Cricket is a popular sport played in many countries, including England, Australia, India, New Zealand, and South Africa. There are several versions of cricket, such as the long form played over five consecutive days, and shorter formats including one-day and Twenty20 (T20) cricket. T20 cricket, which is played over a duration of approximately three hours, has grown in popularity in recent years, and its proliferation has changed the emphasis of certain physical requirements for players (Petersen et al., 2010; 2011). For example, T20 cricket requires approximately 50-100% more maximal sprints per hour for all players when compared to multi-day matches (Petersen et al., 2010). Sprints during cricket are often centered about crucial match situations such as running between the wickets, the run-up and delivery during fast bowling, or sprinting to field a ball (Bartlett, 2003; Duffield and Drinkwater, 2008; Petersen et al., 2010; Rudkin and O'Donoghue, 2008). In cricket only select players will bowl, while certain players will have greater responsibility to score runs when batting. However, all cricketers must field, and complete maximal sprints when fielding.
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A cricket field can be divided into two main sections about the pitch--an infield and an outfield (Figure 1). As defined by the International Cricket Council (2012a), to set the infield, two semi-circles with a radius of 27.43 meters (m) are drawn, with the middle stump at each end of the pitch as the center. The outfield lies from the infield to the boundary. The square boundaries are a minimum of 137.16 m apart, with the shorter of the two being a minimum 59.43 m from the center of the pitch. The straight boundaries at both ends of the pitch are a minimum of 64 m from the pitch center. In one-day (International Cricket Council, 2012a) and T20 (International Cricket Council, 2012b) cricket, there are restrictions on how many players are allowed to field in the outfield during certain overs to increase scoring opportunities for the batsmen. As the match progresses, more players are allowed in the outfield. For example, at the start of a T20 innings, only two players are allowed in the outfield; at the end of an innings, a maximum of five players will be in the outfield (International Cricket Council, 2012b).
Certain players will specialize in particular fielding positions, often due to other skills important to cricket. For example, a good reaction time is needed in the infield, as fielders are closer to the batsman and have less time to react to balls that are hit hard by batsmen (Bartlett, 2003), whereas outfielders require a strong throwing arm to field the ball back to the infield (Figure 1). Nonetheless, cricketers must be adept at fielding in either the infield or outfield, depending on what is required during a match. Fielders are expected to reduce the number of runs a batting side can accumulate by restricting the number of scoring shots and aiding in dismissals, by catching a ball on the full or performing a run-out. Fielding in cricket will often require a maximal sprint in pursuit of the ball after it has been hit by a batsman, and these sprints tend to be over a short distance (Rudkin and O'Donoghue, 2008). For example, state-level Australian cricketers had an average sprint distance of 15 [+ or -] 4 m when in the field (Petersen et al., 2010). As a result, the acceleration capacity of a cricketer takes on paramount importance.
It must be acknowledged that not every time a cricketer fields a ball will involve a maximal sprint. However, in those situations which do, it will be critical to the teams' performance, as the fielder must move to the ball as quickly as possible to dismiss a batsman or to prevent runs being scored. There has been little analysis of sprinting in cricket, with the focus previously upon testing (Johnstone and Ford, 2010, Lockie et al., 2012a; 2013a), and the influence of leg guards when running between the wickets (Webster and Roberts, 2011). It is of interest to analyze the sprint acceleration abilities of those players who field predominantly in the infield or outfield, as there may be certain aspects to technique (e.g. a faster first step for infielders) that are typical of cricketers that field in a certain position. However, there could be no differences given that many players may be required to field in both the infield and outfield during a match. This must be confirmed through analysis of acceleration technique in cricketers.
The technique adopted by cricketers when sprinting in the field should be typical of other team sport athletes. Regarding step kinematics, a high step frequency and low contact time during stance has been advocated for faster sprint times (Lockie et al., 2011, Murphy et al., 2003). Longer step lengths have also been found to be beneficial for speed over 10 m (Lockie et al., 2013). The step kinematics produced will be influenced by upperand lower-body movement. Greater arm range of motion has been said to assist with leg drive during acceleration (Bhowmick and Bhattacharyya, 1988). Greater extension of the drive leg (the leg in contact with the ground) accompanies increased running speed (van Ingen Schenau et al., 1994). For the swing leg (the leg not in contact with the ground), increased hip and knee flexion reduces the moment of inertia of the limb during the recovery phase of the sprint step (Mero et al., 1992). However, the extent to which these movements influence acceleration step kinematics in cricketers has yet to be defined. Given the importance of acceleration for fielders when pursuing the ball (Petersen et al., 2010), this is a situation that should be rectified. This is more pertinent when considering that fielding practice for cricketers may focus purely on throwing and catching, without considering the need to move rapidly to retrieve the ball (Finch et al., 2010).
In modern-day cricket, batsmen attempt more quick singles for balls hit into the infield (Duffield and Drinkwater, 2008), and attempt to complete more runs for balls hit into the outfield (Petersen et al., 2010). Fielders must be able to accelerate effectively to restrict these scoring options. Therefore, this research analyzed the sagittal plane kinematics of experienced cricketers during the first two steps of a 10-m sprint. A 10-m sprint was used as it is a common assessment of acceleration in team sport athletes (Jarvis et al., 2009, Lockie et al., 2011; 2013b). The first two steps were analyzed because of their importance for acceleration (Lockie et al., 2011, Murphy et al., 2003). The first goal of this research was to ascertain whether there are acceleration kinematics that differentiates cricketers who primarily field in the infield or outfield. The second goal was to determine whether there are technique characteristics that have a greater influence on sprint acceleration and step kinematics. It is hypothesized that there will be no differences in sprint kinematics for infielders or outfielders, as all cricketers may field in both the infield and outfield during a match. Furthermore, parameters such as greater joint ranges of motion will relate to faster acceleration, and longer step lengths and faster step frequencies. This research will provide beneficial information for cricket and strength and conditioning coaches, as it will detail acceleration kinematics that should be trained specifically for cricketers.
Eighteen (n = 18) experienced male cricketers from the same cricket club that played in a regional competition (age = 24.06 [+ or -] 4.87 years; height = 1.81 [+ or -] 0.06 m; mass = 79.67 [+ or -] 10.37 kilograms [kg]) were recruited for this study. Subjects were recruited if they: were 18 years of age or older; were currently playing premier league or division one in the regional competition; had at least three years' experience playing cricket; were currently training for cricket (greater than or equal to three hours per week); and did not have any medical conditions that would compromise participation in the study. The methodology and procedures used in this study were approved by the institutional ethics committee, and conformed to the policy statement with respect to the Declaration of Helsinki. All subjects received a clear explanation of the study, including the risks and benefits of participation, and written informed consent was obtained prior to testing.
The method for defining subjects as infielders or outfielders was adapted from research that used subjective methods to rank or define athletes (Wilkinson et al., 2009). The premier league team coach and captain were asked to define each subject as an infielder or outfielder. Although cricketers will field in both the infield and outfield, the coach and captain were asked where they would prefer the subject to field during a match. If there was a difference in opinion, a resolution was obtained through discussion between the coach and captain...