The influence of tracking marker locations on three-dimensional wrist kinematics.

OBJECTIVES: To determine the influence of tracking marker locations on wrist kinematics during free movements and the golf swing, with the intention of recommending a solution that generates meaningful three-dimensional wrist kinematics. DESIGN: Repeated measures. METHODS: Six participants performed free movements of flexion/extension, radial/ulnar deviation and forearm supination/pronation, with a further sixteen participants performing golf drives. A passive motion capture system tracked four different marker sets located on participants' hand and forearm segments. Variables of peak angle and range of motion were used to compare marker sets during free movements and angles at the top of the backswing and impact were compared during the golf swing. RESULTS: Wrist marker set had a large (η2≥0.557) and often significant (p≤0.051) effect on the variables measured during free movements, and a mixed (η2≥0.108, p≤0.198) effect on wrist angles during the golf swing. Wrist axial rotation range of motion during free forearm supination/pronation revealed the greatest difference between marker sets (∼42°). The large values generated by two of the marker sets for this rotation appeared to influence the values of flexion/extension and radial/ulnar deviation during the golf swing. CONCLUSIONS: The location of markers used to measure wrist kinematics can have a large effect on the angles generated. A solution of two markers located at the distal end of the forearm and one at the proximal, appears to minimise values of wrist axial rotation during free forearm supination/pronation and, consequently, produce more meaningful three-dimensional wrist kinematics.

Elite Players' Perceptions of Football Playing Surfaces: A Qualitative Study.

Purpose: The decision by the International Football Association Board in 2004 to approve the use of artificial surfaces in elite football (soccer) competitions remains controversial amongst many players, managers and coaching staff. The aim of this study was to conduct a comprehensive assessment of players' opinions to better understand the influence of playing surfaces on the game of football and identify factors that may contribute to differences of opinion. Method: Qualitative data were collected from 103 elite footballers and 21 coaching staff during a series of interviews and focus groups. A thematic analysis was conducted to identify patterns in the data. Results: Players considered that the type and condition of a playing surface influenced ball-surface interactions, game play, tactics/strategy, footwear selection, movement, risk of injury and fatigue. Together these influence a player's perception of the suitability of a surface and also their mindset, which could ultimately affect their performance. Conclusion: The majority of participants in this study expressed a higher preference for natural grass over artificial turf pitches. A perceived increased risk of injury on artificial turf remains a primary concern despite a lack of supporting evidence in research studies. To address this discrepancy, the reporting of muscle soreness and the effect of constant surface switching merit further consideration. Not all participants shared the same views and player characteristics such as age, surface experience, injury history and playing style/position were found to be potential factors that could account for differences in elite players' opinions regarding the surfaces used in football.

Perceived Links Between Playing Surfaces and Injury: a Worldwide Study of Elite Association Football Players.

BACKGROUND: Injuries in association football (soccer) are debilitating for players and can also be detrimental to the success of a team or club. The type or condition of a playing surface has been empirically linked to injuries, yet results are inconclusive. The overall purpose of this study was to analyse elite football players' perceived links between playing surfaces and injury from a worldwide cohort of players. The results of this study can help to inform areas for future playing surface research aimed at trying to alleviate user concerns and meet user (i.e. the player) needs. METHODS: Quantitative data were collected from 1129 players across the globe to address the aim of this study. RESULTS: Ninety-one percent of players believed the type or condition of a surface could increase injury risk. Abrasive injuries, along with soreness and pain, were perceived to be greater on artificial turf. Surface type, surface properties and age were all potential risk factors identified by the players and linked to the playing surfaces. CONCLUSIONS: The results identified three areas where future research should be focussed to help develop surfaces that alleviate user concerns and meet user (i.e. player) needs: (i) current reporting of soreness, pain or fatigue as injuries, (ii) contribution of surface properties to injury; and (iii) surface experience of players from different countries differentiates their views of injury risk.