Finding the Signal in the Noise-Interday Reliability and Seasonal Sensitivity of 84 Countermovement Jump Variables in Professional Basketball Players

The role of age and maturation on jump performance and postural control in female adolescent volleyball players over a season

BACKGROUND

Jump performance and postural control are essential for success in technical/tactical actions and overall playing performance in volleyball. Youth athletes undergo significant physical and neuromuscular development during adolescence, which can impact these abilities. This study examined the effect of age and biological maturity, assessed as the distance from peak height velocity using the maturity offset (MO), on vertical and plyometric jumping abilities and postural control in adolescent female volleyball players across different age categories throughout a competitive season.

METHODS

Forty-five adolescent volleyball players (aged 12.5 to 17) from four age categories (U13, U14, U16, U18) of the same club participated in three testing sessions during a season. Jump performance was assessed through countermovement (CMJ) and drop jump (DJ) tests, while postural control was measured using a static balance task. All tests were conducted using force plates, sampling at 1000 Hz (for jumps) and 100 Hz (for static balance test), to study force-related and CoP outcomes, respectively. MANCOVA models were applied for each assessment to examine the effects of age category and season timepoint on selected performance variables, including MO as a covariate to account for the maturation effect. Follow-up univariate and linear regression models were performed in case of significance from the multivariate analysis.

RESULTS

MO significantly differed among all the age categories and session timepoints (p < 0.001). CMJ multivariate analysis revealed significant results regarding the session (p = 0.010, η2p = 0.49) and MO (p = 0.025, η2p = 0.29) effects, but not for age category (p = 0.165) or age category × session interaction (p = 0.152). Conversely, DJ and postural control showed no significant results for any studied effect. The session timepoint had a significant effect on the CMJ concentric impulse, while MO was significantly positively associated with peak power, jump momentum, concentric impulse, and eccentric impulse (p < 0.001, R2 = 0.31-0.57).

CONCLUSIONS

The results emphasize the specific influence of biological maturation on power and force production during vertical jumps, while other specific plyometric and postural control adaptations seem to be less sensitive to chronological age and maturational changes during the adolescence period in female volleyball players.

Assessment of Aerobic Fitness and Repeated Sprint Ability in Elite Male Soccer: A Systematic Review of Test Protocols Used in Practice and Research

BACKGROUND

Soccer requires players to cover distances around 10-12 km, with numerous consecutive sprints throughout the 90-min game. As such, aerobic fitness and repeated sprint ability (RSA) are crucial physical qualities for the modern soccer player to cope with the demands of the game. However, a comprehensive and systematic search of aerobic fitness and RSA assessment procedures in elite soccer has yet to be conducted.

OBJECTIVES

The aims of this systematic review were to (1) identify the tests and outcome variables used to assess aerobic fitness and RSA of elite male soccer players, (2) provide normative values for the most common tests of aerobic fitness and RSA across different playing levels, and (3) report the reliability values of these aerobic fitness and RSA tests.

METHODS

A systematic review of the academic databases MEDLINE, CINAHL, SPORTDiscus, Web of Science, and OVID for studies published until August 2023 was conducted, following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Studies were eligible for inclusion if (1) they were original research studies, published in a peer-reviewed journal, and written in English language; (2) they had the primary aim of assessing aerobic fitness and/or RSA; (3) players were male and older than 17 years of age (i.e. mean age of the group); and (4) their playing level was defined as 'professional', 'international', or 'elite'.

RESULTS

For aerobic fitness testing, 124 studies and 35 different tests were identified. Of those, 26 tests (74%) were field-based, whereas only nine (26%) were laboratory-based tests. The incremental treadmill test to exhaustion was the most commonly used aerobic fitness assessment method (56 studies, 45%), with maximal oxygen consumption ( V ˙ O2max) (mL/kg/min) being the most prevalent outcome variable (49 studies, 87%). The YYIR1 and YYIR2 were also commonly used tests, identified in 22 (18%) and ten studies (8%), respectively. The most frequently reported outcome variable in both tests was distance in metres, reported in 20 studies (91%) for YYIR1 and in all ten studies (100%) for YYIR2. For RSA testing, 27 studies and 18 different tests were identified. Substantial variability in the identified RSA testing protocols was observed in terms of direction (linear vs. multidirectional), sprint repetitions (6-15), sprint distance (20-40 m), type of recovery (active vs. passive), and recovery duration (10-30 s). The 6 × 40-m shuttle sprint protocol with a 180° change of direction and 20 s passive recovery was the most common RSA test, employed in eight studies (29%).

CONCLUSIONS

This systematic review provides a comprehensive overview of the testing methods used to assess aerobic fitness and RSA in elite male soccer players. A total of 35 different aerobic fitness tests and 18 RSA tests were identified, highlighting the diversity in methodologies used. The most prevalent aerobic test was the incremental treadmill testing to exhaustion, with a median V ˙ O2max value of 58 mL/kg/min. Field-based tests were preferred due to their practicality, cost-efficiency, and ability to assess multiple athletes simultaneously. A substantial variability in RSA testing protocols was identified in terms of sprint directions, distances, repetitions, and recovery types. Future research should focus on establishing the diagnostic accuracy of the most commonly used aerobic fitness tests to inform their utility in practice and bridge the gap between current testing practices and optimal fitness evaluation.

The Effects of a Low-Volume, High-Intensity Preseason Microcycle on Neuromuscular Performance in Collegiate Female Basketball Players

ABSTRACT

Philipp, NM, Blackburn, SD, Cabarkapa, D, and Fry, AC. The effects of a low-volume, high-intensity pre-season micro-cycle on neuromuscular performance in collegiate female basketball players. J Strength Cond Res 38(12): 2136-2146, 2024-The use of stretch-shortening cycle (SSC)-based measures of vertical jump performance to monitor responses to training exposures is common practice in sport science. However, evidence is limited with regards to which assessments and metrics may be most sensitive toward changes in training volume and intensity. The aim of this study was to investigate how a reduction in training volume, paralleled with an increase in training intensity, affects neuromuscular performance as measured through a countermovement jump (CMJ) and 10-5 hop test over a preseason period in female collegiate basketball players. Over a 3-week baseline period, athletes completed CMJ and 10-5 hop tests to quantify baseline performance. Measures of neuromuscular response to the changes in training volume and intensity were performed 2 and 4 days into the intervention week, as well as post 72 hours, post 7 days, and post 10 days. External workload data and descriptive analyses of resistance training stimuli suggest that during the intervention week, athletes experienced significantly lower training volumes and increases in training intensity. In response to these changes in training stimulus, athletes showed depressed performance acutely in metrics derived from both the CMJ and 10-5 hop test. Authors also observed a supercompensation effect at post 72 h, post one week, and post 2 weeks for metrics related to lower-limb stiffness and braking rate of force development. These findings highlight that in response to a high-intensity, low-volume training phase, female basketball players experienced alterations in lower-limb function, reflected in both decreases and increases in SSC performance.

Assessment of Strength and Power Capacities in Elite Male Soccer: A Systematic Review of Test Protocols Used in Practice and Research

BACKGROUND

Strength and power represent two crucial physical qualities for the attainment of a high level of performance considering the frequency and the importance of explosive actions occurring during elite soccer match-play. Evaluation of strength and power is a multifaceted concept involving a vast array of tests and outcome variables. Nevertheless, a comprehensive and systematic search of strength and power assessment procedures in elite soccer has yet to be undertaken.

OBJECTIVES

The aims of this systematic review were to: (1) identify the tests and outcome variables used to assess strength and power of elite male soccer players; (2) provide normative values for the most common tests of strength and power across different playing levels; and (3) report the reliability values of these strength and power tests.

METHODS

A systematic review of the academic databases MEDLINE, CINAHL, SPORTDiscus, Web of Science and OVID for studies published until August 2023 was conducted, following the Preferred Reporting Items of Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Studies were eligible for inclusion if they: (1) were original research studies, published in a peer-reviewed journal, and written in English language; (2) had the primary aim to assess strength and/or power; (3) players were male and older than 17 years of age (i.e., mean age of the group); and (4) their playing level was defined as "professional", "international" or "elite".

RESULTS

Regarding strength testing, 115 studies and 29 different tests were identified. The three most frequent strength tests were the knee extensor isokinetic strength test (58 studies), the knee flexor isokinetic strength test (55 studies) and the Nordic hamstring strength test (13 studies). In terms of power testing, 127 studies with 31 different tests were included. The three most frequent power tests were the countermovement jump with hands fixed on hips (99 studies), the squat jump (48 studies) and the vertical jump with arm swing (29 studies).

CONCLUSIONS

The wide range of different tests and outcome variables identified in this systematic review highlights the large diversity in the employed testing procedures. The establishment of a hybrid testing approach, combining standardised and widely accepted tests for establishing normative standards and enabling comparisons across different contexts, with flexible context-specific testing batteries, has the potential to maximise the impact of testing information for practitioners. In addition, the limited reporting of reliability data across studies highlights the need for practitioners to establish their own reliability measure within their specific contexts, informing the selection of certain tests and outcome variables.

Muscle and tendon morphology of a world strongman and deadlift champion

This study compared the muscle and tendon morphology of an extraordinarily strong individual, a World's Strongest Man and deadlift champion (WSM), with that of various other athletic, trained, and untrained populations. The WSM completed the following: 1) 3.0-T MRI scans, to determine the volume of 22 individual lower limb muscles, 5 functional muscle groups, patellar tendon (PT) cross-sectional area (CSA), and PT moment arm; and 2) countermovement jumps (CMJ) and isometric midthigh pull (IMTP) contractions. The WSM was compared with previously assessed groups from our laboratory (muscle and tendon) and the wider research literature (CMJ and IMTP). The WSM's CMJ peak power (9,866 W) and gross (9,171 N) and net (7,480 N) IMTP peak forces were higher than any previously published values. The WSM's overall measured leg muscle volume was approximately twice that of untrained controls (+96%) but with pronounced anatomical variability in the extent of muscular development. The plantar flexor group (+120%) and the guy rope muscles (sartorius, gracilis, and semitendinosus: +140% to +202%), which stabilize the pelvis and femur, demonstrated the largest differences relative to that of untrained controls. The WSM's pronounced quadriceps size (greater than or equal to twofold vs. untrained) was accompanied by modest PT moment arm differences and, notably, was not matched by an equivalent difference in PT CSA (+30%). These results provide novel insight into the musculotendinous characteristics of an extraordinarily strong individual, which may be toward the upper limit of human variation, such that the WSM's very pronounced lower limb muscularity also exhibited distinct anatomical variability and with muscle size largely uncoupled from tendon size.NEW & NOTEWORTHY Lower-body muscle size of an extraordinarily strong individual, a World's Strongest Man and deadlift champion (WSM), was approximately twice that of controls but was underpinned by pronounced anatomical variability in the extent of muscular development (+23-202%): the plantar flexor group and guy rope muscles demonstrating the largest differences. The WSM's quadriceps size (more than or equal to twice that of controls) contrasted with modest differences in patella tendon moment arm (+18%) and was uncoupled from patellar tendon size (+30%).

The influence of external loads on post-match neuromuscular fatigue in international rugby union: A partial least squares correlational analysis

The aims were to determine the relationship(s) between match-play external load and post-match neuromuscular fatigue as latent constructs, the contribution of the specific measured variables to these latent constructs, and how these differ between forwards and backs in elite rugby union. Forty-one elite male rugby union players (22 forwards and 19 backs) from the same international rugby union team were tested, with data included from the 2020 and 2021 international seasons (11 matches; 146 player appearances). Player's match-play external loads were quantified using microtechnology (for locomotor activities) and video analysis (for collision actions). Neuromuscular fatigue was quantified using countermovement jump tests on force plates which were conducted ~ 24 to 48 hours pre- and post-match. Partial least squares correlation (PLSC) leave one variable out (LOVO) procedure established the relative variable contribution to both external load (X matrix) and neuromuscular fatigue (Y matrix) constructs. Linear mixed-effects models were then constructed to determine the variance explained by the latent scores applied to the variables representing these constructs. For external load, both locomotor and collision variables were identified for the forwards and the backs, although the identified variables differed between groups. For neuromuscular fatigue, jump height was identified as a high contributor for the forwards and the backs, with concentric impulse and reactive strength index high contributors only for the backs. The explained variance between the external load and neuromuscular fatigue latent constructs at the individual player level was 4.4% and 32.2% in the forwards and the backs models, respectively. This discrepancy may be explained by differences in match-play external loads and/or the specificity of the tests to measure indicators of fatigue. These may differ due to, for example, the activities undertaken in the different positional groups.

Dose-Response Relationship for External Workload and Neuromsuclar Performance Over a Female, Collegiate, Basketball Season

ABSTRACT

Philipp, NM, Cabarkapa, D, Blackburn, SD, and Fry, AC. Dose-response relationship for external workload and neuromsuclar performance over a female, collegiate, basketball season. J Strength Cond Res 38(5): e253-e263, 2024-The aim of this study was to investigate the relationship between external workload exposure and changes in countermovement jump force-time characteristics over the course of an entire basketball season, in a sample of National Collegiate Athletic Association Division I, female, basketball players. Data for 12 players were retrospectively analyzed, with external workload being quantified by means of an exponentially weighted, acute, and chronic workload, as well as an acute:chronic workload ratio derived from an inertial measurement unit-based system worn by athletes for all practices and games during the regular season. Countermovement jumps were performed on a total of 26 test days over the span of the in-season competitive period. To statistically analyze these relationships, and to account for multiple observations of the same athletes in a data set, linear mixed-effects models with athlete identity (ID) intercept as the random effect were used. Study findings suggested that associations between external workload exposure and respective force-time characteristics after controlling for the random effect of athlete ID were dependent on the specific metric or metric subgroup used, as well as the type of workload exposure (e.g., acute vs. chronic). Force-time signatures from the braking phase (e.g., average braking force) seemed to be particularly associated with higher degrees of acute workload exposure, whereas strategy-based metrics such as countermovement depth showed significant associations with chronic workload exposure. Furthermore, model results suggested the importance of analyzing neuromuscular responses to external workload on an individual basis, rather than across an entire team. Findings might help practitioners in their selection process related to metrics of interest in monitoring neuromuscular fatigue and readiness.

Investigating the stretch-shortening cycle fatigue response to a high-intensity stressful phase of training in collegiate men's basketball

Introduction

While using force-plate derived measures of vertical jump performance, reflective of stretch-shortening-cycle (SSC) efficiency is common practice in sport science, there is limited evidence as to which tests and measures may be most sensitive toward neuromuscular fatigue. The aim of this study was to explore the SSC fatigue response to a one-week high-intensity fatiguing phase of training in National Collegiate Athletic Association (NCAA) Division-I basketball players.

Methods

The study timeline consisted of three weeks of baseline measures, one week of high-intensity training, and two weeks of follow-up testing. Countermovement jumps (CMJ) and 10-5 hop tests were performed at baseline, as well as at two time-points during, and three time-points following the fatiguing training period, allowing for performance-comparisons with baseline.

Results

Compared to the weekly training sum at baseline, during the high intensity training phase, athletes were exposed to very large increases in selected external load metrics (ES = 1.44-3.16), suggesting that athletes experienced fatigue acutely, as well as potential longer lasting reductions in performance. Vertical jump data suggested that in the CMJ, traditional metrics such as jump height, as well as metrics reflecting kinetic outputs and movement strategies, were sensitive to the stark increase in high-intensity training exposure. The 10-5 hop test suggested a fatigue-induced loss of tolerance to ground impact reflected by performance reductions in metrics related to jump height and reactive strength qualities.

Discussion

These findings emphasize that when monitoring neuromuscular fatigue, variables and assessments may not be looked at individually, but rather as part of a more global monitoring approach.

Physiological, anthropometric and athletic performance adaptations from completing a 1-month pre-season period. A two-year longitudinal study in female collegiate soccer players

Introduction

Collegiate coaches and integrative support staff often utilize pre-season as a brief and intense training period to prepare athletes technically, tactically, and physiologically, to meet the demands of competition during a soccer season. This study sought to examine the dose-response from performing on-field soccer activities during a four-week pre-season period in female collegiate soccer players, and if the magnitude in response was associated with accumulated exercise stress.

Methods

A total of twenty-seven healthy female soccer players training as part of a collegiate soccer program volunteered to participate in this two-year longitudinal study. Data collection commenced prior to the start of each pre-season period, at the beginning of August, and was completed at the beginning of September, when pre-season ended. Data collection periods were separated by a 31-day period. Indices of cardiovascular function, anthropometry, and athletic performance were examined during each data collection period. Internal and external measures of accumulated exercise stress were recorded using the Polar Team Pro® system.

Results

When comparing the beginning to the end of pre-season, significant improvements were observed in body fat (%) [24.2 ± 6.0 "vs." 23.3 ± 5.6, p = 0.001], heart rate variability (rMSSD) [51.8 ± 25.1 "vs." 67.9 ± 34.6 ms, p = 0.002], resting heart (bpm) [73.8 ± 12.1 "vs." 64.3 ± 8.8, p = 0.001] and cardiorespiratory performance (YoYo IRTL-1) [925.8 ± 272.8 "vs." 1,062.6 ± 223.3 m, p = 0.001]. Significant reductions in musculoskeletal performance were observed through vertical jump height (cm) [24.9 ± 23.7, p = 0.04]. Change in the end of pre-season body weight (kg) was significantly associated with accumulated accelerations and decelerations [r ≥ 0.49, p = 0.01]. End of pre-season change in cardiorespiratory performance was significantly associated with both accumulated training load (au) and TRIMP (au) [r ≥ 0.63, p = 0.01].

Discussion

In conclusion, performing a four-week pre-season period, involving only on-field training, can promote positive and significant adaptations in anthropometry, cardiovascular function, and athletic performance measures in female collegiate soccer players. The magnitudes of these adaptations were associated with both internal and external measures of accumulated exercise stress.

Reliability of Measures of Lower-Body Strength and Speed in Academy Male Adolescent Soccer Players

ABSTRACT

Ferguson, J, Gibson, NV, Weston, M, and McCunn, R. Reliability of measures of lower body strength and speed in academy male adolescent soccer players. J Strength Cond Res 38(3): e96-e103, 2024-The Nordbord and ForceFrame represent a practical and time efficient means of assessing eccentric hamstring and isometric adductor strength in the large number of squads and players associated with youth soccer academies, yet measurement reliability in this population is unexamined. Therefore, over a period of 4 days, with no less than 24 hours and no more than 48 hours between trials, 37 players (age: 14.7 ± 0.8 years, stature: 168.7 ± 7.8 cm, mass: 57.7 ± 9.1 kg, and maturity offset: 0.8 ± 0.9 years) were assessed for eccentric hamstring strength (force, torque), isometric adductor strength (long and short lever positions), and 30-m sprint (5, 10, and 20-m splits), using the Nordbord, ForceFrame, and electronic timing gates, respectively, on 3 separate occasions. Relative reliability (intraclass correlation coefficient) was rated as good for all Nordbord (range: 0.86-0.89) and ForceFrame (0.78-0.85) measures and ranged from moderate (0.53) to excellent (0.93) for the speed measures, improving with increased distance. Absolute reliability (standard error of the measurement [%SEM]) ranged from 7 to 8% (Nordbord), 3 to 11% (ForceFrame), and 1 to 4% (sprints). Our data provide the first Nordbord and ForceFrame reliability estimates in adolescent soccer academy players. To interpret test sensitivity, practitioners are encouraged to interpret our estimates of absolute reliability against meaningful change values derived from personal experience and evidence-based knowledge and not against absolute or standardized thresholds.

Force plate methodologies applied to injury profiling and rehabilitation in sport: A scoping review protocol

Musculoskeletal injuries are a common health problem among sporting populations. Such injuries come with a high financial burden to the involved organisations and can have a detrimental impact on the career attainment of injured individuals. Force plates are now a common tool available to sport and exercise science and medicine professionals to enable them to profile injury risk predisposition and modulate the rehabilitation process within sporting environments. This is because contemporary force plate technology is portable and affordable and often comes with software that enables the automatic and immediate feedback of test variables to key stakeholders. However, to our knowledge, to date, there has been no comprehensive review of the scientific literature pertaining to clinical applications of force plate technology. Therefore, this article presents a protocol and a methodological framework to perform a scoping review to identify and map the available scientific literature in which force plates have been applied to the injury profiling and rehabilitation of athletes. The specific aims of the scoping review are 1) to identify and describe the force plate tests, methodologies, and metrics used to screen for injury risk and guide the return of injured athletes to full-time training and competition, 2) to identify potential trends and/or differences by participants' age, sex, and/or level of performance in tests, methodologies, and metrics selected, and 3) to identify key gaps in the existing evidence base and new questions that should be addressed in future research. The global aim of the scoping review is to improve practitioner decision-making around force plate test and variable selection when applied to the injury prevention and rehabilitation of sporting populations.

Reliability and sensitivity to change of post-match physical performance measures in elite youth soccer players

Introduction

To effectively monitor post-match changes in physical performance, valid, reliable and practical measures which are sensitive to change are required. This study aimed to quantify test-retest reliability and sensitivity to change of a range of physical performance measures recorded during an isometric posterior chain (IPC) lower-limb muscle test and a countermovement jump (CMJ) test.

Methods

Eighteen Italian Serie A academy soccer players performed three IPC repetitions per limb and five CMJ trials in 4 testing sessions. Test-retest reliability was evaluated between two testing sessions seven days apart using typical error of measurement, coefficient of variation and intraclass correlation coefficient. Sensitivity to change was assessed on two additional testing sessions performed before and immediately after a soccer match through Hedges' g effect size (g) and comparisons to typical error.

Results

Absolute reliability (coefficient of variations) ranged from 1.5 to 8.8%. IPC and CMJ measures demonstrated moderate to excellent relative reliability (intraclass correlation coefficients ranged from 0.70 to 0.98). A wide range of physical performance measures showed significant alterations post-match (p < 0.05; g: small to moderate). IPC peak force and torque, CMJ reactive strength index modified, CMJ eccentric forces (mean breaking force, mean deceleration force, peak force, force at zero velocity) and CMJ mean power measures had post-match changes greater than their typical variation, demonstrating acceptable sensitivity in detecting performance changes at post-match.

Discussion

IPC peak force and torque, CMJ reactive strength index modified, CMJ eccentric phase forces and CMJ mean power were found to be both reliable and sensitive to change, and thus may be appropriate for monitoring post-match neuromuscular performance in youth soccer population.

Force Plate-Derived Countermovement Jump Normative Data and Benchmarks for Professional Rugby League Players

The countermovement jump (CMJ) is an important test in rugby league (RL), and the force plate is the recommended assessment device, as it permits the calculation of several variables that explain jump strategy, alongside jump height. The purpose of this study was to produce normative CMJ data and objective benchmarks for professional RL forwards and backs. Normative data for jump height, modified reactive strength index, and jump momentum are provided for 121 professional RL players (66 forwards and 55 backs) who completed CMJ testing on a portable force plate during preseason training. Standardized T-scores (scaled from 0 to 100) were calculated from the respective positional group mean and standard deviation to create CMJ performance bands that were combined with a qualitative description (ranging from extremely poor to excellent) and a traffic light system to facilitate data interpretation and objective benchmark setting by RL practitioners. The jump height and modified reactive strength index benchmarks were larger for the lighter backs, whereas the jump momentum benchmarks were larger for the heavier forwards. The presented novel approach to compiling and presenting normative data and objective benchmarks may also be applied to other data (i.e., from other tests or devices) and populations.