This is one of the first studies to investigate sprint acceleration technique specific to cricketers with implications for fielding. Furthermore, this is the first study to compare the acceleration kinematics of cricketers who field predominantly in the infield or outfield. There were moderate effects for differences in height and body mass for the infielders and outfielders, even though the differences were not significant. This may be attributed to a greater prevalence of bowlers being in the outfield group. Bowlers tend to spend more time in the outfield, which can be partly evidenced through time-motion research that documents the distances these cricketers cover during match-play, where aside from the movement demands of bowling, they will often run from the pitch to the boundary in between overs (Petersen et al., 2009; 2010). In English county cricketers, bowlers were found to be taller (ES = 0.70) and heavier (ES = 0.60) than batsmen, but differences were non-significant with moderate effects (Johnstone and Ford, 2010). Nonetheless, the anthropometrical results infer that the subjects in the current study are physically representative of experienced cricketers. There were relatively few kinematic variables that differentiated between the groups, which is not uncommon for research analyzing the sprint technique of athletes (Murphy et al., 2003). Furthermore, there were no differences in sprint times between infielders and outfielders (Table 1), and no kinematic variables measured in this study that correlated with 0-5 m and 0-10 m time (Tables 5 and 6">6). In line with the study hypothesis, these results indicate that subjects had relatively similar sprint technique, regardless of their tendency to field in a particular area of the cricket field. It must also be acknowledged that out of all the technique correlations, only 18 were significant. A limitation of correlation investigations is that in addition to sprint kinematics, other technique parameters such as stance kinetics, and factors like flexibility, strength, and power, can have an effect on the statistical models (Brughelli et al., 2008). Future research should investigate other aspects of cricket acceleration technique, including stance kinetics and muscle recruitment during the sprint step, as well as the strength and power capabilities of cricketers. Nonetheless, there are important implications for cricketers that can be drawn from the analysis of acceleration technique in this study. Running speed is the product of step length and step frequency, and there can be a negative interaction between these variables, in that if one value is increased, the other may decrease (Hunter et al., 2004). This was seen in the current study, where there were negative relationships between step length and frequency (Table 5). A high step length (Lockie et al., 2013b) and step frequency (Lockie et al., 2011, Murphy et al., 2003) have been advocated for faster acceleration. There were no differences in step length and frequency between the infielders and outfielders (Table 1), and there was no one step variable that appeared to be more notable than the other (Tables 5 and 6">6). These results highlight the similarities in the selected step kinematics between infielders and outfielders. Given the fielding restrictions that occur during one-day and T20 matches (International Cricket Council, 2012a, b), it is important for cricketers to be able to produce step kinematics appropriate for both infielding and outfielding. The results suggest that the cricketers investigated in this study could achieve this. The infielders did have a significantly lower first step contact time when compared to the outfielders (Table 1). Shorter contact times have been recommended for faster acceleration (Lockie et al., 2011, Murphy et al., 2003), and this is needed for first step quickness. An effective first step is important for acceleration over short distances in team sport athletes (Lockie et al., 2011, Murphy et al., 2003), as well as for a fast change-of-direction (Hewit et al., 2013), which may be required to accelerate in the direction of the ball. This could be a function of the requirements of infielders, as they are positioned much closer to the batsmen, and have less time to react to balls when fielding (Bartlett, 2003). In addition, they are in a position to complete run-outs should batsmen attempt a quick single. Speed over short distances is key for cricketers when fielding, with Rudkin and O’Donoghue, 2008 finding high-intensity effort durations last approximately 1.3 s, which is slightly greater than the 0-5 m times from this study (Table 1). Nonetheless, there were no between-group differences in second step contact time (Table 1), and no significant correlations between contact time and lower-body kinematics (Table 6). There was, however, a significant correlation between second step lead elbow flexion and first step contact time (Table 5). This result suggests that a lower contact time relates to a greater degree of elbow flexion. Bhowmick and Bhattacharyya, 1988 suggested that the horizontal component of the arm swing acceleration may aid in increasing step length and regulating leg movement, while the vertical component may create a condition that enhances leg drive during stance. Potentially, a higher degree of elbow flexion could contribute to an enhanced leg drive that reduces the duration of stance. Further to this, the current investigation found that greater left shoulder range of motion related to a longer second step (Table 5). These results could also relate to the need for the arm movements during sprinting to help maintain dynamic stability, by facilitating the transfer of angular momentum between the upper- and lower-body about the vertical axis (Hinrichs, 1992). This is because a longer second step related not only to greater shoulder range of motion, but also greater flexion angles of the hip and knee. There were positive correlations between first step hip and knee flexion with first and second step length (Table 6). In line with the interaction between step length and frequency (Hunter et al., 2004), hip and knee flexion negatively correlated with step frequency (Table 6). As stated previously, flexion of the hip and knee is important for reducing the moment of inertia of the swing leg during this phase of the sprint step, and allows for a more effective leg recovery (Mero et al., 1992). Furthermore, with increases in running velocity, hip and knee range of motion and step length will increase (Mann and Hagy, 1980). Cricketers from this study with longer steps, and a lower step frequency, tended to flex the hip and knee to a greater extent during the swing phase. Additionally, there were no differences in hip and knee flexion during the first two steps of the 10-m sprint between infielders and outfielders (Tables 3 and 4">4), indicating similarities in leg recovery during the sprint step for all cricketers from this study. Knee extension tends to be abbreviated during sprinting, to allow for the leg to clear from the ground more quickly (Mann and Herman, 1985, Murphy et al., 2003). For the cricketers in this study, full knee extension for either the first or second step did not occur (Tables 3 and 4">4). In contrast to the knee, a more complete hip extension has been suggested for acceleration (Van Ingen Schenau et al., 1994). Interestingly, the outfielders had a significantly greater drive leg hip extension in the second step (Table 4). Given the need to balance angular momentum within the body (Hinrichs, 1992), this may be linked to the greater elbow flexion produced by the outfielders (Table 3). Nonetheless, this did not result in any differences in sprint time between the groups. It would be expected that for cricketers, as for other team sport athletes (Murphy et al., 2003), an effective extension of the drive leg is necessary for fast acceleration. There were no differences in first or second step plantar flexion and dorsi flexion between infielders or outfielders (Tables 3 and 4">4). However, a higher degree of first step ankle plantar flexion related to a greater second step length, and in turn a lower step frequency (Table 6). Greater plantar flexion, driven by the triceps surae to facilitate leg drive (Mann and Hagy, 1980), occurs with increases in running speed. As for hip and knee flexion, greater plantar flexion contributed to increased step length in cricketers. The influence of these hip, knee, and ankle actions on increasing step length has important implications for cricket sprint acceleration. Greater step lengths could be more beneficial for acceleration in cricket. Unlike other team sport athletes, cricketers do not have to evade opponents during match-play. This is one of the primary reasons why greater step frequencies have been previously recommended for acceleration in other team sport athletes (Murphy et al., 2003; Sayers, 2000). However, increasing step length has also been encouraged for sprint acceleration (Santana, 2000), and longer steps can enhance speed over short distances (Lockie et al., 2013b), In addition, Donati, 1995 suggested that there are more training mechanisms that can be used to improve step length, more so than for step frequency. This includes traditional sprint training (Kristensen et al., 2006, Lockie et al., 2012b), as well as supplementary protocols such as weights, plyometrics, and resisted sprint training (Lockie et al., 2012b). Cricket and strength and conditioning coaches could target this aspect of technique during speed training. As the results from this study suggested that cricketers demonstrated similar sprint kinematics regardless of whether they tend to field in the infield or outfield, this means that step length development could be beneficial for all cricketers. It should be acknowledged that this research used standard field testing protocols for assessing sprint acceleration, i.e. the subjects used a stationary start. Unless they are fielding in the slips cordon, cricketers will often walk towards the pitch as the bowler enters their delivery, then react while already moving to the path of the ball once hit. There should be further investigation of how cricketers can transition from this slow moving position, into a maximal acceleration, or a maximal acceleration following a change-of-direction to pursue the ball. In addition to the kinematics analysis conducted in this study, this could also incorporate the investigation of stance kinetics, given the importance of this component of technique (Lockie et al., 2013b; Spiteri et al., 2013). The analysis of the transition from maximal sprint acceleration to either catch or retrieve and throw a ball could then be conducted, to make the analysis even more specific to cricket. Perhaps most importantly, research should determine whether an improvement in sprint acceleration capabilities in cricketers will translate to what they do in the field. This would mean that a cricketer who can accelerate faster will decrease the time it takes to field a ball, and potentially make them a more effective fielder. Nevertheless, this research provides valuable insight into the acceleration technique of experienced cricketers. It is suggested that cricketers target step length development to improve acceleration over short distances specific to fielding. |