Quantifying Cricket Fast-Bowling Skill

Home , Bouncer (cricket), Bowling (cricket), Brett Lee, Delivery (cricket), Fast bowling, Grip (cricket bowling)

Simon A. Feros, Warren B. Young, and Brendan J. O’Brien

Objectives: To evaluate the current evidence regarding the quantification of cricket fast-bowling skill. Methods: Studies that assessed fast-bowling skill (bowling speed and accuracy) were identified from searches in SPORTDiscus (EBSCO) in June 2017. The reference lists of identified papers were also examined for relevant investigations. Results: A total of 16 papers matched the inclusion criteria, and discrepancies in assessment procedures were evident. Differences in test environment, pitch, and cricket ball characteristics; the warm-up prior to test; test familiarization procedures; permitted run-up lengths; bowling spell length; delivery sequence; test instructions; collection of bowling speed data; and collection and reportage of bowling accuracy data were apparent throughout the literature. The reliability and sensitivity of fast-bowling skill measures have rarely been reported across the literature. Only 1 study has attempted to assess the construct validity of its skill measures. Conclusions: There are several discrepancies in how fast-bowling skill has been assessed and subsequently quantified in the literature to date. This is a problem, because comparisons between studies are often difficult. Therefore, a strong rationale exists for the creation of match-specific standardized fast-bowling assessments that offer greater ecological validity while maintaining acceptable reliability and sensitivity of the skill measures. If prospective research can act on the proposed recommendations from this review, then coaches will be able to make more informed decisions surrounding player selection, talent identification, return to skill following injury, and the efficacy of short- and long-term training interventions for fast bowlers.

Keywords: speed, accuracy, assessment, reliability, validity

Fast bowling is a specialized discipline within the game of bowler should have the necessary skill to bowl quickly, accurately, cricket. Typically, fast bowlers form the majority of the “bowling and consistently fast and accurately3 during a bowling spell (series attack” against the opposition team. Each fast bowler presents with of overs) or repeated bowling spells. A faster delivery speed simply varying skill sets and abilities. Some bowlers are renowned for their reduces a batter’s reaction time and movement time,4 which may excellent bowling accuracy (eg, Glenn McGrath, James Anderson), result in a greater likelihood of a batter not striking the ball or not whereas others can bowl at express speeds (eg, Brett Lee, Shoaib timing the ball strike correctly. Consistent, fast-bowling speeds Akhtar). Despite these differences, the objective of the bowling maintain this (aforementioned) advantage throughout a bowling attack is to minimize runs scored by the batting side while spell or match (regardless of changes up and down in ball release dismissing opposition batters. speed, which are critical for deceiving a batter). Accurate delivery Currently, the International Cricket Council (ICC) calculates is also important. Accurate delivery refers to a ball that follows the the performance of international-standard fast bowlers. Fast fast bowler’s intended trajectory (line of ball flight, and length of bowlers are ranked and scored in each match format participated where the ball lands on the pitch).5 If fast bowlers can identify a ’ in (eg, Twenty20, One-Day International, and Test/First Class). batter s technical faults, then an accurate delivery can result in a A fast bowler’s performance score is calculated by the number of dismissal or reduce the amount of runs scored from that delivery. fi dismissals taken (ie, wickets), the performance score of the dis- Consistently accurate bowling can make it dif cult for batters to missed batter, and the amount of runs conceded, while other factors score throughout a bowling spell, which can lead to an increase in such as total runs scored in the match, number of overs bowled, and scoring pressure and poorer decision making and stroke play from the match result also have an influence.1 There are 2 main short- the batter. comings of this system: No information on fast bowlers’ speed, Some of these bowling qualities have been assessed in lab accuracy, and consistency is available (ie, skills), and only fast settings to quantify skill in national junior, emerging, and national senior fast bowlers.6 To date, every fast-bowling test has involved bowlers of international standard receive a rating (ie, ratings are not the assessment of closed-skill performance. Given that there is a available for cricketers of national standard and below). The latter lack of competition between bat and ball with a closed-skill problem is significant, as participation in Australian cricket reached assessment (usually because there is no batter), it can be argued approximately 1.3 million during season 2014/2015,2 with only a that lab-based or field tests are useful for measuring fast-bowling very small percentage of those representing their country. This skill (eg, ball release speed, accuracy, and the consistency of both means that a majority of cricketers have no formal assessment of skills), but not “performance.” However, quantification of fast- fast-bowling skill. bowling skill allows coaches to make informed decisions regarding Although there are many elements that determine fast-bowling player selection, talent identification, return to match play follow- 1 performance during match play, it can be argued that an elite fast ing injury, and efficacy of coaching/training interventions. It can also enable a fast bowler to better understand his or her stronger and Feros is with the Centre for Sports Research, School of Exercise and Nutrition weaker skill sets. However, several discrepancies exist across the Sciences, Deakin University, Waurn Ponds, VIC, Australia. Feros, Young, and literature in how fast-bowling skill has been assessed to date. O’Brien are with the Faculty of Health, Federation University Australia, Mt Helen, Therefore, the purpose of this review is to highlight the methodo- VIC, Australia. Feros ([email protected]) is the corresponding author. logical inconsistencies in quantifying fast-bowling skill. 830 Quantifying Cricket Fast-Bowling Skill 831

Methods (Literature Search) Although an indoor facility may reduce the ecological validity of the assessment, it is beneficial for controlling environmental factors During June 2017, an English language search of the SPORTDis- such as wind, rain, temperature, and humidity, especially when the cus (EBSCO) database was performed to identify papers that had effects of these variables on fast-bowling skill is not understood. In measured fast-bowling skill for cricketers of any playing level. attempt to enhance the ecological validity of the assessment, 5 of Combinations of the following keywords were used as search the reviewed studies conducted testing outdoors.15–19 All 5 studies terms: “pace bowlers,”“fast bowlers,”“pace bowling,”“fast reported ambient temperature (ranging from 16.0°C to 31.9°C). bowling,” and “cricket.” The reference lists of identified papers Four of the studies collected relative humidity data (ranging from were also examined for relevant studies. 55.0% to 77.5%).16–19 However, none of the studies recorded the Studies were selected based on the following inclusion criteria: barometric pressure or wind speed/direction in the assessment. (1) bowling speed and accuracy were measured and reported in the fast-bowling assessment, (2) the assessment of skill was conducted Pitch Characteristics on fast bowlers only, irrespective of playing level, (3) the full text of the investigation was available in English, and (4) the investigation In Australian cricket, amateur club-level cricketers and above was published in a peer-reviewed scientific journal. Sixteen papers usually play on turf pitches, whereas synthetic carpet pitches identified met the inclusion criteria for this review (Figure 1). (overlaying concrete) are used for junior cricket. The variety and Because of limited original peer-reviewed investigations and condition of surfaces are likely to produce differences in ball bounce 20 the broad range of methodological approaches in assessing fast- characteristics (ie, speed, angle, and consistency) off the pitch, bowling skill, this article was constructed as a descriptive review affecting bowling accuracy measurement for some assessments 6–9,11–15,17–19 article. These studies are summarized in Table 1, along with skill using a vertical target sheet at the batting end. Ball 20 data in Table 2, to demonstrate the variability across the literature. and Hrysomallis investigated the ball bounce characteristics of 2 fi This review is presented in separate sections to highlight the synthetic cricket pitches and compared their ndings to natural turf methodological discrepancies in fast-bowling assessments within data. The traditional synthetic pitch produced similar speed ratios the literature. (before and after bounce) to natural turf, whereas the all-seasons synthetic pitch resulted in a lower speed ratio. Both synthetic pitches displayed rebound angles greater than natural turf,20 highlighting Test Environment potential implications for the assessment of bowling accuracy. The majority of fast-bowling tests have been conducted indoors, in Finally, the consistency of all measures (defined as the coefficient a lab setting that is quite possibly foreign to participants.3,6–14 of variation) appears to be related to the initial speed prebounce. Both synthetic surfaces were most consistent at fast speeds (29 m·s−1), while the traditional and all-seasons were least consistent at slow (13 m·s−1) and medium speeds (20 m·s−1), respectively.20 Eight of the reviewed fast-bowling assessments did not report the pitch surface.3,5,10,11,13,15,16,19 Others mentioned using a synthetic grass pitch,6–8,14 a synthetic rubber pitch,9 and a natural turf pitch.17,18 None of the assessments reported measuring ball bounce characteristics. Nevertheless, given that a variety of pitches have been used in assessment, it is reasonable to assume that there would be considerable variance in the quantification of bowling accuracy. The control of pitch surface and condition presents an interesting challenge in fast-bowling skill assessment. There may be some fast bowlers who perform better on particular pitches, and some who adapt more quickly to pitch conditions than others do. Given the logistical challenge for controlling pitch type, it is probably best to provide an adequate familiarization period before testing, where fast bowlers have sufficient time to adapt to the pitch surface and condition and learning effects can be controlled.

Ball Characteristics The traditional cricket ball is composed of an inner core made of cork and/or rubber composite, followed by 5 layers of wet yarn and compressed cork sheets that are covered by a plastic or leather inner cap.21 The outer cover of the cricket ball can be made of polyure- thane, rubber, or leather.21 It is possible that the differences in outer covers would affect ball ﬂight and bounce characteristics. Ball and Hrysomallis20 reported no signiﬁcant differences (P > .05) in ball bounce characteristics in 2-piece and 4-piece senior leather Kook- aburra balls. Only one of the examined studies reported the composition of the cricket balls used,9 which involved a rubber ball for U’11 bowlers and a leather ball for U’13 and U’15 bowlers. Figure 1 — Visualization of the systematic searching process. The ball bounce characteristics were not investigated.

IJSPP Vol. 13, No. 7, 2018 Table 1 Summary of the Assessment Procedures Discussed in This Review Ball characteristics (mass/2- or 4-piece/ Test Deliveries/ Reference Setting Pitch cover/color) Warm-up instruction Sequence BAT #T Devlin et al16 Outdoor ––/–/–/– First 5 stages of shuttle Match intensity 2 × 6 overs/no No 1 run followed by gentle change stretching Duffield et al15 Outdoor ––/–/–/–– –2 × 6 overs/PPR No 6 Elliott et al9 Indoor SR U’11: 110 g/–/ Regular fast-bowling Match intensity 15 balls/no No 1 rubber/– warm-up change U’13: 142 g/–/ leather/– U’15: 156 g/–/ leather/– Feros et al7 Mainly SG 156 g/–/–/– General and specific warm- Match intensity 1 × 4 overs/ No 5 indoor up, including practice PPR deliveries of gradually increasing speed and at different targets Feros et al14 Mainly SG 156 g/2-piece/ General and specific warm- Match intensity 1 × 8 overs/ Yes 5 indoor leather/red up, including practice PPR deliveries of gradually increasing speed and at different targets Feros et al8 Mainly indoor SG –/–/–/– General and specific Match intensity 1 × 8 overs/ Yes 5 warm-up PPR Gamage et al19 Outdoor ––/–/–/– Provided, but no Match intensity 18 balls/no No 1 details change McNamara et al5 –––/–/–/–– –2 × 6 overs/ Yes 1 nominated by bowler Minett et al17 Outdoor T 156 g/4-piece/ Standardized 10-min warm- Match intensity 1 × 10 overs/ No 6 leather/red up (jogging, stretching, and PPR practice deliveries) in 1 × 4 overs/ match-like conditions PPR Minett et al18 Outdoor T 156 g/4-piece/ Standardized 10-min warm- Match intensity 1 × 6 overs/ No 6 leather/white up, including jogging, PPR stretching, and 10 practice deliveries with a gradual increase in bowling speed to match intensity Petersen et al10 Indoor – 156 g/4-piece/leather/red Standardized warm-up, Match intensity 18 balls/no No 1 consisting of a 5-min jog, change stretching, and several warm-up deliveries of gradually increasing speed Phillips et al6 Indoor SG –/–/–/–– Match intensity 30 balls /PPR 2D 3 Portus et al11 Indoor ––/4-piece/leather/white Participants undertook a – 1 × 8 overs/ No 2 warm-up routine commonly minimal used and specific to fast changea bowling Spratford et al12 Indoor S –/–/–/– Typical of normal routine Match intensity 1 × 4 overs/ No 3 PPR Taliep et al3 Indoor ––/4-piece/–/– 20-m shuttle runs and Match intensity 1 × 12 overs/no No 1 stretches. Subjects allowed change to bowl as many balls as needed to further warm-up Wickington and Indoor – Variable/4-piece/–/– A standardized warm-up Match intensity 1 × 13 balls/no No 3 Linthorne13 that included bowling at change least 6 deliveries at gradu- 1 × 10 balls/no ally increasing speed change Abbreviations: BAT, batter; PPR, preplanned but randomized; S, synthetic; SG, synthetic grass; SR, synthetic rubber; T, turf; 2D, two dimensional; #T, number of targets; —, not reported. aBowlers nominated 3 “yorker” (full-pitched delivery) deliveries in test, acting as the second target in this test.

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Table 2 Summary of the Skill Data From Each Fast-Bowling Assessment Participants Age in years Bowling speed Bowling accuracy References (number/gender/level) (mean [SD]) (mean [SD]) (mean [SD]) Devlin et al16 7/male/subelite 21 (1) EUH: 104.8 (8.2) km·h−1 Data not reported in text DHY: 101.5 (4.1) km·h−1 Duffield et al15 6/male/national 23 (3) F6: 125.7 (5.1) km·h−1 F6: 40.4 (16.1) AU S6: 125.4 (4.5) km·h−1 S6: 41.6 (18.0) AU Elliott et al9 37/–/– U’11: 10.6 19.8–20.1 m·s−1 Data not reported in text U’13: 12.5 21.1–21.4 m·s−1 U’15: 14.7 23.3–23.6 m·s−1 Feros et al7 17/male/amateur club 22.4 (6.1) Peak: 105.8 (7.8) km·h−1 RE: 451.6 (92.7) mm Mean: 101.2 (8.1) km·h−1 Feros et al14 13/male/amateur club 22.8 (5.6) Test 1 Test 1 Peak: 33.0 (2.2) m·s−1 RE: 43.3 (7.5) cm Mean: 31.3 (2.4) m·s−1 BVE: 40.0 (7.3) cm Variability: 0.8 (0.2) m·s−1 Test 2 Test 2 RE: 41.3 (8.1) cm Peak: 33.1 (2.3) m·s−1 BVE: 36.0 (7.3) cm Mean: 31.3 (2.4) m·s−1 Variability: 0.8 (0.3) m·s−1 Feros et al8 31/male/amateur club 21.7 (4.7) RE ME: 29.7 (1.9) m·s−1 RE ME: 42.5 (14.3) cm RE MI: 28.8 (2.1) m·s−1 RE MI: 42.3 (5.9) cm Gamage et al19 10/–/international 22.2 (2.1)a FR before training: 124.5 (5.5) km·h−1 Delivery line only: FR after training: 123.2 (5.2) km·h−1 FR before training: 34.4 (4.2) AU FR after training: 27.5 (6.4) AU McNamara et al5 7/–/first class or international 22.3 (3.4) 124.2 (6.1) km·h−1 Data not reported in text Minett et al17 8/male/state 23.3 (4.9) Peak: 125.0 (7.0) km·h−1 46.6 (5.9) AU Mean: 118.0 (8.0) km·h−1 Minett et al18 10/male/amateur club and 23 (8) 114.1 (7.2) km·h−1 44.2 (12.5) AU junior state Petersen et al10 20/male/amateur club 22 (3) CON, before training: 108.3 (4.4) km·h−1 CON, before training: 19% (9%) CON, after training: 109.6 (4.3) km·h−1 CON, after training: 22% (7%) Phillips et al6 8/–/nationally contracted 29.0 (3.2) Data presented only in figure Data not reported in text 12/–/emerging state 21.2 (3.3) 12/–/junior national 17.3 (0.7) Portus et al11 14/–/first grade 23.3 (3.7) 32.1 m·s−1 Overs 1–2: 727 points Overs 3–4: 798 points Overs 5–6: 702 points Overs 7–8: 779 points Spratford et al12 69/male/national U’19, 21.3 (4.5) Short DS: 120.1 (6.1) km·h−1 Short DS: 41.4% (11.5%) senior state, Medium DS: 122.5 (6.1) km·h−1 Medium DS: 37.0% (19.0%) and international Long DS: 123.4 (4.2) km·h−1 Long DS: 32.3% (11.3%) Taliep et al3 22/–/premier club 21.0 (2.3) Over 1: 32.9 (2.1) m·s−1 Over 1: 21.6 (79.0) cm Over 12: 32.1 (1.8) m·s−1 Over 12: 20.1 (81.0) cm Wickington and 10/male/county academy 24 (5) CON, before training: 29.7 (1.7) m·s−1 Data not reported in text Linthorne13 CON, after training: 29.2 (1.2) m·s−1 Abbreviations: AU, arbitrary units; BVE, bivariate variable error; CON, control; DHY, dehydrated condition; DS, delivery stride; EUH, euhydrated condition; FR, fluid- retention trial; F6, first spell of 6 overs; ME, maximal-effort deliveries; MI, match-intensity deliveries; RE, radial error; S6, second spell of 6 overs; —, not reported. a Age representative of 30 participants in this study.

Junior cricketers (under 13 y) are required to bowl with a may influence bowling speed and accuracy. However, further lighter ball (133–144 g) compared with that used by senior males investigation on the optimal size (mass and circumference) for (156–163 g) and senior females (140–151 g).22 The Marylebone juniors and females is required. Nevertheless, some of the reviewed Cricket Club also states that juniors are to bowl with a cricket ball studies have not explicitly reported the mass of the that is slightly smaller in diameter (20.5–22 cm) than that used by ball,3,5,6,8,11,12,15,16,19 and most investigations have not stated the senior males (22.4–22.9 cm) and senior females (21–22.5 cm).22 ball’s circumference.3,5–12,15–19 It is important to note that simply These rules were probably designed so that bowlers can grip the stating the brand of the cricket ball without specifying further ball more comfortably and deliver the ball efficiently. Because fast details can make it difficult to ascertain ball mass and circumfer- bowling is a highly coordinated motion,23 disturbances to bowlers’ ence, as some ball names from a particular brand come in junior and optimal coordination through inappropriately scaled equipment senior sizes, sizes for males and females, and a variety of colors.

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It is possible that 2-piece cricket balls laterally deviate Permitted Run-up Lengths (or “swing”)moreinflight compared with 4-piece cricket balls. Anecdotally, the run-up is important for the fast bowler in attaining Two-piece cricket balls are often used in Australian junior cricket, “rhythm”27 and allows time for gradual acceleration into the whereas 4-piece cricket balls are used in top-tier community-level delivery phase of the motion. The length of a fast bowler’s run- cricket and above. Only 7 of the examined studies reported the type up is typically 17.7 (4.1) m (mean [SD]),15 with approach velocities of cricket ball used, which was mainly a 4-piece design.3,10,11,13,17,18 − ranging from 5.3 to 6.3 m·s 1.15,28,29 Approach velocity is likely to Four of these studies stated that a new cricket ball was used.10,14,17,18 influence the linear and angular velocities of some segments in The condition of the cricket ball may affect its ability to laterally delivering the ball. Fast bowlers are possibly accustomed to this deviate in flight, affecting measures of bowling accuracy with a segmental timing with their preferred approach velocity, so any vertical target sheet at the batting end.6–9,11–15,17–19 disruptions may detract from optimal coordination and reduce There is speculation on the color of the cricket ball and its effects bowling speed and accuracy. Bowling from a shorter run-up on lateral deviation in flight.24 Some assume that white cricket balls may prevent bowlers from attaining their typical approach velocity swing more in flight than the traditional red balls, even though and “rhythm.” Eight of the examined studies reported using a full manufacturers state the balls are made the same.21,24 The white cricket run-up,3,7–10,13–15 whereas others have not stated permitted run-up ball is used in limited-overs cricket (eg, Twenty/20 and One-Day lengths.5,6,11,12,16–19 International) so the ball can be better seen by batters under flood- lights.24 In recent times, test cricket has witnessed the introduction of the pink ball in its move to day/night cricket. Five of the reviewed Bowling Spell Length investigations reported the color of the cricket ball used in the fast- bowling assessment.10,11,14,17,18 Further research comparing the ball In Twenty20 and One-Day International cricket, bowlers are flight characteristics of different colored cricket balls is warranted. restricted to delivering 4 and 10 overs, respectively. There are no over restrictions in place for Test/First Class cricket. The equal most frequent spell length of choice in a fast-bowling assessment is Warm-up Prior to Test 4 overs,7,12,17 which is more specific to the demands of Twenty20 Performing a warm-up prior to an event of short duration cricket. Other studies have comprised 6,18 8,8,11,14 and 10 overs,17 (eg, bowling a cricket ball) has been shown to enhance muscle relating to the demands of One-Day International cricket, but also temperature, resulting in decreased muscle and joint stiffness, Test/First Class cricket, where a longer spell can also occur. Some enhanced transmission rate of nerve impulses, increased glycogen- attempt has been made to physically challenge the fast bowler, olysis, increased glycolysis, and increased phosphate degrada- similar to what would occur in Test/First Class cricket, with 2 tion.25 A warm-up prior to any explosive movement should blocks of 6-over spells,5,15,16 and a 12-over spell.3 However, it is encompass 3 to 5 minutes of moderate-intensity activity that not uncommon for a fast bowler to perform more than 12 overs in a sufficiently elevates muscle temperature.25 Because fast bowling day during a Test match.30 Although most of the reviewed studies is a coordinated motion, bowlers should also integrate bowling have chosen a spell length that happens to meet a specific match within the warm-up so they are ready for match play. Seven of the format, there are no match-specific fast-bowling assessments. This examined investigations implemented specific bowling in the is surprising, as the current ICC player rankings reveal that there are warm-up.3,7,10,13,14,17,18 Nine studies reported that a warm-up specialist fast bowlers in each match format,1 indicating possible was performed prior to the fast-bowling assessment, but insuffi- differences in required skill sets. For example, Mitchell Starc from cient detail was provided for replication.3,8–10,13,16–19 Three studies Australia is currently ranked the third best bowler in the world for failed to report a warm-up prior to the fast-bowling assess- One-Day International cricket but is ranked 10th for Test match ment,5,6,15 while 2 studies stated a typical routine was used, cricket and 25th in Twenty20 cricket.1 with no details provided.11,12 Only 1 study has provided sufficient detail of the warm-up and can be considered replicable for a Delivery Sequence subsequent fast-bowling assessment.7 All reviewed fast-bowling assessments have involved bowlers aim- 3,10,11,13,19,31 6–9,12,14,15,17,18 Test Familiarization Procedures ing at a particular target or several targets. Three studies adopted a randomized delivery order,5,9,12 whereas To minimize the amount of measurement error within each depen- others employed a preplanned but randomized delivery dent variable, researchers have been advised to choose or design sequence.6–8,14,15,17,18 Frequent variation in ball-to-ball trajectory tests requiring minimal learning.26 If the test is complex and is arguably more challenging for a fast bowler to execute with requires a lot of learning, familiarization trials should be imple- precision, but nevertheless is more specific to the skill requirements mented to reduce the SEM.26 Fast bowlers typically require of Twenty20 and One-Day International cricket. Batters in these familiarization trials to become accustomed to the testing environ- match formats play more flamboyant strokes (with a higher risk of ment, test and/or delivery instructions, trajectory of the ball in the dismissal) to create greater run-scoring opportunities than they air, and ball bounce characteristics off the pitch. Nine of the would in Test/First Class cricket. Therefore, it is important that reviewed studies did not report any familiarization proce- fast bowlers can frequently alter their delivery trajectory and speed dures,5,6,8,10–13,17,18 which may have led to greater intraindividual between balls. However, in Test/First Class cricket, it is more variability in fast-bowling skill. Three studies implemented unlim- important for a bowler to consistently land the ball on a “good ited deliveries prior to the fast-bowling assessment,3,9,13 whereas line and length,” as most batters take lower risks in their stroke play others reported separate familiarization sessions without sufficient and perform more traditional cricket strokes. A fast-bowling assess- detail for replication.7,14,15 Two investigations stated that bowlers ment that involves repeated bowling to a particular target3,10,11,13,19 were already familiarized leading up to assessment, with no might therefore be more specific to the skill requirements of Test/ description of how this took place.3,16 First Class cricket.

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Prior to commencing their run-up, a fast bowler knows what zone-based scoring system to score bowling accuracy,6,9–13,15–19 and type of delivery they will bowl. However, sometimes a batter there are noticeable differences in scoring approaches. For example, performs late foot movements (known as premovements) just prior Devlin et al16 provided a delivery line score on a scale of 1 to 6, and a to ball release, to challenge the bowlers’ intended line and length. delivery length score of 1 to 10 based on the pitch of the ball in This occurs more frequently in Twenty20 and One-Day Interna- relation to the target. Petersen et al10 scored accuracy as a percentage tional cricket. The late movement from the batter requires a fast of successful deliveries to strike the target on the pitch. Taliep et al3 bowler to react and adjust his or her delivery trajectory. Surprisingly, measured the radial error from the center of the pitch target to ball this quality has never been examined in a fast-bowling assessment. impact location. Interestingly, the 0.36 m2 target on the pitch was Further research is warranted to explore this quality in fast bowlers. placed in accordance with the bowlers’ nomination prior to assessment, and remained in place for the entire test.3 Recently, McNamara 5 Test Instructions et al asked bowlers to nominate a delivery line (4 options) and length (3 options), and the accuracy score was validated by both The instructions provided before the fast-bowling assessment bowler and coach. A majority have reported the overall mean score arguably have an influence on fast-bowling skill. Feros et al8 found in arbitrary units (AU),11,13,15,17–19 while Phillips et al6 reported that the bowlers deliver the ball significantly faster with a maximal- mean score for each delivery length (short, good, and full). Others effort instruction compared with a match-intensity instruction, with have also adopted the radial error measurement with a vertical target no significant differences in bowling accuracy. The majority of sheet.6–8 Knowledge of radial error is likely to provide the fast reviewed fast-bowling assessments have included the instruction bowler with more meaningful feedback on bowling accuracy skill for bowlers to bowl at “match intensity,” with an equal emphasis on rather than a score in AU.6 bowling speed and accuracy.3,7–10,12–14,17–19 However, the actual instruction provided differs among fast-bowling assessments. For Missing Skill Measures example, Elliott et al9 instructed bowlers to “bowl as fast as possible, while maintaining good line and length to score maxi- Only 2 of the examined studies calculated how consistently accu- mally on the target.” Whereas, Feros et al14 instructed bowlers to: rate fast bowlers performed at a variety of targets.6,14 This measure, termed the bivariate variable error, represents the mean absolute Bowl as fast, accurate and consistently as possible as you distance from the bowlers’ centroid of a particular target (average x would in a match. We are measuring all of these elements. At and y coordinates).6,14 All other studies just reported mean bowling different times throughout the test, you will be instructed to accuracy,3,7–13,15–19 which does not account for the variability of bowl some deliveries at maximal speed and some deliveries delivery impact locations about a particular target. In fact, all of with your preferred slower ball. Your speed and accuracy with these studies3,7–13,15–19 could have measured and reported the these balls is also measured. consistency of bowling accuracy simply by calculating the SD of all deliveries from a bowler, and then pooling these across the One study reported that bowlers were to perform at match group to obtain the mean. intensity, but there were no further details on the instruction The consistency of bowling speed has only been reported by provided.6 Surprisingly, 3 studies did not state an instruction prior Feros et al.14 This is a concern, as this data, along with the to the fast-bowling assessment.5,11,16 consistency of bowling accuracy, is meaningful for fast bowlers, because it has potential to provide insight into fatigue throughout a Collection of Bowling Speed Data bowling spell.3 Most studies have stated mean bowling speed across the spell,5–13,15–19 but this does not explain the variability The majority of reviewed fast-bowling assessments collected ball of bowling speeds within the spell. The variability in bowling speed release speed data by radar gun, aimed at the direction of ball can be calculated by obtaining the SD of all “match-intensity” release. Variation in the location and angle of the radar gun exists deliveries (ie, not maximal-effort or slower-ball deliveries) and between studies. Only 2 studies reported the angles of the radar then pooling these across the group to obtain the mean.14 gun, which were at 10° and 25°.7,14 The cosine effect error must be considered with a radar gun that is angled to the trajectory of delivery. A radar gun positioned on a 25° angle to an object’s linear Reliability, Sensitivity, and Validity motion results in a loss of approximately 10% in speed.32 The To date, only 3 of the 16 reviewed investigations reported reliabil- cosine error can easily be corrected for; however, just 1 study that ity data of bowling speed and accuracy.5,13,14 Feros et al14 reported adopted an angled radar gun has made this adjustment with the ball an SEM for mean bowling speed and mean radial error to be release speed data.14 Furthermore, of the investigations that 0.3 m·s−1 and 4.6 cm, respectively. Wickington and Linthorne13 adopted an angled radar gun, there was no mention of whether observed an SEM for bowling speed and accuracy to be 0.6 m·s−1 it was adjusted for each bowler based on variability in ball release and 0.6 AU, respectively.13 McNamara et al5 found the relative ball position (eg, straighter arm at release vs rounder arm at speed and relative peak Player-Load™ to exhibit the most stability, release).7,8,11,12 These limitations can be countered by placing with bowling accuracy (execution) displaying the largest variance. the radar gun directly behind the bowler’s arm.10,15,17,18 Nevertheless, only Feros et al14 reported the SEM and/or coefficient of variation for consistency of bowling speed and bivariate Collection and Reportage of Bowling Accuracy variable error. The SE of a measure is obtained from repeated Data testing, and when this value is multiplied by 1.5, it represents the smallest worthwhile change, a measure of sensitivity.26 However, The majority of examined fast-bowling assessments collected bowl- the smallest worthwhile change can also be calculated by multi- ing accuracy data with a suspended vertical target sheet positioned at plying the between-participant SD by 0.2.5 the batting end.6–9,11–15,17–19 Others assessed bowling accuracy with Petersen et al10 and Wickington and Linthorne13 arbitrarily set aspecific target on the pitch.3,10,16 Some authors implemented a the smallest worthwhile change for mean bowling speed to

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1.4 m·s−1. For bowling accuracy, Petersen et al10 set the smallest sensitivity data are lacking in most assessments. These limitations worthwhile change to 8%, compared with 0.1 AU by Wickington are of concern, because comparisons between studies are often and Linthorne13. A subjective assignment of the smallest worth- difficult. Therefore, there is a need to create standardized fast- while change is probably not as accurate as using the established bowling assessments that reflect the match format relevant for the calculations.5,26 Recently, McNamara et al5 reported the smallest fast bowler. Prospective research in this area needs to shift toward worthwhile change for a variety of spell lengths and delivery creating a more simulated testing environment in which there are combinations for ball speed, relative ball speed, bowling accuracy, batters and fielders with set “plays,” albeit controlled as to maintain peak Player-Load™, and relative peak Player-Load™. This is a acceptable test–retest reliability and sensitivity of measurement. If significant advancement on previous fast-bowling research; how- this can be achieved, then the creation of ecologically valid fast- ever, sensitivity data on the consistency of bowling speed and bowling assessments will result in coaches making more informed bivariate variable error have been reported only by Feros et al.14 decisions regarding player selection, talent identification, return to Most reviewed studies have not reported any measures of test skill following injury, and the efficacy of short- and long-term validity. One exception is Phillips et al,6 who reported significant training interventions for fast bowlers. differences in bowling speed and bowling accuracy (radial error) between junior elite and international fast bowlers, indicating construct validity with these measures. However, these skill dif- Practical Recommendations ferences could probably be explained by a mean 12.7-year age gap Based on the limited evidence available, there are several recom- between both groups, not by playing level. Others have attempted mendations for improving the quality of future fast-bowling as- to enhance the ecological validity of the fast-bowling assessment. sessments. Although outdoor testing presents greater ecological These include a variety of bowling targets,6–8,11,12,14,15,17,18 a real validity, assessment of fast-bowling skill should be conducted batter,5,8,14 an outdoor test,15–19 fielding activities between indoors to control for environmental conditions, as the effects of overs,8,11,14,15,17,18 including change-up deliveries in speed,8,14 ambient temperature, relative humidity, barometric pressure, and nomination of delivery line and length,3,5 and the instruction to wind speed/direction on fast-bowling skill are not well understood. bowl at match intensity throughout the assessment, with equal The type of pitch selected for assessment should be one that the fast weighting on bowling speed and accuracy.3,7–10,12–14,17–19 Further bowler is most familiar with. Natural turf pitches are common for research is warranted to establish the construct validity of skill senior fast bowlers, whereas traditional synthetic pitches are typical measures in a fast-bowling assessment. for junior fast bowlers. If using a natural turf pitch, care should be While the assessment of bowling accuracy is most reliable taken to ensure it is prepared in a consistent manner and to ensure it when using a vertical target sheet with radial error measurement,14 would be in a similar condition across repeated days of testing. a more ecologically valid (but slightly less reliable) approach is to Regardless of what pitch surface is selected, an adequate familiari- adopt a line and length nomination system in which the fast bowler zation period should be factored in prior to testing, so that fast is assessed based on his or her ability to execute the intended bowlers can adjust to pitch conditions and to rule out learning delivery.5 This recommendation is fine for when the batter is effects from the collected skill data. These procedures would serve stationary at the crease (not moving about, trying to distract the to enhance the test–retest reliability of the fast-bowling skill bowler), which is most common in Test/First Class cricket. How- measures. ever, for assessments of fast-bowling skill to advance in ecological Ball bounce characteristics (ie, speed, angle, and consistency) validity, a revolution is required in how bowling accuracy data are should be measured if possible, as the type of ball and pitch surface/ quantified. The aggressive foot movement and improvisation of condition will influence these characteristics and therefore assess- batters in One-Day International and Twenty20 cricket occur just ment of bowling accuracy measures. Measurement of ball bounce prior to the fast bowler releasing the ball, and this has arguably characteristics can be achieved with modern smartphone cameras meant that there are a wide variety of delivery lines, lengths, and and analysis through appropriate software. The type of cricket ball speeds that a fast bowler uses in response to the batter. Prospective chosen for assessment ultimately comes down to the age and fast-bowling assessments in a lab setting should account for this gender of the bowler, and the color of the ball used should reflect reactive component (albeit in a controlled manner). Therefore, what match format the assessment is designed for (eg, red/pink ball instead of measuring bowling accuracy through the lens of delivery for Test match cricket). Researchers are encouraged to report the trajectory and/or targets, it should be based on how successful the details of the ball chosen, as particular cricket balls of a certain delivery was in achieving a particular objective (normally mini- brand can have both junior or senior variations, as well as different mizing runs scored from the delivery by bowling to a particular color options. field setting). This recommendation is not discounting the possi- A standardized warm-up that involves bowling with a gradual bility of in-match fast-bowling skill assessment; however, it must increase in intensity should be encouraged. Fast bowlers should be be acknowledged that there would be numerous challenges to provided as many deliveries as necessary to become accustomed to overcome to maintain acceptable test–retest reliability and sensi- the testing environment, test and/or delivery instructions, trajectory tivity in fast-bowling skill measures (eg, weather, pitch surface/ of the ball in the air, and ball bounce characteristics off the pitch. condition, batter, ball type/condition, etc). Without acceptable test– There should be enough space for a full run-up to be performed as retest reliability, there is no validity in measurement, and therefore to not disrupt the coordination of the fast bowler. it is difficult for inferences to be made regarding changes in fast- The selection of bowling spell length should consider the bowling skill. average length of a bowling spell in the particular game format that the fast bowler is preparing for (or specializes in). It is common for Conclusions bowling spells to be repeated in each game format, despite over restrictions in Twenty20 and One-Day International cricket. The Assessment and quantification of fast-bowling skill have varied fast-bowling assessment should incorporate multiple spells based significantly throughout the literature. Surprisingly, reliability and on the average number of spells that a fast bowler performs in the

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