with different cutoff frequencies to the acceleration signals used as input for finite element modeling of the brain. Signals were generated from reconstructions of concussion events from American football and ice hockey in the laboratory using a Hybrid III headform. The resulting acceleration signals were used as input for the University College Dublin Brain Trauma Model after b...
Source: Sports Engineering - October 17, 2016 Category: Sports Medicine Source Type: research
The influence of gravimetric moisture content on studded shoe –surface interactions in soccer
This study investigates the relationships between: the gravimetric moisture content of a natural sand-based so ccer surface; surface stiffness measured via a bespoke impact test device; and surface traction measured via a bespoke mechanical test device. Regression analysis revealed that surface stiffness decreases linearly with increased gravimetric moisture content (p = 0.04). Traction was found to initially increase and then decrease with gravimetric moisture content. It was observed that: a surface of low moisture content provides low stud penetration and therefore reduced traction; a surface of high moisture content ...
Source: Sports Engineering - October 10, 2016 Category: Sports Medicine Source Type: research
Development of a markerless optical motion capture system for daily use of training in swimming
AbstractThe main objective of this research was to develop a markerless optical motion capture system that can be used for daily use in swimming training. The butterfly stroke was targeted since it is considered bilaterally symmetric in motion. The system consisted of a segmentation process to obtain the participant ’s silhouettes and a matching process to estimate the pose of the participant. A variable thresholding method was used to extract the silhouettes to solve non-uniform illumination in the recorded swimming video. Prior to the matching process, the human body was modeled as a series of nine segments to help the...
Source: Sports Engineering - September 20, 2016 Category: Sports Medicine Source Type: research
Chemical degradation of a paraffin wax-based binder used in granular composite sport surfaces
AbstractChemical changes in high-oil wax-based binders used in Thoroughbred horse racing synthetic surfaces are studied over a 7-year period in an effort to understand the effect of changes in the binder on track behavior. A wax or polymer binder is used to hold the sand, fiber, and rubber constituents together in addition to creating a hydrophobic coating on the sand. The binder was extracted from bulk samples obtained from sampling of a racetrack surface at the same location on a single racetrack. During the 7 years, the material components of the track were not altered nor was material added, although normal maintenan...
Source: Sports Engineering - September 12, 2016 Category: Sports Medicine Source Type: research
