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Abstract

Maximal force can be expressed across a range of conditions influenced by the external load and the time available to express force. As a result, several distinct and specific strength qualities exist. Conversely, some expressions of maximal force are similar and can be categorized as a single quality. Therefore, strength assessment systems must be sophisticated enough to isolate and measure each quality while minimizing redundant information. This article presents a contemporary, evidence-based and practical framework that reduces the many strength and speed-strength metrics into 5 distinct qualities. Alongside this, we present case examples of the application of strength diagnosis.

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... Forms of lower body extensor strength (e.g., "power," peak force, 1 repetition maximum [1RM], reactive strength) are important physical qualities for field sport athletes, because they are linked to athletic tasks such as kicking, tackling, cutting, and sprinting (35). Accordingly, different forms of lower body strength are frequently assessed in the strength and conditioning environment and include multijoint isometric tests (e.g., the isometric-midthigh pull [IMTP]), heavy dynamic tests (e.g., back squat 1RM), and ballistics tasks (e.g., the countermovement jump [CMJ] (12,20,35)). The growing popularity of force platforms and their associated analysis software has enabled precise measurement of a wide range of strength expressions in athletes (7,23,25,26). ...
... At T2, however, IMTP force and impulse at 0.100 and 0.075 seconds, respectively, emerged as a second domain of strength. There are physiologic differences between the ability to produce force within 0.100 seconds and producing force at or after 0.150 seconds in multijoint isometric contractions (1,2,12). Although bordering the line of distinction (r 2 5 0.519-0.777), ...
... Thus, the common domain across T1 and T2 represented by net force at 0.150 seconds was termed "maximal-isometric" strength. In accordance with previous research (7,12,41), isometric force-time metrics were identified as unique from dynamic strength in this study. Furthermore, these distinctions were replicable, which is supported by most (3,4,13) but not all (10,34) research showing a distinction between isometric and heavy dynamic strength over time. ...
Article
Geneau, MC, Carey, DL, Gastin, PB, Robertson, S, and James, LP. Replicability of strength domains in Australian rules football athletes. J Strength Cond Res XX(X): 000-000, 2024-Maximal lower body strength is a multidimensional construct defined as the maximum force application under specific task constraints. It is crucial for many athletic tasks and is frequently assessed in strength and conditioning environments. Recent technological advancements have increased the number of measurement options for lower body strength, making data interpretation and translation challenging. Principal component analyses (PCA) methods have been proposed to inform strength test and metric selection in field sport athletes, but these methods are limited to cross-sectional designs. This study aimed to investigated the replicability of a PCA method for metric reduction and selection at 2 time points. Thirty-three Australian rules football athletes completed 7 lower body extensor strength tests during preseason (T1) and end of season (T2), each resulting in 280 force-time metrics. At each time point, 9 PCA components were required to explain at least 70% of the variance in the data set, and 7 components demonstrated similar metric loadings onto the components. However, the variable selection procedure did not return the exact same set of variables at both time points. These results suggest that while the number and loading of strength domains are consistent in Australian rules football athletes, the variable selection procedure was not fully replicable. Overall, practitioners can use this information to select tests and metrics within the domains and subdomains identified in this study to capture a range of lower body strength information from their athletes.
... The assessment of neuromuscular capabilities of handball players has traditionally been performed using the 1 repetition maximum (1RM) test to determine maximal strength (15) and the countermovement jump (CMJ) to examine jump height performance (51). However, current scientific evidence suggests that practitioners should use several tests to assess the player's ability to generate force in several time-restricted conditions and against several external loads (21). Therefore, the aim of this study is to determine the effects of a short-term detraining period on lower limbs' neuromuscular performance, assessing the maximum, rapid force production, and ballistic capabilities, in female handball players. ...
... The average of the 3 recorded trials was used for the statistical analyses. These variables have been selected to evaluate maximum force and rapid force production capabilities based on previous literature (10,16,21). ...
... In addition, future research using neurophysiological research methods should be used to elucidate the hypothetical neuromuscular adaptations. The CMJ is a dynamic sporting task commonly used to assess the player's lower limbs' ballistic capabilities and detect changes in the neuromuscular performance (8,21). In this study, female handball players had a significant detriment in CMJ height (3.7%, p 5 0.005) and mRSI (9.3%, p 5 0.005). ...
Article
García-Sánchez, C, Jiménez-Ormeñ o, E, Lominchar-Ramos, JM, Giráldez-Costas, V, McMahon, JJ, and Soriano, MA. Effects of a short-term detraining period on neuromuscular performance in female handball players. J Strength Cond Res XX(X): 000-000, 2024-The aim of this study was to determine the effects of a 3-week detraining period on lower limbs' neuromuscular performance in female handball players. Fourteen semi-professional players (age: 20.50 6 2.98 years; height: 1.67 6 0.06 m; body mass: 66.89 6 8.75 kg) were evaluated using force plates on 3 separate occasions to assess the maximum and rapid force production by the isometric mid-thigh pull (IMTP) and the ballistic capabilities by countermovement jump (CMJ). The intraclass correlation coefficient, coefficient of variation, standard error of the measurement, and smallest detectable difference were calculated using the first 2 testing sessions. Pre-and postdetraining differences were calculated comparing the first and third testing sessions, using paired t-tests or Wilcoxon test when appropriate and Hedges g effect sizes (ES). The level of significance was set at r # 0.05. There were no significant or meaningful differences in maximum and rapid force production capabilities assessed during the IMTP (p. 0.05). However, there was a significant detriment with small ES in CMJ jump height, modified reactive strength index, peak and mean propulsive force, peak and mean braking force, and braking phase duration (p , 0.05). These findings suggest that although maximum and rapid force production capabilities were not altered among female handball players after a 3-week detraining period, their ballistic capabilities decreased, especially those affecting the eccentric part of a fast dynamic task. They also highlight the importance of testing, planning, and programming in response to the fluctuations in handball players' physical performance over the season.
... Although the variance in performance explained by these factors is distance dependent (41), their role is substantial for both long-distance and mid-distance events (16,33). However, there is a wide variety of tests for measuring the neuromuscular capabilities (e.g., squat jump, countermovement jump [CMJ], broad jump, drop jump, sprint, isokinetic knee extension, isometric midthigh pull [IMTP], 1 repetition maximum [1RM]) (13,21,27,41), all of them reporting variables as a result of the force production for a given time (17). However, their relationship with running performance (6) or their sensitivity to illustrating running performance improvements (3,39) has been rejected on different occasions. ...
... These results give rise to the need to analyze the features of the different tests available to understand these discrete correlations and explore other options. In this regard, James et al. (17) proposed to classify the force-time demands into 5 strength categories (i.e., maximal isometric strength, explosive strength, reactive strength, fast and heavy dynamic strength). Although these qualities present a commonality, each represents a unique capacity of the neuromuscular system, whose role in the running performance requires to be explored yet. ...
... Subjects were tested on 4 separate occasions by 48-72 hours (14,26). The first session was used to assess each strength quality (17) through different testing procedures: IMTP (i.e., RFD, PF), drop jump (i.e., RSI), horizontal F-V profiles (running sprint; F 0, v 0, Pmax), and vertical L-V profiles (CMJ; load-axis intercept [L 0 ], v0, and area under the L-V profile [A line ]). The mentioned order was followed to minimize any potential onset of fatigue (43). ...
Article
This study examined the relationship between different strength qualities and running performance at different intensities in recreational runners. Eleven men (maximal oxygen uptake [VO2max]: 55.6 ± 4.1 ml/kg/min) and ten women (VO2max: 53.8 ± 5.0 ml/kg/min) were tested on four occasions. In the first session, each strength quality was tested through the isometric midthigh pull (peak force [PF], rate of force development [RFD]), drop jump (reactive strength index [RSI]), horizontal (theoretical maximal force [F0], theoretical maximal horizontal velocity [v0H], maximal power output [Pmax]) and vertical (theoretical maximal load [L0], theoretical maximal vertical velocity [v0V], area under the load-velocity profile [Aline]) and vertical force- and load-velocity profiles. In the second session, the VO2max was determined to control its influence on the relationship between the strength qualities and running performance. In the third and fourth testing sessions, their running performance at a 10-km distance and at two-time trials of 9- and 3-min were determined. Partial correlations revealed that the 10-km was not significantly correlated with any strength quality, 9-min with L0 (r = -0.474, p = 0.035) and Aline (r = -0.457, p = 0.043), and 3-min with L0 (r = -0.644, p = 0.002), Aline (r = -0.485, p = 0.030), v0V (r = 0.756, p < 0.001), F0, (r = 0.700, p = 0.001), Pmax (r = 0.579; p = 0.009). These correlations facilitated the differentiation of running performance between sexes, highlighting also unique strength qualities within each group.
... Lower-body muscular strength is an underpinning quality for many sport-specific tasks such as sprinting, change of direction, tackling, and kicking (31) and is therefore a primary target for training and monitoring athletes. Some of the most popular methods of evaluating lower-body strength are multi-joint weight-bearing movements in the vertical plane used to assess expressions of lower-body extensor strength, which can vary considerably as a product of temporal and external constraints (13,23). When conducted with maximal intent, force-time metrics measured under these conditions (e.g., jump height, peak force, or rate of force development) are believed to represent different expressions of strength (13,29,33). ...
... Some of the most popular methods of evaluating lower-body strength are multi-joint weight-bearing movements in the vertical plane used to assess expressions of lower-body extensor strength, which can vary considerably as a product of temporal and external constraints (13,23). When conducted with maximal intent, force-time metrics measured under these conditions (e.g., jump height, peak force, or rate of force development) are believed to represent different expressions of strength (13,29,33). Previous work proposed that lower-body extensor strength be classified into 5 or 6 distinct expressions of strength that include reactive, fast or light maximal dynamic, slow or heavy maximal dynamic, maximal isometric, and rate-dependent or explosive isometric strength (13,29,33). ...
... When conducted with maximal intent, force-time metrics measured under these conditions (e.g., jump height, peak force, or rate of force development) are believed to represent different expressions of strength (13,29,33). Previous work proposed that lower-body extensor strength be classified into 5 or 6 distinct expressions of strength that include reactive, fast or light maximal dynamic, slow or heavy maximal dynamic, maximal isometric, and rate-dependent or explosive isometric strength (13,29,33). The present study aims to revisit these classifications by incorporating data classification and reduction with sparsity on a wide range of force-time metrics commonly used in the contemporary sport science environment to measure lower-body extensor strength. ...
Article
Geneau, MC, Carey, DL, Gastin, PB, Robertson, S, and James, LP. Classification of force-time metrics into lower-body strength domains. J Strength Cond Res XX(X): 000–000, 2024—The purpose of this study was to classify force-time metrics into distinct lower-body strength domains using a systematic data reduction analysis. A cross-sectional design was used, whereby competitive field sport athletes ( F = 39, M = 96) completed a series of drop jumps, squat jumps, countermovement jumps (CMJs), loaded CMJs, and 2 isometric tasks on portable force platforms, resulting in a total of 285 force-time performance metrics. The metrics were split into 4 test “families” and each was entered into a sparse principal component analysis (sPCA) model. A single metric from each component of each family-specific sPCA were selected based on the loading, reliability, and simplicity of the metric and entered into a second sPCA that included metrics across all tests. The final sPCA revealed 7 principal components each containing 2 metrics and explained a total of 53% variance of the dataset. The final principal components were interpreted as 7 lower-body strength domains: (a) dynamic force, (b) dynamic timing, (c) early isometric, (d) maximal isometric, (e) countermovement velocity, (f) reactive output, and (g) reactive timing. The findings demonstrate that a total of 7 metrics from a drop jump, CMJ, and isometric test can be used to represent ∼50% of variance in lower-body strength performance of field sport athletes. These results can help guide and simplify the lower-body strength diagnosis process in field sport athletes.
... 3,4 Muscular strength can be expressed across various conditions that are influenced by external load and the time available to express force, and as a result, several strength qualities exist. 10 Maximum strength is usually evaluated to obtain the potential of players' maximum force-generating capacity. 4,10 Lower-body maximum strength has commonly been evaluated in football players using the 1-repetition maximum (1RM) test during the squat exercise, 4 permitting strength coaches to effectively monitor changes in lowerbody maximum dynamic strength across the season and categorize the players' training level and program training loads (ie, intensities) using percentages of the 1RM. ...
... 10 Maximum strength is usually evaluated to obtain the potential of players' maximum force-generating capacity. 4,10 Lower-body maximum strength has commonly been evaluated in football players using the 1-repetition maximum (1RM) test during the squat exercise, 4 permitting strength coaches to effectively monitor changes in lowerbody maximum dynamic strength across the season and categorize the players' training level and program training loads (ie, intensities) using percentages of the 1RM. 4,10 However, although the 1RM test is highly reliable and requires no sophisticated or expensive equipment, 11 assessing the 1RM squat in professional football can be perceived as a fatiguing, time-consuming protocol that may impose an increased potential for injury risks in players, since the exercise must be performed with proficient technique. ...
... 4,10 Lower-body maximum strength has commonly been evaluated in football players using the 1-repetition maximum (1RM) test during the squat exercise, 4 permitting strength coaches to effectively monitor changes in lowerbody maximum dynamic strength across the season and categorize the players' training level and program training loads (ie, intensities) using percentages of the 1RM. 4,10 However, although the 1RM test is highly reliable and requires no sophisticated or expensive equipment, 11 assessing the 1RM squat in professional football can be perceived as a fatiguing, time-consuming protocol that may impose an increased potential for injury risks in players, since the exercise must be performed with proficient technique. 12,13 An alternative to evaluating the players' lower-body maximum strength is the implementation of the isometric midthigh pull (IMTP) test using a force plate. ...
Article
Objective : This study aimed to compare the maximum and rapid force production of Spanish football players and explore the differences between age group and level of competition. Methods : A cross-sectional study was developed to evaluate the peak force (PF), relative PF, and rate of force development over 250 ms (RFD 0−250 ) during the isometric midthigh pull between groups of football players based on age group (senior vs junior) and level of competition (national vs regional). Using a portable isometric rig, 111 football players performed 2 isometric midthigh-pull trials on a force plate. Two-way analysis of variance with Bonferroni post hoc correction was applied, and statistical significance was set at P ≤ .05. The PF, relative PF, and RFD 0−250 0, 25, 50, 75, and 100 percentiles were also calculated and descriptively reported, separated by age group and level of competition. Results : The analysis of variance revealed a significant main effect of the level of competition for the PF ( P < .001), relative PF ( P = .003), and RFD 0−250 ( P < .001). There was a significant main effect of age group for the PF ( P < .001). There was a significant interaction effect of the age group × level of competition for relative PF ( P = .014). National players were stronger than regional players on the PF and RFD 0−250 ( P < .001). Senior players were stronger than junior players for the PF ( P < .001). Conclusions : Maximum and rapid force production are crucial for Spanish football players as they progress in both level of competition and age group. Practitioners should encourage young football players to prioritize strength development to improve their athletic performance.
... The CMJ and DJ are widely used because they involve movements that are common in an athlete's training and competition, and both engage the muscle's stretch-shortening cycle (SSC). However, their utilization of the SSC in each jump type is distinctly different and therefore the CMJ and DJ provide unique insights into an athlete's physiological state (13). Specifically, the CMJ is representative of an athlete's fast dynamic strength capabilities characterized by long-slow SSC movement times of .0.30 seconds. ...
... Specifically, the CMJ is representative of an athlete's fast dynamic strength capabilities characterized by long-slow SSC movement times of .0.30 seconds. Conversely, the DJ is representative of an athlete's ability to produce power in a short-fast SSC (commonly referred to as reactive strength) indicated by movement times of ,0.25 seconds and an ability to tolerate high eccentric loading (13,17,21). Previous research has demonstrated that performance in these 2 jump tests share only 35% commonality indicating that they are indeed measuring distinctly different aspects of muscle function (25). ...
Article
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Talpey, SW, Drake, M, Haintz, L, Belanger, A, O'Grady, MW, Young, WB, Mundy, PD, James L, Gabbett, TJ, Gardner, EC. The reliability and validity of the rebound countermovement jump in National Collegiate Athletic Association Division I American Football Players. J Strength Cond Res XX(X): 000-000, 2024-The purpose of this study was to investigate the reliability and validity of the rebound countermovement jump (R-CMJ), as an alternate test of leg muscle function to the CMJ and drop jumps (DJs). Because the first phase of the R-CMJ mimics that of the CMJ, it is hypothesized that variables obtained in phase I of the R-CMJ will be like those of a CMJ. Similarly, because the second phase of a R-CMJ mimics a DJ, it is believed that the variables obtained from phase II will be like those from a DJ. Collegiate male American football players (N = 46) aged 18-24 years completed CMJs and R-CMJs on a portable force plate. Tests were completed on 3 separate days to determine the repeatability of select variables and to establish their validity. In addition, a subgroup (N = 20) of players from the cohort completed DJs from both 30 cm (DJ30) and 45 cm (DJ45) to determine the concurrent validity of the variables obtained from the second phase of the R-CMJ. Most variables obtained from the CMJ and R-CMJ phase I were found to be reliable, except for time-to-take-off. The variables from the DJ30, DJ45, and R-CMJ phase II displayed moderate to good reliability; however, all coefficient of variations were >10%. Jump height achieved in the CMJ was significantly greater than that achieved in phase I of the R-CMJ. The reactive strength index was significantly different in the R-CMJ compared with the DJ from both 30 and 45 cm heights. Although the R-CMJ may be inviting for coaches to use owing to its ease and time efficiency, the results of this study highlight that it may not provide a valid representation of an athlete's reactive strength.
... The physical preparation of athletes requires a determination and assessment of relevant physical qualities (e.g., strength, power, speed, endurance characteristics) to identify strengths or weakness, and inform training interventions (1). Decisions regarding test selection that seek to measure these physical qualities are therefore a critical part of the training process (2). ...
... Therefore, the influence of specific decision making factors may change depending which aspect of the physical preparation plan is of interest. To strengthen the interpretability of these metrics, normalization within a team or comparative benchmarking against competitors or comparable sports can offer a contextual reference, resulting in improved utility of the data (1,40). A performance metrics' responsiveness reflects its accuracy in detecting meaningful changes in response to a defined stimulus (41,42). ...
Article
Full-text available
Preparing athletes for competition requires the diagnosis and monitoring of relevant physical qualities (e.g., strength, power, speed, endurance characteristics). Decisions regarding test selection that attempt to measure these physical attributes are fundamental to the training process yet are complicated by the myriad of tests and measurements available. This article presents an evidenced based process to inform test measurement selection for the physical preparation of athletes. We describe a method for incorporating multiple layers of validity to link test measurement to competition outcome. This is followed by a framework by which to evaluate the suitability of test measurements based on contemporary validity theory that considers technical, decision-making, and organisational factors. Example applications of the framework are described to demonstrate its utility in different settings. The systems presented here will assist in distilling the range of measurements available into those most likely to have the greatest impact on competition performance.
... Conversely, pivots engage in more isometric actions against opponents (e.g., screenings and blocks; García-Sánchez et al., 2023), where they have more time to apply force (≥500 ms). Therefore, because not all strength capabilities are developed equally (Taber et al., 2016;Turner et al., 2020), strength and conditioning coaches should use various tests to better assess players' neuromuscular capacity (James et al., 2022;McMaster et al., 2014). ...
... The countermovement jump (CMJ) is a commonly used method for assessing ballistic force production during dynamic tasks (James et al., 2022;McMaster et al., 2014). However, the peak force obtained during this test is not indicative of maximal force capabilities, as they are influenced by the player's jump strategy (Comfort et al., 2018b). ...
Article
The aim of this study was to explore the reliability and feasibility of the isometric mid-thigh pull (IMTP) and dynamic strength index (DSI) in semi-professional handball players (seventeen male and eighteen female). A cross-sectional design was used to determine the test-retest reliability of several kinetic metrics registered with a force plates. The peak force, peak relative force, rate of force devel- opment (RFD 0–250 ms), and impulse 0–250 ms were selected from the IMTP test, whereas the peak propulsive force was chosen from the countermovement jump test to obtain the DSI. The intraclass cor- relation coefficient (ICC), coefficient of variation (CV), standard error of the measurement (SEM) and smallest detectable difference (SDD) were calculated. A paired sample t-test was also performed. No significant differences were found between the testing sessions for all variables, except for peak propulsive force for all players (p = 0.036) and DSI for female players (p = 0.037). Reliability for all kinetic metrics was good to excellent (ICC = 0.78–0.97), with low variability (CV ≤ 8.64%), being the SEM scores lower than SDD. In conclusion, the IMTP test and DSI are highly reliable and feasible tools for assessing neuromuscular performance in semi-profes- sional handball players.
... These include potential detrimental effects of measurement itself on athlete behaviors (24,41), and concern with how well KPIs can truly approximate performance in complex dynamic events such as team sports (35). Furthermore, the increasing attention on sports performance support and abundance of available data may induce pressure to use KPIs to quantify the value of performance support and try to demonstrate return on investment (12,31). Conversely, practitioners are keen to demonstrate how the data amassed and the subsequent interventions used have a positive impact on performance. ...
... This is perhaps because of the abundance of metrics, thanks to the expansion of data collection in today's sporting environments. Indeed, a recent article described how the increase in data streams within the contemporary training environment may cloud parsimonious and valid applications if not used appropriately (31). It may also be because of the breaking down of sports performance into silos in traditional fields such as physiology, biomechanics, and performance analysis (53), in which the term "performance indicator" may have a specific context. ...
Article
Key performance indicators (KPIs) are commonplace in business and sport. They offer an objective means to link data and processes with performance outcomes. Yet, their application in sports performance, particularly team sports, is not without issue. Here, we review 4 key issues relating to KPI application in team sports; lack of a universal definition, complexity of performance , drifting from on-field performance goals with off-field targets, and agency issues across different key stakeholders. With these issues relating to sports performance KPIs in mind, we propose a complementary approach to help practitioners focus on implementing the conditions that create performance environments and opportunities for success in a complex sporting environment. Ongoing process trackers (OPTs) are quantifiable measures of the execution of behaviors and processes that create the environments, cultures, and conditions for successful performance outcomes. This approach equips sports science practitioners with key questions they can ask themselves and their team when starting to select and use OPTs in their program.
... As this activity is generally unfamiliar to most individuals, participants could complete unrecorded practice jumps to familiarise and ensure correct technique if required. Trials were considered valid if the contact time was less than 250 milliseconds [28] to ensure the task represented a fast stretch-shortening cycle movement and represented a unique action when compared with the CMJ [29]. Appropriate feedback on contact time (i.e., whether the participant needed to decrease contact time) and jump technique was provided after each trial [30]. ...
Article
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Background/Objectives: The movement and vibration of the body’s soft tissues during dynamic exercise are mechanisms that attenuate force from ground impacts. However, repeated exposure to such vibrations over time can contribute to the development of lower-body soreness and/or injuries. The previous literature has established the benefit of compression garments for the minimisation of soft tissue movement during running, though little is known about this mechanism during other forms of dynamic exercise. The current study aimed to investigate the effect of compression tights on lower-body soft tissue movement during jumping, sprinting and change-of-direction tasks typical of those found in team sports. Methods: In a randomised crossover design, twelve recreationally active males (age 26 ± 2 years) completed countermovement jumps, drop jumps from 45 cm, 10 m straight line sprints and change-of-direction tasks wearing either commercially available sports compression tights or regular exercise tights. Marker-based motion capture was used to quantify soft tissue displacement at the thigh and calf and lower-body kinematic variables during the exercise tasks. Results: No significant (p < 0.05) differences were observed between conditions for soft tissue displacement at the thigh and calf and performance variables for all tasks. There were significant (p = 0.003) differences in peak knee flexion and hip flexion during the 10 m sprint and change-of-direction task between conditions; however, effect sizes were unclear. Conclusions: Compression tights do not appear to influence soft tissue movement or performance during sports-specific forms of locomotion but may alter some kinematic aspects of sprinting and change-of-direction tasks compared with regular exercise tights.
... Similarly, Ben Moussa Zouita et al. [51] revealed that only the strength of trunk extensors effectively separated high-level athletes and recreational populations, whereas no such associations were found for trunk flexors. Future research is needed to investigate how different UB strength tests, with a particular emphasis on those involving back extension, and different UB strength qualities (e.g., fast dynamic, heavy dynamic, reactive, maximal isometric, and explosive) are associated with sprinting [105]. It is also important to understand how these qualities may differ in importance for different sprint phases (i.e., acceleration and maximal velocity) that have unique kinetic and kinematic requirements [86]. ...
Article
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Purpose: To investigate the influence of upper body (UB) strength qualities and UB strength training on the performance of high-intensity running and jumping actions and to identify gaps and recommendations for future research. Methods: A systematic search using the PRISMA Scoping Review protocol was conducted in February 2024 using PubMed, Scopus, and ICTRP. Studies eligible for inclusion were those that reported associations between UB or trunk maximal strength qualities (e.g., absolute strength, forces, power) and high-intensity running or jumping actions or investigated the influence of an isolated UB strength training intervention on high-intensity running or jumping performances. Results: Of the 4730 articles, 7 studies met the inclusion criteria, reporting correlations for 16 high-intensity running or jumping tests. No intervention studies were identified. Preliminary findings of the limited number of studies highlight that greater UB maximal strength-generating capacity may positively influence repeated sprint ability. While a significant moderate correlation between greater absolute UB strength and faster “flying” sprint was also reported, mixed results were found for sprint acceleration. There is also evidence that change-of-direction performance may greatly benefit from high maximal isometric strength of all trunk muscles and that strong trunk extensors may enhance drop jumps. Conclusions: This review identifies the potential of UB strength to contribute to high-intensity running and jumping actions. Future research is warranted to investigate this link via various UB strength tests and UB strength training protocols aimed at maximising neuromuscular adaptations.
... Las capacidades de producción de fuerza y potencia en los jugadores y su conexión con el rendimiento deportivo se pueden evaluar a través de pruebas de salto vertical (16). El salto con contramovimiento (CMJ, por sus siglas en inglés) es un método comúnmente utilizado para evaluar la producción de fuerza balística durante tareas dinámicas (17,18), además de ser una de las pruebas más utilizadas para monitorizar el estado neuromuscular de los deportistas en deportes individuales y de equipo (19). Los factores específicos del rendimiento en el salto CMJ incluyen diferentes variables cinemáticas y cinéticas, como por ejemplo: altura del salto, potencia máxima, o tasa de desarrollo de la fuerza, entre otras (19,20). ...
Conference Paper
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El objetivo principal del presente estudio fue realizar un análisis comparativo del rendimiento neuromuscular en jugadores de balonmano de diferentes categorías del campeonato nacional español. Para este estudio participaron cuarenta y nueve jugadores masculinos del balonmano español; dieciséis pertenecientes a la máxima categoría (ASOBAL), diecisiete a la segunda categoría (División de Honor Plata Masculina) y dieciséis a la tercera categoría (Primera Nacional Masculina). Se realizó un diseño experimental, de corte transversal, para comparar las diferencias en las métricas obtenidas de las pruebas isometric mid thigh pull (IMTP) y countermovemente jump (CMJ). Ambas pruebas se desarrollaron sobre un set de plataformas de fuerza duales (Hawkin Dynamics Inc. Westbrook, USA), con una frecuencia de muestreo de 1000 Hz. Se seleccionaron las variables cinéticas pico de fuerza (N), pico de fuerza relativo (N/kg) y RFD0-250 ms (tasa de desarrollo de la fuerza) (N⋅s-1) del IMTP, y altura del salto (m), momentum del salto (m⋅kg) y “mRSI” (índice de fuerza reactivo modificado) (u.a.) del CMJ. El análisis comparativo de grupo se llevó a cabo a través de un ANOVA de un solo factor para las variables dependientes y posteriormente se realizó un análisis post-hoc de Tukey. Tras el análisis, se hallaron diferencias significativas en las variables pico de fuerza, RFD 0-250 ms y momentum del salto para los grupos ASOBAL con DHPM y PNM (p<0.01 y p< 0.001 respectivamente), ASOBAL con PNM (p<0.05) y ASOBAL con DHPM (p<0.01) respectivamente, para el resto de variables analizadas no se hallaron diferencias significativas. En conclusión podemos decir que los jugadores que compiten al máximo nivel en balonmano presentan un rendimiento superior en pruebas de fuerza máxima, fuerza rápida y capacidad balística en comparación a los que compiten en categorías inferiores. PALABRAS CLAVE Plataformas de fuerza, tirón isométrico de medio muslo, fuerza, salto vertical.
... The examiner started a countdown, which lasted for three seconds. At the end of the countdown, the participants were instructed to pull from a light preload as hard and fast as possible on the force sensor for a duration of five seconds [45,46] in each of the four test positions (flexion, extension, and lateral flexion right and left). For each test position, participants were required to complete three practice trials with submaximal effort followed by three test trials with maximal effort. ...
Article
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Background/objectives: Core strength diagnostics often focus on measuring core endurance rather than maximal core strength or core power. This study investigates whether core strength can be considered as a general ability that can be measured by a single core strength test or whether it needs to be differentiated into several components. Methods: Forty-two adult sports students (nfemale = 20; nmale = 22; age: 24.0 ± 2.9 years; body height: 179.0 ± 9.8 cm; body mass: 75.2 ± 12.7 kg; body fat: 18.0 ± 6.8%) participated in two randomized testing sessions in a laboratory setting. Standard measurements, such as peak rate of force development (pRFD), maximal voluntary contraction (MVC), and holding time, were taken isometrically during four exercises (ventral, dorsal, and lateral right and left). Results: A principal component analysis (PCA) extracted three principal components from twelve different core strength variables. The three identified components explained 73.3% of the total variance and were labeled as (a) maximal core strength, (b) core endurance, and (c) core power. Conclusions: The results suggest three principal components of the core strength construct, as well as their differentiation, may be imperative. These findings should be taken into account in sport science and sports practice as they may be helpful in planning sport-specific diagnostic, performance-oriented training, and injury prevention programs.
... Although these tests are useful for guiding the training process, they do not provide detailed information about how the athlete generates force. To address this shortcoming, researchers have proposed that multi-joint isometric testing, such as the isometric midthigh pull (IMTP) and isometric squat, should be used in addition to these tests to provide a greater diagnostic picture of the athlete's forcegenerating capacities (19). Incorporating these types of tests into the monitoring plan allows for the creation of force-time curves that can be systematically analyzed to provide detailed information about various aspects of the athlete's force-generating capacities (5,6,30). ...
Article
The isometric midthigh pull (IMTP) is a commonly used strength diagnostic tool that can give insight into an athlete's force-generating capacities. The resulting force-time curves generated are commonly analyzed using commercial software packages that provide a variety of metrics. Although these software packages are useful, they are often costly and operate as a “black box,” limiting the control over how these metrics are calculated. A template created in Excel can be used to analyze isometric data. However, creating a custom script to analyze isometric trials can be more time-efficient. To provide users with an alternative analysis option, this article provides a guide for selecting IMTP force-time curves and variables for analysis and how to use Python to perform these analyses. Basic procedures are provided to ensure that accurate force-time curves are selected and analyzed, followed by strategies for using Python to read files, filter data, calculate force-time curve variables, graphically present data, and write results to a report are discussed. Although the script provided can be used to analyze the IMTP force-time curve data, it can be modified to examine other metrics as needed by the user (see, Supplemental Digital Content 1, http://links.lww.com/SCJ/A412).
... Within these expressions of strength, maximum strength (the ability to provide maximum strength with a simple action and under specific conditions) 37 -which, for this project, was recorded using the Nordic Centile curves using BCCG Centile curves using BCCG test -has been recognised as a characteristic of strength susceptible to constant assessment and with sufficient evidence to be considered as an injury risk factor, such as is the case when it is diminished for a type of specialist sport and a type of athlete in particular. There is a large body of literature supporting the use of the Nordic test and one of the variables -maximum strength, obtained from the software -to assess hamstring muscles 12 . ...
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The main cause of injury in athletes is of muscular origin and of all those of the hamstrings it is the most important. The inadequate eccentric strength of these is a factor that is related to lower limb injuries. At the Sports Science Center of the Ministry of Sports, the eccentric strength of the hamstrings is evaluated with the Nordic test. In Colombia, it is not known if this is related to lower limb injuries in the different world-class high-performance athletes who attend there. A descriptive work was proposed with a quantitative approach and analytical phase, evaluating the pre-participation medical records of 195 athletes who underwent the Nordic test during the year 2021. The athletes analyzed were 56% men, with ages for both sexes on average of 21.5 years, with body mass indexes of approximately 22.1 k/m 2. The most frequent injury to the lower limbs was muscle (38.5%), followed by tendinopathies (27%). Of the muscle, the hamstrings were injured in 69%. An average maximum force was found for all athletes of 292.4 ± 67.06 N and a relative force of 4.52 ± 1 N/kg. The bivariate analyzes show an association between the presence of injury and lower maximum eccentric hamstring strength for both sexes. Furthermore, it was found that asymmetries less than 15% of the maximum eccentric hamstring strength were associated with a lower presence of injury. From a multivariate analysis, normative reference curves were constructed for weight, sex, and maximum eccentric strength of these athletes. It contributes to the conceptual gap of the behavior of eccentric hamstring strength and its relationship with the presence of lower limb injuries in different Colombian elite athletes. Resumen La principal causa de lesión de los deportistas es de origen muscular y de todas la de los isquiotibiales es la más importante. La inadecuada fuerza excéntrica de éstos es un factor que se relaciona con lesión de miembros inferiores. En el Centro de Ciencias del Deporte del Ministerio del Deporte se evalúa la fuerza excéntrica de los isquiotibiales con el test Nórdico. En Colombia, no se sabe si esta se relaciona con lesión de miembros inferiores en los diferentes deportistas de alto rendimiento de talla mundial que allí asisten. Se planteó un trabajo descriptivo con enfoque cuantitativo y fase analítica evaluando las historias clínicas preparticipativas de 195 deportistas a los que se les realizó el test Nórdico durante el año 2021. Los deportistas analizados 56% fueron hombres, con edades para ambos sexos en promedio de 21,5 años, con índices de masa corporal de aproxima-damente 22,1 k/m 2. La lesión más frecuente en miembros inferiores fue la muscular (38,5%), seguida por las tendinopatías (27%). De la muscular, los isquiotibiales se lesionaron en el 69%. Se encontró un promedio de fuerza máxima para el total de deportistas de 292,4 ± 67,06 N y una fuerza relativa de 4,52 ± 1 N/kg. Con los análisis bivariados se evidencia una asociación entre la presencia de lesión y menor fuerza máxima excéntrica de isquiotibiales para ambos sexos. Además, se encontró que las asimetrías menores al 15% de la fuerza máxima excéntrica de isquiotibiales se asociaron con menor presencia de lesión. A partir de un análisis multivariado se construyeron las curvas de referencia normativas para peso, sexo, fuerza excéntrica máxima de estos deportistas. Se aporta al vacío conceptual del comportamiento de la fuerza excéntrica de isquiotibiales y su relación con la presencia de lesión de miembros inferiores en diferentes atletas élite colombianos. Palabras clave: Deportes. Rendimiento. Lesión de extremidades. Isquiotibiales. Fuerza. Excéntrica. Links between Eccentric Hamstring Strength and a History of Lower Limb Injury in Colombian High-performance Athletes 85 Arch Med Deporte 2024;41(2):84-91
... Within these expressions of strength, maximum strength (the ability to provide maximum strength with a simple action and under specific conditions) 37 -which, for this project, was recorded using the Nordic Centile curves using BCCG Centile curves using BCCG test -has been recognised as a characteristic of strength susceptible to constant assessment and with sufficient evidence to be considered as an injury risk factor, such as is the case when it is diminished for a type of specialist sport and a type of athlete in particular. There is a large body of literature supporting the use of the Nordic test and one of the variables -maximum strength, obtained from the software -to assess hamstring muscles 12 . ...
Article
The main cause of injury in athletes is of muscular origin and of all those of the hamstrings it is the most important. The inadequate eccentric strength of these is a factor that is related to lower limb injuries. At the Sports Science Center of the Ministry of Sports, the eccentric strength of the hamstrings is evaluated with the Nordic test. In Colombia, it is not known if this is related to lower limb injuries in the different world-class high-performance athletes who attend there. A descriptive work was proposed with a quantitative approach and analytical phase, evaluating the pre-participation medical records of 195 athletes who underwent the Nordic test during the year 2021. The athletes analyzed were 56% men, with ages for both sexes on average of 21.5 years, with body mass indexes of approximately 22.1 k/m2. The most frequent injury to the lower limbs was muscle (38.5%), followed by tendinopathies (27%). Of the muscle, the hamstrings were injured in 69%. An average maximum force was found for all athletes of 292.4 ± 67.06 N and a relative force of 4.52 ± 1 N/kg. The bivariate analyzes show an association between the presence of injury and lower maximum eccentric hamstring strength for both sexes. Furthermore, it was found that asymmetries less than 15% of the maximum eccentric hamstring strength were associated with a lower presence of injury. From a multivariate analysis, normative reference curves were constructed for weight, sex, and maximum eccentric strength of these athletes. It contributes to the conceptual gap of the behavior of eccentric hamstring strength and its relationship with the presence of lower limb injuries in different Colombian elite athletes.
... Participants were familiarized at two separate sessions to the CMJ, SJ and IMTP protocols, alongside the Stroop Color and Word Test, during the first 2 days of the training camp.Specific familiarization was not undertaken for the power pass or 20 m sprint as these are regularly performed as part of the National Rugby League testing battery. These tests were selected as they represent different domains of performance(James et al., 2023), ...
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We examined performance across one menstrual cycle (MC) and 3 weeks of hormonal contraceptives (HC) use to identify whether known fluctuations in estrogen and progesterone/progestin are associated with functional performance changes. National Rugby League Indigenous Women's Academy athletes [n = 11 naturally menstruating (NM), n = 13 using HC] completed performance tests [countermovement jump (CMJ), squat jump (SJ), isometric mid‐thigh pull, 20 m sprint, power pass and Stroop test] during three phases of a MC or three weeks of HC usage, confirmed through ovulation tests alongside serum estrogen and progesterone concentrations. MC phase or HC use did not influence jump height, peak force, sprint time, distance thrown or Stroop effect. However, there were small variations in kinetic and kinematic CMJ/SJ outputs. NM athletes produced greater mean concentric power in MC phase four than one [+0.41 W·kg⁻¹ (+16.8%), p = 0.021] during the CMJ, alongside greater impulse at 50 ms at phase one than four [+1.7 N·s (+4.7%), p = 0.031] during the SJ, without differences between tests for HC users. Among NM athletes, estradiol negatively correlated with mean velocity and power (r = −0.44 to −0.50, p < 0.047), progesterone positively correlated with contraction time (r = 0.45, p = 0.045), and both negatively correlated with the rate of force development and impulse (r = −0.45 to −0.64, p < 0.043) during the SJ. During the CMJ, estradiol positively correlated to 200 ms impulse (r = 0.45, p = 0.049) and progesterone to mean power (r = 0.51, p = 0.021). Evidence of changes in testing performance across a MC, or during active HC use, is insufficient to justify “phase‐based testing”; however, kinetic or kinematic outputs may be altered in NM athletes.
... Identifying the key strength qualities related to sprint swimming performance should be mandatory when prescribing dryland resistance training programs. 15,16 In this regard, VBT allows for not only the estimation of maximal neuromuscular capacities but also the ability to maintain high-velocity outputs within a set. Specifically, 2 variables have been proposed to explore the ability to maintain mechanical performance using velocity monitoring: mean velocity maintenance (ie, overall capacity to maintain maximum velocity performance; MVM) and mean velocity decline (ie, degree of muscular fatigue experienced at the end of the set; MVD). ...
Article
Purpose: To explore the association of the load-velocity (L-V) relationship variables and ability to maintain maximal mechanical performance during the prone bench pull exercise with sprint swimming performance and in-water forces. Methods: Eleven competitive adult male swimmers (50-m front crawl World Aquatics points: 488 ± 66, performance level 4) performed one experimental session. The L-V relationship variables (L0 [i.e., maximal theorical load at zero velocity]; v0 [i.e., maximal theorical velocity at zero load] and, Aline [i.e., area under the L-V relationship]) and maximal mechanical maintenance capacity were assessed at the beginning of the session. Afterwards, sprint swimming performance and in-water forces production were tested through a 50-m front crawl all-out trial and 15-s fully-tethered swimming, respectively. Results: Only v0 presented high positive associations with 50-m time and swimming kinematics (r > 0.532; p < 0.046). The L0, v0 and Aline showed very high positive associations with the in-water forces during tethered swimming (r > 0.523; p < 0.049). However, the ability to maintain maximal mechanical performance, assessed by the mean velocity decline during the PBP, was only significant correlated with stroke rate ( r = -0.647; p = 0.016) and stroke index (r = 0.614;p = 0.022). Conclusions: These findings indicate that maximal neuromuscular capacities, especially v0, have a stronger correlation with swimming performance and in-water force production than the ability to maintain maximal mechanical performance in level 4 swimmers.
... Regular evaluation of an athlete's strength characteristics is an effective means of assessing physical readiness (54), and allows coaches to compare performance relative to normative values or previous results while also informing programming direction (28). Each strength quality can be reliably measured through multijoint assessments such as the isometric midthigh pull (IMTP; maximal strength), the countermovement jump (CMJ; explosive strength), and the reactive strength index (RSI). ...
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Hughes, W, Healy, R, Lyons, M, Higginbotham, C, Lane, A, and Beattie, K. The strength characteristics of elite and subelite female Gaelic football players. J Strength Cond Res XX(X): 000–000, 2023—There is currently an underrepresentation of sports science research focused on the female athlete, specifically in the context of Gaelic football. The aims of this study are to (a) compare the strength characteristics of elite and subelite players and (b) establish normative-based values and percentile scores for the strength characteristics of female Gaelic football players. Ninety-two female Gaelic football players were recruited for this study and subsequently categorized as elite (intercounty n = 30, age; 25.1 ± 5.3 years, stature; 1.69 ± 0.06 m, mass; 69.5 ± 5.9 kg) or subelite (club n = 62, age; 25.4 ± 6.8 years, stature; 1.66 ± 0.06 m, mass; 65.1 ± 8.9 kg). The physical strength characteristics of the subjects were assessed through the isometric midthigh pull (IMTP), countermovement jump (CMJ), and 10–5 repeated jump test. Statistically significant differences were found in the physical strength characteristics between the groups with elite players demonstrating greater peak force (large effect), relative peak force (moderate effect), and reactive strength index (large effect). Statistically significant differences were also observed for key CMJ phase characteristics with elite players producing greater RSI mod (moderate effect), jump height (large effect), and propulsion peak power (large effect) than subelite players. This study demonstrated that there are moderate to large differences between playing standards with elite players displaying superior reactive-, explosive-, and maximal-strength than their subelite counterparts. The strength characteristics evaluated in this study may be used in conjunction with other performance indices to distinguish between elite and subelite playing standards in female Gaelic football players.
... This lack of correlation agrees with findings from Suchomel et al. [33], who found a poor relationship between IMTP PF and CMJ variables, such as CMJ PF (r < 0.21) and CMJ height (r < 0.18). A recent review by James et al. [17] corroborates these findings, stating that the variables derived from CMJ differs from the force-time characteristics of the IMTP or isometric squat. However, some studies showed a contrast in findings, with moderate correlations found between IMTP PF and CMJ PF (r = 0.45) [38]. ...
Article
Dynamic strength index (DSI) and percentage of isometric mid-thigh pull (IMTP) peak force (PF) produced during early epoch, expressed as a percentage of net PF (%PF), are useful strength assessments to evaluate an athlete’s training status. Due to the similarity in diagnosis that the DSI ratio and %PF provides, it is not known whether %PF can reflect closely to an athlete’s DSI ratio. Therefore, the aim of this study is to establish the relationship between DSI and %PF. Thirty-seven national athletes (age = 22.9 ± 3.12 years; height = 1.73 ± 0.08 m; body mass = 69.1 ± 10.68 kg) were recruited for this study. Participants performed the countermovement jump test (CMJ) and isometric mid-thigh pull (IMTP) during both familiarisation and testing sessions. IMTP and CMJ force–time variables were collected to compute the DSI ratio and %PF for analysis. Trivial to small correlations between DSI and %PF was observed across all epochs (50 ms: r = 0.09, 95% CI − 0.241–0.402, P > 0.598; 100 ms: r = − 0.021, 95% CI − 0.343–0.305, P > 0.9; 150 ms: r = − 0.058, 95% CI − 0.375–0.271, P > 0.734; 200 ms: r = 0.126, 95% CI − 0.207–0.432, P > 0.458). DSI ratio and %PF are two distinct monitoring tools and not interchangeable. Both DSI and the percentage of IMTP net PF at early time points are useful in evaluating athletes’ previous training phases and current physical performance.
... Identifying the key strength qualities underpinning sports performance should be mandatory when making training decisions. 10 In this regard, although a recent systematic review showed that the parameters of the F-V relationship present significant correlations with some outcomes of sports performance (vertical jumps, maximal sprint acceleration, or change of direction), 2 volleyball-specific skills have been largely overlooked. Baena-Raya et al 3 reported strong correlations between F 0 and P max obtained from CMJ and BPT exercises with spike ball speed. ...
Article
Background Physical testing is crucial for athlete monitoring, talent identification, optimizing training, and tailoring programs to enhance game-performance in elite competitions. Hypothesis Load-velocity (L-V) relationship variables discriminate between elite and junior volleyball players, correlate with volleyball-specific performance, and are generalizable across lower- and upper-body exercises. Study Design Cross-sectional study. Level of Evidence Level 3. Methods A total of 9 elite and 11 junior volleyball players were assessed for the L-V relationship (load-axis intercept [ L 0 ], velocity-axis intercept [ v 0 ], and area under the L-V relationship line [ A line ]) during the countermovement jump (CMJ) and bench press throw (BPT) exercises. Block and spike jump height, as well as standing and jumping spike speed were assessed 24 hours later. Results Elite players presented greater magnitude in the L-V variables ( P ≤ 0.03; effect size [ES] ≥ 1.06) and higher volleyball-specific performance ( P ≤ 0.03; ES ≥ 1.09) than juniors (except for CMJ v 0 and A line ). The L-V relationship variables were significantly associated with the block and spike jump height and jumping spike speed only in elite players ( r ≥ 0.703 and P ≤ 0.04 in 11 out of 18 correlations). No significant associations were observed between CMJ and BPT for any L-V relationship variable ( r ≤ 581; P ≥ 0.08, except for A line in junior players). Conclusion The L-V relationship is a practical procedure to assess volleyball players’ maximal mechanical capacities, which are associated with volleyball-specific performance in elite players. However, these data should not be used interchangeably between playing standards or exercises. Clinical Relevance This information might help strength and conditioning coaches to prescribe more effective training programs that focus on developing the specific physical capacities necessary for players to potentially advance to elite status.
... Pearson correlation coefficients were used to determine the strength of association between IMU variables as well as timing light splits, and coefficients of determination (R 2 ) were used to quantify shared variance. The authors used a 50% shared variance threshold to determine the independence of variables (Baker, Wilson, & Carlyon, 1994;James et al., 2023;Young, Wilson, & Byrne, 1999). ...
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Timing gates are currently the most common piece of equipment for measuring change of direction (COD) performance, however, they provide only a total time metric. A better understanding of the kinematics and kinetics during a COD movement beyond total time would provide coaches with a more comprehensive understanding of COD movement and how it can be improved. Therefore, the aim of this study was to determine the reliability of an inertial measurement unit (IMU) insole for measuring peak acceleration, peak deceleration, maximum speed, and ground contact time during a modified 5-0-5 change of direction (COD) test. Additionally, the strength of association between these IMU variables and timing light metrics was explored. Ten elite female netball athletes (age = 24.9 ± 5.0 years, height = 180.1 ± 6.5 cm, weight = 81.3 ± 15.0 kg) performed a modified 5-0-5 COD test across three testing occasions. Analysis revealed moderate to excellent relative consistency (ICC = 0.57-0.94) and acceptable absolute consistency (CV = 1.8-9.5%). Correlations ranged from 0.04 to 0.95, with peak acceleration having the strongest correlation with total time (r = 0.95). It appears that IMU insoles can be used to reliably measure performance during a COD task and provide additional diagnostics beyond time metrics.
... [5][6][7] Assessment systems should be specific enough to isolate and track independent attributes while also minimizing redundant information. 8 In many cases, the most important physical quality that requires assessment in sport is maximal strength. 9 This quality refers to the force-generating capacity of the athlete against an external resistance. ...
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Background: Maximal lower-body strength can be assessed both dynamically and isometrically; however, the relationship between the changes in these 2 forms of strength following resistance training is not well understood. Purpose: To systematically review and analyze the effects of resistance training on changes in maximal dynamic (1-repetition-maximum back squat, deadlift, and power clean) and position-matched isometric strength (isometric midthigh pull and the isometric squat). In addition, individual-level data were used to quantify the agreement and relationship between changes in dynamic and isometric strength. Methods: Databases were systematically searched to identify eligible articles, and meta-analysis procedures were performed on the extracted data. The raw results from 4 studies were acquired, enabling bias and absolute reliability measures to be calculated using Bland-Altman test of agreement. Results: Eleven studies met the inclusion criteria, which resulted in 29 isometric-dynamic change comparisons. The overall pooled effect was 0.13 in favor of dynamic testing; however, the prediction interval ranged from g = -0.49 to 0.75. There was no evidence of bias (P = .825) between isometric and dynamic tests; however, the reliability coefficient was estimated to be 16%, and the coefficient of variation (%) was 109.27. Conclusions: As a range of future effects can be expected when comparing isometric to dynamic strength changes following resistance training, and limited proportionality exists between changes in these 2 strength qualities, there is strong evidence that isometric and dynamic strength represent separate neuromuscular domains. These findings can be used to inform strength-assessment models in athlete populations.
... 3 As there are multiple forms of strength, the strength and conditioning coach must determine the strength characteristics most important for a given sport. 4,5 Specifically, the lower body extensor muscle group can be classified into different characteristics 6 assessed through various tests and metrics. To understand which characteristic(s) of lower body strength are most important for ice hockey athletes, relationships between the strength qualities and on-ice performance measures should be explored. ...
Article
Purpose: Ice hockey is a team invasion sport characterized by repeated high-intensity skating efforts, technical and tactical skill, physical contact, and collisions requiring considerable levels of muscular strength. The purpose of this study was to evaluate the relationships between lower-body vertical force-time metrics and skating qualities in subelite female ice hockey players. Methods: A cross-sectional cohort design was employed utilizing 14 athletes (body mass = 66.7 [1.8] kg; height = 171.6 [6.2] cm; age = 21.1 [1.7] y). The relationships between metrics of lower-body strength collected from a drop jump, squat jump, countermovement jump, loaded countermovement jump, and an isometric squat and 4 skating qualities collected from a linear sprint, repeated sprint test, and a multistage aerobic test were evaluated. Results: The regression models revealed a positive relationship between relative peak force in the isometric squat and skating multistage aerobic test performance (r2 = .388; P = .017) and a positive relationship between repeated-sprint ability and eccentric mean force during the loaded countermovement jump (r2 = .595; P = .001). No significant relationships were observed between strength metrics and skating acceleration or maximal velocity. Conclusions: These data suggest that skating ability is most affected by relative isometric strength in female ice hockey players. It is recommended that practitioners focus training on tasks that improve relative force output. It is also recommended that isometric relative peak force be used as a monitoring metric for this cohort.
Article
Pairwise comparison of heavy dynamic strength and fast dynamic strength interventions on sprint performance: a systematic review and meta-analysis. J Strength Cond Res 38(8): 1509–1520, 2024—Previous studies have shown that both heavy dynamic strength (HDS) and fast dynamic strength (FDS) training can be used to improve sprint performance; however, a review and meta-analysis investigating pairwise studies that compare these two training interventions have not been performed. The aims of the study were to systematically review and analyze HDS and FDS training methodologies and evaluate their effect size difference, in pairwise comparison studies to determine and compare their effects on sprint performance. Databases were systematically searched using Boolean phrasing to identify eligible articles, and meta-analyses were performed on the extracted data. Seven studies met the inclusion criteria, which resulted in data from 138 subjects across 24 separate sprint assessments. Overall, there was a small effect in favor of FDS (standardized mean difference = 0.27, 95% confidence intervals [−0.07; 0.60], 95% prediction intervals [−1.01; 1.55]), but this was deemed not significant because of the wide-ranging prediction intervals. There is no distinguishable difference between HDS and FDS training on sprint performance. The wide-ranging prediction intervals suggest the variability is too great to determine whether one training type is more effective than the other. Practitioners should consider the individual needs of their athletes when deciding which training type to use for long-term sprint development.
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This study aimed to reduce the dimensionality of countermovement jump (CMJ) force-time characteristics and evaluate differences among positional groups (Skills, Hybrid, Linemen, Specialists) within National Collegiate Athletic Association (NCAA) Division I American football. Eighty-two football athletes performed two maximal effort, no arm-swing, CMJs on force plates. The average absolute and relative (e.g., power / body mass) metrics were analyzed using analysis of variance and principal component analysis procedures (p<0.05). Linemen had the heaviest body mass and produced greater absolute forces than hybrid and skills but had lower propulsive abilities demonstrated by longer propulsive phase durations and greater eccentric to concentric mean force ratios. Skills and hybrid produced the most relative concentric and eccentric forces and power, as well as modified reactive strength indexes (RSIMOD). Skills (46.7±4.6 cm) achieved the highest jump height compared to hybrid (42.8±5.5 cm), specialists (38.7±4.0 cm), and linemen (34.1±5.3 cm). Four principal components explained 89.5% of the variance in force-time metrics. Dimensions were described as the 1) explosive transferability to concentric power (RSIMOD, concentric power, eccentric to concentric forces) 2) powerful eccentric loading (eccentric power and velocity), 3) countermovement strategy (depth and duration), 4) jump height and power. The many positional differences in CMJ force-time characteristics may inform strength and conditioning program designs tailored to each position, as well as identify important explanatory metrics to routinely monitor by position. The overwhelming number of force-time metrics to select from may be reduced using PCA methods, although practitioners should still consider the various metric’s applicability and reliability.
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Jumps occur frequently in basketball and can be executed from a single-leg take-off following a run-up or bilaterally from a standing start. Understanding the type of jumps performed in competition and how different muscular qualities influence their performance, informs training prescription. Firstly, to quantify the occurrence of different jump types performed in competition an analysis of 15 semi-professional basketball games was undertaken. Secondly, to understand the influence of muscular qualities on performance of different jump types, Semi-professional male basketball players (N=17) performed jump tests; standing vertical jump, running vertical jumps with a double leg take-off (RVJ2) and a single leg take-off (RVJ1) and tests of lower-body speed-strength; reactive strength index (RSI) from a drop jump, counter movement jump (CMJ) and squat jump. A stationary approach was employed for 69%, a running approach for 26% and a one-step approach for 5%. RVJ1 displayed non-significant (P=0.07) moderate correlation with jump height attained from the CMJ (r=0.439) and a very large (r =.806) significant (P<0.01) correlation with RSI. Most jumps were executed from a stationary start with a bilateral take-off while a run-up occurred prior to a substantial proportion of jumps. Jumps with a single-leg take-off from a run-up strongly correlate with RSI.
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Background Reactive strength index (RSI) is used frequently in the testing and monitoring of athletes. Associations with sports performance measures may vary dependent on the task but a literature synthesis has not been performed. Objectives The aim of this meta-analysis was to examine associations between RSI measured during rebound jumping tasks and measures of strength, linear and change of direction speed, and endurance performance. Methods A systematic literature search with meta-analysis was conducted using databases PubMed, SPORTDiscus, Web of Science, and Ovid. Inclusion criteria required studies to (1) examine the relationship between RSI and an independent measure of physical or sporting performance for at least one variable; and (2) provide rebound test instructions to minimise ground contact time and maximise displacement of the jump. Methodological quality was assessed using a modified version of the Downs and Black Quality Index tool. Heterogeneity was examined via the Q statistic and I². Pooled effect sizes were calculated using a random-effects model, with Egger’s regression test used to assess small study bias (inclusive of publication bias). Results Of the 1320 citations reviewed, a total of 32 studies were included in this meta-analysis. RSI was significantly and moderately associated with strength (isometric: r = 0.356 [95% CI 0.209–0.504]; isotonic: r = 0.365 [0.075–0.654]; pooled strength measures: r = 0.339 [0.209–0.469]) and endurance performance (r = 0.401 [0.173–0.629]). Significant moderate and negative associations were indicated for acceleration (r = − 0.426 [− 0.562 to − 0.290]), top speed (r = − 0.326 [− 0.502 to − 0.151]), and significant large negative associations were noted for change of direction speed (r = − 0.565 [− 0.726 to − 0.404]). Heterogeneity was trivial to moderate across all measures (I² = 0–66%), and significant for isotonic strength and change of direction speed (p < 0.1). Evidence of small study bias was apparent for both acceleration and change of direction speed (p < 0.05). Conclusions We identified primarily moderate associations between RSI and independent measures of physical and sporting performance, and the strength of these relationships varied based on the task and physical quality assessed. The findings from this meta-analysis can help practitioners to develop more targeted testing and monitoring processes. Future research may wish to examine if associations are stronger in tasks that display greater specificity.
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Researchers and practitioners have highlighted the necessity to monitor jump strategy metrics as well as the commonly reported outcome measures during the countermovement (CMJ) and drop jump (DJ) tests. However, there is a risk of confusion for practitioners, given the vast range of metrics that now seem to be on offer via analysis software when collecting data from force platforms. As such, practitioners may benefit from a framework that can help guide metric selection for commonly used jump tests, which is the primary purpose of this article. To contextualise the proposed framework, we have provided two examples for how this could work: one for the CMJ and one for the DJ, noting that these tests are commonly utilized by practitioners during routine testing across a range of sport performance and clinical settings.
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Velocity-based training (VBT) is a contemporary method of resistance training that enables accurate and objective prescription of resistance training intensities and volumes. This review provides an applied framework for the theory and application of VBT. Specifically, this review gives detail on how to: use velocity to provide objective feedback, estimate strength, develop load-velocity profiles for accurate load prescription, and how to use statistics to monitor velocity. Furthermore, a discussion on the use of velocity loss thresholds, different methods of VBT prescription, and how VBT can be implemented within traditional programming models and microcycles is provided.
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The purpose of this article was to review the data on the relationship between multi-joint isometric strength test (IsoTest) force-time characteristics (peak force, rate of force development and impulse) and dynamic performance that is available in the current literature. Four electronic databases were searched using search terms related to IsoTest. Studies were considered eligible if they were original research studies that investigated the relationships between multi-joint IsoTest and performance of dynamic movements; published in peer-reviewed journals; had participants who were athletes or active individuals who participate in recreational sports or resistance training, with no restriction on sex; and had full text available. A total of 47 studies were selected. These studies showed significant small to large correlations between isometric bench press (IBP) force-time variables and upper body dynamic performances (r 2 = 0.221 to 0.608, p < 0.05) and significant small to very large correlation between isometric squat (ISqT) (r 2 = 0.085 to 0.746, p < 0.05) and isometric mid-thigh pull (IMTP) (r 2 = 0.120 to 0.941, p < 0.05) force-time variables with lower body dynamic performances. IsoTest force-time characteristics were shown to have small to very large correlations with dynamic performances of the upper and lower limbs as well as performance of sporting movements (r 2 = 0.118 to 0.700, p < 0.05). These data suggest that IsoTest force-time characteristics provide insights into the force production capability of athletes which give insight into dynamic performance capabilities.
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This review will revisit practitioner understanding of the development of power, before outlining some of the key mechanical parameters that contribute to power development. This understanding will help with planning and periodization of strength and power training, which is explored in part 2 of this 2-part review. This review (part 1) discusses the force-time and force-velocity curve and addresses recent criticism in using terms such as power, rate of force development, and explosiveness, over impulse. These terms are distinguished mechanically and conceptually for the benefit of the scientist and coach, and are essential for effective sharing of data and practice.
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Purpose:: This investigation examined the inter-day reliability and usefulness of reactive strength index (RSI) derived from a maximal 5 rebound jump test (5max RJT) and a maximal 10 rebound jump test (10/5 RJT). Methods:: Twenty male field sport athletes (24.5±3.0 y; 1.78±0.1 m; 84.9±5.2 kg) performed 2 maximal repetitions of the 5max RJT and the 10/5 RJT on two testing days following a specific warm up. A one week period separated each testing day and these sessions were proceeded by a familiarisation session. RSI was calculated by dividing jump height (m) by contact time (s). The 5max RJT and the 10/5 RJT trial with the highest RSI on each testing day was used for reliability and usefulness analysis. Results:: Both tests were deemed reliable for determining RSI for male, female and pooled male and female cohorts as the ICCs ≥ 0.80 and the CV ≤ 10%. Only the 5max RJT was rated as 'good' at detecting the smallest worthwhile change (SWC) in performance for female athletes (SWC: 0.10 > TE:0.07). The 5max RJT for males and the 10/5 RJT for males and females were rated as 'good' in detecting a moderate change in performance only. Conclusions:: Both tests are reliable for the determination of RSI but the usefulness of the tests in detecting the SWC is questionable.
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We examined the effects of probiotic (Bacillus subtilis) supplementation during offseason training in collegiate athletes. Twenty-three Division I female athletes (19.6 ± 1.0 years, 67.5 ± 7.4 kg, and 170.6 ± 6.8 cm) participated in this study and were randomized into either a probiotic (n = 11; DE111) or placebo (n = 12; PL) group while counterbalancing groups for sport. Athletes completed a 10-week resistance training program during the offseason, which consisted of 3–4 workouts per week of upper- and lower-body exercises and sport-specific training. Athletes consumed DE111 (DE111; 5 billion CFU/day) or PL supplement daily for the entire 10-week program. Before and after training, all athletes underwent 1 repetition maximum (1RM) strength testing (squat, deadlift, and bench press), performance testing (vertical jump and pro-agility), and isometric midthigh pull testing. Body composition (body fat [BF]%) was completed using BODPOD and bioelectrical impedance analysis, as well as muscle thickness (MT) measurement of the rectus femoris (RF) and vastus lateralis using ultrasonography. Separate repeated-measures analyses of variance were used to analyze all data. Significant (p ≤ 0.05) main effects for time were observed for improved squat 1RM, deadlift 1RM, bench press 1RM, vertical jump, RF MT, and BF%. Of these, a significant group × time interaction was noted for BF% (p = 0.015), where greater reductions were observed in DE111 (−2.05 ± 1.38%) compared with PL (−0.2 ± 1.6%). No other group differences were observed. These data suggest that probiotic consumption in conjunction with post-workout nutrition had no effect on physical performance but may improve body composition in female Division I soccer and volleyball players after offseason training.
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Two reactive strength index (RSI) variants exist, the RSI and RSI modified (RSImod) which are typically calculated during the drop jump (DJ) and countermovement jump (CMJ), respectively. Both RSI variants have been used to monitor athletes’ ability to complete stretch-shortening cycle actions quickly, but they have never been compared. The purpose of this study was to determine if they yield relatable information about reactive strength characteristics. Male professional rugby league players (n = 21, age = 20.8±2.3 years, height = 1.82±0.06 m and body mass = 94.3±8.4 kg) performed three DJs (30 cm) and CMJs on a force plate. RSI and RSImod were subsequently calculated by dividing jump height by ground contact time (GCT) and time to take-off (TTT), respectively. All variables were highly reliable (intraclass correlation coefficient ≥0.78) with acceptable levels of variability (coefficient of variation ≤8.2%), albeit larger variability was noted for DJ variables. Moreover, there was a large relationship between RSI and RSImod (r=0.524, P=0.007), whereas very large relationships were noted between jump heights (r=0.762, P<0.001) and between GCT and TTT (ρ=0.705, P<0.001). Additionally, RSI (0.90±0.22) was largely and significantly (d=2.57, P<0.001) greater than RSImod (0.47±0.08). The DJ-derived RSI yields much larger values than the CMJ-derived RSImod and although a large relationship was noted between them, it equated to just 22% shared variance. These results suggest that the two RSI variants do not explain each other well, indicating that they do not assess entirely the same reactive strength qualities and should not be used interchangeably.
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This review covers underlying physiological characteristics and training considerations that may affect muscular strength including improving maximal force expression and time-limited force expression. Strength is underpinned by a combination of morphological and neural factors including muscle cross-sectional area and architecture, musculotendinous stiffness, motor unit recruitment, rate coding, motor unit synchronization, and neuromuscular inhibition. Although single- and multi-targeted block periodization models may produce the greatest strength-power benefits, concepts within each model must be considered within the limitations of the sport, athletes, and schedules. Bilateral training, eccentric training and accentuated eccentric loading, and variable resistance training may produce the greatest comprehensive strength adaptations. Bodyweight exercise, isolation exercises, plyometric exercise, unilateral exercise, and kettlebell training may be limited in their potential to improve maximal strength but are still relevant to strength development by challenging time-limited force expression and differentially challenging motor demands. Training to failure may not be necessary to improve maximum muscular strength and is likely not necessary for maximum gains in strength. Indeed, programming that combines heavy and light loads may improve strength and underpin other strength-power characteristics. Multiple sets appear to produce superior training benefits compared to single sets; however, an athlete’s training status and the dose–response relationship must be considered. While 2- to 5-min interset rest intervals may produce the greatest strength-power benefits, rest interval length may vary based an athlete’s training age, fiber type, and genetics. Weaker athletes should focus on developing strength before emphasizing power-type training. Stronger athletes may begin to emphasize power-type training while maintaining/improving their strength. Future research should investigate how best to implement accentuated eccentric loading and variable resistance training and examine how initial strength affects an athlete’s ability to improve their performance following various training methods.
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The countermovement jump (CMJ) test is commonly conducted to assess neuromuscular function and is being increasingly performed using force platforms. Comprehensive insight into athletes’ neuromuscular function can be gained through detailed analyses of force-time curves throughout specific phases of the CMJ, beyond jump height alone. Confusingly, however, many different terms and methods have been used to describe the different phases of the CMJ. This article describes how six key phases of the CMJ (weighing, unweighting, braking, propulsion, flight, and landing) can be derived from force-time records to facilitate researchers’ and practitioners’ understanding and application to their own practice.
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The impact that technology has today and will have in the future in sport is unquestionable. We are constantly exposed to a multitude of new devices and products claimed to be "critical for performance success or injury prevention." This has led to a situation where sports organizations that are using or are considering the use of these tools can be, and are actually harassed by numerous promoters of the next "holy grail." This manuscript aims to provide a guideline to help organizations with the technology vetting process and on the implementation of technology.
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The purpose of this study was to explore the relationships between isometric mid-thigh pull (IMTP) force-time characteristics (peak force and time-specific force vales (100–250 ms)) and dynamic performance and compare dynamic performance between stronger and weaker athletes. Forty-three athletes from different sports (rowing, soccer, bicycle motocross, and hockey) performed three trials of the squat jump (SJ), countermovement jump (CMJ), and IMTP, and performed a one repetition maximum power clean (PC). Reactive strength index modified (RSImod) was also calculated from the CMJ. Statistically significant large correlations between IMTP force-time characteristics and PC (ρ = 0.569–0.674, p < 0.001), and moderate correlations between IMTP force-time characteristics (excluding force at 100 ms) and RSImod (ρ = 0.389–0.449, p = 0.013–0.050) were observed. Only force at 250 ms demonstrated a statistically significant moderate correlation with CMJ height (ρ = 0.346, p = 0.016) and no statistically significant associations were observed between IMTP force-time characteristics and SJ height. Stronger athletes (top 10) demonstrated statistically significantly greater CMJ heights, RSImods, and PCs (p ≤ 0.004, g = 1.32–1.89) compared to weaker (bottom 10) athletes, but no differences in SJ height were observed (p = 0.871, g = 0.06). These findings highlight that the ability to apply rapidly high levels of force in short time intervals is integral for PC, CMJ height, and reactive strength.
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Objectives: The purpose of this study was to examine the relationship among isometric mid-thigh pull (IMTP) variables, jump variables and sprint times in collegiate soccer players. Additionally, this study was conducted to demonstrate that strength characteristics influence the relationship between jump variables and sprint times. Design and Methods: Twenty-five collegiate soccer players performed IMTP, jump and sprint assessments. For IMTP, the force output at 100ms (F100ms) and peak force (PF) were analyzed. Countermovement jump (CMJ) and drop jump (DJ) index were measured. A 30m sprint was performed, and the times at 10m, 20m and 30m were recorded. Pearson’s product-moment correlation and a one-way analysis of variance (ANOVA) were used at p = 0.05. A cluster analysis was performed to divide all the subjects. Results: The F100ms significantly correlated with DJ-index (r = 0.433) and sprint times at 20-30m (r = -0.444). All the subjects were separated into high (HG: N = 9), medium (MG: N = 7) and low (LG: N = 9) groups based on the F100ms, because the coefficient of variation for F100ms was high (34.3%). There was a strong significant relationship between CMJ and sprint time at 10-20m in HG (r = -0.915), however there were no significant relationship in MG and LG. Conclusions: The F100ms can be used as an indicator for identifying athletes who have a statistically significant relationship between CMJ and flying sprint times. The results of the present study suggested that coaches should realize F100ms might pro vide the foundation to improve the sprint performance.
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Purpose: To examine the relationships between isometric mid-thigh pull (IMTP) force, athletic performance measures, and sprint kinetics in Division I men's and women's basketball players. Methods: Twenty-three (male = 8, female = 15) division 1 basketball players completed a maximal 20-m sprint trial while tethered to a device which provided kinetic feedback (peak and average sprinting power, velocity and force). Additionally, one repetition-maximal (1RM) front squat, 1RM hang clean, vertical jump height, and agility (pro-agility and lane agility) tests were performed. Rate of force development (RFD) at 50ms, 100ms, 150ms, 200ms and 250ms of IMTP, as well as peak force (PF) were also collected. Pearson product-moment correlation analysis was used to examine the relationships between these measures. Results: Significant (p < 0.05) relationships were observed between IMTP PF and sprint time over all distances (5 - 20m; r = -0.62 to 0.69), average sprint velocity (r = 0.50 to 0.70), peak sprint velocity (r = 0.50 to 0.54), average sprint force (r = 0.48 to 0.69), and average sprint power (r = 0.62 to 0.73). Sprinting kinetic measures (average force and power) over the first 5 meters were also significantly (p < 0.05) related to IMTP RFD (50 - 250ms; r = 0.42 to 0.62). Conclusion: Results indicate that IMTP variables are significantly associated with 20-m sprint kinetics. Specifically, IMTP RFD appears to be related to the initial acceleration kinetics of a sprint. Strength and conditioning professionals can possibly implement the IMTP for improved assessment and monitoring of athletic performance and training.
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Banyard, HG, Nosaka, K, and Haff, GG. Reliability and validity of the load-velocity relationship to predict the 1RM back squat. J Strength Cond Res 31(7): 1897-1904, 2017-This study investigated the reliability and validity of the load-velocity relationship to predict the free-weight back squat one repetition maximum (1RM). Seventeen strength-trained males performed three 1RM assessments on 3 separate days. All repetitions were performed to full depth with maximal concentric effort. Predicted 1RMs were calculated by entering the mean concentric velocity of the 1RM (V1RM) into an individualized linear regression equation, which was derived from the load-velocity relationship of 3 (20, 40, 60% of 1RM), 4 (20, 40, 60, 80% of 1RM), or 5 (20, 40, 60, 80, 90% of 1RM) incremental warm-up sets. The actual 1RM (140.3 ± 27.2 kg) was very stable between 3 trials (ICC = 0.99; SEM = 2.9 kg; CV = 2.1%; ES = 0.11). Predicted 1RM from 5 warm-up sets up to and including 90% of 1RM was the most reliable (ICC = 0.92; SEM = 8.6 kg; CV = 5.7%; ES =-0.02) and valid (r = 0.93; SEE = 10.6 kg; CV = 7.4%; ES = 0.71) of the predicted 1RM methods. However, all predicted 1RMs were significantly different (p ≤ 0.05; ES = 0.71-1.04) from the actual 1RM. Individual variation for the actual 1RM was small between trials ranging from-5.6 to 4.8% compared with the most accurate predictive method up to 90% of 1RM, which was more variable (-5.5 to 27.8%). Importantly, the V1RM (0.24 ± 0.06 m·s⁻¹) was unreliable between trials (ICC = 0.42; SEM = 0.05 m·s⁻¹; CV = 22.5%; ES = 0.14). The load-velocity relationship for the full depth free-weight back squat showed moderate reliability and validity but could not accurately predict 1RM, which was stable between trials. Thus, the load-velocity relationship 1RM prediction method used in this study cannot accurately modify sessional training loads because of large V1RM variability.
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The barbell hip thrust may be an effective exercise for increasing horizontal force production and may thereby enhance performance in athletic movements requiring a horizontal force vector, such as horizontal jumping and sprint running. The ergogenic ability of the squat is well known. The purpose of this study was to compare the effects of six-week front squat and hip thrust programs in adolescent male athletes. Vertical jump height, horizontal jump distance, 10 m and 20 m sprint times, and isometric mid-thigh pull peak force were among the measured performance variables, in addition to front squat and hip thrust three-repetition maximum (3 RM) strength. Magnitude-based effect-sizes revealed potentially beneficial effects for the front squat in both front squat 3 RM strength and vertical jump height when compared to the hip thrust. No clear benefit for one intervention was observed for horizontal jump performance. Potentially beneficial effects were observed for the hip thrust compared to the front squat in 10 m and 20 m sprint times. The hip thrust was likely superior for improving normalized isometric mid-thigh pull strength, and very likely superior for improving hip thrust 3 RM and isometric mid-thigh pull strength. These results support the force vector theory.
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This review article discusses previous literature that has examined the influence of muscular strength on various factors associated with athletic performance and the benefits of achieving greater muscular strength. Greater muscular strength is strongly associated with improved force-time characteristics that contribute to an athlete’s overall performance. Much research supports the notion that greater muscular strength can enhance the ability to perform general sport skills such as jumping, sprinting, and change of direction tasks. Further research indicates that stronger athletes produce superior performances during sport specific tasks. Greater muscular strength allows an individual to potentiate earlier and to a greater extent, but also decreases the risk of injury. Sport scientists and practitioners may monitor an individual’s strength characteristics using isometric, dynamic, and reactive strength tests and variables. Relative strength may be classified into strength deficit, strength association, or strength reserve phases. The phase an individual falls into may directly affect their level of performance or training emphasis. Based on the extant literature, it appears that there may be no substitute for greater muscular strength when it comes to improving an individual’s performance across a wide range of both general and sport specific skills while simultaneously reducing their risk of injury when performing these skills. Therefore, sport scientists and practitioners should implement long-term training strategies that promote the greatest muscular strength within the required context of each sport/event. Future research should examine how force-time characteristics, general and specific sport skills, potentiation ability, and injury rates change as individuals transition from certain standards or the suggested phases of strength to another.
Conference Paper
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This study examined the role of maximal strength in plyometric exercise performance in twenty strength-trained rugby players. Players' maximal leg strength was assessed using a 3 or 5RM barbell back squat strength testing procedure. Plyometric ability was assessed using ground contact times and the reactive strength index variable during depth jumps from a variety of box heights (12, 36 and 51cm) performed on a force plate. The data indicated a strong positive relationship between strength levels and plyometric ability. Stronger subjects achieved better reactive strength indices than weaker counterparts and are more capable of performing depth jumps at higher intensities. Stronger athletes may benefit more from fast SSC plyometric training than their weaker counterparts. INTRODUCTION: Plyometric exercises use rapid, powerful movements that are preceded by a preloading countermovement that activates the stretch-shortening cycle (SSC). Schmidtbleicher (1992) has suggested that the SSC can be classified as either slow or fast. These SSCs are underpinned by different biomechanical mechanisms. The fast SSC is characterized by short contraction or ground contact times (CT) or 0.25 seconds or less and small angular displacements of the hips, knees, and ankles. Depth jumps are one of the most commonly used fast SSC plyometric exercises. A depth jump requires the athlete to step from a specific box height and, on landing on the ground, perform a maximal effort vertical jump with a short ground-contact period. The intensity of plyometric depth jumps is determined by the height of box used: the greater the box height, the greater the eccentric loading the player must overcome to successfully complete the jump. Fast SSC plyometrics are commonly used in training for strength and power sports such as rugby. Plyometric exercises have been demonstrated to improve power output (Luebbers et al. 2003), agility (Miller et al. 2006) and running economy (Saunders et al. 2006). The reactive strength index (RSI) describes an individual's ability to explosively transition from an eccentric to concentric muscular contraction (Young, 1995). The RSI can be used to optimise box height during depth jump training or to assess improvements in reactive strength following a plyometric training intervention (Flanagan & Comyns, 2008). Strength is the ability to generate maximal external force. Traditionally, lower body maximal strength is trained and/or assessed through resistance training exercises such as the barbell bar squat. Anecdotally it has been suggested that athletes should reach a specific level of lower body strength before undertaking specific plyometric exercises such as depth jumps. While studies have examined the relationship between maximal strength and jumping ability, research has not been undertaken which investigates the relationship between maximal strength and fast SSC plyometric ability using the RSI. The goal of this study was to examine the role of maximal strength in plyometric exercise performance and to establish optimal box heights for use in plyometric depth jumping for rugby players of specific strength levels.
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The purpose of this investigation was to evaluate an assessment method for the lower body and its ability to detect training induced changes in athletes. A repeated measures study design was used to assess reliability; in addition several longitudinal single subject case-studies are reported, justifying the sensitivity of the test to detect training induced changes. Inter-day reliability of the measures was assessed with repeated measures 48 h apart and the detection of training induced changes was evaluated by tracking athletes over a normal conditioning period which included resistance and sport specific training. Peak force for the isometric mid-thigh pull was 2879±613 N and 1988±412 N for the squat jump, resulting in a mean Dynamic Strength Deficit of 0.70±0.10. The coefficient of variation ranged from 2.01-3.19 % and intra-class correlation coefficients of 0.952-0.987 were observed. For athletes involved in lower-body maximal strength training, their pre and post measurements recorded changes in isometric mid-thigh pull peak force (215-362 N), and changes in the Dynamic Strength Deficit ratio (0.03-0.14) that exceeded the measures technical error. The Dynamic Strength Deficit ratio, is a reliable means of assessing an athlete's strength qualities, and comparisons of the force measures appear to be a valid means to detect training induced changes in athletes.
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Purpose: To examine the reliability and magnitude of change after fatiguing exercise in the countermovement-jump (CMJ) test and determine its suitability for the assessment of fatigue-induced changes in neuromuscular (NM) function. A secondary aim was to examine the usefulness of a set of alternative CMJ variables (CMJ-ALT) related to CMJ mechanics. Methods: Eleven male college-level team-sport athletes performed 6 CMJ trials on 6 occasions. A total of 22 variables, 16 typical (CMJ-TYP) and 6 CMJ-ALT, were examined. CMJ reproducibility (coefficient of variation; CV) was examined on participants' first 3 visits. The next 3 visits (at 0, 24, and 72 h postexercise) followed a fatiguing high-intensity intermittent-exercise running protocol. Meaningful differences in CMJ performance were examined through effect sizes (ES) and comparisons to interday CV. Results: Most CMJ variables exhibited intraday (n = 20) and interday (n = 21) CVs of <10%. ESs ranging from trivial to moderate were observed in 18 variables at 0 h (immediately postfatigue). Mean power, peak velocity, flight time, force at zero velocity, and area under the force-velocity trace showed changes greater than the CV in most individuals. At 24 h, most variables displayed trends toward a return to baseline. At 72 h, small increases were observed in time-related CMJ variables, with mean changes also greater than the CV. Conclusions: The CMJ test appears a suitable athlete-monitoring method for NM-fatigue detection. However, the current approach (ie, CMJ-TYP) may overlook a number of key fatigue-related changes, and so practitioners are advised to also adopt variables that reflect the NM strategy used.
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Aim: The purpose of this study was to evaluate the relationship between weightlifting performance (snatch, clean and jerk, and total) and variables obtained from the isometric mid-thigh pull (IMTP). Methods: Twelve weightlifters, ranging from novice to advanced, performed the IMTP 10 days after a competition. Correlations were used to evaluate relationships between variables of the IMTP and absolute and scaled competition results. Results: Unscaled competition results correlated strongly with IRFD (0-200ms: r=0.567-0.645, 0-250ms: r=0.722-0.781) while results correlated weakly with Peak IRFD (5ms window, r=0.360-0.426). Absolute peak force values correlated very strongly with absolute values for the competition performance (r=0.830-0.838). Force at 100ms, 150ms, 200ms and 250ms also correlated strongly with competition results (r=0.643-0.647, r=0.605-0.636, r=0.714-0.732, r=0.801-0.804). Similar findings were noted for allometrically scaled values. Conclusion: Measures of average IRFD probably represent a more relevant variable to dynamic performance than does Peak IRFD (5ms). Maximum isometric strength also is likely to have a strong role in weightlifting performance.
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A common suggestion is that a predetermined level of maximal leg strength is required before drop jump (DJ) training can begin. This study sought to examine the relationship between maximal squat strength (1RM) and DJ performance in 15 female rugby players (n=15). The subjects were tested for 1RM, countermovement jump (CMJ), squat jump (SJ) and DJs from 0.24m, 0.36m, 0.48m, 0.60m, 0.72m and 0.84m. Jump height (JH) was calculated for all jumps and relative peak eccentric force (RPEF), relative peak concentric force (RPCF), ground contact time (GCT) and Reactive Strength Index (RSI) were also calculated for DJs. Pearson correlations were used to examine the relationship between 1RM relative to body mass (1RM/BM) and JHs, RSI and GCTs during DJs. Subjects were placed into a high strength (HS) or low strength (LS) group depending on whether or not their 1RM/BM was >1 or <1. T tests and two way ANOVAs were used to compare the groups. A Fishers post hoc test was used for the ANOVAs with significance set at p<0.05. A large correlation between JH and 1RM/BM was shown at the 0.84m dropping height (r=0.56). A significant overall different was found between the HS and LS group for DJ JH with a post hoc analysis revealing a significant difference at the 0.84m drop height (p=0.029). It is likely beneficial for female athletes to achieve high levels of maximal leg strength if they are going to use high (>0.8m) drop heights when performing drop jumps.
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This paper illustrates the ability to derive valid and reliable representations of maximal isometric strength (lower body) under bilateral and unilateral conditions using a portable force plate; a practical strength testing solution to organisations with limited facilities or equipment. Also presented at the International Conference of Applied Strength and Conditioning - Gold Coast, Australia, (2011).
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To establish the reliability of various measures obtained during single and repeated countermovement jump (CMJ) performance in an elite athlete population. Two studies, each involving 15 elite Australian Rules Football (ARF) players were conducted where subjects performed two days, separated by one week, of AM and PM trials of either a single (CMJ1) or 5 repeated CMJ (CMJ5). Each trial was conducted on a portable force-plate. The intraday, interday, and overall typical error (TE) and coefficient of variation (CV%) were calculated for numerous variables in each jump type. A number of CMJ1 and CMJ5 variables displayed high intraday, interday, and overall reliability. In the CMJ1 condition, mean force (CV 1.08%) was the most reliable variable. In the CMJ5, flight time and relative mean force displayed the highest repeatability with CV of 1.88% and 1.57% respectively. CMJ1Mean force was the only variable with an overall TE < smallest worthwhile change (SWC). Selected variables obtained during CMJ1 and CMJ5 performance can be used to assess the impact of both acute and chronic training and competition. Variables derived from the CMJ5 may respond differently than their CMJ1 counterparts and should provide insights into differential mechanisms of response and adaptation.
Article
The purpose of this study was: i) to determine the reliability of alternate forms of the dynamic strength index (DSI) calculated over time-specific intervals that represent decisive actions in sport and ii) to assess the association between the original form of the DSI (DSItrad) and its variants. Twenty-three resistance-trained males (BM = 80.4 ± 10.18 kg; age = 26.3 ± 10.2 y; 1-RM squat kg/kg/BM = 1.61 ± 0.37) performed trials of the countermovement jump (CMJ) and isometric squat. Several variations of the DSI were calculated by dividing the mean force in the CMJ by the mean force in the isometric squat calculated over the following epochs: 100 ms (DSI100), 150 ms (DSI150) and CMJ propulsive phase duration (DSIprop). In the fourth method, mean force across the CMJ propulsive phase duration was divided by mean force in the isometric squat between initiation and peak force (DSIpeak). All alternate DSI measures achieved acceptable absolute reliability (CV < 10%), however they did not achieve at least a moderate relative reliability. DSIprop (R2 = 0.41), DSI100 (R2 = 0.03) and DSI150 (R2 = 0.14) demonstrated limited commonality with DSItrad. The alternate forms of DSI can cautiously be considered in strength assessment systems.
Article
Purpose: Dozens of variables can be derived from the countermovement jump (CMJ). However, this does not guarantee an increase in useful information because many of the variables are highly correlated. Furthermore, practitioners should seek to find the simplest solution to performance testing and reporting challenges. The purpose of this investigation was to show how to apply dimensionality reduction to CMJ data with a view to offer practitioners solutions to aid applications in high-performance settings. Methods: The data were collected from 3 cohorts using 3 different devices. Dimensionality reduction was undertaken on the extracted variables by way of principal component analysis and maximum likelihood factor analysis. Results: Over 90% of the variance in each CMJ data set could be explained in 3 or 4 principal components. Similarly, 2 to 3 factors could successfully explain the CMJ. Conclusions: The application of dimensional reduction through principal component analysis and factor analysis allowed for the identification of key variables that strongly contributed to distinct aspects of jump performance. Practitioners and scientists can consider the information derived from these procedures in several ways to streamline the transfer of CMJ test information.
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Bartolomei, S, Nigro, F, Malagoli Lanzoni, I, Masina, F, Di Michele, R, and Hoffman, JR. A comparison between total body and split routine resistance training programs in trained men. J Strength Cond Res XX(X): 000-000, 2020-The purpose of the present investigation was to compare the effects of total body (TB) versus split routine (SR) resistance training workouts on maximal strength and muscle hypertrophy in trained men. Twenty-one resistance-trained men were randomly assigned to either a TB (TB: age = 24.1 ± 4.4 years; body mass = 78.7 ± 11.3 kg; body height = 177.0 ± 3.9 cm) or the SR group (SR: age = 24.9 ± 4.2 years; body mass = 79.2 ± 9.5 kg; body height = 175.2 ± 6.0 cm). Both groups performed a 10-week resistance training program. Isokinetic bench press at 75 and 25 cm·s (ISOK75 and ISOK25, respectively), isometric bench press (ISOBP), isometric squat (ISOSQ), and one repetition maximum BP and SQ assessments were performed before and after training. Muscle thickness of the pectoralis major (PECMT), superior part of trapezius (TRAPMT), and vastus lateralis (VLMT) muscles was also evaluated at the same timepoints using ultrasonography. Improvements were observed in both groups for all strength assessments and muscle thicknesses. Only changes in ISOK25 were significantly (p = 0.015) greater in TB than in SR, while significantly greater (p = 0.037) changes in VLMT were detected in SR compared with TB. Results indicated that a TB training paradigm may be more appropriate for maximal strength improvement, while an SR training protocol may be more optimal in stimulating muscle growth in experienced, resistance-trained men.
Article
Purpose: To determine the reliability of early force production (50, 100, 150, 200, and 250 ms) relative to peak force (PF) during an isometric mid-thigh pull and to assess the relationships between these variables. Methods: Male collegiate athletes (N = 29; age 21.1 [2.9] y, height 1.71 [0.07] m, body mass 71.3 [13.6] kg) performed isometric mid-thigh pulls during 2 separate testing sessions. Net PF and net force produced at each epoch were calculated. Within- and between-session reliabilities were determined using intraclass correlation coefficients and coefficient of variation percentages. In addition, Pearson correlation coefficients and coefficient of determination were calculated to examine the relationships between PF and time-specific force production. Results: Net PF and time-specific force demonstrated very high to almost perfect reliability both within and between sessions (intraclass correlation coefficients .82-.97; coefficient of variation percentages 0.35%-1.23%). Similarly, time-specific force expressed as a percentage of PF demonstrated very high to almost perfect reliability both within and between sessions (intraclass correlation coefficients .76-.86; coefficient of variation percentages 0.32%-2.51%). Strong to nearly perfect relationships (r = .615-.881) exist between net PF and time-specific net force, with relationships improving over longer epochs. Conclusion: Based on the smallest detectable difference, a change in force at 50 milliseconds expressed relative to PF > 10% and early force production (100, 150, 200, and 250 ms) expressed relative to PF of >2% should be considered meaningful. Expressing early force production as a percentage of PF is reliable and may provide greater insight into the adaptations to the previous training phase than PF alone.
Article
The isometric mid-thigh pull (IMTP) is commonly used to assess an athlete’s force generation ability. This test is highly reliable and is simple and relatively quick to perform. The data that can be determined from the force-time curves generated by the test have been shown to be closely related to performance capacities in a variety of dynamic athletic tasks. However, within the scientific literature there are inconsistencies in the data collection procedures and methods used for data analysis that may impact the resultant output and the ability to compare and generalize results. Therefore, the primary aim of this review is to identify the differences in IMTP testing procedures and data analysis techniques, while identifying the potential impact this may have on the data collected. The secondary aim is to provide recommendations for the standardization of testing procedures to ensure that future IMTP data is of maximal benefit to practitioners and researchers.
Article
The purpose of this investigation was to determine if the magnitude of adaptation to integrated ballistic training is influenced by initial strength level. Such information is needed to inform resistance training guidelines for both higher- and lower-level athlete populations. To this end, two groups of distinctly different strength levels (stronger: one-repetition-maximum (1RM) squat = 2.01 ± 0.15 kg.BM⁻¹; weaker: 1.20 ± 0.20 kg.BM⁻¹) completed 10 weeks of resistance training incorporating weightlifting derivatives, plyometric actions and ballistic exercises. Testing occurred at pre-, mid- and post-training. Measures included variables derived from the incremental-load jump squat and the 1RM squat, alongside muscle activity (electromyography), and jump mechanics (force-time comparisons throughout the entire movement). The primary outcome variable was peak velocity derived from the unloaded jump squat. It was revealed that the stronger group displayed a greater (P = 0.05) change in peak velocity at midtest (baseline: 2.65±0.10 m∙s⁻¹, midtest: 2.80±0.17 m∙s⁻¹) but not posttest (2.85±0.18 m∙s⁻¹) when compared to the weaker participants (baseline 2.48 ±0.09, midtest. 2.47 ±0.11, posttest: 2.61 ±0.10 m∙s⁻¹). Different changes occurred between groups in the force-velocity relationship (P=0.001–0.04) and jump mechanics (P≤0.05), while only the stronger group displayed increases in muscle activation (P=0.05). In conclusion, the magnitude of improvement in peak velocity was significantly influenced by pre-existing strength level in the early stage of training. Changes in the mechanisms underpinning performance were less distinct.
Article
Defending and attacking agility tests for Australian football do not exist, and it is unknown whether any physical qualities correlate to these types of agility. The purposes of this study were to develop new field tests of defending and attacking agility for Australian Rules football, to determine if they were reliable, and to describe the relationship between the agility tests to determine their specificity. Since the reactive strength (RS) of the lower limb muscles has been previously correlated to change‐of‐direction speed, we also investigated the relationship between this quality and the agility tests. Nineteen male competitive recreational‐level Australian Rules football players were assessed on the agility tests and a drop jump test to assess RS. Inter‐day and inter‐rater reliability was also assessed. The agility tests involved performing 10 trials of one‐on‐one agility tasks against two testers (opponents), where the objective was to be in a position to tackle (defending) or to evade (attacking) the opponent. Both agility tests had good reliability (ICC>0.8, %CV<3, and no significant differences between test occasions (P>0.05), and inter‐rater reliability was very high (r=0.997, P<0.001). The common variance between the agility tests was 45%, indicating they represented relatively independent skills. There was a large correlation between RS and defending agility (r=0.625, P=0.004), and a very large correlation with attacking agility (r=0.731, P<0.001). Defending and attacking agility have different characteristics, possibly related to the footwork, physical and cognitive demands of each. Nonetheless, RS appears to be important for agility, especially for attacking agility.
Article
The purpose of this study was to determine the relationships between selected physical qualities, change-of-direction speed and defensive agility performance in Australian Rules football players. Twenty-four male community-level players were assessed on sprint acceleration (10-m time), maximum strength (3 repetition-maximum half squat), leg power (countermovement jump), reactive strength (drop jump), as well as a single change-of-direction speed test and a defensive agility test. Change-of-direction speed was correlated with reactive strength (r = -0.645, p = 0.001) and sprint acceleration (r = 0.510, p = 0.011). Multiple regression indicated the combined physical qualities explained 56.7% of the variance associated with change-of-direction speed (adjusted R = 0.567, p < 0.05). Participants were median-split into faster and slower change-of-direction speed groups, and these were compared by independent t-tests. The faster group was significantly better (p < 0.05) on the sprint acceleration and reactive strength tests (large effect size). The correlations between physical qualities and agility were trivial to small (r = - 0.101 to 0.123, p > 0.05) and collectively explained only 14.2% of the variance associated with agility performance (adjusted R = - 0.142, p > 0.05). When faster and slower agility groups were compared, there were trivial to moderate differences (p > 0.05) in all physical qualities. It was concluded that reactive strength and sprint acceleration are important for change-of-direction speed but the physical qualities assessed are not associated with defensive agility performance. For agility tasks similar to this study, sprint and resistance training should not be emphasized, and training other factors such as the development of sport-specific technique and cognitive skill is recommended.
Article
Research has often examined the relationship between one or two measures of strength and change of direction (COD) ability reporting inconsistent relationships to performance. These inconsistences may be the result of the strength assessment utilized and the assumption that one measure of strength can represent all "types" of strength required during a COD task. Therefore the purpose of this study was to determine the relationship between several lower body strength and power measures, COD and agility performance. Twelve (n=12) elite female basketball athletes completed a maximal dynamic back squat, isometric mid-thigh pull, eccentric and concentric only back squat, and a counter-movement jump, followed by two COD tests (505 and T-Test) and a reactive agility test. Pearson product moment correlation and stepwise regression analysis were performed on all variables. The percentage contribution of each strength measure to an athletes total strength score was also determined. Our results demonstrated that both COD tests were significantly correlated to maximal dynamic, isometric, concentric and eccentric strength (r = -0.79 to -0.89), with eccentric strength identified as the sole predictor of COD performance. Agility performance did not correlate with any measure of strength (r = -0.08 to -0.36), while lower body power demonstrated no correlation to either agility or COD performance (r = -0.19 to -0.46). These findings demonstrate the importance of multiple strength components for COD ability, highlighting eccentric strength as a deterministic factor of COD performance. Coaches should aim to develop a well-rounded strength base in athletes; ensuring eccentric strength is developed as effectively as the often-emphasized concentric or overall dynamic strength capacity.
Article
This presentation will consider what performance analysis is, what biomechanical and notational analysis have in common and how they differ. The main focus will be how they have helped, and can better help, coaches and athletes to analyse and improve sports performance. Biomechanics and notational analysis both involve the analysis and improvement of sport performance. They make extensive use of video analysis and technology. They require careful information management for good feedback to coaches and performers and systematic techniques of observation. They have theoretical models- based on performance indicators - amenable to AI developments and strong theoretical links with other sport science and IT disciplines. They differ in that biomechanists analyse, iinnffine-detail, individual sports techniques and their science is grounded in mechanics and anatomy. Notational analysis studies gross movements or movement patterns in team sports, is primarily concerned with strategy and tactics and has a history in dance and music notation. The practical value of performance analysis is that well-chosen performance indicators highlight good and bad techniques or team performances. They help coaches to identify good and bad performances of an individual or a team member and facilitate comparative analysis of individuals, teams and players. In addition, biomechanics helps to identify injurious techniques while notational analysis helps to assess physiological and psychological demands of sports. Drawing on a range of sports examples, I will argue that performance analysts require a unified approach, looking at interactions between players and their individual skill elements. Of fundamental importance is the need for us to pay far greater attention to the principles of providing feedback- technique points that a coach can observe from video and simple counts of events are unlikely to enhance individual or team performance. We should also address the role of variability in sports skills and its implications for coaching. We must pay more attention to normalisation of performance indicators to aid coaches. Finally, further development of IT- and AI-based coaching tools by performance analysts is a high priority.
Article
This study compared a countermovement jump (CMJ) and drop jumps performed according to 3 objectives: maximum jump height (DJ-H), minimum contact time (DJ-t), and maximum jump height/contact time ratio (DJ-H/t). Subjects (N = 17 males) performed all 4 jump conditions on a contact mat/computer system that recorded the contact and flight times. DJ-H produced significantly greater jump height/contact time at all drop heights than DJ-H/t. DJ-H/t produced significantly greater jump height, longer contact time, and greater jump height/contact time at all drop heights than DJ-t. CMJ and best height in DJ-H height and best DJ-H/t performance was low. As DJ drop height increased, so did the jumps resulting in heel-ground contact. DJ characteristics are similar to CMJ when jump height is the only objective. But when DJ contact time is shortened, the imposed stretch loads probably increase and different qualities are required for successful jumps. (C) 1995 National Strength and Conditioning Association
Article
Eight trained men were used to compare isometric and dynamic force-time variables. Subjects performed maximum isometric and dynamic pulls at 80% (DP80), 90% (DP90), and 100% (DP100) of their current 1-RM power clean from a standardized postion on a 61.0- x 121.9-cm AMTI force plate. Isometric peak force showed moderate to strong correlations with peak force during DP80, DP90, and DP100 (r = 0.66, 0.77, and 0.80, respectively). Isometric rate of force development showed moderate to strong correlations with dynamic peak force during DP80, DP90, and DP100 (r = 0.65, 0.73, and 0.75, respectively) and was strongly correlated with peak dynamic rate of force development during DP80, DP90, and DP100 (r = 0.84, 0.88, and 0.84, respectively). This suggests that the ability to exert both isometric and dynamic peak force shares some structural and functional foundation with the ability to generate force rapidly. (C) 1997 National Strength and Conditioning Association
Article
Certain strength measures represent specific or independent qualities of neuromuscular performance that can be assessed and trained independently. Strength diagnosis is the process of determining an athlete's level of development in each of these distinct strength qualities. Application of strength diagnosis has the potential to increase training efficiency, reduce injury, and facilitate rehabilitation by determining the relative assets and deficits of strength qualities. More research in this field is required, but several papers allude to the promise of strength diagnosis in making training program design more objective, more individualized, and safer.
Article
To determine whether the magnitude of performance improvements and the mechanisms driving adaptation to ballistic power training differ between strong and weak individuals. Twenty-four men were divided into three groups on the basis of their strength level: stronger (n = 8, one-repetition maximum-to-body mass ratio (1RM/BM) = 1.97 +/- 0.08), weaker (n = 8, 1RM/BM = 1.32 +/- 0.14), or control (n = 8, 1RM/BM = 1.37 +/- 0.13). The stronger and weaker groups trained three times per week for 10 wk. During these sessions, subjects performed maximal-effort jump squats with 0%-30% 1RM. The impact of training on athletic performance was assessed using a 2-d testing battery that involved evaluation of jump and sprint performance as well as measures of the force-velocity relationship, jumping mechanics, muscle architecture, and neural drive. Both experimental groups showed significant (P < or = 0.05) improvements in jump (stronger: peak power = 10.0 +/- 5.2 W.kg, jump height = 0.07 +/- 0.04 m; weaker: peak power = 9.1 +/- 2.3 W.kg, jump height = 0.06 +/- 0.04 m) and sprint performance after training (stronger: 40-m time = -2.2% +/- 2.0%; weaker: 40-m time = -3.6% +/- 2.3%). Effect size analyses revealed a tendency toward practically relevant differences existing between stronger and weaker individuals in the magnitude of improvements in jump performance (effect size: stronger: peak power = 1.55, jump height = 1.46; weaker: peak power = 1.03, jump height = 0.95) and especially after 5 wk of training (effect size: stronger: peak power = 1.60, jump height = 1.59; weaker: peak power = 0.95, jump height = 0.61). The mechanisms driving these improvements included significant (P < or = 0.05) changes in the force-velocity relationship, jump mechanics, and neural activation, with no changes to muscle architecture observed. The magnitude of improvements after ballistic power training was not significantly influenced by strength level. However, the training had a tendency toward eliciting a more pronounced effect on jump performance in the stronger group. The neuromuscular and biomechanical mechanisms driving performance improvements were very similar for both strong and weak individuals.
Article
To determine whether the magnitude of improvement in athletic performance and the mechanisms driving these adaptations differ in relatively weak individuals exposed to either ballistic power training or heavy strength training. Relatively weak men (n = 24) who could perform the back squat with proficient technique were randomized into three groups: strength training (n = 8; ST), power training (n = 8; PT), or control (n = 8). Training involved three sessions per week for 10 wk in which subjects performed back squats with 75%-90% of one-repetition maximum (1RM; ST) or maximal-effort jump squats with 0%-30% 1RM (PT). Jump and sprint performances were assessed as well as measures of the force-velocity relationship, jumping mechanics, muscle architecture, and neural drive. Both experimental groups showed significant (P < or = 0.05) improvements in jump and sprint performances after training with no significant between-group differences evident in either jump (peak power: ST = 17.7% +/- 9.3%, PT = 17.6% +/- 4.5%) or sprint performance (40-m sprint: ST = 2.2% +/- 1.9%, PT = 3.6% +/- 2.3%). ST also displayed a significant increase in maximal strength that was significantly greater than the PT group (squat 1RM: ST = 31.2% +/- 11.3%, PT = 4.5% +/- 7.1%). The mechanisms driving these improvements included significant (P < or = 0.05) changes in the force-velocity relationship, jump mechanics, muscle architecture, and neural activation that showed a degree of specificity to the different training stimuli. Improvements in athletic performance were similar in relatively weak individuals exposed to either ballistic power training or heavy strength training for 10 wk. These performance improvements were mediated through neuromuscular adaptations specific to the training stimulus. The ability of strength training to render similar short-term improvements in athletic performance as ballistic power training, coupled with the potential long-term benefits of improved maximal strength, makes strength training a more effective training modality for relatively weak individuals.
Article
A total of 16 strength, work, and power tests were administered to a random sample of 50 male college students. The raw scores and residual scores which controlled for individual differences in height and weight were analyzed by multiple factor analytic models. Of the six factors hypothesized, four were confirmed by the isolation of factors robust over models. The remaining two factors were tentatively supported in the analyses of the residualized variables.
Article
.HÄKKUKINEN, K., KOMI, P.V. & ALÉN, M. 1985. Effect of explosive type strength training on isometric force‐ and relaxation‐time, electromyographic and muscle fibre characteristics of leg extensor muscles. Acta Physiol Scand 125, 587–600. Received 26 January 1985, accepted 9 May 1985. ISSN 0001–6772. Department of Biology of Physical Activity and Department of Health Sciences, University of Jyväskylä, Finland. To investigate the influence of explosive type strength training on isometric force‐ and relaxation‐time and on electromyographic and muscle fibre characteristics of human skeletal muscle, 10 male subjects went through progressive training which included primarily jumping exercises without extra load and with light extra weights three times a week for 24 weeks. Specific training‐induced changes in force‐time curve were observed and demonstrated by great ( P < 0.05–0.001) improvements in parameters of fast force production and by a minor ( P< 0.05) increase in maximal force. The continuous increases in fast force production during the entire training were accompanied by and correlated with the increases ( P < 0.05) in average IEMG‐time curve and with the increase (P < 0.05) in the FT:ST muscle fibre area ratio. The percentage of FT fibres of the muscle correlated ( P < 0.05) with the improvement of average force‐time curve during the training. The increase in maximal force was accompanied by significant ( P < 0.05) increases in maximum IEMGs of the trained muscles. However, the hypertrophic changes, as judged from the anthropometric and muscle fibre area data, were only slight during the training. It can be concluded that in training for fast force production considerable neural and selective muscular adaptations may occur to explain the improvement in performance, but that genetic factors may determine the ultimate potential of the trainability of this aspect of the neuromuscular performance.
Article
The study investigated the factor structure of the three-factor strength model proposed by Fleishman. A theoretical model of nine hypothesized factors was developed, and 25 tests sampled the hypothesized factors. The data collected on 76 college men were subjected to eight derived factor solutions. The evidence presented in these analyses did not support the three-factor strength model reported by Fleishman. The analyses yielded five common factors which were robust among all eight derived solutions. The analyses of four derived solutions suggested that an additional two factors may exist in the domain sampled by the 25 experimental tests.
Article
The relationships of muscle structure to the potentiation of myoelectrical activity and to the use of prestretching in five lower limb muscles were studied in different vertical jumping conditions. The subjects for the study were six male students, divided according to the muscle fiber distribution in m. vastus lateralis into "fast" and "slow" groups. The subjects performed vertical jumps (1) from a static squatting position (DJ) from five different heights. Myoelectrical (EMG) activity was recorded from mm. gluteus maximus, vastus lateralis, vastus medialis, rectus femoris and gastrocnemius in each jumping condition and integrated (IEMG) for the eccentric and concentric phases of contact. EMG activity showed potentiation during the eccentric phase of movement when compared to the concentric phase. The "fast" and "slow" groups did not differ significantly in this respect, whereas in DJ conditions the relative (% from SJ) height of rise of the center of gravity was greater in the "slow" than in the "fast" group. The result indicated that the utilization of elastic energy during jumping was possible better in subjects having a high percentage of slow twitch muscle fibres in their vastus lateralis muscles.