Effect of Loading Condition on Traction Coefficient Between Shoes and Artificial Turf Surfaces

Background. The interaction between a shoe and a turf surface is highly complex and difficult to characterize. Over the three decades since artificial turf was introduced, researchers have attempted to understand the traction caused by the interaction. However, some of the methodologies used for traction measurements have not capitalized on advances in currently available technology for testing and most testing conditions have not simulated realistic physiological loads. Method of Approach. To assess the effect of test condition on traction results, the newly designed TurfBuster testing device was used to collect traction data on FieldTurf™ brand artificial turf under varying conditions. Four cleated athletic shoes were tested under eight different vertical loads ranging from 222-1780 N. The static, dynamic, and peak traction coefficient values were calculated and averaged over three trials for each shoe and condition. Results. In all but the lowest vertical load condition, the static traction coefficient was less than the dynamic traction coefficient. There was a distinct separation found between 666 N and 888 N loading conditions for all three variables measured. Below the load condition of 666 N only one significant difference was found in all comparisons across and within shoe styles. Above 888 N multiple differences were found across shoe styles, but differences were not found within a shoe style until a load of at least 1554 N. Conclusions. At loads below 666 N the cleats perform almost identically at all three variables measured, static, dynamic, and peak traction coefficients. At loads above 888 N, shoe traction was different among the cleat styles for all traction variables. However, at loads between 888 N and 1334 N there were no differences found within a shoe style. This implies that each shoe has no performance difference in loads representative of up to one bodyweight. Due to these results the measurement of traction characteristics between cleated shoes and FieldTurf should be conducted at a load of at least 888 N to determine differences across shoe styles and loads ranging from 888 N to at least 1554 N to determine individual shoe characteristics

Influence of Towing Force Magnitude on the Kinematics of Supramaximal Sprinting

The purpose of this study was to determine the influence of towing force magnitude on the kinematics of supramaximal sprinting. Ten high school and collegiate aged track and field athletes ran 60m maximal sprints under 5 different conditions: non-towed (NT), Tow A (2.0% body weight), Tow B (2.8%BW), Tow C (3.8%BW), and Tow D (4.7%BW). Three-dimensional kinematics of a 4-segment model of the right side of the body were collected starting at the 35m point of the trial. Significant differences were observed in stride length (SL) and horizontal velocity of the center of mass (VH) during Tow C and Tow D. For Tow D, a significant increase in the distance from the center of mass to the foot at touchdown (DH) was also observed. Contact time (CT) decreased significantly in all towing conditions, while stride rate (SR) increased slightly (\u3c 2.0%) under towed conditions. There were no significant changes in joint or segment angles at touchdown, with the exception of a significant decrease in the flexion/extension angle at the hip during the Tow D condition. We concluded that towing force magnitude does influence the kinematics of supramaximal running. Furthermore, we suggest that coaches and practitioners adjust towing force magnitude for each individual and avoid using towing forces in excess of 3.8%BW

Muscle Synergies During a Single-Leg Drop-Landing in Boys and Girls

The purpose of this study was to investigate muscle activation patterns during a landing task in boys and girls through the use of muscle synergies. Electromyographical (EMG) data from six lower extremity muscles were collected from 11 boys and 16 girls while they performed single-leg drop-landings. EMG data from six leg muscles were rectified, smoothed, and normalized to maximum dynamic muscle activity during landing. Data from 100 ms before to 100 ms after touchdown were submitted to factor analyses to extract muscle synergies along with the associated activation and weighing coefficients. Boys and girls both used three muscle synergies. The activation coefficients of these synergies captured muscle activity during the pre-landing, touchdown, and post-landing phases of the single-leg drop-landing. Analysis of the weighing coefficients indicated that within the extracted muscle synergies the girls emphasized activation of the medial hamstring muscle during the pre-landing and touchdown synergy whereas boys emphasized activation of the vastus medialis during the post-landing synergy. Although boys and girls use similar muscle synergies during single-leg drop-landings, they differed in which muscles were emphasized within these synergies. The observed differences in aspects related to the muscle synergies during landing may have implications with respect to knee injury risk

Light-induced nuclear export reveals rapid dynamics of epigenetic modifications

We engineered a photoactivatable system for rapidly and reversibly exporting proteins from the nucleus by embedding a nuclear export signal in the LOV2 domain from phototropin 1. Fusing the chromatin modifier Bre1 to the photoswitch, we achieved light-dependent control of histone H2B monoubiquitylation in yeast, revealing fast turnover of the ubiquitin mark. Moreover, this inducible system allowed us to dynamically monitor the status of epigenetic modifications dependent on H2B ubiquitylation

Correlating in Vitro and in Vivo Activities of Light-Inducible Dimers: A Cellular Optogenetics Guide

Light-inducible dimers are powerful tools for cellular optogenetics, as they can be used to control the localization and activity of proteins with high spatial and temporal resolution. Despite the generality of the approach, application of light-inducible dimers is not always straightforward, as it is frequently necessary to test alternative dimer systems and fusion strategies before the desired biological activity is achieved. This process is further hindered by an incomplete understanding of the biophysical/biochemical mechanisms by which available dimers behave and how this correlates to in vivo function. To better inform the engineering process, we examined the biophysical and biochemical properties of three blue-light-inducible dimer variants (cryptochrome2 (CRY2)/CIB1, iLID/SspB, and LOVpep/ePDZb) and correlated these characteristics to in vivo colocalization and functional assays. We find that the switches vary dramatically in their dark and lit state binding affinities and that these affinities co..

Engineering an improved light-induced dimer (iLID) for controlling the localization and activity of signaling proteins

Photoactivatable proteins are powerful tools for studying biological processes. Light-induced dimers are especially useful because they can be turned on and off with high spatial and temporal resolution in living systems, allowing for control of protein localization and activity. Here, we develop and apply methods for identifying mutations that improve the effectiveness of a light-induced dimer. The engineered switch is modular, can be used in most organisms, has more than 50-fold change in binding affinity upon light stimulation, and can be used to initiate signaling pathways in a specific region of a cell

Lamellipodia are crucial for haptotactic sensing and response

Haptotaxis is the process by which cells respond to gradients of substrate-bound cues, such as extracellular matrix proteins (ECM); however, the cellular mechanism of this response remains poorly understood and has mainly been studied by comparing cell behavior on uniform ECMs with different concentrations of components. To study haptotaxis in response to gradients, we utilized microfluidic chambers to generate gradients of the ECM protein fibronectin, and imaged the cell migration response. Lamellipodia are fan-shaped protrusions that are common in migrating cells. Here, we define a new function for lamellipodia and the cellular mechanism required for haptotaxis – differential actin and lamellipodial protrusion dynamics lead to biased cell migration. Modest differences in lamellipodial dynamics occurring over time periods of seconds to minutes are summed over hours to produce differential whole cell movement towards higher concentrations of fibronectin. We identify a specific subset of lamellipodia regulators as being crucial for haptotaxis. Numerous studies have linked components of this pathway to cancer metastasis and, consistent with this, we find that expression of the oncogenic Rac1 P29S mutation abrogates haptotaxis. Finally, we show that haptotaxis also operates through this pathway in 3D environments

Determining crystal structures through crowdsourcing and coursework

We show here that computer game players can build high-quality crystal structures. Introduction of a new feature into the computer game Foldit allows players to build and real-space refine structures into electron density maps. To assess the usefulness of this feature, we held a crystallographic model-building competition between trained crystallographers, undergraduate students, Foldit players and automatic model-building algorithms. After removal of disordered residues, a team of Foldit players achieved the most accurate structure. Analysing the target protein of the competition, YPL067C, uncovered a new family of histidine triad proteins apparently involved in the prevention of amyloid toxicity. From this study, we conclude that crystallographers can utilize crowdsourcing to interpret electron density information and to produce structure solutions of the highest quality

The Influence of Manga on the Graphic Novel

This material has been published in The Cambridge History of the Graphic Novel edited by Jan Baetens, Hugo Frey, Stephen E. Tabachnick. This version is free to view and download for personal use only. Not for re-distribution, re-sale or use in derivative works. © Cambridge University PressProviding a range of cogent examples, this chapter describes the influences of the Manga genre of comics strip on the Graphic Novel genre, over the last 35 years, considering the functions of domestication, foreignisation and transmedia on readers, markets and forms

Biomechanical Evaluation of Provocative Tests for Superior Glenoid Labrum Lesions

During the recent era of arthroscopic surgery, many distinct shoulder pathologies such as the superior labrum anterior to posterior (SLAP) lesion have been identified. The unfortunate fact of arthroscopy is that it is invasive and extremely costly. There are clinical examinations that aid in the diagnosis of SLAP lesions, but they are not considered stand-alone diagnoses like arthroscopy. Therefore, it is beneficial to improve the overall accuracy of the current clinical tests used to diagnose SLAP lesions. Of the existing tests, 10 are meant to actively engage the long head of the biceps brachii (LHBB) to create tension in the biceps tendon. The tension in the LHBB elicits pain and/or apprehension in the superior glenoid region, a positive sign of superior labral pathology. Eleven male subjects with no history of shoulder pathology were recruited to participate in the study. Their average age was 25 years. Each subject was subjected to 10 provocative tests for SLAP lesions. The ten tests were: Active Compression, Anterior Slide, Biceps Load, Biceps Load II, Compression Rotation, Crank, Pronated Load, Resisted Supination External Rotation, Speed\u27s and Supination Sign test. Each test was performed three times in a random order. During the tests electromyography (EMG) of seven muscles surrounding the shoulder was monitored (Noraxon Telemyo 900, 1250Hz). The muscles monitored included: long and short head of biceps brachii, anterior deltoid, pectoralis major, latissimus dorsi, infraspinatus, and supraspinatus. Six of the muscles were monitored with surface electrodes while the supraspinatus was monitored using an indwelling electrode. Maximum voluntary isometric contractions (MVIC) were used to normalize the EMG data among subjects. The variables analyzed from the EMG data were LHBB activation (% MVIC) and selectivity, which measured the contribution of the LHBB to the total muscle activation recorded during the test. Of the 11 subjects, six were instrumented with electromagnetic motion capture hardware (Polhemus Fastrak, 30Hz) to monitor the translation of the humeral head relative to the scapula. The subjects were instrumented with sensors on the thorax (C7), humerus (proximal to epicondyles), and scapula (scapular tracker). There was a statistical difference between tests based on LHBB activation (p=0.000), selectivity (p=0.005), and superior/inferior translation of the humeral head (p=0.023). The Biceps Load, Biceps Load II, Speed\u27s and Active Compression (palm up) tests yielded the highest activation. The Biceps Load, Biceps Load II, Speed\u27s, and Resisted Supination External Rotation tests elicited the best selectivity. The Supination Sign test had the most superior translation of all the tests. The top tests based on EMG were the Biceps Load, Biceps Load II, and Speed\u27s tests. The Supination Sign test was the best based on the amount of superior humeral head translation generated