Sprint Running Performance Monitoring: Methodological and Practical Considerations

Testing in Intermittent Sports-Importance for Training and Performance Optimization in Adult Athletes

ABSTRACT

Performance in intermittent sports relies on the interplay between multiple physiological systems determining the capacity to perform short explosive efforts as well as repeated intense actions with limited recovery over the course of an entire game. Testing should reflect these demands to allow for sport- and position-specific capacity analyses that eventually may translate into optimized training and improved performance. This may include individual load management and optimized training prescription, intensity targeting for specific positions or individual athletes, as well as benchmarking for monitoring of training progression and enhanced engagement of athletes. This review provides an overview of available tests in different exercise domains identified as relevant (from assessment of single explosive actions to intermittent endurance capacity), forming the basis for recommendations on how to compose a comprehensive yet feasible test battery that may be integrated into the seasonal competition and training plan. The test procedures should cover the performance spectrum of relevance for the individual athlete-also in team sports to account for positional differences. We emphasize the benefits of sport-specific tests, highlight parameters of importance for test standardization, and discuss how the applied test battery may be supplemented with secondary tests directed toward specific energy systems to allow for more in-depth analyses when required (e.g., in terms of an underperforming athlete). The synergy between testing and tracking of match performance (utilizing time-motion or global positioning systems) is highlighted, and although tracking cannot substitute for testing, combining the tools may provide a comprehensive overview of the physiological demands and performance during competition contextualized to the athletes' maximal exercise capacity.

Running sprint force-velocity-power profile obtained with a low-cost and low frame rate acquisition video technique: reliability and concurrent validity

The Force-velocity (F-v) and Power-velocity (P-v) relationships quantify athlete's horizontal force production capacities during sprinting. Efforts are underway to enhance ecological validity for practitioners and sports coaches. This study provides detailed data comparison of a low frames per second setup (30 Hz; FPSlow) with splits from a high FPS camera to derive F-v and P-v relationships. Sixty-six sprints performed by 11 university track and field athletes (6 male, 5 female) were evaluated. Data were recorded using FPSlow, photocells, and a high-speed camera (240 Hz; MySprint). In the FPSlow setup, bias was 0.17s, and Limits of agreement was 0.09s compared to photocells. ICC was 1.00, and the coefficient of variation (CV) was 1.0% [0.8-1.1%]. Time acquisition comparison between MySprint and FPSlow setups revealed high consistency (ICC = 0.99) and low CV (2.9% [2.8-3.1%]). F-v profile variables exhibited biases from trivial to small, with ICC ranging from moderate to nearly perfect. CV ranged from 2.7% to 11.8%, and improved using the average of three sprints (CV between 1.8% and 8.6%). The 'simple method' applied to data from the low FPS video setup yielded kinetic and kinematic parameters comparable to those obtained by the validated previous method and photocells.

A review of evidence on mechanical properties of running specific prostheses and their relationship with running performance

Background

Although mechanical properties of running specific prostheses (RSPs) can affect running performance, manufacturers do not consistently report them. This study aimed to review existing literature on RSP mechanical and structural properties and their relationship with running performance.

Methods

A comprehensive search was conducted using keywords related to mechanical properties of RSPs and running performance. Search terms included stiffness and hysteresis, as well as performance outcomes including metabolic cost and running speed. Non-peer-reviewed and non-English publications were excluded.

Results

Twenty articles were included in the review. Sixteen studies used a material testing machine to measure RSP material properties, and four articles used other techniques including 2D/3D video capture and force platforms. Both measurement techniques and reporting of outcomes were inconsistent, which limits the ability to draw broad conclusions. Additionally, several studies did not report the numerical data for material properties despite measuring them. Relatively few articles measured both material properties and running performance and assessed correlations.

Conclusion

Several articles connected prosthesis properties to running performance. However, inconsistent measurement and reporting of mechanical properties, along with the multifactorial nature of the athlete-prosthesis system, limit the ability to draw broad conclusions regarding the relationship between material and structural properties and athlete performance. Current evidence may be useful for clinicians seeking ways to optimize RSP stiffness in a case-by-case basis; however, clinicians would benefit from more consistent and systematic comparisons of the attributes of different RSPs and their role in performance.

Olympic Weightlifting Training for Sprint Performance in Athletes: A Systematic Review with Meta-analysis

This systematic review and meta-analysis aimed to determine whether Olympic weightlifting (OW) exercises would improve sprint performance when compared to a control intervention, (no training, standard sport-specific training, traditional resistance training, or plyometric training). Medline, Web of Science, SportDiscus, CINAHL, and Biological Science from inception to September 2022 was searched. Two authors independently selected the included studies, extracted data, and appraised the risk of bias. Certainty of the evidence was assessed using the Grading of Recommendations Assessment, Development, and Evaluation methodology. The primary meta-analysis combined the results of the sprint performance over the full length of each sprint test. The secondary meta-analyses combined the results of the sprint performance at 5, 10, and 20 m distance to capture information about the acceleration phase of the sprint tests. Eight studies with 206 athletes (female n=10, age range: 18.9-24.2 years) were identified. Sprint performance did not differ significantly comparing OW to the control intervention, nor at the full length (standardized mean difference=-0.07, 95% CI=-0.47 to 0.34, p=0.75, I2=46%) or during the acceleration phase (p≥0.26) of the sprint test. OW training does not improve sprint performance to a greater extent than comparator interventions.

Physiological and Locomotor Profiling Enables to Differentiate Between Sprinters, 400-m Runners, and Middle-Distance Runners

ABSTRACT

Thron, M, Woll, A, Doller, L, Quittmann, OJ, Härtel, S, Ruf, L, and Altmann, S. Physiological and locomotor profiling enables to differentiate between sprinters, 400-m runners, and middle-distance runners. J Strength Cond Res XX(X): 000-000, 2024-Different approaches exist for characterizing athletes, e.g., physiological and locomotor profiling. The aims of this study were to generate and compare physiological and locomotor profiles of male and female runners and to evaluate relationships between the different approaches. Thirty-four highly trained adolescent and young adult female and male athletes (n = 11 sprinters; n = 11,400-m runners; n = 12 middle-distance runners) performed two 100-m sprints on a running track to determine maximal sprinting speed (MSS) and maximal lactate accumulation rate (ċLamax). A cardiopulmonary exercise test was performed on a treadmill to determine maximal aerobic speed (MAS) and maximal oxygen uptake (V̇o2max). Anaerobic speed reserve (ASR) was calculated as the difference between MSS and MAS. Group comparisons were conducted with a 2-way ANOVA (discipline × sex; p < 0.05) and Bonferroni post hoc tests and Cohen's d as effect size. Parameters were correlated by Pearson's correlation coefficients. Maximal aerobic speed and V̇o2max were higher in 400-m and middle-distance runners compared with sprinters (p ≤ 0.02; -2.24 ≤ d ≤ -1.29). Maximal sprinting speed and ċLamax were higher in sprinters and 400-m runners compared with middle-distance runners (0.03 ≤ p ≤ 0.28; 0.73 ≤ d ≤ 1.23). Anaerobic speed reserve was highest in sprinters and lowest in middle-distance runners (p ≤ 0.03; 1.24 ≤ d ≤ 2.79). High correlations were found between ASR and MAS, MSS, and ċLamax (p < 0.01; -0.55 ≤ r ≤ 0.91) and between ċLamax and MSS (p < 0.01; r = 0.74). Our results indicate that athletes of different sprinting and running disciplines show differing physiological and locomotor profiles, and that the parameters of these approaches are related to each other. This can be of interest for assessing strengths and weaknesses (e.g., for talent identification) or training prescription in these disciplines.

Advancing 100m sprint performance prediction: A machine learning approach to velocity curve modeling and performance correlation

This study presents a novel approach to modeling the velocity-time curve in 100m sprinting by integrating machine learning algorithms. It critically addresses the limitations of traditional speed models, which often require extensive and intricate data collection, by proposing a more accessible and accurate method using fewer variables. The research utilized data from various international track events from 1987 to 2019. Two machine learning models, Random Forest (RF) and Neural Network (NN), were employed to predict the velocity-time curve, focusing on the acceleration phase of the sprint. The models were evaluated against the traditional exponential speed model using Mean Squared Error (MSE), with the NN model demonstrating superior performance. Additionally, the study explored the correlation between maximum velocity, the time of maximum velocity occurrence, the duration of the maximum speed phase, and the overall 100m sprint time. The findings indicate a strong negative correlation between maximum velocity and final time, offering new insights into the dynamics of sprinting performance. This research contributes significantly to the field of sports science, particularly in optimizing training and performance analysis in sprinting.

Effects of the Flying Start on Estimated Short Sprint Profiles Using Timing Gates

Short sprints are predominantly assessed using timing gates and analyzed through parameters of the mono-exponential equation, including estimated maximal sprinting speed (MSS) and relative acceleration (TAU), derived maximum acceleration (MAC), and relative propulsive maximal power (PMAX), further referred to as the No Correction model. However, the frequently recommended flying start technique introduces a bias during parameter estimation. To correct this, two additional models (Estimated TC and Estimated FD) were proposed. To estimate model precision and sensitivity to detect the change, 31 basketball players executed multiple 30 m sprints. Athlete performance was simultaneously measured by a laser gun and timing gates positioned at 5, 10, 20, and 30 m. Short sprint parameters were estimated using a laser gun, representing the criterion measure, and five different timing gate models, representing the practical measures. Only the MSS parameter demonstrated a high agreement between the laser gun and timing gate models, using the percent mean absolute difference (%MAD) estimator (%MAD < 10%). The MSS parameter also showed the highest sensitivity, using the minimum detectable change estimator (%MDC95), with an estimated %MDC95 < 17%. Interestingly, sensitivity was the highest for the No Correction model (%MDC95 < 7%). All other parameters and models demonstrated an unsatisfying level of sensitivity. Thus, sports practitioners should be cautious when using timing gates to estimate maximum acceleration indices and changes in their respective levels.

Test-retest reliability of lower limb muscle strength, jump and sprint performance tests in elite female team handball players

PURPOSE

This study aimed to assess the reliability of lower limb muscle function (knee extensor/flexor peak torque, rate of torque development (RTD), impulse, and countermovement jump (CMJ) performance) and sprint performance (acceleration capacity).

METHODS

CMJ performance was evaluated on a force plate. MVIC, RTD and impulse variables were investigated using a portable isometric dynamometer and sprint performance was assessed with dual-beam photocells in elite female athletes.

RESULTS

CMJ test variables maximal vertical jump height, peak and mean power, concentric work, and body center of mass displacement demonstrated good-to-excellent test-retest correlations between Test 1 and Test 2 (ICC ≥ 0.70, CWw-s = 3.4-11.0%). Peak MVIC torque for the knee extensors and flexors demonstrated excellent test-retest correlations (both ICC = 0.84) along with CVw-s values of 6.8 and 6.0%, respectively. Late-phase (0-100 ms, 0-200 ms) RTD for the knee flexors demonstrated excellent test-retest correlations (ICC = 0.89-0.91, CVw-s = 4.8-8.5%). Sprint times at 10- and 20-m demonstrated excellent test-retest reproducibility (ICC = 0.83 and ICC = 0.90, respectively) with CVw-s values of 1.9 and 1.5%. For 5-m sprint times, test-retest reproducibility was good (ICC = 0.71) with CVw-s of 2.8%. Sprint testing performed while dribbling a handball improved (p < 0.05) from test to retest at 5-, 10- and 20-m.

CONCLUSION

In conclusion, the force plate, the mobile isometric dynamometer, and dual-beam photocells provide reproducible tools for field-based testing of countermovement jump performance, knee extensor and flexor strength and sprint performance.

Concurrent-Validity and Reliability of Photocells in Sport: A Systematic Review

Specific physical qualities such as sprint running, change-of-direction or jump height are determinants of sports performance. Photocell systems are practical and easy to use systems to assess the time from point A to point B. In addition, these photoelectric systems are also used to obtain the time of vertically displaced movements. Knowing the accuracy and precision of photocell timing can be a determinant of ensuring a higher quality interpretation of results and of selecting the most appropriate devices for specific objectives. This systematic review aimed to identify and summarize studies that have examined the validity and reliability of photocells in sport sciences. A systematic review of PubMed, SPORTDiscus, and Web of Science databases was performed according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. From the 164 studies initially identified, 16 were fully reviewed, and their outcome measures were extracted and analyzed. Photocells appear to have a strong agreement with force plates (gold standard), but are not interchangeable to measure the vertical jump. For monitoring horizontal displacement, double beam systems, compared to single beam systems, are more valid and reliable when it comes to avoiding false triggers caused by swinging arms or legs.

Implementing Velocity-Based Training to Optimize Return to Sprint After Anterior Cruciate Ligament Reconstruction in Soccer Players: A Clinical Commentary

After anterior cruciate ligament reconstruction (ACLR), return to sprint is poorly documented in the literature. In soccer, return to sprint is an essential component of return to play and performance after ACLR. The characteristics of running in soccer are specific (velocity differences, nonlinear, intensity). It is important to address these particularities, such as curvilinear running, acceleration, deceleration, changes of direction, and variations in velocity, in the patient's rehabilitation program. Force, velocity, and acceleration capacities are key elements to sprint performance. Velocity-based training (VBT) has gained much interest in recent years and may have a role to play in optimizing return to play and return to sprint after ACLR. Force, velocity, and acceleration can be assessed using force-velocity-power and acceleration-speed profiles, which should inform rehabilitation. The purpose of this commentary is to describe a velocity-based return to sprint program which can be used during ACLR rehabilitation.

Estimation of maximum sprinting speed with timing gates: greater accuracy of 5-m split times compared to 10-m splits

This study assessed the validity of 5-m (TG5) and 10-m (TG10) split times measured with timing gates to estimate maximum sprint speed (MSS) against a criterion measure radar gun (RG) during the maximum velocity phase of a 30-m sprint. Nineteen amateur rugby players performed two 30-m sprints. The timing gates were placed at the starting line and at 5-, 10-, 20-, 25- and 30-m. In addition, a RG was used to measure instantaneous velocity. Both trials per participant were used selected as references. MSS obtained from TG10, TG5 and RG showed high intraclass correlation coefficients (0.971-0.978), low coefficients of variation (1.14-1.70%) and smallest detectable changes (<0.02 m/s). Pairwise comparison revealed differences (p = 0.002) in MSS when comparing TG10 to RG, but not TG5 and RG (p = 0.957). Almost perfect correlations were found between RG, TG5 and TG10 (r > 0.926, p < 0.001). In conclusion, MSS obtained from TG5, TG10 and RG presented good intra-session reliability. However, practitioners should be aware that substantial differences exist between TG10 and RG. For the assessment of MSS in team-sport athletes, it is recommended the use of TG5 for more accurate estimations when a gold standard criterion is not available.

Reference Values of Physical Performance in Handball Players Aged 13-19 Years: Taking into Account Their Biological Maturity

Biological maturity status significantly influences success in handball, impacting an athlete's performance and overall development. This study aimed to examine the anthropometric and physical performance variables concerning age and maturity status, establishing reference values for physical performance among Tunisian players. A total of 560 handball players (309 males and 251 females aged 13-19 years) were categorized based on maturity status: early (n = 98), average (n = 262), and late (n = 200), determined through Mirwald and colleagues' equations. Anthropometric, physical fitness, and physiological data were collected for reference value creation. Our findings revealed significantly higher anthropometric parameters (p = 0.003) in late-maturing athletes compared to their early-maturing counterparts. Post-pubertal athletes showed significantly superior (p = 0.002) jumping ability, change of direction, and aerobic performance compared to their pre-pubertal peers. Additionally, male athletes outperformed females in both fitness (p = 0.001) and aerobic (p = 0.001) performance. A notable age-by-maturity interaction emerged for most performance outcomes (η2 ranging from 0.011 to 0.084), highlighting increased sex-specific differences as athletes progressed in age. Percentile values are provided for males and females, offering valuable insights for coaches and sports scientists to design personalized training programs. Understanding a player's performance relative to these percentiles allows trainers to tailor workouts, addressing specific strengths and weaknesses for enhanced development and competitiveness.

Evaluation of multi-directional speed qualities throughout adolescence in youth soccer: The non-linear nature of transfer

Training and assessment of agility is often prioritised by soccer coaches and practitioners aiming to develop multi-directional speed. Although the importance of agility is advocated throughout childhood and adolescence, limited data evidence agility performance at different stages of adolescence. The purpose of this study was to examine differences in multi-directional speed performance in youth soccer players spanning an entire soccer academy. A total of 86 male junior-elite soccer players volunteered to participate. Anthropometric data were collected, alongside performance data from a battery of physical tests including sprinting, jumping, change of direction, reaction time, and agility. Bayesian models using log-likelihoods from posterior simulations of parameter values displayed linear or curvilinear relationships between both chronological and biological age and performance in all tests other than agility and reaction time. For agility and reaction time tests, performance improved until ~14 years of age or the estimated age of peak height velocity whereby arrested development in performance was observed. Our results demonstrate that while most performance skills improve as chronological or biological age increases, measures of agility and reaction time may not. These findings support the notion that agility performance is complex and multifaceted, eliciting unique, challenging physical demands and non-linear development.

The Interunit Reliability of Global Navigation Satellite Systems Apex (STATSports) Metrics During a Standardized Intermittent Running Activity

ABSTRACT

Beato, M, Wren, C, and de Keijzer, KL. The interunit reliability of global navigation satellite systems Apex (STATSports) metrics during a standardized intermittent running activity. J Strength Cond Res 38(2): e49-e55, 2024-This study aimed to evaluate the interunit reliability of global navigation satellite systems (GNSS) STATSports Apex metrics and to assess which metrics can be used by practitioners for the monitoring of short-distance intermittent running activities. Fifty-four male soccer players were enrolled (age = 20.7 ± 1.9 years, body mass = 73.2 ± 9.5 kg, and height = 1.76 ± 0.07 m) in this observational study. 10-Hz GNSS Apex (STATSports, Northern Ireland, Newry) units recorded total distance, high speed running (HSR), accelerations, decelerations, peak speed, average metabolic power, metabolic distance, dynamic stress load (DSL), relative distance, and speed intensity. The standardized intermitted running protocol used was a Yo-Yo intermittent recovery level 1. This study reported that Apex interunit analysis did not show any significant difference (delta difference and 95% confidence interval [CIs]) in total distance = 2.6 (-2.6; 7.9) m, HSR = 3.2 (-0.2; 6.8) m, accelerations = 0.09 (-0.9; 1.1), decelerations = 0.3 (-0.4; 1.1), peak speed = 0.02 (-0.03; 0.07) m·s -1 , average metabolic power = 0.01 (-0.02; 0.04) W·kg -1 , metabolic distance = 0.9 (-6.2; 8.0) m, DSL = 2.8 (-5.6; 10.7) au, relative distance = 0.14 (-0.19; 0.47) m·min -1 , and speed intensity = 0.21 (-0.21; 0.64) au. All metrics presented a delta d between trivial to small. The interunit intraclass correlation coefficient (ICC) was good or excellent for all metrics, with the exception of DSL, which was considered questionable . In conclusion, this study reports that all the metrics analysis in this study presents a low interunit bias and high reliability (ICC), with the exception of DSL.

A Systematic Review and Meta-Analysis of Wearable Satellite System Technology for Linear Sprint Profiling: Technological Innovations and Practical Applications

ABSTRACT

Cormier, P, Meylan, C, Agar-Newman, D, Geneau, D, Epp-Stobbe, A, Lenetsky, S, and Klimstra, M. A systematic review and meta-analysis of wearable satellite system technology for linear sprint profiling: technological innovations and practical applications. J Strength Cond Res 38(2): 405-418, 2024-An emerging and promising practice is the use of global navigation satellite system (GNSS) technology to profile team-sports athletes in training and competition. Therefore, the purpose of this narrative systematic review with meta-analysis was to evaluate the literature regarding satellite system sensor usage for sprint modeling and to consolidate the findings to evaluate its validity and reliability. Following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, an electronic search of the databases, PubMed and SPORTDiscus (EBSCO), was conducted. Concurrent validity and reliability studies were considered, and 16 studies were retained for the review from the initial 1,485 studies identified. The effects on outcomes were expressed as standardized mean differences (SMDs, Cohen's d ) for each outcome (i.e., maximal sprint speed [MSS], the acceleration constant [τ], maximal theoretical velocity [ V0 ], relative force [ F0 ], and relative power [P max ]). Effect magnitudes represented the SMD between GNSS-derived and criterion-derived (i.e., radar and laser) and resulted in the following estimates: small for MSS ( d = 0.22, 95% CI 0.01 to 0.42), τ ( d = -0.18, 95% CI -0.60 to 0.23), V0 ( d = 0.14, 95% CI -0.08 to 0.36), relative F0 ( d = 0.15, 95% CI -0.25 to 0.55), and relative P max ( d = 0.21, 95% CI -0.16 to 0.58). No publication bias was identified in meta-analyzed studies and moderator analysis revealed that several factors (sampling rate and sensor manufacturer) influenced the results. Heterogeneity between studies was considered moderate to high. This highlighted the differences between studies in sensor technology differences (i.e., sampling rate, sensor fusion, and satellite network acquisition), processing techniques, criterion technology used, sprint protocols, outcome reporting, and athlete characteristics. These findings may be useful in guiding improvements in sprint modeling using GNSS technology and enable more direct comparisons in future research. Implementation of all-out linear sprint efforts with GNSS technology can be integrated into sport-specific sessions for sprint modeling when robust and consistent data processing protocols are performed, which has important implications for fatigue monitoring, program design, systematic testing, and rehabilitation in individual and team sports.

Assessing anaerobic speed reserve: A systematic review on the validity and reliability of methods to determine maximal aerobic speed and maximal sprinting speed in running-based sports

PURPOSE

Locomotor profiling using anaerobic speed reserve (ASR) enables insights into athletes' physiological and neuromuscular contributing factors and prescription of high-intensity training beyond maximal aerobic speed (MAS). This systematic review aimed to determine the validity and reliability of different methods to assess the characteristics of ASR, i.e., MAS and maximal sprinting speed (MSS).

METHODS

A comprehensive search of the PubMed and Web of Science databases was conducted according to the PRISMA guidelines. Studies were included if they reported data on validity and/or reliability for methods to assess MAS or MSS.

RESULTS

58 studies were included with 28 studies referring to MAS and 30 studies to MSS. Regarding MAS, different methods for cardiopulmonary exercise testing yielded different values (four out of seven studies) of MAS (Cohen's d (ES) = 0.83-2.8; Pearson's r/intraclass correlation coefficient (r/ICC) = 0.46-0.85). Criterion validity of different field tests showed heterogeneous results (ES = 0-3.57; r/ICC = 0.40-0.96). Intraday and interday reliability was mostly acceptable for the investigated methods (ICC/r>0.76; CV<16.9%). Regarding MSS, radar and laser measurements (one out of one studies), timing gates (two out of two studies), and video analysis showed mostly good criterion validity (two out of two studies) (ES = 0.02-0.53; r/ICC = 0.93-0.98) and reliability (r/ICC>0.83; CV<2.43%). Criterion validity (ES = 0.02-7.11) and reliability (r/ICC = 0.14-0.97; CV = 0.7-9.77%) for global or local positioning systems (seven out of nine studies) and treadmill sprinting (one out of one studies) was not acceptable in most studies.

CONCLUSION

The criterion validity of incremental field tests or shuttle runs to examine MAS cannot be confirmed. Results on time trials indicate that distances adapted to the participants' sporting background, fitness, or sex might be suitable to estimate MAS. Regarding MSS, only sprints with radar or laser measures, timing gates, or video analysis provide valid and reliable results for linear sprints of 20 to 70 m.

Individual In-Situ GPS-Derived Acceleration-Speed Profiling: Toward Automatization and Refinement in Male Professional Rugby Union Players

BACKGROUND

Recently a proof-of-concept was proposed to derive the soccer players' individual in-situ acceleration-speed (AS) profile from global positioning system (GPS) data collected over several sessions and games. The present study aimed to propose an automatized method of individual GPS-derived in-situ AS profiling in a professional rugby union setting.

METHOD

AS profiles of forty-nine male professional rugby union players representing 61.5 million positions, from which acceleration was derived from speed during 51 training sessions and 11 official games, were analyzed. A density-based clustering algorithm was applied to identify outlier points. Multiple AS linear relationships were modeled for each player and session, generating numerous theoretical maximal acceleration (A0), theoretical maximal running speed (S0) and AS slope (ASslope, i.e., overall orientation of the AS profile). Each average provides information on the most relevant value while the standard deviation denotes the method accuracy. In order to assess the reliability of the AS profile within the data collection period, data were compared over two 2-week phases by the inter-class correlation coefficient. A0 and S0 between positions and type of sessions (trainings and games) were compared using ANOVA and post hoc tests when the significant threshold had been reached.

RESULTS

All AS individual profiles show linear trends with high coefficient of determination (r2 > 0.81). Good reliability (Inter-class Correlation Coefficient ranging from 0.92 to 0.72) was observed between AS profiles, when determined 2 weeks apart for each player. AS profiles depend on players' positions, types of training and games. Training and games data highlight that highest A0 are obtained during games, while greatest S0 are attained during speed sessions.

CONCLUSIONS

This study provides individual in-situ GPS-derived AS profiles with automatization capability. The method calculates an error of measurement for A0 and S0, of paramount importance in order to improve their daily use. The AS profile differences between training, games and playing positions open several perspectives for performance testing, training monitoring, injury prevention and return-to-sport sequences in professional rugby union, with possible transferability to other sprint-based sports.

KEY POINTS

AS profiles computed from rugby union GPS data provide positional benchmarks during training and competition. This study provides automatic detection of atypical data and the computation of error measurement of theoretical maximal acceleration and speed components. This refinement constitutes a step forward for a daily use of ecological data by considering data collection and method reliabilities. This easy-to-implement approach may facilitate its use to the performance management process (talent identification, training monitoring and individualization, return-to-sport).

Bias in estimated short sprint profiles using timing gates due to the flying start: simulation study and proposed solutions

Short sprints are most frequently evaluated and modeled using timing gates. Flying start distance is often recommended to avoid premature timing system triggering by lifting knees or swinging arms. This results in timing system initiation not being aligned with the initial force application, which yields bias in estimated short sprint parameters. This simulation study aims to explore the effects of the flying start distance on bias and sensitivity to detect changes in short sprint parameters using three models: the contemporary No Correction model and two proposed Estimated time correction (Estimated TC), and Estimated flying distance (Estimated FD) models. In conclusion, both the Estimated TC and Estimated FD models provided more precise parameter estimates, but surprisingly, the No correction model provided higher sensitivity for specific parameter changes. Besides standardizing the sprint starting technique for the short sprint performance monitoring, practitioners are recommended to utilize and track the results of all three models.

Anthropometric and physical characteristics in U16, U18 and U20 elite French youth rugby union players

The aims of this study in elite youth French players were to 1) describe the anthropometric and physical characteristics of international and non-international players from U16 to U20, and 2) compare these characteristics across age categories and playing standard (international or non-international). Altogether, 1423 players from the French Rugby Federation's academies participated in a physical testing battery, part of its national young player development pathway. From seasons 2010 to 2020, players were assessed for anthropometric (body mass and height), off-field (bench press; isometric squat, vertical jump) and on-field physical characteristics (aerobic capacity: maximal aerobic speed [MAS]; speed: 10-m, 50-m sprint). A 2-way mixed model analysis of variance (ANOVA) was used to compare physical characteristics across age categories and playing standards. Two separate models were used for forwards and backs. A main statistical effect was observed for age category and playing standard (range p < 0.05 -p < 0.001). Pair-wise category comparisons showed that older players were generally taller, heavier, stronger, faster and demonstrated better aerobic qualities than younger peers. The same results were observed for INT compared with NI players while INT forwards were also taller and heavier than NI peers (range p < 0.01 -p < 0.001). Findings revealed a clear progression in anthropometric characteristics and physical qualities throughout the age development pathway in elite young French rugby players. Findings also identified certain physical qualities (strength, power and speed) necessary at younger levels to achieve international standard.

Validity of Global Positioning System Technology to Measure Maximum Velocity Sprinting in Elite Sprinters

ABSTRACT

Thome, M, Thorpe, RT, Jordan, MJ, and Nimphius, S. Validity of global positioning system (GPS) technology to measure maximum velocity sprinting in elite sprinters. J Strength Cond Res 37(12): 2438-2442, 2023-The objective of this study was to assess the concurrent validity of 10-Hz wearable Global Positioning System (GPS) technology to measure maximum velocity sprinting (Vmax) relative to Doppler radar in elite sprinters. Data were collected from a single training session performed by elite 100 and 200 m sprinters (males: n = 5; 100 m best times: 10.02 ± 0.07 seconds, range: 9.94-10.10 seconds; 200 m best times: 20.29 ± 0.42 seconds, range: 19.85-20.80 seconds; females: n = 2; age: 28.0 ± 4.2 years; body mass: 65.8 ± 4.6 kg; 100 m best times: 11.18 ± 0.34 seconds; 200 m best times: 22.53 ± 0.04 seconds). Velocity and time data from 16 maximal, 60-m sprint efforts were recorded simultaneously with 10 Hz GPS and 47 Hz radar. Validity was assessed using Bland-Altman 95% limits of agreement (LOA) and intraclass correlation coefficient (ICC), each with respective 95% confidence intervals (CI). Vmax measured with 10 Hz GPS demonstrated a LOA of -0.11 m·s-1 (-0.17, -0.05) and an ICC of 0.99 (0.98, 1.0) relative to the radar device.10 Hz GPS overestimated Vmax by 0.11 m·s-1 relative to the radar but could still be considered a suitable tool for monitoring external load in elite sprinters. However, the much smaller average annual improvement in this population (∼0.1-0.2%) in comparison with the ∼1% overestimation reduces the utility of 10 Hz GPS to detect meaningful performance changes in maximum velocity.

What Factors Discriminate Young Soccer Players Perceived as Promising and Less Promising by Their Coaches?

Purpose: This study aimed to verify whether there are differences in physical, technical, and tactical assessment outcomes derived from field-based tests and small-sided games (SSG) in addition to anthropometric and maturational characteristics between players classified as promising and less promising as per the coaches' perception. Method: A total of 53 male U-15 youth soccer players (age: 14.8 ± 0.2 years, weight: 61.7 ± 6.9 kg, height: 171.8 ± 6.7 cm) and three experienced coaches from three distinct sports clubs were enrolled in this study. Based on the coaches' perception, players were split into three group levels for both short- and long-term success ranking: (i) promising (PL; top 5 players; n = 15), (ii) intermediate (IL; n = 23) and (iii) less promising (LPL; 5 bottom players; n = 15). The following measures were determined: anthropometry, maturity offset, vertical jump, and aerobic-anaerobic running performance, soccer- specific skills tests, GPS-based running metrics, technical and tactical actions during SSG, and minutes played throughout the season. Results: There were no differences between groups for anthropometrical, maturational, and physical outcomes. PL players in both rankings covered more distances at sprinting and presented more offensive technical and tactical actions during SSG than their LPL peers. PL and IL presented more minutes played in competitive seasons than LPL of short-term ranking. Conclusion: The biggest differences between the players ranked by their coaches were apparent only during a representative game task, emphasizing the importance of SSG as a tool to assess the players' technical-tactical awareness. In addition to the SSG, the coach's eye plays a key role during the talent identification and selection process.

In-situ acceleration-speed profile of an elite soccer academy: A cross-sectional study

Speed is an essential skill in sports performance and an important performance metric in talent identification. This study aims to evaluate and compare the sprint acceleration characteristics across different age groups in an elite soccer academy. A total of 141 elite academy soccer players were recruited to participate in the study, and they were assigned to their respective competitive age groups, ranging from under-14 to the B-team. An individual in-situ acceleration-speed (A-S) profile was assessed and derived from Global Position System (GPS) speed-acceleration raw data, from 10 consecutive football sessions, in the beginning of the season. The results showed that under-14 players exhibited significantly lower theoretical maximum speed (S0) (η p 2  = 0.215, p < 0.01) when compared with all other age groups. However, no differences were found between maximum theoretical acceleration (A0) and A-S slope between age groups. The results suggest that sprint mechanical profiles of young soccer athletes remain stable throughout their athletic development. Nevertheless, younger athletes have less capacity to apply horizontal force at higher speeds (S0).

Concurrent Validity and Reliability of the Sprint Force-Velocity Profile Assessed with K-AI Wearable Tech

Establishing a sprint acceleration force-velocity profile is a way to assess an athlete's sprint-specific strength and speed production capacities. It can be determined in field condition using GNSS-based (global navigation satellite system) devices. The aims of this study were to (1) assess the inter-unit and the inter-trial reliability of the force-velocity profile variables obtained with K-AI Wearable Tech devices (50 Hz), (2) assess the concurrent validity of the input variables (maximal sprint speed and acceleration time constant), and (3) assess the validity of the output variables (maximal force output, running velocity and power). Twelve subjects, including one girl, performed forty-one 30 m sprints in total, during which the running speed was measured using two GPS (global positioning system) devices placed on the upper back and a radar (Stalker® Pro II Sports Radar Gun). Concurrent validity, inter-device and inter-trial reliability analyses were carried out for the input and output variables. Very strong to poor correlation (0.99 to 0.38) was observed for the different variables between the GPS and radar devices, with typical errors ranging from small to large (all < 7.6%). Inter-unit reliability was excellent to moderate depending on the variable (ICC values between 0.65 and 0.99). Finally, for the inter-trial reliability, the coefficients of variation were low to very low (all < 5.6%) for the radar and the GPS. The K-AI Wearable Tech used in this study is a concurrently valid and reliable alternative to radar for assessing a sprint acceleration force-velocity profile.

Are Late-Born Young Soccer Players Less Mature Than Their Early-Born Peers, Although No Differences in Physical and Technical Performance Are Evident?

The aim of the study was to compare the status of somatic maturity, anthropometry, strength, speed, and soccer-specific technical skills of players from leading youth soccer academies born in different quarters of the same calendar year. A total of 678 young male soccer players from eight leading Russian soccer academies took part in the study. The following anthropometric measures and physical characteristics were measured: height, weight, body mass index, countermovement jumps (CMJ), 5, 10, and 20 m sprints, speed dribbling, foot and body ball juggling, and short and long pass accuracy. The determination of somatic maturity as a percentage of projected adult height was collected. All subject dates of birth were divided into four quartiles according to the month of birth. The analysis of all data obtained was conducted both within the total sample and by quartiles of birth, according to the age group categories of 12-13 years, 14-15 years, and 16-17 years and the degree of somatic maturity. There was a widespread relative age effect, with 43.5% of early-born players and only 9.6% of late-born players representing the sample. Early-born players were more mature than late-born players (p < 0.001 and p < 0.001) but had no statistically significant differences in strength, speed, or soccer-specific skills.

Effects of physical training programs on female tennis players' performance: a systematic review and meta-analysis

Background: Tennis is among the world's most popular and well-studied sports. Physical training has commonly been used as an intervention among athletes. However, a comprehensive review of the literature on the effects of physical training programs on female tennis players' performance is lacking. Therefore, this systematic review and meta-analysis aimed to determine the effects of physical training on performance outcomes in female tennis players. Methods: A comprehensive search was conducted on Web of Science, PubMed, SPORTDicus, Scopus, and CNKI from inception until July 2023 to select relevant articles from the accessible literature. Only controlled trials were included if they examined the effects of physical training on at least one measure of tennis-specific performance in female tennis players. The Cochrane RoB tool was employed to assess the risk of bias. The CERT scale was used to examine the quality of program information. The GRADE approach was adopted to evaluate the overall quality of the evidence. The Comprehensive Meta-Analysis software was used for the meta-analysis. Results: Nine studies were selected for the systematic review and seven for the meta-analysis, totaling 222 individuals. The study's exercise programs lasted 6-36 weeks, with training sessions ranging from 30 to 80 min, conducted one to five times per week. Muscle power (ES = 0.72; p = 0.003), muscle strength (ES = 0.65; p = 0.002), agility (ES = 0.69; p = 0.002), serve velocity (ES = 0.72; p = 0.013), and serve accuracy (ES = 1.14; p = 0.002) demonstrated significant improvement following physical training, while no notable changes in linear sprint speed (ES = 0.63; p = 0.07) were detected. Conclusion: Although research on physical training in sports is diversified, studies on training interventions among female tennis players are scarce. This review found that existing training programs yield some favorable outcomes for female tennis players. However, further research with high methodological quality is warranted on the tailoring of specific training programs for female tennis players. There should be more consistent measuring and reporting of data to facilitate meaningful data pooling for future meta-analyses.

The Acute Demands of Repeated-Sprint Training on Physiological, Neuromuscular, Perceptual and Performance Outcomes in Team Sport Athletes: A Systematic Review and Meta-analysis

BACKGROUND

Repeated-sprint training (RST) involves maximal-effort, short-duration sprints (≤ 10 s) interspersed with brief recovery periods (≤ 60 s). Knowledge about the acute demands of RST and the influence of programming variables has implications for training prescription.

OBJECTIVES

To investigate the physiological, neuromuscular, perceptual and performance demands of RST, while also examining the moderating effects of programming variables (sprint modality, number of repetitions per set, sprint repetition distance, inter-repetition rest modality and inter-repetition rest duration) on these outcomes.

METHODS

The databases Pubmed, SPORTDiscus, MEDLINE and Scopus were searched for original research articles investigating overground running RST in team sport athletes ≥ 16 years. Eligible data were analysed using multi-level mixed effects meta-analysis, with meta-regression performed on outcomes with ~ 50 samples (10 per moderator) to examine the influence of programming factors. Effects were evaluated based on coverage of their confidence (compatibility) limits (CL) against elected thresholds of practical importance.

RESULTS

From 908 data samples nested within 176 studies eligible for meta-analysis, the pooled effects (± 90% CL) of RST were as follows: average heart rate (HRavg) of 163 ± 9 bpm, peak heart rate (HRpeak) of 182 ± 3 bpm, average oxygen consumption of 42.4 ± 10.1 mL·kg-1·min-1, end-set blood lactate concentration (B[La]) of 10.7 ± 0.6 mmol·L-1, deciMax session ratings of perceived exertion (sRPE) of 6.5 ± 0.5 au, average sprint time (Savg) of 5.57 ± 0.26 s, best sprint time (Sbest) of 5.52 ± 0.27 s and percentage sprint decrement (Sdec) of 5.0 ± 0.3%. When compared with a reference protocol of 6 × 30 m straight-line sprints with 20 s passive inter-repetition rest, shuttle-based sprints were associated with a substantial increase in repetition time (Savg: 1.42 ± 0.11 s, Sbest: 1.55 ± 0.13 s), whereas the effect on sRPE was trivial (0.6 ± 0.9 au). Performing two more repetitions per set had a trivial effect on HRpeak (0.8 ± 1.0 bpm), B[La] (0.3 ± 0.2 mmol·L-1), sRPE (0.2 ± 0.2 au), Savg (0.01 ± 0.03) and Sdec (0.4; ± 0.2%). Sprinting 10 m further per repetition was associated with a substantial increase in B[La] (2.7; ± 0.7 mmol·L-1) and Sdec (1.7 ± 0.4%), whereas the effect on sRPE was trivial (0.7 ± 0.6). Resting for 10 s longer between repetitions was associated with a substantial reduction in B[La] (-1.1 ± 0.5 mmol·L-1), Savg (-0.09 ± 0.06 s) and Sdec (-1.4 ± 0.4%), while the effects on HRpeak (-0.7 ± 1.8 bpm) and sRPE (-0.5 ± 0.5 au) were trivial. All other moderating effects were compatible with both trivial and substantial effects [i.e. equal coverage of the confidence interval (CI) across a trivial and a substantial region in only one direction], or inconclusive (i.e. the CI spanned across substantial and trivial regions in both positive and negative directions).

CONCLUSIONS

The physiological, neuromuscular, perceptual and performance demands of RST are substantial, with some of these outcomes moderated by the manipulation of programming variables. To amplify physiological demands and performance decrement, longer sprint distances (> 30 m) and shorter, inter-repetition rest (≤ 20 s) are recommended. Alternatively, to mitigate fatigue and enhance acute sprint performance, shorter sprint distances (e.g. 15-25 m) with longer, passive inter-repetition rest (≥ 30 s) are recommended.

Functional measurement of canine muscular fitness: refinement and reliability of the Penn Vet Working Dog Center Sprint Test

Working, sporting, and companion dogs require muscular fitness to perform their daily tasks, competitive activities, and operational functions effectively and with a low risk of injury. There are currently no methods to measure the muscular fitness of dogs who are not debilitated. Sprint performance is highly correlated with muscular fitness in humans, and various sprint assessments are used to measure performance for sporting and tactical athletes. The Penn Vet Working Dog Center Sprint Test (ST) is a 25 m maximal effort sprint from a down position and was developed to be a low-cost measure of muscular fitness suitable for field use. The purpose of this project was to describe the refinements to the ST, detail the performance and measurement protocol, evaluate the measurement inter-rater and intra-rater reliability, characterize the acceleration profile, and explore the inter-day reliability. Both naïve and experienced raters demonstrated excellent intra-rater and inter-rater reliability. The acceleration profile of the dogs in this study was similar to that of average adult human sprinters and demonstrated the role of muscular fitness in performance over this short distance. Finally, a small group of dogs showed moderate inter-day reliability and provided initial performance data to inform future studies. The ST appears to be a reliable measure of canine muscular fitness and could be used to assess performance in healthy dogs and guide the return to sport or work of debilitated dogs.

Intra-Session Reliability of Sprint Performance on a Non-Motorised Treadmill for Healthy Active Males and Females

This study examined the intra-session reliability of sprint performance on a non-motorized treadmill amongst healthy, active male and female adults. One hundred and twenty participants (males n = 77; females n = 45) completed two familiarization sessions, followed by a third session that consisted of three trials (T1, T2, T3) of maximal sprints (4-s), interspersed by three minutes of recovery. Combining males and females exhibited moderate-to-excellent test-retest reliability (intra-class correlation coefficient, ICC), minimal measurement error (coefficient of variation, CV) and trivial differences between trials (effect size, ES) for speed, power, total work and acceleration (ICC = 0.82-0.98, CV = 1.31-8.45%, ES = 0.01-0.22). The measurement error was improved between comparisons of T1 vs. T2 (CV = 1.62-8.45%, ES = 0.12-0.22) to T2 vs. T3 (CV = 1.31-6.56%, ES = 0.01-0.07) and better for females (CV = 1.26-7.94%, ES = 0.001-0.26) than males (CV = 1.33-8.53%, ES = 0.06-0.31). The current study demonstrated moderate-to-excellent reliability and good-moderate measurement error during a 4-s sprint on a non-motorized treadmill. However, sex had a substantial impact with females exhibiting better values. Practitioners should employ at least two separate trials within a session, in addition to multiple familiarization sessions, to achieve reliable non-motorized treadmill sprint performances.

Validity, Reliability, and Sensitivity of Mobile Applications to Assess Change of Direction Speed

This study aimed to assess the validity, reliability, and sensitivity of mobile applications for assessing change-of-direction speed (CODS) performance. Thirty college athletes performed two Illinois CODS tests during one session. Assessments were carried out simultaneously using six devices (the CODTimer app, Seconds Count app, StopwatchCamera app, two analog stopwatches, and timing gates). Validity analyses included Pearson's product-moment correlation analysis, a linear regression model, and Bland-Altman plots. Reliability analyses included the intraclass correlation coefficient (ICC), the coefficient of variation (CV%), and the paired-sample t test. Sensitivity analyses included the typical error and smallest worthwhile change (SWC). The results showed that validity, reliability, and sensitivity values were higher for the CODTimer app (r = 0.99, R2 = 0.99, mean bias = -0.03 ± 0.10, CV% = 3.21, ICC = 0.89, SWC rating: good, p = 0.84) and the Seconds Count app (r = 0.99, R2 = 0.99, mean bias = -0.03 ± 0.08, CV% = 3.28, ICC = 0.88, SWC rating: good, p = 0.84) relative to the StopwatchCamera app (r = 0.98, R2 = 0.97, mean bias = -0.11 ± 0.22, CV% = 3.43, ICC = 0.86, SWC rating: marginal, p = 0.10), Analog Stopwatch 1 (r = 0.98, R2 = 0.96, mean bias = -0.09 ± 0.42, CV% = 2.95, ICC = 0.90, SWC rating: good, p = 0.91), and Analog Stopwatch 2 (r = 0.99, R2 = 0.97, mean bias = -0.12 ± 0.88, CV% = 3.51, ICC = 0.87, SWC rating: marginal, p = 0.96). In conclusion, compared to timing gates, the CODTimer app and Seconds Count app provided lower measurement bias and higher sensitivity for assessing CODS performance.

High-intensity Actions in Elite Soccer: Current Status and Future Perspectives

Over the years, soccer has become more physically demanding; the number and frequency of high-intensity actions have increased, and these activities are decisive in determining the match outcome. Importantly, the reductionist approach commonly used to analyze high-intensity actions does not contemplate a more contextualized perspective on soccer performance. Traditionally, most investigations have only provided quantitative data regarding sprints (i. e. time, distances, frequency) without examining "how" (e. g. type of trajectory or starting position) and "why" (e. g. tactical role) soccer players sprint. In fact, other high-intensity actions, apart from running, are not even mentioned (i. e. curve sprints, change of direction, and specific-jump tasks). This has led to the use of tests and interventions that do not accurately reflect real game actions. Given the true technical-tactical-physical demands of each playing position, this narrative review collected a wide-spectrum of current soccer-related articles and provided a discussion regarding high-intensity actions, with a positional-based approach. In this narrative review, practitioners are encouraged to contemplate and consider the different elements that characterize high-intensity actions in soccer, in order to assess and train soccer players under a more sport-specific and integrative perspective.

Force-velocity profile in sprinting: sex effect

The ability to produce muscle power during sprint acceleration is a major determinant of physical performance. The comparison of the force-velocity (F-v: theoretical maximal force, F₀; velocity, v₀ and maximal power output, P_max) profile between men and women has attracted little attention. Most studies of sex differences have failed to apply a scaling ratio when reporting data. The present study investigated the sex effect on the F-v profile using an allometric model applied with body mass (BM), fat-free mass (FFM), fat-free mass of the lower limb (FFMLL), cross-sectional area (CSA) and leg length (LL) to mechanical parameters. Thirty students (15 men, 15 women) participated. Raw velocity-time data for three maximal 35 m sprints were measured with a radar. Mechanical parameters of the F-v relationship were calculated from the modelling of the velocity-time curve. When F₀ and P_max were allometrically scaled with BM (p = 0.538; ES = 0.23) and FFM (p = 0.176; ES = 0.51), there were no significant differences between men and women. However, when the allometric model was applied to P_max with FFMLL (p = 0.015; ES = 0.52), F₀ with CSA (p = 0.016; ES = 0.93) and v₀ with LL (p ≤ 0.001; ES = 1.98) differences between men and women persisted. FFM explained 83% of the sex differences in the F-v profile (p ≤ 0.001). After applying an allometric model, sex differences in the F-v profile are explained by other factors than body dimensions (i.e., physiological qualitative differences).

The Effect of Flying Sprints at 90% to 95% of Maximal Velocity on Sprint Performance

PURPOSE

Submaximal sprinting allows for larger accumulated work to be reached before the onset of fatigue, compared with maximal efforts. The aim of this study was to investigate the effect of sprint running at 90% to 95% of maximal velocity (Vmax) on sprint performance.

METHODS

Recreationally active adults were randomly assigned into a control group (n = 12, 27 [5] y, 172 [9] cm, 72 [15] kg) and a training group (n = 14, 26 [4] y, 171 [9] cm, 69 [11] kg). Both groups completed pretesting and posttesting in form of a 30-m sprint separated by a 6-week period. The training group performed a weekly sprint-training session consisting of 30-m flying sprints at 90% to 95% of Vmax, while the control group performed no intervention training.

RESULTS

Significant improvements in the training group were observed for 10- (P = .003), 20- (P = .001), and 30-m sprint time (P = .002). These improvements were accompanied by higher step rate (P = .006) and theoretical Vmax (P = .007) and maximal power (P = .004). Significant between-groups differences were observed for 10- (P = .008), 20- (P < .001), and 30-m sprint time (P < .001), as well as for step rate (P = .015), theoretical Vmax (P = .016), and maximal power (P = .008). All within- and between-groups differences were in the range of trivial to small.

CONCLUSION

Sprint running at 90% to 95% of Vmax can enhance 10- to 30-m sprint performance in recreationally active adults.

Reliability and validity of an indoor local positioning system for measuring external load in ice hockey players

This study determined the reliability and validity of a Kinexon local positioning system (LPS) for measuring external load in ice hockey players during an on-ice session. Fourteen ice hockey players (25.1 y, 78.6 kg, 176.9 cm) wore two LPS sensors to examine the inter-sensor reliability of the LPS during an on-ice session, and LPS speed and acceleration were measured during 40 m linear on-ice sprints and compared to a previously validated robotic sprint device to examine LPS accuracy. The coefficient of variation (CV), standard error of measurement (SEM), and intra-class correlation coefficient (ICC) were calculated for each LPS measure. Pearson's correlations, simple linear regressions, and Bland-Altman plots were used to test the agreement and relationship between the two systems. Statistical significance was determined at p < 0.05. The majority of LPS measures were reliable (CV < 10% and ICC > 0.9) when comparing the two sensors worn by each player. Peak speed, speed at 5 m, and 0-5 m acceleration were all comparable to those reported by the robotic sprint device, with nearly perfect (peak speed and 0-5 m acceleration) and very large (speed at 5 m) magnitudes of correlation and mean biases <0.5 km/hr for speed measures and <0.01 m/s² for acceleration. The present results demonstrate that the Kinexon LPS is reliable and accurate for investigating on-ice external load in ice hockey players when sensors are consistently secured on the back of the players' shoulder pads.

Why age categories in youth sport should be eliminated: Insights from performance development of youth female long jumpers

Long-term sports participation and performance development are major issues in popular sports and talent development programs. This study aimed to provide longitudinal trends in youth female long jump performance development, participation, and relative age effects (RAEs), as longitudinal data for female athletes are missing. 51'894 season's best results of female long jump athletes (n = 16'189) were acquired from the Swiss Athletics online database and analyzed within a range of 6-22 years of age. To examine longitudinal performance development and RAEs, data from athletes who participated in at least three seasons were selected (n = 41'253) and analyzed. Performance development was analyzed using age groups (AGs) and exact chronological age (CA) at competition. Differences between performances of birth quarters were analyzed using 83% confidence intervals (CIs) and smallest worthwhile change. Odds ratios (ORs) with 95% CI were used to quantify RAEs. With the traditional classification into age groups (AG), performances of athletes born between January and March (Q1) were significantly better than those born between October and December (Q4) from U8 to U17. Using exact CA resulted in similar performances in Q1 and Q4 until the U20 age category. The peak of participation was reached in the U12 category, and then decreased until the U23 category with a substantial drop at U17. Significant RAEs were observed from U8 to U19 and at U22. RAEs continuously decreased from U8 (large effect) to U14 (small effect). The present results show that differences in performance arise from the comparison of athletes in AGs. Thus, going beyond AGs and using exact CA, Q4 athletes could benefit from a realistic performance comparison, which promotes fair performance evaluation, un-biased talent development, realistic feedback, and long-term participation.

Strength and Conditioning Practices of Brazilian Olympic Sprint and Jump Coaches

Olympic coaches are likely to have adequate knowledge and implement effective training programs. This study aimed to describe and critically examine the strength and conditioning practices adopted by Brazilian Olympic sprint and jump coaches. Nineteen Olympic coaches (age: 50.2 ± 10.8 years; professional experience: 25.9 ± 13.1 years) completed a survey consisting of eight sections: 1) background information; 2) strength-power development; 3) speed training; 4) plyometrics; 5) flexibility training; 6) physical testing; 7) technology use; and 8) programming. It was noticed that coaches prioritized the development of explosiveness, power, and sprinting speed in their training programs, given the specific requirements of sprint and jump events. Nevertheless, unexpectedly, we observed: (1) large variations in the number of repetitions performed per set during resistance training in the off-season period, (2) a higher volume of resistance training prescribed during the competitive period (compared to other sports), and (3) infrequent use of traditional periodization models. These findings are probably related to the complex characteristics of modern competitive sports (e.g., congested competitive schedule) and the individual needs of sprinters and jumpers. Identification of training practices commonly used by leading track and field coaches may help practitioners and sport scientists create more effective research projects and training programs.

Training load comparison between small, medium, and large-sided games in professional football

This study aimed to assess if internal and external load parameters were different between sided game formats, if players' positions influenced these parameters, and if load parameters were different among sided game types (from 2vs2 to 10vs10) in professional football players. Twenty-five male players of the same club were enrolled in this study (age = 27 ± 9 years and body mass = 78 ± 14 kg). Sided games were categorized in formats as small-sided games (SSG, n = 145), medium-sided games (MSG, n = 431), and large-sided games (LSG, n = 204). Players were divided into roles such as center backs (CB), fullbacks (FB), center midfielders (CM), attacking midfielders (AM), and strikers (ST). STATSports 10 Hz GNSS Apex units were used to monitor external load parameters such as distance, high-speed running (HSR), sprinting distance, accelerations, and decelerations. The linear mixed model analysis found differences between formats (p < 0.001) for the rate of perceived exertion (RPE), distance, HSR, sprinting, accelerations, and decelerations. Differences were found between positions for HSR (p = 0.004), sprinting (p = 0.006), and decelerations (p < 0.001). Moreover, a significant difference was found between sided game types (p < 0.001) for RPE, distance, HSR, sprinting, accelerations, and decelerations. In conclusion, some sided games formats are more suitable for specific load-specific parameters (e.g., distance per minute, HSR, and sprinting are greater during LSG). The number of accelerations and decelerations is higher in MSG compared to other formats. Finally, players' positions influenced external load metrics, specifically HSR and decelerations but not RPE and distance.

Variations in Physical and Competitive Performance of Highly Trained Sprinters Across an Annual Training Season

ABSTRACT

Loturco, I, Fernandes, V, Bishop, C, Mercer, VP, Siqueira, F, Nakaya, K, Pereira, LA, and Haugen, T. Variations in physical and competitive performance of highly trained sprinters across an annual training season. J Strength Cond Res XX(X): 000-000, 2022-We assessed the changes in sprint, jump, and power parameters across the annual training cycle and tested the longitudinal correlations among these variables in top-level sprinters. Thirteen sprinters training with 4 different Olympic sprint coaches were sequentially assessed over 14 months, from January 2019 to March 2020, within 4 consecutive training camps. Performance tests were conducted as follows: standing long jump, squat and countermovement jumps, 10-m and 60-m sprint time, and maximum power output in the half-squat, jump-squat, and hip-thrust exercises. The competitive results of the sprinters throughout the study period were also recorded and analyzed. A repeated measures analysis of variance was used to compare the physical measurements between different testing sessions. A Pearson product-moment correlation was applied to examine the longitudinal relationships between changes in speed-related and power-related parameters. Percentage change was computed and compared with coefficient of variation values to determine whether changes in performance metrics were higher than the test variance, thus providing an indication of whether true changes occurred on an individual basis. Overall, sprinters did not exhibit significant changes in sprint speed, jumping ability, and power output. In addition, variations in competitive times (i.e., 100 m races) followed a similar pattern, within an average range of ±1.36%, for both male and female sprinters. As expected, top-level sprinters presented only small variations in physical and competitive performance over time. Nevertheless, the use of an individual statistical technique (i.e., true changes calculation) revealed that these nonsignificant increases or decreases may represent meaningful changes in their competitive potential.

Study on Hamstring Re-injury Prevention (SHARP): protocol for an international multicentre, randomised controlled trial

INTRODUCTION

Previous studies showed that the Nordic hamstring exercise (NHE) effectively prevents primary hamstring injury. However, no study investigated the secondary preventing effect of the NHE on hamstring reinjury. The primary purpose of this study is to investigate the effectiveness of the NHE for preventing hamstring reinjury after return to play (RTP) following a hamstring injury in football players. The secondary purpose is to determine the effect of the NHE on sprint and jump performance.

METHODS AND ANALYSIS

This is an international multicentre, prospective, parallel-group randomised controlled trial study. Subjects include male or female football players aged 18-40 years and within 1 week of RTP following a hamstring injury will be randomised into Nordics or a control group. Subjects in both groups continue their regular football training, but the Nordics group will perform an additional NHE programme. An online questionnaire will be sent to the subjects in both groups once per week within the first 10 weeks, then continued at months 6, 9 and 12. In a (performance) substudy, we will evaluate the effect of the NHE on sprint and vertical jump performance at three time points (at the beginning of the study, after 10 weeks and 12 months of follow-up).The primary outcomes are the incidence of hamstring reinjury within 2 and 12 months. The secondary outcomes are sprint and jump performance, adherence to the programme, duration of reinjury and reinjury burden.

ETHICS AND DISSEMINATION

This study is approved by the medical ethics committee of Amsterdam University Medical Center (UMC) in the Netherlands (METC 2021_117), Faculty of Medicine Universitas Gadjah Mada in Indonesia (KE/FK/1248/EC/2021), Norwegian School of Sport Sciences in Norway (number 216-2 70 122) and Denmark (ethical submission in process). The study's findings will be disseminated in scientific peer-reviewed journals and presented at international conferences.

TRIAL REGISTRATION NUMBER

NL9711.

Sprint Acceleration Mechanical Outputs Derived from Position- or Velocity-Time Data: A Multi-System Comparison Study

To directly compare five commonly used on-field systems (motorized linear encoder, laser, radar, global positioning system, and timing gates) during sprint acceleration to (i) measure velocity−time data, (ii) compute the main associated force−velocity variables, and (iii) assess their respective inter-trial reliability. Eighteen participants performed three 40 m sprints, during which five systems were used to simultaneously and separately record the body center of the mass horizontal position or velocity over time. Horizontal force−velocity mechanical outputs for the two best trials were computed following an inverse dynamic model and based on an exponential fitting of the position- or velocity-time data. Between the five systems, the maximal running velocity was close (7.99 to 8.04 m.s−1), while the time constant showed larger differences (1.18 to 1.29 s). Concurrent validity results overall showed a relative systematic error of 0.86 to 2.28% for maximum and theoretically maximal velocity variables and 4.78 to 12.9% for early acceleration variables. The inter-trial reliability showed low coefficients of variation (all <5.74%), and was very close between all of the systems. All of the systems tested here can be considered relevant to measure the maximal velocity and compute the force−velocity mechanical outputs. Practitioners are advised to interpret the data obtained with either of these systems in light of these results.

Accelerometery-Based Load Symmetry in Track Running Kinematics concerning Body Location, Track Segment, and Distance in Amateur Runners

Background: Previous studies indicate that running at maximum speed on short or curved sections is slower than running on straight sections. This study aimed to analyse the external load symmetry in track running kinematics concerning body location (left vs. right, caudal vs. cephalic), track segment (straight vs. curved) and distance (150 m vs. 300 m). Methods: Twenty experienced athletes ran 150 m and 300 m on an official athletic track and were monitored by Magnetic, Angular Rate and Gravity sensors attached to six different body segments (thorax, lumbar, knees and malleolus). Player Load was quantified as a valid, effective and representative Accelerometery-based variable. Results: (1) Principal component analysis explained 62–93% of the total variance and clustered body locations relevance in curved (knees and malleolus) vs. straight (lumbar, knees, malleolus) running segments; (2) Player Load statistical differences by track segment (curved vs. straight) were found in all body locations; and (3) there were no differences in bilateral symmetries by distance or running segment. Conclusions: Track segment and body location directly impacted accelerometery-based load. Acceleration in straight segments was lower compared to that in curved segments in all the body locations (lumbar, knee and ankle), except in the thorax. Strength and conditioning programs should consider the singularity of curved sprinting (effects of centripetal–centrifugal force) for performance enhancement and injury prevention and focus on the knees and malleolus, as shown in the principal component analysis results.

Repeated Sprint Protocols With Standardized Versus Self-Selected Recovery Periods in Elite Youth Soccer Players: Can They Pace Themselves? A Replication Study

PURPOSE

Replicating the studies of Gibson et al and Brownstein et al to assess performance, and physiological, and perceived variables during a repeated sprint protocol (RSP) with standardized versus self-selected recovery in youth soccer players.

METHODS

Nineteen male soccer players (age 13.1 [1.3] y) completed 2 separate RSPs. RSP1: 10 × 30-m sprints with 30-second recovery and RSP2: 10 × 30-m sprints interspersed with self-selected recovery periods. Mean time of both 10 × 30-m RSPs and self-selected recovery periods of RSP2 were assessed. Heart rate, blood lactate concentration, and rates of perceived exertion were measured following RSPs.

RESULTS

RSP2 revealed longer recovery periods (RSP1: 30.0 [0.0] s; RSP2: 39.0 [7.7] s; P < .001; effect size d = 1.648) with shorter repeated sprint time (mean 30-m sprint time: RSP1: 4.965 [0.256] s; RSP2: 4.865 [0.227] s; P = .014; d = 0.414). Blood lactate concentration (P = .002-.005; d = 0.730-0.958), heart rate (P < .001; d = 1.353), and rates of perceived exertion (RSP1: 14.9 [1.9]; RSP2: 12.9 [2.1]; P = .016; d = 1.046) were higher following RSP1.

CONCLUSION

In contrast to the original studies, the present replication study demonstrated that self-selected recovery periods during a RSP leads to better repeated sprint performance compared with standardized recovery periods in youth soccer players. The better repeated sprint performance with individual recovery durations in RSP2 was achieved with less physiological and perceived effort.

Reliability of My Jump 2 Derived from Crouching and Standing Observation Heights

The crouching or prone-on-the-ground observation heights suggested by the My Jump app are not practical in some settings, so users usually hold smartphones in a standing posture. This study aimed to analyze the reliability of My Jump 2 from the standardized and standing positions. Two identical smartphones recorded 195 countermovement jump executions from 39 active adult athletes at heights 30 and 90 cm, which were randomly assessed by three experienced observers. The between-observer reliability was high for both observation heights separately (ICC~0.99; SEM~0.6 cm; CV~1.3%) with low systematic (0.1 cm) and random (±1.7 cm) errors. The within-observer reliability for the three observers comparing the standardized and standing positions was high (ICC~0.99; SEM~0.7 cm; CV~1.4%), showing errors of 0.3 ± 1.9 cm. Observer 2 was the least accurate out of the three, although reliability remained similar to the levels of agreement found in the literature. The reliability of the mean observations in each height also revealed high reliability (ICC = 0.993; SEM = 0.51 cm; CV = 1.05%, error 0.32 ± 1.4 cm). Therefore, the reliability in the standing position did not change with respect to the standardized position, so it can be regarded as an alternative method to using My Jump 2 with practical added benefits.

BUILDING A PROFILE OF SPECIFIC FITNESS INDICES FOR MALE TEENAGE CHINESE SPRINTERS

ABSTRACT Objectives: This study aimed to construct a profile of specific fitness indices for male teenage sprinters on the Chinese National Team to provide sprinting fitness assessments for teenage training. Material and Methods: 229 male teenage sprinters at the same level were recruited to participate in this test for the indices. The t- and Kruskal-Wallis tests were conducted for the first selection of fitness indices. In the second selection, principal components analysis was applied to select common factors with greater characteristic values. The fitness indices chosen were height, leg length, measurement B (ankle circumference/heel length×100%) and measurement A (thigh circumference/leg length×100%), hemoglobin, 60m sprint time, 100m sprint time, countermovement jump (CMJ), maximum countermovement jump velocity, CMJ flight time, CMJ maximum force, and CMJ force. Results: Thirteen indices were chosen for the specific fitness of male teenage Chinese male sprinters with 3 general categories and 9 subcategories. The weight of each fitness index was confirmed and used to construct a standard fitness assessment scale. Conclusion: Anthropometric indices indicate the athlete’s innate limits in the structure of the sprinting motion. Physiological indices indicate the athlete’s potential to expend energy and recover in a short time. Motor indices indicate the athlete’s maximum sprinting ability, lower limb reaction strength, power, and maximum strength. Level of evidence II, Diagnostic studies - Investigation of a diagnostic test.

Validation of a LiDAR-based player tracking system during football-specific tasks

Tracking players’ movements in sports is important to monitor and optimise exercise volume, avoid injuries, and enhance game performance. A new LiDAR-based system (Sportlight®) purports to provide accurate velocity and acceleration metrics derived from player movements. This study examined the validity of the LiDAR-based system against a 3D motion analysis system. Two competitive football players (age: 18 years, height: 1.74 ± 0.01 m, mass: 66.5 ± 7.8 kg; playing experience at this level: 3 years) completed nine trials each of six sport-specific movements, consisting of straight-line sprints, cuts, and curved runs. Trials were recorded concurrently by a four-unit LiDAR system and a 64-camera 3D motion analysis system. Instantaneous velocity and acceleration, and time spent within key performance indicator bands (defined by velocity and acceleration thresholds) were compared between systems. Agreement between the systems was evaluated by root mean square error. Differences in time spent within each key performance indicator band between systems were assessed with t tests and standardised effect sizes. Velocity root mean square error values ranged from 0.04 to 0.14 m·s−1 across all movements and acceleration root mean square error values ranged from 0.16 to 0.7 m·s−2. Differences between systems for time spent within each key performance indicator band were mostly trivial. These results show that the LiDAR-based system can provide valid measures of velocity and acceleration in football-specific tasks, thus providing accurate tracking of players and calculation of relevant key performance indicators.

Effect of the COVID-19 Confinement Period on Selected Neuromuscular Performance Indicators in Young Male Soccer Players: Can the Maturation Process Counter the Negative Effect of Detraining?

The COVID-19 outbreak has led to an unprecedented long-term cessation in athletes’ training routines. This study examined the effect of a 32-week detraining period, caused by the COVID-19 pandemic lockdown, on selected neuromuscular performance indicators in 29 young male soccer players, assessed close to their adolescent growth spurt (age = 13.0 ± 0.8 years). Change of direction ability of both lower limbs (COD), linear sprint times (10 and 20 m), and vertical jump height (CMJ) was evaluated twice, once before the first national lockdown, and one week after the return to training activities. Paired-sample t-tests detected significant improvements in all three testing variables (COD: 2.82 ± 0.23 vs. 2.66 ± 0.22 s, p ≤ 0.005, 0.001, effect size [ES] = 0.91 to 1.05 for the right and left limb, respectively; 10 m: 2.12 ± 0.16 vs. 1.96 ± 0.15 s, p ≤ 0.001, effect size [ES] = 1.67, 20 m: 3.56 ± 0.3 vs. 3.42 ± 0.27 s, p ≤ 0.001, effect size [ES] = 1.02 and CMJ: 23.3 ± 7.5 vs. 24.5 ± 7.6 cm, p = 0.033, ES = 0.42). These results indicate that maturation-related adaptations can lead to enhanced change of direction, linear sprint, and vertical jump performance, even in the absence of exposure to any level of exercise. Soccer coaches and practitioners working with youth athletes should consider the stage of maturation when planning and implementing training programs aiming to enhance neuromuscular performance.

Reliability and Minimal Detectable Change of Sprint Times and Force-Velocity-Power Characteristics

ABSTRACT

Edwards, T, Banyard, HG, Piggott, B, Haff, GG, and Joyce, C. The reliability and minimal detectable change of sprint times and force-velocity-power characteristics. J Strength Cond Res 36(1): 268-272, 2022-Research has not yet provided critical information for practitioners to determine the minimal detectable change (MDC) in sprint times or force-velocity-power characteristics. Therefore, the aim of this study was to establish the interday reliability and MDC of sprint times and sprint force-velocity-power characteristics in junior Australian football (AF) players. Seventeen players were assessed using a radar device that recorded instantaneous velocity during 3 maximal 30-m sprint accelerations performed on 2 nonconsecutive days. Sprint force, velocity, and power characteristics were derived through inverse dynamics applied to the raw velocity-time data. Relative and absolute reliability was determined by calculating the intraclass correlation coefficient (ICC), coefficient of variation (CV), and MDC. Data analysis was assessed for (a) the first trial, (b) the best trial (the fastest 30-m split time), (c) the average of the first 2 trials, and (d) the average of all 3 trials from each testing session. The main findings were (a) absolute theoretical maximum force (F0), theoretical maximal velocity (V0), absolute and relative maximum power (Pmax), maximum ratio of force (RFmax), maximum velocity (Vmax), and all sprint distance times (5-30 m) displayed acceptable reliability (CV < 10% and ICC >0.75) and 2) the average of 2 and 3 trials was the best method of establishing reliable sprint times and force-velocity-power characteristics between sessions. This study provides important information for practitioners to determine the MDC in sprint times and force-velocity-power characteristics that allow coaches to identify true changes in performance.

International female rugby union players' anthropometric and physical performance characteristics: A five-year longitudinal analysis by individual positional groups

Longitudinal changes in anthropometric and physical performance characteristics of International female rugby union players were evaluated across 5-seasons, according to field position. Sixty-eight international female rugby union players from a top 2 ranked international team, undertook anthropometric and physical performance measurements across five seasons. Anthropometric and physical performance changes occurred, with skinfolds decreasing between 2015 and 2017 and body mass increasing between 2017 and 2019. Single-leg isometric squat (SL ISO), 0-10 m momentum (0-10 Mom) and 20-30 m momentum (20-30Mom) were higher in 2018 and 2019 than all years. Front-row players were characterised by greater SL ISO and 1-RM bench press than inside and outside backs, with higher skinfolds and lower endurance levels than all positions. Between 2017 and 2019, front-row players had larger decreases and increases in endurance and one repetition maximum (1-RM) bench press, respectively, compared to all other positions. Forwards had the highest 0-10Mom and 20-30Mom, and scrum-half the lowest, while outside backs had faster 0-10, 30-40, and 40 m (TT40 m) times, and greater peak velocity (V_max) compared to forward positions. These longitudinal findings show that physical performance has increased, with anthropometric and performance characteristics becoming more distinctive between positions, among elite female rugby union players.