The relationship between inertial measurement unit-derived ‘force signatures’ and ground reaction forces during cricket pace bowling

Can an inertial measurement unit, combined with machine learning, accurately measure ground reaction forces in cricket fast bowling?

This study examined whether an inertial measurement unit (IMU) could measure ground reaction force (GRF) during a cricket fast bowling delivery. Eighteen male fast bowlers had IMUs attached to their upper back and bowling wrist. Each participant bowled 36 deliveries, split into three different intensity zones: low = 70% of maximum perceived bowling effort, medium = 85%, and high = 100%. A force plate was embedded into the bowling crease to measure the ground truth GRF. Three machine learning models were used to estimate GRF from the IMU data. The best results from all models showed a mean absolute percentage error of 22.1% body weights (BW) for vertical and horizontal peak force, 24.1% for vertical impulse, 32.6% and 33.6% for vertical and horizontal loading rates, respectively. The linear support vector machine model had the most consistent results. Although results were similar to other papers that have estimated GRF, the error would likely prevent its use in individual monitoring. However, due to the large differences in raw GRFs between participants, researchers may be able to help identify links among GRF, injury, and performance by categorising values into levels (i.e., low and high).

Self-efficacy assessment hinders improvement on a deliberate cricket bowling practice task

Introduction

Previous research indicates that external focused attention is linked to superior performance on motor tasks. This study examined how attention directed toward one's self-efficacy affected performance in a cricket bowling task.

Methods

In the pre-test phase, participants attempted to bowl in a designated "good length" zone across 12 trials. Following this, participants were randomly assigned to either an experimental group, where they rated their own general and task-specific self-efficacy, or a control group, where they rated someone else's ability. They each then bowled 12 more trials. Their performance was measured based on the number of trials that were bowled within the standard "good length" zone.

Results

Paired t-tests showed that while the performance of the control group improved significantly from pre-test to post-test, t = 2.613, p = 0.008; the experimental group did not show a significant improvement, t = 1.156, p = 0.131.

Discussion

Results indicate that asking people to rate their self-efficacy level may reduce their improvement on a deliberate practice task. Implications for sport performance and researchers are discussed.

Effect of IMU location on estimation of vertical ground reaction force during jumping

Introduction: Several investigations have examined utilizing inertial measurement units (IMU) to estimate ground reaction force (GRF) during exercise. The purpose of this investigation was to determine the effect of inertial measurement units location on the estimation of ground reaction force during vertical jumping. Methods: Eight male subjects completed a series of ten countermovement jumps on a force plate (FP). The subjects had an inertial measurement units attached to the sacrum, back and chest. Ground reaction force was estimated from data from the individual inertial measurement units and by using a two-segment model and combined sensor approach. Results: The peak ground reaction force values for the sacrum, back, chest and combined inertial measurement units were 1,792 ± 278 N, 1,850 ± 341 N, 2,054 ± 346 N and 1,812 ± 323 N, respectively. The sacral inertial measurement units achieved the smallest differences for ground reaction force estimates providing a root mean square error (RMSE) between 88 N and 360 N. The inertial measurement units on the sacrum also showed significant correlations in peak ground reaction force (p < 0.001) and average ground reaction force (p < 0.001) using the Bland-Altman 95% Limits of Agreement (LOA) when in comparison to the force plate. Discussion: Based on assessment of bias, Limits of Agreement, and RMSE, the inertial measurement units located on the sacrum appears to be the best placement to estimate both peak and average ground reaction force during jumping.

Comparing tibial accelerations between delivery and follow-through foot strikes in cricket pace bowling

Foot strikes of the pace-bowling delivery stride produce large ground reaction forces, which may be linked to injury, yet the biomechanics of the follow-through are unknown. This study assessed tibial accelerations across the delivery and follow-through foot strikes in pace bowlers and evaluated relationships between these measures and five common pace-bowling intensity metrics. Fifteen sub-elite male pace bowlers performed deliveries at warm-up, match, and maximal intensities. Tibial accelerations were measured using tibial-mounted inertial measurement units and recorded at back- and front-foot initial and re-contacts. A trunk-worn global navigation satellite system unit measured PlayerLoad™, run-up speed, and distance. Ball speed and perceived exertion measures were also recorded. A linear mixed model showed statistical significance of prescribed intensities (p < .001) and foot strike for tibial acceleration (p < .001). Tibial accelerations showed positive increases with changes in prescribed intensity (p < .05). The greatest magnitude of tibial acceleration was found at back foot re-contact (mean ± SD; 1139 ± 319 m/s2). Repeated-measures correlations of tibial acceleration between foot contacts were weak (r = 0.2-0.4). The greatest magnitude of tibial acceleration reported at back foot re-contact may have implications for injury incidence, representing an important avenue for future pace bowling research.

Differences in Fitness between Firefighter Trainee Academy Classes and Normative Percentile Rankings

Fire academy training classes may have trainees with a range of different fitness capabilities. Documentation of trainee fitness could indicate the need for flexibility in physical training emphases. Therefore, data from six academy classes (males = 274; females = 31) were analyzed, including: Illinois agility test (IAT), push-ups, pull-ups, leg tucks, multistage fitness test, backwards overhead 4.54 kg medicine ball throw (BOMBT), 10-repetition maximum deadlift, and 18 kg kettlebell farmers carry. A one-way ANOVA, with the Bonferroni post hoc test, calculated between-class fitness differences. Normative fitness test data were produced via percentile ranks. Classes 5 and 6 had the most females (n = 15). Class 1 completed the IAT faster than all classes (p ≤ 0.009). Classes 1 and 4 had a further BOMBT distance than Classes 5 and 6, and Class 3 outperformed Class 6 (p ≤ 0.044). Class 4 completed more leg tucks than Class 5 (p = 0.047). Class 1 had a greater deadlift than Classes 3, 4, and 6, and Class 2 outperformed Classes 3–6 (p ≤ 0.036). Class 3 was slower in the farmers carry compared to all classes (p ≤ 0.002). Percentile rankings showed that most females (48–100%) were in the 0–29% rank. Staff should implement individualized programs where appropriate for trainees as cohort fitness differences exist. Female trainees may need targeted maximal strength and power development.

Extending Research on Law Enforcement Academy Graduation and Fitness: A Research Note on Receiver Operating Characteristic Curves

ABSTRACT

Lockie, RG, Dawes, JJ, Dulla, JM, and Orr, RM. Extending research on law enforcement academy graduation and fitness: A research note on receiver operating characteristic curves. J Strength Cond Res XX(X): 000-000, 2022-Fitness level contributes to a law enforcement recruit's ability to graduate from a training academy. However, limited research has used receiver operating characteristic (ROC) curves to ascertain whether fitness tests can accurately predict academy graduation. The investigators analyzed archival data from 311 recruits (260 males and 51 females) across 4 academy classes from 1 law enforcement agency. A robust, broad battery of fitness test data included grip strength for both hands, vertical jump, 75-yard pursuit run (75PR), 2-kg medicine ball throw, push-ups, sit-ups, arm ergometer revolutions in 60 seconds, and 20-m multistage fitness test (20MSFT) shuttles. Recruits were split into those who graduated (n = 269) or those who separated (did not complete academy; n = 42). A univariate ANOVA, with sex as a control variable, determined between-group fitness differences. Receiver operating characteristic curves were plotted for each fitness test, and the area under the curve (AUC) determined accuracy. Except for grip strength, graduated recruits were superior in all fitness tests (p < 0.001). The 75PR (AUC = 0.708) and 20MSFT (AUC = 0.727) had fair accuracy in predicting academy graduation. The data suggested that, ideally, fitness tests should not be used for diagnostic purposes in relation to academy graduation potential. Fitness test data can be used to provide specific feedback to at-risk recruits. These results suggest that the 75PR (change-of-direction speed) and 20MSFT (aerobic fitness) could contribute to successful graduation in law enforcement recruits. Law enforcement training staff could use this information to provide targeted training for recruits lacking in these qualities.

Fit (and Healthy) for Duty: Blood Lipid Profiles and Physical Fitness Test Relationships from Police Officers in a Health and Wellness Program

This research analyzed archival health and wellness program data (2018: 169 males, 39 females; 2019: 194 males, 43 females) to document police officer lipid profiles, and correlate lipids with fitness. Bloodwork included total cholesterol (TC), low-density lipoproteins (LDL-C), high-density lipoproteins (HDL-C), and triglycerides (TG). Fitness data included maximal aerobic capacity (V·O2max); sit-and-reach; push-ups; vertical jump; grip strength; sit-ups; and relative bench press (RBP). Lipid profiles were compared to national standards. Spearman’s correlations derived relationships between lipids and fitness (p < 0.05). Over 2018−2019, 68−76% of officers had desirable TC (<200 mg/dL) and HDL-C (≥60 mg/dL); 67−72% had desirable TG (<150 mg/dL). 54−62% of officers had LDL-C above desirable (≥100 mg/dL); 13−14% had mildly high TG (150−199 mg/dL); 16−18% had high TG (200−499 mg/dL). In 2018, HDL-C correlated with V·O2max, push-ups, grip strength, and RBP in males, and sit-ups in females. TG correlated with V·O2max (both sexes), sit-ups (males), and grip strength (females). In 2019, TG related to V·O2max, push-ups, vertical jump, sit-ups, and RBP in males. TG and LDL-C related to push-ups, and HDL-C to sit-ups and RBP in females. Relationship strengths were trivial-to-small (ρ = ±0.157 − 0.389). Most officers had good lipid profiles relative to cardiovascular disease risk. Nonetheless, the data highlighted the need for comprehensive approaches to decreasing risk.

Objective assessment of fast bowling delivery intensity in amateur male cricketers

Wearable microtechnology is effective in detecting fast deliveries in cricket, however methods to quantify delivery intensity have not been established. This study aimed to investigate the utility of wearable sensors in quantifying cricket fast bowling intensity.Fifteen sub-elite male fast bowlers performed deliveries at warm-up, match, and maximal intensities. A principal component analysis resulted in the selection of perceived exertion and seven variables of bowling exertion derived from trunk- (PlayerLoad™, trunk flexion velocity, trunk forward rotation velocity) and tibia-mounted (tibial acceleration at back foot contact, front foot contact, back foot re-contact and front foot re-contact) inertial measurement units for further analysis. Repeated measures ANOVAs were used to investigate the effect of intensity on outcome variables. Significant main effects of intensity and large effect sizes were identified for all variables (p < .05, n_p² > 0.14). Measures from the match and maximal conditions were significantly larger compared with the warm-up condition (P_holm < .05). No differences were observed between the match and maximal conditions (p > .05). Inertial measurement metrics can distinguish between a warm-up effort and both match and maximal fast bowling delivery intensity. These devices provide a unique, time-efficient approach to cricket fast bowling exertion quantification.

Quantifying cricket fast bowling volume, speed and perceived intensity zone using an Apple Watch and machine learning

This study examined whether an inertial measurement unit (IMU) and machine learning models could accurately measure bowling volume (BV), ball release speed (BRS), and perceived intensity zone (PIZ). Forty-four male pace bowlers wore a high measurement range, research-grade IMU (SABELSense) and a consumer-grade IMU (Apple Watch) on both wrists. Each participant bowled 36 deliveries, split into two different PIZs (Zone 1 = 70-85% of maximum bowling effort, Zone 2 = 100% of maximum bowling effort). BRS was measured using a radar gun. Four machine learning models were compared. Gradient boosting models had the best results across all measures (BV: F-score = 1.0; BRS: Mean absolute error = 2.76 km/h; PIZ: F-score = 0.92). There was no significant difference between the SABELSense and Apple Watch on the same hand when measuring BV, BRS, and PIZ. A significant improvement in classifying PIZ was observed for IMUs located on the dominant wrist. For all measures, there was no added benefit of combining IMUs on the dominant and non-dominant wrists.

Quantification of the demands of cricket bowling and the relationship to injury risk: a systematic review

BACKGROUND

Bowling in cricket is a complex sporting movement which, despite being well characterised, still produces a significant number of injuries each year. Fast bowlers are more likely to be injured than any other playing role. Frequency, duration, intensity and volume of bowling, which have been generalised as measurements of workload, are thought to be risk factors for injuries. Injury rates of fast bowlers have not reduced in recent years despite the implementation of various workload monitoring practices.

OBJECTIVE

To identify the variables used to quantify frequency, intensity, time and volume of bowling; and evaluate relationships between these variables and injury risk.

METHODS

Six online databases were systematically searched for studies on fast bowling that included terms related to workload. Population characteristics, variables relating to demand and their relationship to standardised definitions of physical activity were extracted from all included studies.

RESULTS

Bowling workload is typically quantified through measures of frequency, duration, or indirect intensity, with few studies reporting on bowling volume.

CONCLUSIONS

When reported on, volume was often described using imprecise or insufficient measures of intensity. There is a need to develop more appropriate measures of intensity during bowling and improve the quality of evidence to inform on bowling programme management practices.

Skeletal Muscle Mass and Fat Mass Relationships With Physical Fitness Test Performance in Law Enforcement Recruits Before Academy

ABSTRACT

Lockie, RG, Carlock, BN, Ruvalcaba, TJ, Dulla, JM, Orr, RM, Dawes, JJ, and McGuire, MB. Skeletal muscle mass and fat mass relationships with physical fitness test performance in law enforcement recruits before academy. J Strength Cond Res 35(5): 1287-1295, 2021-The purpose of this study was to analyze relationships between skeletal muscle mass percentage (SMM%) and fat mass percentage (FM%) relative to fitness test performance in law enforcement recruits. Retrospective analysis was conducted on 338 recruits (271 men and 67 women) from 4 academy classes. Skeletal muscle mass percentage and FM% were measured using cost-effective and practical bioelectrical impedance analysis (BIA) equipment that used hand and foot placement. The fitness tests included grip strength; vertical jump; 75-yard pursuit run; 2-kg medicine ball throw (MBT); push-ups and sit-ups completed in 60 seconds; and the 20-m multistage fitness test. Partial correlations controlling for sex-derived relationships between SMM%, FM%, and the tests. Recruits were split into quartile groups for SMM% and FM% (group 1 had the lowest SMM% or highest FM% and group 4 the highest SMM% or lowest FM%). A 1-way multivariate analysis of variance (MANOVA), with sex as a covariate and Bonferroni post-hoc, compared between-group results. Skeletal muscle mass percentage correlated with all fitness tests expect for MBT; FM% with all but grip strength and MBT (r = ±0.107-0.293). Greater SMM% or lesser FM% tended to relate to better fitness test performance. The MANOVA data indicated groups 3 and 4 (better SMM% or FM% profiles) exhibited superior fitness than group 1 (poorest SMM% or FM% profile) (p ≤ 0.048). Recruits should ideally increase SMM% and decrease FM% before academy to optimize fitness training and testing performance, although specific guidelines should be agency specific. Staff could use BIA to monitor body composition during academy to indicate how recruits are tolerating training.

Can an inertial measurement unit (IMU) in combination with machine learning measure fast bowling speed and perceived intensity in cricket?

This study examined whether an inertial measurement unit (IMU), in combination with machine learning, could accurately predict two indirect measures of bowling intensity through ball release speed (BRS) and perceived intensity zone (PIZ). One IMU was attached to the thoracic back of 44 fast bowlers. Each participant bowled 36 deliveries at two different PIZ zones (Zone 1 = 24 deliveries at 70% to 85% of maximum perceived bowling effort; Zone 2 = 12 deliveries at 100% of maximum perceived bowling effort) in a random order. IMU data (sampling rate = 250 Hz) were downsampled to 125 Hz, 50 Hz, and 25 Hz to determine if model accuracy was affected by the sampling frequency. Data were analysed using four machine learning models. A two-way repeated-measures ANOVA was used to compare the mean absolute error (MAE) and accuracy scores (separately) across the four models and four sampling frequencies. Gradient boosting models were shown to be the most consistent at measuring BRS (MAE = 3.61 km/h) and PIZ (F-score = 88%) across all sampling frequencies. This method could be used to measure BRS and PIZ which may contribute to a better understanding of overall bowling load which may help to reduce injuries.

The Effects of the Barbell Hip Thrust on Post-Activation Performance Enhancement of Change of Direction Speed in College-Aged Men and Women

This study investigated whether the barbell hip thrust (BHT) enhanced change-of-direction (COD) speed measured by the 505 COD speed test. Forty recreationally trained individuals completed three sessions. Session 1 included one-repetition maximum (1RM) BHT testing to measure absolute and relative strength. Sessions 2 and 3 involved two counter-balanced conditioning activities (CAs): 3 sets × 5 repetitions of the BHT at 85% 1RM and a control condition (CC; 6 min rest). The 505 COD speed test was performed 5 and 2.5 min pre-CA, and 4, 8, 12, and 16 min post-CA in each session. A 2 × 5 repeated-measures ANOVA (p < 0.05) calculated performance changes across time post-CA. A 2 × 2 repeated-measures ANOVA analyzed best potentiated performance. Partial correlations controlling for sex calculated relationships between the 1RM BHT and 505 COD speed test percent potentiation. There was a significant main effect for time (p < 0.001), but not for condition (p = 0.271) or condition × time (p = 0.295). There were no significant correlations between 1RM BHT and potentiation. The 85% 1RM BHT did potentiate the 505 4–16 min post-CA but no more than the CC. Nonetheless, a heavy BHT could be programmed prior to COD drills as COD speed could be potentiated and performance improved in men and women.

We Need You: Influence of Hiring Demand and Modified Applicant Testing on the Physical Fitness of Law Enforcement Recruits

A challenge for law enforcement agencies is the many positions that need filling. Agencies may modify their applicant test battery (ATB; multilevelled testing including fitness, background checks, psychological evaluations) to increase the hiring pool of potential recruits by augmenting the utility of testing. This study determined fitness differences of law enforcement recruits hired under two different ATB protocols. Retrospective analysis was conducted on seven academy classes (442 males, 84 females) hired under an older ATB, and one class (45 males, 13 females) hired under a newer ATB. Recruits completed the following before academy: 60 s push-ups and sit-ups (muscular endurance); vertical jump (lower-body power); medicine ball throw (upper-body power); 75 yard pursuit run (75PR; change-of-direction speed); and 20 m multistage fitness test (20MSFT; aerobic fitness). Independent sample t-tests (p ≤ 0.001) and effect sizes (d) evaluated between-group fitness differences for recruits hired under the different ATB protocols (combined sexes, males, and females). There were no significant differences between the ATB groups. However, newer ATB female recruits completed 13% fewer 20MSFT shuttles than the older ATB group, which, although not significant (p = 0.007), did have a moderate effect (d = 0.62). Females hired under the newer ATB had lower aerobic fitness, which could impact physical training performance and graduation.

Physical Fitness, Sex Considerations, and Academy Graduation for Law Enforcement Recruits

Lockie, RG, Dawes, JJ, Dulla, JM, Orr, RM, and Hernandez, E. Physical fitness, sex considerations, and academy graduation for law enforcement recruits. J Strength Cond Res 34(12): 3356-3363, 2020-This study investigated the influence of fitness on academy graduation, and any between-sex differences, in law enforcement recruits. Data collected at the start of 4 training academies were retrospectively analyzed, including age, height, and body mass; waist circumference; waist-to-hip ratio; grip strength; vertical jump (VJ); 75-yard pursuit run; 2-kg medicine ball throw (MBT); push-ups, sit-ups, and arm ergometer revolutions in 60 seconds; and 20-m multistage fitness test (20MSFT) shuttles. Recruits were categorized into graduated (GRAD = 269) and separated (did not graduate; SEP = 42) groups. SEP recruits were not split according to separation reasons, just whether they did or not. This categorization also occurred for male subjects (GRAD = 228; SEP = 32) and female subjects (GRAD = 41; SEP = 10). Independent samples t-tests calculated between-group differences for all recruits combined, male subjects, and female subjects. Correlations and stepwise linear regression calculated relationships between the data and graduation. The t-test (p ≤ 0.016) and correlation (r = ±0.137-0.296; p < 0.05) data indicated that SEP recruits (both sexes combined) were older and performed poorer in every fitness test except grip strength and VJ. SEP male subjects were older and performed poorer in all tests except grip strength (p ≤ 0.009). SEP female subjects scored lower in the arm ergometer (p = 0.008). The regression equation for all recruits found that age, 20MSFT (aerobic fitness), MBT (upper-body power), and arm ergometer (upper-body endurance) were academy graduation predictors (r = 0.169; p < 0.001). For the male recruits, the predictors were age, MBT, and 20MSFT (r = 0.182; p ≤ 0.001), and for female recruits, arm ergometer and 20MSFT (r = 0.213; p ≤ 0.003). Recruits should improve multiple fitness aspects, including muscular endurance, power, and aerobic fitness, to enhance graduation potential.

Does Delivery Length Impact Measures of Whole-Body Biomechanical Load During Pace Bowling?

PURPOSE

To investigate whether changes in delivery length (ie, short, good, and full) lead to alterations in whole-body biomechanical loading as determined by ground reaction force during front-foot contact of the delivery stride for pace bowlers. Current load-monitoring practices of pace bowling in cricket assume equivocal biomechanical loading as only the total number of deliveries are monitored irrespective of delivery length.

METHODS

A total of 16 male pace bowlers completed a 2-over spell at maximum intensity while targeting different delivery lengths (short, 7-10 m; good, 4-7 m; and full, 0-4 m from the batter's stumps). In-ground force plates were used to determine discrete (vertical and braking force, impulse, and loading rates) and continuous front-foot contact ground reaction force. Repeated-measures analysis of variance (P < .05), effects size, and statistical parametrical mapping were used to determine differences between delivery lengths.

RESULTS

There were no significant differences between short, good, and full delivery lengths for the discrete and continuous kinetic variables investigated (P = .19-1.00), with trivial to small effect sizes.

CONCLUSION

There were minimal differences in front-foot contact biomechanics for deliveries of different lengths (ie, short, good, and full). These data reinforce current pace bowling load-monitoring practices (ie, counting the number of deliveries), as changes in delivery length do not affect the whole-body biomechanical loading experienced by pace bowlers. This is of practical importance as it retains simplicity in load-monitoring practice that is used widely across different competition levels and ages.

Biomechanical risk factors of lower back pain in cricket fast bowlers using inertial measurement units: a prospective and retrospective investigation

Objectives

To investigate spinal kinematics, tibial and sacral impacts during fast bowling, among bowlers with a history of low back pain (LBP) (retrospective) and bowlers who developed LBP in the follow-up season (prospective).

Methods

35 elite male fast bowlers; senior (n=14; age=24.1±4.3 years; height=1.89±0.05 m; weight=89.2±4.6 kg) and junior (n=21; age=16.9±0.7; height=1.81±0.05; weight=73.0±9.2 kg) were recruited from professional county cricket clubs. LBP history was gathered by questionnaire and development of LBP was monitored for the follow-up season. Spinal kinematics, tibial and sacral impacts were captured using inertial measurement units placed over S1, L1, T1 and anteromedial tibia. Bonferroni corrected pairwise comparisons and effect sizes were calculated to investigate differences in retrospective and prospective LBP groups.

Results

Approximately 38% of juniors (n=8) and 57% of seniors (n=8) reported a history of LBP. No differences were evident in spinal kinematics or impacts between those with LBP history and those without for seniors and juniors. Large effect sizes suggest greater rotation during wind-up (d=1.3) and faster time-to-peak tibial impacts (d=1.5) in those with no history of LBP. One junior (5%) and four (29%) seniors developed LBP. No differences were evident in spinal kinematics or impacts between those who developed LBP and those who did not for seniors. In seniors, those who developed LBP had lower tibial impacts (d=1.3) and greater lumbar extension (d=1.9) during delivery.

Conclusion

Retrospective analysis displayed non-significant differences in kinematics and impacts. It is unclear if these are adaptive or impairments. Prospective analysis demonstrated large effect sizes for lumbar extension during bowling suggesting a target for future coaching interventions.

The Effects of Lateral Bounds on Post-Activation Potentiation of Change-of-Direction Speed Measured by the 505 Test in College-Aged Men and Women

Forty recreationally-trained individuals completed four testing sessions to determine whether lateral bounds (LB) or weighted lateral bounds enhanced change-of-direction (COD) speed measured by the 505 COD speed test. Session 1 included vertical jump and lateral bound (LB) testing to measure power. Sessions 2–4 involved three randomized conditioning activities (CA): 3 × 5 LB; 3 × 5 weighted LB (10% body mass provided by a weighted vest); and a control condition (4-min rest). The 505 COD speed test was performed 5- and 2.5-min pre-CA, and ~15 s, 4, 8, 12, and 16 min post-CA. A 3 × 6 repeated measures analysis of variance (ANOVA) calculated performance changes across time points post-CA. A 3 × 2 repeated measures ANOVA analyzed best potentiated performance. Smallest worthwhile change (SWC) measured within-subject 505 COD speed test performance. Partial correlations controlling for sex calculated relationships between the vertical jump, LB, and percent potentiation. There were no differences (p = 0.919) in 505 time relative to baseline for any CA, nor was the SWC exceeded. The best potentiated 505 time was faster (p < 0.001) than baseline for all CA, with no between-CA differences. There were no significant (p = 0.056–0.993) correlations between power and potentiation. LB and weighted LB did not potentiate the 505 COD speed test, although performance was not hindered.

The Effects of an Eight over Cricket Bowling Spell upon Pace Bowling Biomechanics and Performance within Different Delivery Lengths

Pace bowlers must often perform extended bowling spells with maximal ball release speed (BRS) while targeting different delivery lengths when playing a multi-day match. This study investigated the effect of an eight over spell upon pace bowling biomechanics and performance at different delivery lengths. Nine male bowlers (age = 18.8 ± 1.7 years) completed an eight over spell, while targeting different lengths (short: 7-10 m, good: 4-7 m, full: 0-4 m from the batter's stumps, respectively) in a randomized order. Trunk, knee and shoulder kinematics and ground reaction forces at front foot contact (FFC), as well as run-up velocity and BRS were measured. Paired sample t-tests (p ≤ 0.01), Hedges' g effect sizes, and statistical parametrical mapping were used to assess differences between mean variables from the first and last three overs. No significant differences (p = 0.05-0.98) were found in any discrete or continuous variables, with the magnitude of difference being trivial-to-medium (g = 0.00-0.73) across all variables. Results suggest pace bowlers sustain BRS through a single eight over spell while tolerating the repeatedly high whole-body biomechanical loads as suggested by maintaining the kinematics or technique at the assessed joints during FFC. Practically, the findings are advantageous for bowling performance and support current bowling load monitoring practices.