Misuse of "Power" and Other Mechanical Terms in Sport and Exercise Science Research

Unrestrained Versus Vertically Restrained Loaded Countermovement Jumps: Are There Any Differences in the Components of Force Application?

The objective of this study was to compare a number of variables derived from the vertical and horizontal force components between loaded countermovement jumps performed in a Smith machine (SM modality; vertically restrained jumps) and with free weights (FW modality; unrestrained jumps). Twenty-three recreationally trained individuals, 6 women and 17 men, performed on a 3D force platform 5 maximal countermovement jump trials against 3 external loads (30%, 50%, and 70% of the SM 1-repetition maximum) using the SM and FW jumping modalities on separate sessions. The SM modality promoted greater values for virtually all the variables derived from the vertical force component (maximal force, maximal and minimum velocity, and impulse) and also shorter durations of the braking and propulsive phases. Regardless of the countermovement jump phase (braking or propulsive), the impulse directed toward the backward direction was always considerably greater for the SM compared with the FW modality. These results evidence that for recreationally trained individuals, the SM modality could be more effective to increase the general force capacity of the leg muscles due to increased external stability, while the FW modality is preferable when the orientation of force application is a crucial consideration, as it reduces the horizontal force component.

A comparison of three different work to rest periods during intermittent sprint training on maintaining sprint effort performance

Background/objectives

Team sports are characterised by repeated maximal intensity bursts of activity, requiring significant energy contribution from the phosphagen pathways. The objective of this study was to evaluate the impact of different rest periods on repeated maximal intensity efforts.

Methods

The effect of three different recovery periods (60 s, 90 s and 120 s) during a 10 × six-seconds intermittent sprint training protocol performed on a cycle ergometer was investigated. Thirteen part-time female athletes from two sports, Rugby Sevens and Netball competing for their state participated in the study. Peak Power (PPO), Mean Power (MPO), "total work" in the form of calorie expenditure, performance decrement, repetitions over 95% PPO, blood lactate, and RPE were recorded.

Results

There was a significant effect of condition on MPO and calorie expenditure (p < 0.050). MPO was significantly lower for 60 s compared to 90 s (710.4 vs 734.4 W, ES = 0.27-0.42) and 120 s (710.4 vs 743.3 W, ES = 0.36-0.47). Calorie expenditure was significantly lower for 60 s compared to 90 s (4.41 vs 4.56 cal, ES = 0.25-0.46) and 120 s (4.41 vs 4.59 cal, ES = 0.40-0.48). There was a significant effect of time (60 s 11.7, 90 s 11.1.120 s 10.9 mmol/L, p < 0.010) but not condition (p = 0.617) for blood lactate accumulation, and a significant difference in session RPE between 60 and both 90 s and 120 s (60 s 15.5, 90 s 14.2. p = 0.034 120 s 13.9, p = 0.039).

Conclusion

Shorter recovery durations resulted in decreased mean power and calorie expenditure, but higher RPE when compared to longer recovery periods. All three recovery periods may have fallen between the fast and slow phases of PCr resynthesis of approximately 20 and 180 s resulting in partial but not complete recovery. Total training time should be a consideration when determining what protocol to implement.

Inverse dynamics, joint reaction forces and loading in the musculoskeletal system: guidelines for correct mechanical terms and recommendations for accurate reporting of results

Inverse Dynamics is routinely used in biomechanics for the estimation of loading in the musculoskeletal system but there are problems with the terms and definitions and even official recommendations introduce artificial and incorrect mechanical constructs to justify arbitrary and inappropriate terms. These terminology problems lead to further confusion and misinterpretations rather than to standardisation of mechanically correct nomenclature and accurate interpretation of joint loading. The perspective in this paper exposes some of the flawed foundational premises of these constructs and makes recommendations for accurate reporting of inverse dynamics outcomes and musculoskeletal loading. The inverse dynamics approach is based on free body diagrams that include the actual forces as applied ('Actual Forces' approach) or the replacement of actual forces with an equivalent resultant force and moment ('Resultant Moments' approach). Irrespective of the approach used to model the muscle and other forces, the inverse dynamics outputs always include the joint reaction forces representing the interactions with adjacent segments. The different terms suggested to distinguish the calculated joint reaction forces from the two approaches such as 'net joint force', 'resultant force', 'intersegmental force' and 'bone-on-bone force' are inappropriate, misleading and confusing. It is recommended to refer to joint reaction forces as Total or Partial when using an Actual Forces or a Resultant Moments approach, respectively.

Assessing the reliability of biomechanical variables during a horizontal deceleration task in healthy adults

Horizontal deceleration technique is an underpinning factor to musculoskeletal injury risk and performance in multidirectional sport. This study primarily assessed within- and between-session reliability of biomechanical and performance-based aspects of a horizontal deceleration technique and secondarily investigated the effects of limb dominance on reliability. Fifteen participants completed four horizontal decelerations on each leg during test and retest sessions. A three-dimensional motion analysis system was used to collect kinetic and kinematic data. Completion time, ground contact time, rate of horizontal deceleration, minimum centre of mass height, peak eccentric force, impulse ratio, touchdown distance, sagittal plane foot and knee angles at initial contact, maximum sagittal plane thorax angle, and maximum knee flexion moment were assessed. Coefficients of variation (COV) and intraclass correlation coefficients (ICC) were used to assess within- and between-session reliability, respectively. Seven variables showed "great" within-session reliability bilaterally (COV ≤9.13%). ICC scores were 'excellent' (≥0.91; n = 4), or 'good' (0.76-0.89; n = 7), bilaterally. Limb dominance affected five variables; three were more reliable for the dominant leg. This horizontal deceleration task was reliable for most variables, with little effect of limb dominance on reliability. This deceleration task may be reliably used to assess and track changes in deceleration technique in healthy adults.

Scientific writing in physiology: confused/misused terms and phrases

One aspect of effective scientific writing in physiology is the ability to select the correct words or short phrases to use when developing your narratives. This task is made difficult because many commonly used terms have seemingly viable alternatives, leading to confusion, uncertainty, and possible misuse of those words and phrases. In this perspective, we attempt to provide general guidance when selecting between or among options for commonly confused and misused terms in scientific writing. We have organized inaccurate, confusing, commonly misused, and misleading words and phrases into separate tables categorized as general language, demographic descriptors, general science, physiological sciences, and exercise physiology. Our modest hope is that the current perspective facilitates effective writing and encourages discussion regarding the importance of clarity in writing.

The intensity of a resistance exercise session can be quantified by the work rate of exercise

PURPOSE

Athletes regularly perform resistance training, yet it is unknown how best to monitor its intensity. This study compared different resistance exercise intensity metrics to determine their sensitivity to manipulating work rate (via altering inter-set rest and load).

METHODS

Following baseline testing for 10- and 3-repetition maximum (RM; squat and bench press), fourteen trained participants completed four volume-matched protocols in a randomised order: 3x10 with 85% 10RM, 60 s rest (3x1060s); 3x10 with 85% 10RM, 180 s (3x10180s); 8x3 with 85% 3RM, 120 s (8x3120s); 8x3 with 85% 3RM, 300 s (8x3300s). Internal intensity was quantified via rate of oxygen consumption ([Formula: see text]), heart rate, blood lactate concentration, and rating of perceived exertion (RPE). External intensity was assessed via previously developed "Training-Intensity" (TI) and "Intensity-Index" (II) metrics, and from exercise work rate (expressed as kg∙min-1 and joules∙min-1).

RESULTS

Internal intensity and work-rate metrics were highest for 3x1060s, followed by 3x10180s, 8x3120s and 8x3300s (p≤0.027). TI and II were higher for 8x3 than 3x10 protocols (p<0.001), but not different within these configurations. Internal intensity measures were more strongly correlated with work rate (r = 0.37-0.96) than TI and II (r = -0.42-0.33) metrics.

CONCLUSIONS

Work rate corroborated objective internal intensity metrics during resistance exercise, with the highest work rate session (3x1060s) also eliciting greater RPE scores than other protocols. In contrast, the TI and II did not agree with other intensity measures, likely because they do not consider rest periods. Practitioners can plan for the physiological and perceptual demands of resistance training by estimating work rate.

Network Meta-analysis of Combined Strength and Power Training for Countermovement Jump Height

Combined strength and power training in a training program is considered to improve the vertical jump, which is frequently quantified using the countermovement jump height. It is not yet clear whether one of the different training set structures, such as complex training, contrast training, compound training and traditional training, is superior to another. The aim of this review is to describe and assess the comparative effects of the set structures on countermovement jump height in healthy subjects. A systematic review and network meta-analysis (NMA) was conducted in accordance with Preferred Reporting Items for Systematic Reviews and Meta-Analyses for Network Meta-Analyses. Three databases were systematically searched. Risk of bias was assessed using the Risk of Bias 2 tool. NMAs were performed using a random-effects model. Twenty-four studies were included. All interventions were superior to control (no intervention) with mean differences ranging from 2.87 [95% confidence interval (CI): 1.99 to 3.74] for complex training to 3.43 (95% CI: 2.61 to 4.26) for traditional training. None of the training interventions were superior compared to each other in strength and/or power trained subjects, as well as in non-strength and/or power trained subjects. The findings support the combination of strength and power training to improve countermovement jump height.

Toward a New Conceptual Approach to "Intensity" in Soccer Player's Monitoring: A Narrative Review

ABSTRACT

Pillitteri, G, Clemente, FM, Petrucci, M, Rossi, A, Bellafiore, M, Bianco, A, Palma, A, and Battaglia, G. Toward a new conceptual approach to "intensity" in soccer player's monitoring: A narrative review. J Strength Cond Res 37(9): 1896-1911, 2023-In the last decade, monitoring physiological and match-related demands in soccer has become an increasingly common practice in sports sciences. One of the great challenges during monitoring process is the identification of key indicators that permit to generalize evidence and sustain decision-making process during training prescription. Actually, one of the major debates in the scientific community and among practitioners is the identification of the "intensity" concept. Defining a given training session or exercise based on "intensity" is difficult due to the fact that a huge amount of indicators are available (related both to the performed activities and to the athletes' psychophysiological responses). These indicators can lead to specific outcomes with different interpretations. The current narrative review aims to discuss the different measures approaches used in soccer to describe the intensity for both internal and external demands. In addition, a second purpose of this review is to propose general recommendations for combining intensity indicators with the aim of defining an overall intensity score of a training session or drill.

The Addition of Sprint Interval Training to Field Lacrosse Training Increases Rate of Torque Development and Contractile Impulse in Female High School Field Lacrosse Players

Field lacrosse requires sudden directional changes and rapid acceleration/deceleration. The capacity to perform these skills is dependent on explosive muscle force production. Limited research exists on the potential of sprint interval training (SIT) to impact explosive muscle force production in field lacrosse players. The purpose of this study is to examine SIT, concurrent to field-lacrosse-specific training, on the rate of torque development (RTD), contractile impulse, and muscle function in female high school field lacrosse players (n = 12; 16 ± 1 yrs.). SIT was performed three times per week, concurrent to field-lacrosse-specific training, for 12 weeks. Right lower-limb muscle performance was assessed pre-, mid-, and post-SIT training via isometric and isokinetic concentric knee extensor contractions. Outcomes included RTD (Nm·s^-1), contractile impulse (Nm·s), and peak torque (Nm). RTD for the first 50 ms of contraction improved by 42% by midseason and remained elevated at postseason (p = 0.004, effect size (ES) = -577.3 to 66.5). Contractile impulse demonstrated a training effect across 0-50 ms (42%, p = 0.004, ES = -1.4 to 0.4), 0-100 ms (33%, p = 0.018, ES = 3.1 to 0.9), and 0-200 ms (22%, p = 0.031, ES = -7.8 to 1.6). Isometric (0 rad·s^-1) and concentric (3.1 rad·s^-1) strength increased by 20% (p = 0.002, ES = -60.8 to -20.8) and 9% (p = 0.038, ES = -18.2 to 0.0) from SIT and field-lacrosse-specific training, respectively (p < 0.05). SIT, concurrent to field-lacrosse-specific training, enhanced lower-limb skeletal muscle performance, which may enable greater sport-specific gains.

Estimation of horizontal running power using foot-worn inertial measurement units

Feedback of power during running is a promising tool for training and determining pacing strategies. However, current power estimation methods show low validity and are not customized for running on different slopes. To address this issue, we developed three machine-learning models to estimate peak horizontal power for level, uphill, and downhill running using gait spatiotemporal parameters, accelerometer, and gyroscope signals extracted from foot-worn IMUs. The prediction was compared to reference horizontal power obtained during running on a treadmill with an embedded force plate. For each model, we trained an elastic net and a neural network and validated it with a dataset of 34 active adults across a range of speeds and slopes. For the uphill and level running, the concentric phase of the gait cycle was considered, and the neural network model led to the lowest error (median ± interquartile range) of 1.7% ± 12.5% and 3.2% ± 13.4%, respectively. The eccentric phase was considered relevant for downhill running, wherein the elastic net model provided the lowest error of 1.8% ± 14.1%. Results showed a similar performance across a range of different speed/slope running conditions. The findings highlighted the potential of using interpretable biomechanical features in machine learning models for the estimating horizontal power. The simplicity of the models makes them suitable for implementation on embedded systems with limited processing and energy storage capacity. The proposed method meets the requirements for applications needing accurate near real-time feedback and complements existing gait analysis algorithms based on foot-worn IMUs.

Career-Best Changes in Body Mass and Physical Fitness Test Performance Among Division 1 College Football Players Encompassing 28 Years at the Same Institution

ABSTRACT

Baur, DA, Johnson, JB, Giron-Molina, LG, Caterisano, M, Shaner, C, Caterisano, A, and Gentry, M. Career-best changes in body mass and physical fitness test performance among Division 1 college football players encompassing 28 years at the same institution. J Strength Cond Res 37(4): 806-815, 2023-Understanding typical changes induced by collegiate American football strength and conditioning programs is essential for optimizing program design and athletic development. The purpose of the study was to evaluate body mass and physical fitness test performance changes at a Division 1 program with 28 years of coaching stability. Initial and personal record results were collected from 1,102 players who were subdivided into 3 position groups: combination players (COMBO), skill players (SKILL), and line of scrimmage players. Players followed a linear periodized training program with biannual body mass and performance testing. Tested variables included body mass, strength (bench press, back squat, and front squat), impulse (power clean, push jerk, and vertical jump [VJ]), and speed/agility (10-yard dash [10YD], 40-yard dash, and 20-yard shuttle). The fixed effect of time and position group on the dependent variables was assessed using linear mixed models. If appropriate, post hoc tests using the estimated marginal means were used to evaluate the source of any significant effects. Significance was accepted as p < 0.05. Normative values were produced by descriptive statistics (i.e., weighted means). All players and position groups increased/improved across all tested variables ( p < 0.05). Improvements were 8.2%, 11.9-18.3%, 13.5-17.5%, and 3.6-6.0% for body mass, strength, impulse, and speed/agility, respectively. Line of scrimmage improvements were absolutely larger across most tested variables and relatively larger for back squat, VJ, and 10YD vs. SKILL and with VJ vs. COMBO/SKILL ( p < 0.05). These results reveal typical expectations for 4-5 years performance improvements and that position group differences in trainability may influence game readiness and training needs.

Relationships between External, Wearable Sensor-Based, and Internal Parameters: A Systematic Review

Micro electro-mechanical systems (MEMS) are used to record training and match play of intermittent team sport athletes. Paired with estimates of internal responses or adaptations to exercise, practitioners gain insight into players' dose-response relationship which facilitates the prescription of the training stimuli to optimize performance, prevent injuries, and to guide rehabilitation processes. A systematic review on the relationship between external, wearable-based, and internal parameters in team sport athletes, compliant with the PRISMA guidelines, was conducted. The literature research was performed from earliest record to 1 September 2020 using the databases PubMed, Web of Science, CINAHL, and SportDISCUS. A total of 66 full-text articles were reviewed encompassing 1541 athletes. About 109 different relationships between variables have been reviewed. The most investigated relationship across sports was found between (session) rating of perceived exertion ((session-)RPE) and PlayerLoad™ (PL) with, predominantly, moderate to strong associations (r = 0.49-0.84). Relationships between internal parameters and highly dynamic, anaerobic movements were heterogenous. Relationships between average heart rate (HR), Edward's and Banister's training impulse (TRIMP) seem to be reflected in parameters of overall activity such as PL and TD for running-intensive team sports. PL may further be suitable to estimate the overall subjective perception. To identify high fine-structured loading-relative to a certain type of sport-more specific measures and devices are needed. Individualization of parameters could be helpful to enhance practicality.

Bilateral index, power, force, and velocity during bench press with different loads in male handball players

Bilateral index for upper limbs was determined for maximal force, speed and power in 18 male handball players. Variables were individually assessed with a functional electromechanical dynamometer during unilateral and bilateral bench press push-off for 40%, 60%, and 75% of the maximal isometric force. Limb dominance (symmetry indices) and load effects in the bilateral index were analysed. Bilateral index showed a bilateral deficit for power (range = -8.50 to -41.48) and velocity (range = -11.15 to -38.41), that increases with the load (p < 0.05). For maximum force, a bilateral facilitation (range = 2.26-5.57), which did not vary significantly as a function of load, was observed. Symmetry indices showed no association with the bilateral index (40% load: r = 0.45, 60% load: r = 0.05, 75% load: r = 0.39). These results contribute to understanding the phenomenon; however, individual-to-individual observation reflects that caution should be kept when assessing an individual athlete. In conclusion, bilateral deficit or facilitation for bench press depends on the variable considered, whereas its magnitude depends on the load. Moreover, limb dominance does not affect it. This finding must be regarded as a general trend, but a different situation may occur during the assessment of a particular athlete.

Methodological considerations for determining the volume and intensity of drop jump training. A systematic, critical and prepositive review

This systematic review provides critical and propositional information on criteria for determining the volume and intensity of drop jumps during plyometric training programs. Eligibility criteria were defined according to PICOS: Participants: male or female athletes, trained or recreationally active (16-40 years). Intervention duration: more than 4 weeks.

COMPARATORS

passive or active control group during a plyometric training program.

OUTCOMES

information on improvement with Drop Jump or Depth Jump, with other jumps, acceleration, sprint, strength, and power output.

DESIGN

randomized controlled trials. We searched articles published in PubMed, SPORTDiscus, Web of Science, and Scopus. The search was conducted until 10 September 2022 for English-language articles only. The risk of bias was assessed using Grading of Recommendations, Assessment, Development and Evaluation (GRADE) for randomized controlled studies. We identified 31495 studies, of which only 22 were included. We found that six groups presented results with women, 15 presented results with men, and the remaining four presented mixed studies. Of the 686 people recruited, 329 participants aged 25.79 ± 4.76 years were involved in training. Methodological problems in training intensity, volume distribution, and individualization were noted, but methodological recommendations for their solution are also provided. It is concluded that the drop height should not be understood as the intensity determinant of plyometric training. Intensity is determined by ground reaction forces, power output, and jump height, among other factors. Furthermore, the athletes' experience level selection should be based on the formulas recommended within this research. These results could be helpful for those who intend to conduct new plyometric training programs and research.

Assessment of the Speed and Power of Push-Ups Performed on Surfaces with Different Degrees of Instability

(I) Training in unstable conditions, with different elements, platforms, or situations, has been used because there is a significant increase in muscle activation, balance, proprioception, and even sports performance. However, it is not known how the devices used are classified according to performance variables, nor the differences according to instability experience. (II) This study aims to analyze the differences in power and speed in push-ups with different situations of instability in trained and untrained male subjects. Power and speed in push-up exercise were analyzed in 26 untrained and 25 trained participants in 6 different situations (one stable and five unstable) (1) stable (PS), (2) monopodal (PM), (3) rings (PR), (4) TRX^® (PT), (5) hands-on Bosu^® (PH) (6) feet on Bosu^® (PF). The variables were analyzed using a linear position transducer. (III) The best data were evidenced with PS, followed by PR, PM, PT, PH and PF. The trained subjects obtained better results in all the conditions analyzed in mean and maximum power and speed values (p < 0.001). The decrease in these variables was significantly greater in the untrained subjects than in the trained subjects in the PR situation (8% and 18% respectively). In PF there were differences between groups (p < 0.001), reaching between 32-46% in all variables. The difference between the two groups was notable, varying between 12-58%. (IV) The results showed a negative and progressive influence of instability on power and speed in push-ups. This suggests that instability should be adapted to the subject's experience and is not advisable in untrained subjects who wish to improve power.

Quantifying CrossFit®: Potential solutions for monitoring multimodal workloads and identifying training targets

The design of high-intensity functional training (HIFT; e. g., CrossFit^®) workouts and targeted physiological trait(s) vary on any given training day, week, or cycle. Daily workouts are typically comprised of different modality and exercise combinations that are prescribed across a wide range of intensities and durations. The only consistent aspect appears to be the common instruction to maximize effort and workout density by either completing "as many repetitions as possible" within a time limit (e.g., AMRAP, Tabata) or a list of exercises as quickly as possible. However, because effort can vary within and across workouts, the impact on an athlete's physiology may also vary daily. Programming that fails to account for this variation or consider how targeted physiological systems interrelate may lead to overuse, maladaptation, or injury. Athletes may proactively monitor for negative training responses, but any observed response must be tied to a quantifiable workload before meaningful changes (to programming) are possible. Though traditional methods exist for quantifying the resistance training loads, gymnastic movements, and cardiorespiratory modalities (e.g., cycling running) that might appear in a typical HIFT workout, those methods are not uniform, and their meaning will vary based on a specific exercise's placement within a HIFT workout. To objectively quantify HIFT workloads, the calculation must overcome differences in measurement standards used for each modality, be able to account for a component's placement within the workout and be useful regardless of how a workout is commonly scored (e.g., repetitions completed vs. time-to-completion) so that comparisons between workouts are possible. This review paper discusses necessary considerations for quantifying various HIFT workout components and structures, and then details the advantages and shortcomings of different methods used in practice and the scientific literature. Methods typically used in practice range from being excessively tedious and not conducive for making comparisons within or across workouts, to being overly simplistic, based on faulty assumptions, and inaccurate. Meanwhile, only a few HIFT-related studies have attempted to report relevant workloads and have predominantly relied on converting component and workout performance into a rate (i.e., repetitions per minute or second). Repetition completion rate may be easily and accurately tracked and allows for intra- and inter-workout comparisons. Athletes, coaches, and sports scientists are encouraged to adopt this method and potentially pair it with technology (e.g., linear position transducers) to quantify HIFT workloads. Consistent adoption of such methods would enable more precise programming alterations, and it would allow fair comparisons to be made between existing and future research.

The soccer season: performance variations and evolutionary trends

The physiological demands of soccer challenge the entire spectrum of the response capacity of the biological systems and fitness requirements of the players. In this review we examined variations and evolutionary trends in body composition, neuromuscular and endurance-related parameters, as well as in game-related physical parameters of professional players. Further, we explore aspects relevant for training monitoring and we reference how different training stimulus and situational variables (e.g., competition exposure) affect the physiological and performance parameters of players. Generally, improvements of small magnitude in non- (non-CMJ) and countermovement-based jumps (CMJBased) and in the sprint acceleration (ACCPhase) and maximal velocity phase (MVPhase) are observed from start of preparation phase (PPS) to beginning of competition phase (BCP). A greater magnitude of increases is observed in physiological and endurance performance measures within this period; moderate magnitude in sub-maximal intensity exercise (velocity at fixed blood lactate concentrations; V2-4mmol/l) and large magnitude in VO2max, maximal aerobic speed (MAS) and intense intermittent exercise performance (IE). In the middle of competition phase (MCP), small (CMJBased and ACCPhase), moderate (non-CMJ; MVPhase; VO2max; sub-maximal exercise) and large (MAS and IE) improvements were observed compared to PPS. In the end of competition period (ECP), CMJBased and MVPhase improve to a small extent with non-CMJ, and ACCPhase, VO2max, MAS, sub-maximal intensity exercise and IE revealing moderate increments compared to PPS. Although less investigated, there are generally observed alterations of trivial magnitude in neuromuscular and endurance-related parameters between in-season assessments; only substantial alterations are examined for IE and sub-maximal exercise performance (decrease and increase of small magnitude, respectively) from BCP to MCP and in VO2max and IE (decrements of small magnitude) from MCP to ECP. Match performance may vary during the season. Although, the variability between studies is clear for TD, VHSR and sprint, all the studies observed substantial increments in HSR between MCP and ECP. Finally, studies examining evolutionary trends by means of exercise and competition performance measures suggests of a heightened importance of neuromuscular factors. In conclusion, during the preseason players "recover" body composition profile and neuromuscular and endurance competitive capacity. Within in-season, and more robustly towards ECP, alterations in neuromuscular performance seem to be force-velocity dependent, and in some cases, physiological determinants and endurance performance may be compromised when considering other in-season moments. Importantly, there is a substantial variability in team responses that can be observed during in-season. Consequently, this informs on the need to both provide a regular training stimulus and adequate monitorization throughout the season.

Impact of maximal strength training on countermovement jump phase characteristics in athletes with cerebral palsy

Analysis of the countermovement jump (CMJ) force-time curve phases provides insight into athlete neuromuscular function and methods by which jump height improves in response to training. A CMJ phase analysis and the dynamic strength index (DSI) have yet to be explored in athletes with cerebral palsy (CP). This study aimed to address this knowledge gap. Eleven state- to international-level athletes with CP completed a pre-post maximal strength training intervention with waitlist control. CMJ was assessed via force plate pre/post baseline and after the 12-week intervention. Following the intervention, CMJ height, takeoff velocity, and concentric phase peak and mean force, impulse and mean acceleration improved significantly (p = 0.006-0.001). No changes were observed in any eccentric braking phase variable (p = 0.79-0.13), while DSI lowered (p = 0.03). In athletes with CP, strength training increased CMJ concentric phase peak and mean force and impulse, increasing velocity and acceleration and therefore jump height. DSI lowered due to moderate and small increases in isometric mid-thigh pull and CMJ peak force, respectively. Unlike in non-disabled athletes, strength training did not alter any eccentric phase variable; therefore, other modalities may be required to further optimize jumping performance in athletes with CP.

Toward a New Paradigm in Resistance Training by Means of Velocity Monitoring: A Critical and Challenging Narrative

For more than a century, many concepts and several theories and principles pertaining to the goals, organization, methodology and evaluation of the effects of resistance training (RT) have been developed and discussed between coaches and scientists. This cumulative body of knowledge and practices has contributed substantially to the evolution of RT methodology. However, a detailed and rigorous examination of the existing literature reveals many inconsistencies that, unless resolved, could seriously hinder further progress in our field. The purpose of this review is to constructively expose, analyze and discuss a set of anomalies present in the current RT methodology, including: (a) the often inappropriate and misleading terminology used, (b) the need to clarify the aims of RT, (c) the very concept of maximal strength, (d) the control and monitoring of the resistance exercise dose, (e) the existing programming models and (f) the evaluation of training effects. A thorough and unbiased examination of these deficiencies could well lead to the adoption of a revised paradigm for RT. This new paradigm must guarantee a precise knowledge of the loads being applied, the effort they involve and their effects. To the best of our knowledge, currently this can only be achieved by monitoring repetition velocity during training. The main contribution of a velocity-based RT approach is that it provides the necessary information to know the actual training loads that induce a specific effect in each athlete. The correct adoption of this revised paradigm will provide coaches and strength and conditioning professionals with accurate and objective information concerning the applied load (relative load, level of effort and training effect). This knowledge is essential to make rational and informed decisions and to improve the training methodology itself.

Within Session Exercise Sequencing During Programming for Complex Training: Historical Perspectives, Terminology, and Training Considerations

The primary aim of this narrative review was to outline the historical genesis of resistance training strategies that incorporate high-load, low-velocity exercises and low-load, high-velocity exercises in the same training session allowing for different "exercise sequences" to be simultaneously implemented. Discrepancies between scientific works and the terminology used within contemporary sport science publications are identified. Upon review of the literature, we propose "complex training" to be considered an umbrella term with 4 different implementations, generally used to indicate a method in which movement velocity or load is altered between sets and/or exercises within the same session with the aim of improving slow and fast force expression. We propose the following terminology for said implementations: contrast training-exercise sequence with alternating high-load and low-load (higher-velocity) exercises in a set-by-set fashion within the same session (corresponding with 'contrast pairs' and 'intra-contrast rest'); descending training-several sets of high-load (e.g., back squat) exercises completed before the execution of several sets of low-load, higher-velocity (e.g., vertical jump) exercises within the same session; ascending training-several sets of low-load, higher-velocity exercises completed before several sets of high-load exercises within the same session; and French contrast training-subset of contrast training in which a series of exercises are performed in sequence within a single session: heavy compound exercise, plyometric exercise, light-to-moderate load compound exercise that maximises movement speed (i.e., external power), and a plyometric exercise (often assisted). Finally, practical applications and training considerations are presented.

The Role of Strength on Punch Impact Force in Boxing

ABSTRACT

Beattie, K and Ruddock, AD. The role of strength on punch impact force in boxing. J Strength Cond Res XX(X): 000-000, 2022-The ability to punch with a high impact force is beneficial to boxers as there is an increased likelihood of success. Punch impact force differentiates between performance level, weight class, gender, and punch type in competitive boxers. Although technique is likely to play a major role in punch impact force, the capabilities of the neuromuscular system may also be a limiting factor. This review examines the role of strength on punch impact force in amateur and professional boxers. The maximal strength qualities of the lower body, as well as explosive strength qualities of both the upper and lower body, are largely associated with punch impact force in elite amateur boxers. Specifically, elite amateur boxers who punch with "high" impact forces have greater levels of lower-body maximal strength and explosive strength when compared with elite amateurs who punch with "low" impact forces. However, the maximal strength capabilities of the upper body are not associated with punch impact force and does not differentiate between elite boxers who punch with "high" and "low" impact forces. Therefore, based off the present evidence, this review recommends that for boxers who aim to develop their punch impact force, it may be advantageous to emphasize both maximal and explosive strength development of the legs, with only an explosive strength focus in the upper body. However, it is important to highlight that, to date, there are a lack of experimental studies in both elite amateur and professional boxing. Furthermore, there is a dearth of research in female boxing. Future experimental studies are needed to infer causality regarding the role that strength training has on punch impact force in both elite amateur and professional boxers.

Relationships between highly skilled golfers' clubhead velocity and kinetic variables during a countermovement jump

Previous research has sought to establish the relationship countermovement jump (CMJ) performance has with clubhead velocity (CHV). However, these investigations either assessed lower skilled golfers, or utilised field-based protocols, which are unable to assess a number of biomechanical variables. Fifty highly skilled golfers performed CMJs on Kistler force platforms in laboratory conditions. The CMJ variables included positive impulse, net impulse, average power, peak power, peak force, force at zero velocity and jump height. Clubhead velocity was measured using a TrackMan 3e launch monitor at a driving range. A Pearsons correlation was employed to measure the strength and direction of the relationships between CHV and CMJ derived performance variables. Results indicated strong positive relationships (all p's <0.001) between CHV and positive impulse (r = 0.695), net impulse (r = 0.689), average power (r = 0.645), peak power (r = 0.656), peak force (r = 0.517) and force at zero velocity (r = 0.528) with no significant relationship with jump height. However, if investigators only have access to field-based protocols, it is recommended that they measure jump height and utilise inverse dynamics to calculate take-off velocity. By multiplying take-off velocity by mass, this allows the attainment of net impulse.

Submaximal Fitness Tests in Team Sports: A Theoretical Framework for Evaluating Physiological State

Team-sports staff often administer non-exhaustive exercise assessments with a view to evaluating physiological state, to inform decision making on athlete management (e.g., future training or recovery). Submaximal fitness tests have become prominent in team-sports settings for observing responses to a standardized physical stimulus, likely because of their time-efficient nature, relative ease of administration, and physiological rationale. It is evident, however, that many variations of submaximal fitness test characteristics, response measures, and monitoring purposes exist. The aim of this scoping review is to provide a theoretical framework of submaximal fitness tests and a detailed summary of their use as proxy indicators of training effects in team sports. Using a review of the literature stemming from a systematic search strategy, we identified five distinct submaximal fitness test protocols characterized in their combinations of exercise regimen (continuous or intermittent) and the progression of exercise intensity (fixed, incremental, or variable). Heart rate-derived indices were the most studied outcome measures in submaximal fitness tests and included exercise (exercise heart rate) and recovery (heart rate recovery and vagal-related heart rate variability) responses. Despite the disparity between studies, these measures appear more relevant to detect positive chronic endurance-oriented training effects, whereas their role in detecting negative transient effects associated with variations in autonomic nervous system function is not yet clear. Subjective outcome measures such as ratings of perceived exertion were less common in team sports, but their potential utility when collected alongside objective measures (e.g., exercise heart rate) has been advocated. Mechanical outcome measures either included global positioning system-derived locomotor outputs such as distance covered, primarily during standardized training drills (e.g., small-sided games) to monitor exercise performance, or responses derived from inertial measurement units to make inferences about lower limb neuromuscular function. Whilst there is an emerging interest regarding the utility of these mechanical measures, their measurement properties and underpinning mechanisms are yet to be fully established. Here, we provide a deeper synthesis of the available literature, culminating with evidence-based practical recommendations and directions for future research.

Contextual considerations using the 'control-chaos continuum' for return to sport in elite football - Part 1: Load planning

The 'control-chaos continnum' is an adaptable framework developed to guide the on-pitch rehabilitation process in elite football. One of the key objectives of the continuum is to progressively return players to their preinjury chronic running load, while incorporating the qualitative aspects of movement and cognitive stresses integral to competitive match-play. Whilst injury and player-specific considerations are key to an individualised rehabilitation approach, a host of contextual factors also play an important role in return to sport (RTS) planning. In this article, we highlight some key intrinsic and extrinsic contextual factors for the practitioner to consider in the RTS planning process to help mitigate reinjury risk upon a return to team training. While a return to chronic running load is generally a critical component of the framework, we highlight circumstances in elite football where it is a less relevant factor in RTS decision-making.

Power profiling and the power-duration relationship in cycling: a narrative review

Emerging trends in technological innovations, data analysis and practical applications have facilitated the measurement of cycling power output in the field, leading to improvements in training prescription, performance testing and race analysis. This review aimed to critically reflect on power profiling strategies in association with the power-duration relationship in cycling, to provide an updated view for applied researchers and practitioners. The authors elaborate on measuring power output followed by an outline of the methodological approaches to power profiling. Moreover, the deriving a power-duration relationship section presents existing concepts of power-duration models alongside exercise intensity domains. Combining laboratory and field testing discusses how traditional laboratory and field testing can be combined to inform and individualize the power profiling approach. Deriving the parameters of power-duration modelling suggests how these measures can be obtained from laboratory and field testing, including criteria for ensuring a high ecological validity (e.g. rider specialization, race demands). It is recommended that field testing should always be conducted in accordance with pre-established guidelines from the existing literature (e.g. set number of prediction trials, inter-trial recovery, road gradient and data analysis). It is also recommended to avoid single effort prediction trials, such as functional threshold power. Power-duration parameter estimates can be derived from the 2 parameter linear or non-linear critical power model: P(t) = W′/t + CP (W′—work capacity above CP; t—time). Structured field testing should be included to obtain an accurate fingerprint of a cyclist’s power profile.

Misuse of the term 'load' in sport and exercise science

Despite the International System of Units (SI), as well as several publications guiding researchers on correct use of terminology, there continues to be widespread misuse of mechanical terms such as 'work' in sport and exercise science. A growing concern is the misuse of the term 'load'. Terms such as 'training load' and 'PlayerLoad' are popular in sport and exercise science vernacular. However, a 'load' is a mechanical variable which, when used appropriately, describes a force and therefore should be accompanied with the SI-derived unit of the newton (N). It is tempting to accept popular terms and nomenclature as scientific. However, scientists are obliged to abide by the SI and must pay close attention to scientific constructs. This communication presents a critical reflection on the use of the term 'load' in sport and exercise science. We present ways in which the use of this term breaches principles of science and provide practical solutions for ongoing use in research and practice.

A systematic review of resistance training methodologies for the development of lower body concentric mean power, peak power, and mean propulsive power in team-sport athletes

This study aimed to systematically review training methods prescribed to develop lower-body power, determine their effectiveness for the development of lower-body mechanical power and their implementation in an annual training cycle amongst team-sport athletes. The absolute and relative outcome values of concentric mean power, peak power and mean propulsive power were extracted from 19 studies. Outcomes were assessed using baseline to post intervention percent change, effect sizes, and the level of evidence concerning the method's effectiveness. A thorough analysis of the literature indicated that, based on the high level of evidence, traditional (e.g., strength training alone) and combination training (e.g., complex and contrast) methods should be considered. Further, optimal load and velocity-based training can be implemented if coaches have access to the appropriate equipment to monitor movement velocity and mechanical power in every session. This is of particular importance in periods of the season where high volumes of technical-tactical training and congested fixture periods are present. Also, flywheel, eccentric overload and weightlifting methods have been shown to be effective although the level of evidence is low. Future research should expand on current training practices whilst adequately reporting actual training loads from sport-specific training and games alongside strength-power training protocols.

Strengthening the Case for Cluster Set Resistance Training in Aged and Clinical Settings: Emerging Evidence, Proposed Benefits and Suggestions

Resistance training (RT) is a fundamental component of exercise prescription aimed at improving overall health and function. RT techniques such as cluster set (CS) configurations, characterized by additional short intra-set or inter-repetition rest intervals, have been shown to maintain acute muscular force, velocity, and 'power' outputs across a RT session, and facilitate positive longer-term neuromuscular adaptations. However, to date CS have mainly been explored from a human performance perspective despite potential for application in health and clinical exercise settings. Therefore, this current opinion piece aims to highlight emerging evidence and provide a rationale for why CS may be an advantageous RT technique for older adults, and across several neurological, neuromuscular, cardiovascular and pulmonary settings. Specifically, CS may minimize acute fatigue and adverse physiologic responses, improve patient tolerance of RT and promote functional adaptations (i.e., force, velocity, and power). Moreover, we propose that CS may be a particularly useful exercise rehabilitation technique where injury or illness, persistent fatigue, weakness and dysfunction exist. We further suggest that CS offer an alternative RT strategy that can be easily implemented alongside existing exercise/rehabilitation programs requiring no extra cost, minimal upskilling and/or time commitment for the patient and professional. In light of the emerging evidence and likely efficacy in clinical exercise practice, future research should move toward further direct investigation of CS-based RT in a variety of adverse health conditions and across the lifespan given the already demonstrated benefits in healthy populations.

Relationships among countermovement vertical jump performance metrics, strategy variables, and inter-limb asymmetry in females

Dependent variables commonly studied during countermovement vertical jump (CMVJ) tests largely stem from male-only studies despite females'distinct energy storage and reutilisation strategies. This could limit progress among females seeking increased CMVJ performance through targeted changes in certain variables. We explored relationships between CMVJ performance metrics (jump height, modified reactive strength index, jump power, and takeoff momentum) and (a) temporal and force application variables and (b) inter-limb force and yank (i.e., rate of force development) asymmetry in 31 recreationally active females. Participants performed eight CMVJs while ground reaction force (GRF) data were obtained. Pearson product-moment correlation coefficients assessed the strength and direction of the associations. Twenty-six significant relationships (r ≥ ±0.357; p < 0.05) were detected across the CMVJ performance variables. The significantly correlated variables were generally isolated to only one of the four performance metrics. Only the percentage of concentric phase inter-limb force asymmetry was significantly associated with CMVJ performance, specifically jump power and takeoff momentum. Coaches and physical performance professionals should be aware of popular strategy variables' association or lack of association with commonly studied performance metrics when seeking to understand or improve specific CMVJ jumping abilities in females.

Effect of Barbell Load on Vertical Jump Landing Force-Time Characteristics

ABSTRACT

Lake, JP, Mundy, PD, Comfort, P, McMahon, JJ, Suchomel, TJ, and Carden, P. Effect of barbell load on vertical jump landing force-time characteristics. J Strength Cond Res 35(1): 25-32, 2021-The aim of this study was to quantify the effect that barbell load has on the jump height and force-time characteristics of the countermovement jump (CMJ). Fifteen strength-trained men (mean ± SD: age 23 ± 2 years, mass 84.9 ± 8.1 kg, and height 1.80 ± 0.05 m) performed 3 CMJs with no additional load, and with barbell loads of 25, 50, 75, and 100% of body mass on 2 force plates recording at 1,000 Hz. Propulsion and landing force-time characteristics were obtained from force-time data and compared using analysis of variance and effect sizes. Jump height decreased significantly as load increased (26-71%, d = 1.80-6.87). During propulsion, impulse increased with load up to 75% of body mass (6-9%, d = 0.71-1.08), mean net force decreased (10-43%, d = 0.50-2.45), and time increased (13-50%, d = 0.70-2.57). During landing, impulse increased as load increased up to 75% of body mass (5 to 12%, d = 0.54-1.01), mean net force decreased (13-38%, d = 0.41-1.24), and time increased (20-47%, d = 0.65-1.47). Adding barbell load to CMJ significantly decreases CMJ height. Furthermore, CMJ with additional barbell load increases landing phase impulse. However, while mean net force decreases as barbell load increases, landing time increases so that jumpers are exposed to mechanical load for longer. Practitioners should exercise caution when implementing loaded CMJ to assess their athletes.

Non-local Muscle Fatigue Effects on Muscle Strength, Power, and Endurance in Healthy Individuals: A Systematic Review with Meta-analysis

BACKGROUND

The fatigue of a muscle or muscle group can produce global responses to a variety of systems (i.e., cardiovascular, endocrine, and others). There are also reported strength and endurance impairments of non-exercised muscles following the fatigue of another muscle; however, the literature is inconsistent.

OBJECTIVE

To examine whether non-local muscle fatigue (NLMF) occurs following the performance of a fatiguing bout of exercise of a different muscle(s).

DESIGN

Systematic review and meta-analysis.

SEARCH AND INCLUSION

A systematic literature search using a Boolean search strategy was conducted with PubMed, SPORTDiscus, Web of Science, and Google Scholar in April 2020, and was supplemented with additional 'snowballing' searches up to September 2020. To be included in our analysis, studies had to include at least one intentional performance measure (i.e., strength, endurance, or power), which if reduced could be considered evidence of muscle fatigue, and also had to include the implementation of a fatiguing protocol to a location (i.e., limb or limbs) that differed to those for which performance was measured. We excluded studies that measured only mechanistic variables such as electromyographic activity, or spinal/supraspinal excitability. After search and screening, 52 studies were eligible for inclusion including 57 groups of participants (median sample = 11) and a total of 303 participants.

RESULTS

The main multilevel meta-analysis model including all effects sizes (278 across 50 clusters [median = 4, range = 1 to 18 effects per cluster) revealed a trivial point estimate with high precision for the interval estimate [- 0.02 (95% CIs = - 0.14 to 0.09)], yet with substantial heterogeneity (Q₍₂₇₇₎ = 642.3, p < 0.01), I² = 67.4%). Subgroup and meta-regression analyses showed that NLMF effects were not moderated by study design (between vs. within-participant), homologous vs. heterologous effects, upper or lower body effects, participant training status, sex, age, the time of post-fatigue protocol measurement, or the severity of the fatigue protocol. However, there did appear to be an effect of type of outcome measure where both strength [0.11 (95% CIs = 0.01-0.21)] and power outcomes had trivial effects [- 0.01 (95% CIs = - 0.24 to 0.22)], whereas endurance outcomes showed moderate albeit imprecise effects [- 0.54 (95% CIs = - 0.95 to - 0.14)].

CONCLUSIONS

Overall, the findings do not support the existence of a general NLMF effect; however, when examining specific types of performance outcomes, there may be an effect specifically upon endurance-based outcomes (i.e., time to task failure). However, there are relatively fewer studies that have examined endurance effects or mechanisms explaining this possible effect, in addition to fewer studies including women or younger and older participants, and considering causal effects of prior training history through the use of longitudinal intervention study designs. Thus, it seems pertinent that future research on NLMF effects should be redirected towards these still relatively unexplored areas.

The Implementation of Velocity-Based Training Paradigm for Team Sports: Framework, Technologies, Practical Recommendations and Challenges

While velocity-based training is currently a very popular paradigm to designing and monitoring resistance training programs, its implementation remains a challenge in team sports, where there are still some confusion and misinterpretations of its applications. In addition, in contexts with large squads, it is paramount to understand how to best use movement velocity in different exercises in a useful and time-efficient way. This manuscript aims to provide clarifications on the velocity-based training paradigm, movement velocity tracking technologies, assessment procedures and practical recommendations for its application during resistance training sessions, with the purpose of increasing performance, managing fatigue and preventing injuries. Guidelines to combine velocity metrics with subjective scales to prescribe training loads are presented, as well as methods to estimate 1-Repetition Maximum (1RM) on a daily basis using individual load–velocity profiles. Additionally, monitoring strategies to detect and evaluate changes in performance over time are discussed. Finally, limitations regarding the use of velocity of execution tracking devices and metrics such as “muscle power” are commented upon.

Jump Training in Rugby Union Players: Barbell or Hexagonal Bar?

ABSTRACT

Weakley, JJS, Till, K, Read, DB, Leduc, C, Roe, GAB, Phibbs, PJ, Darrall-Jones, J, and Jones, B. Jump training in rugby union players: barbell or hexagonal bar?. J Strength Cond Res 35(3): 754-761, 2021-The countermovement jump (CMJ) is an exercise that can develop athletic performance. Using the conventional barbell (BAR) and hexagonal barbell (HEX) while jumping, the intensity can be increased. However, the bar that provides greater adaptations is unknown. Therefore, this study aimed to assess changes in loaded and unloaded CMJ with either a BAR or HEX across a 4-week mesocycle in rugby union players. Twenty-nine subjects were strength-matched and randomized into 2 groups. Subjects completed 3 sets of CMJ at 20% of 1 repetition maximum back squat, 3 times per week for 4 weeks, using either a BAR or HEX. Subjects completed an unloaded CMJ on a force plate before and after, whereas the highest peak concentric velocity during the jump squat was recorded in the first and last training sessions using a linear position transducer. Magnitude-based inferences assessed meaningful changes within- and between-groups. Possibly greater improvements in unloaded CMJ were found in the HEX group in jump height (effect size ± 90% confidence intervals: 0.27 ± 0.27), relative peak (0.21 ± 0.23), and mean power (0.32 ± 0.36). In addition, likely to very likely greater improvements were observed in the HEX group in peak velocity (0.33 ± 0.27), relative mean power (0.53 ± 0.30), mean force (0.47 ± 0.27), and 100-ms impulse (0.60 ± 0.48). Similar raw changes in jump squat peak velocity occurred (0.20-0.25 m·s-1), despite the likely greater ES occurring with the BAR (0.32 ± 0.26). These results indicate that training with the HEX leads to superior unloaded CMJ adaptations. In addition, practitioners should use either the HEX or BAR when aiming to enhance loaded jump ability.

Relationship of Limb Lengths and Body Composition to Lifting in Weightlifting

Weightlifting is a discipline where technique and anthropometric characteristics are essential to achieve the best results in competitions. This study aims to analyse the relationships between body composition, limb length and barbell kinematics in the performance of weightlifters. It consists of an observational and descriptive study of 19 athletes (12 men [28.50 ± 6.37 years old; 84.58 ± 14.11 kg; 176.18 ± 6.85 cm] and 7 women [27.71 ± 6.34 years old; 64.41 ± 7.63 kg; 166.94 ± 4.11 cm]) who met the inclusion criteria. A level I anthropometrist took anthropometric measures according to the methodology of the International Society for the Advancement of Kinanthropometry (ISAK), and the measurement of the barbell velocity was made with the software Kinovea. In terms of body composition, both genders are within the percentage range of fat mass recommended for this sport. In female weightlifters, there is a positive correlation between foot length, maximal velocity in the Snatch (ρ = 0.775, p = 0.041), and performance indicator in the Snatch and the Clean & Jerk (ρ = 0.964, p < 0.001; ρ = 0.883, p = 0.008, respectively). In male weightlifters, a positive correlation between tibial length and average velocity of the barbell in the Snatch is observed (ρ = 0.848, p < 0.001). Muscle mass percentage correlates positively with performance indicator in both techniques (ρ = 0.634, p = 0.027; ρ = 0.720, p = 0.008). Also, the relative length of the upper limb is negatively correlated with the performance indicator (ρ = −0.602, p = 0.038). Anthropometry and body composition may facilitate skill acquisition among this sport population, contributing to increase the limited body of scientific knowledge related to weightlifting.

The Effects of Set Structure Manipulation on Chronic Adaptations to Resistance Training: A Systematic Review and Meta-Analysis

BACKGROUND

The acute effects of resistance training (RT) set structure alteration are well established; however, less is known about their effects on chronic training adaptations.

OBJECTIVE

The aim of this systematic review and meta-analysis was to synthesise the available evidence on the effectiveness of traditional (TS), cluster (CS) and rest redistribution (RR) set structures in promoting chronic RT adaptations, and provide an overview of the factors which might differentially influence the magnitude of specific training adaptations between set structure types.

METHODS

This review was performed using the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines encompassing the literature search of five databases. Studies in English that compared muscular strength, endurance, and/or hypertrophy adaptations, as well as vertical jump performance, velocity and power at submaximal loads and shifts in the slopes of force-velocity profiles between TS and CS or RR set structures (i.e., alternative set structures) were included. Risk of bias assessment was performed using a modified Cochrane Collaboration's tool for assessing risk of bias in randomised trials. Random-effects meta-analyses and meta-regressions were performed where possible.

RESULTS

17 studies met the inclusion criteria, none had more than one risk of bias item assessed as high risk. Pooled results revealed that none of the set structures were more effective at inducing strength (standardised mean difference (SMD) = - 0.06) or hypertrophy (SMD = - 0.03). TS were more effective at improving muscular endurance compared to alternative set structures (SMD = - 0.38), whereas alternative set structures tended to be more effective for vertical jump performance gains (SMD = 0.13), but this effect was not statistically significant (p = 0.190). Greater velocity and power outputs at submaximal loads (SMD = 0.18) were observed when using alternative set structures compared to TS. In addition, alternative set structures promoted greater shifts of the slope of force-velocity profiles towards more velocity dominant profiles compared to TS (SMD = 0.28). Sub-group analyses controlling for each alternative set structure independently showed mixed results likely caused by the relatively small number of studies available for some outcomes.

CONCLUSION

Modifying TS to an alternative set structure (CS or RR) has a negligible impact on strength and hypertrophy. Using CS and RR can lead to greater vertical jump performance, velocity and power at submaximal loads and shifts to more velocity dominant force-velocity profiles compared to training using TS. However, TS may provide more favourable effects on muscle endurance when compared to CS and RR. These findings demonstrate that altering TS to alternative set structures may influence the magnitude of specific muscular adaptations indicating set structure manipulation is an important consideration for RT program design.

PROTOCOL REGISTRATION

The original protocol was prospectively registered (CRD42019138954) with the PROSPERO (International Prospective Register of Systematic Reviews).

Improving the Signal-To-Noise Ratio When Monitoring Countermovement Jump Performance

ABSTRACT

Kennedy, RA and Drake, D. Improving the signal-to-noise ratio when monitoring countermovement jump performance. J Strength Cond Res 35(1): 85-90, 2021-Countermovement jump (CMJ) performance has been routinely used to monitor neuromuscular status. However, the protocol used to establish the criterion score is not well documented. The purpose of this study was to examine how the protocol used would influence of the sensitivity of CMJ variables in rugby union players. Fifteen male (age: 19.7 ± 0.5 years) rugby union players performed 8 CMJs on 2 occasions, separated by 7 days. The between-session coefficient of variation (CV) was calculated using 2 techniques for treating multiple trials, the average, and the trial with the best jump height (JH), and then compared with the smallest worthwhile change (SWC). The signal-to-noise ratio was measured as the group mean change in a variable divided by the CV. Using the average value across multiple trials is superior to the best trial method, based on lower CVs for all variables. Only the average performance across 6 or more trials was classified as ideal (CV < 0.5 × SWC) for peak velocity (PV). In addition, the signal-to-noise ratio for peak concentric power (PCP), PV, and JH were classified as good, irrespective of the treatment method. Although increasing the number of trials can reduce the random error, it may be pragmatic to simply take the average from 2 to 3 trials, facilitating a CV < SWC for PV, PCP, and JH. Due to its simplicity, JH may be considered the principal variable to monitor neuromuscular fatigue.

Relationship Between Tennis Serve Velocity and Select Performance Measures

ABSTRACT

Hayes, MJ, Spits, DR, Watts, DG, and Kelly, VG. Relationship between tennis serve velocity and select performance measures. J Strength Cond Res 35(1): 190-197, 2021-The purpose of this study was to determine whether there was a relationship between tennis serve speed and isometric midthigh pull (IMTP) kinetic variables: countermovement jump (CMJ) height, shoulder internal and external rotation strength, and anthropometric measures in elite adolescent tennis players. Twenty-one elite junior tennis players from the Tennis Australia National Academy were recruited for this study (male, n = 12 and female, n = 9). Correlations between the performance variables and peak tennis serve speed were calculated using a Pearson's product-moment correlation coefficient. A significant positive correlation was found between peak serve speed and body height (r = 0.80, p < 0.01), IMTP peak force (r = 0.87, p < 0.01), CMJ height (r = 0.77, p ≤ 0.01), and impulse at 300 ms (r = 0.71, p ≤ 0.01). A significant, strong correlation was found between peak serve speed and impulse at 100 ms (r = 0.58, p ≤ 0.01), impulse at 200 ms (r = 0.64, p ≤ 0.01), internal rotation <90° (r = 0.63, p ≤ 0.01), and external rotation <90° (r = 0.63, p ≤ 0.01). Because of the significant positive correlations between IMTP variables, CMJ height and peak serve speed, strength and conditioning coaches with access to a force plate should consider using the IMTP to athletically profile athletes in regards to their strength, power, and injury risk.

A Comparison of Kinetic and Kinematic Variables During the Midthigh Pull and Countermovement Shrug, Across Loads

Meechan, D, Suchomel, TJ, McMahon, JJ, and Comfort, P. A comparison of kinetic and kinematic variables during the midthigh pull and countermovement shrug, across loads. J Strength Cond Res 34(7): 1830-1841, 2020-This study compared kinetic and kinematic variables during the midthigh pull (MTP) and countermovement shrug (CMS). Eighteen men (age: 29.43 ± 3.95 years, height: 1.77 ± 0.08 m, body mass: 84.65 ± 18.79 kg, and 1 repetition maximum [1RM] power clean: 1.02 ± 0.18 kg·kg) performed the MTP and CMS at intensities of 40, 60, 80, 100, 120, and 140% 1RM, in a progressive manner. Peak force (PF), mean force (MF), peak velocity, peak barbell velocity (BV), peak power, (PP), mean power (MP), and net impulse were calculated from force-time data during the propulsion phase. During the CMS, PF and MF were maximized at 140% 1RM and was significantly greater than the MTP at all loads (p ≤ 0.001, Hedges g = 0.66-0.90); p < 0.001, g = 0.74-0.99, respectively). Peak velocity and BV were significantly and meaningfully greater during the CMS compared with the MTP across all loads (p < 0.001, g = 1.83-2.85; p < 0.001, g = 1.73-2.30, respectively). Similarly, there was a significantly and meaningfully greater PP and MP during the CMS, across all loads, compared with the MTP (p < 0.001, g = 1.45-2.22; p < 0.001, g = 1.52-1.92). Impulse during the CMS was also significantly greater across all loads (p < 0.001, g = 1.20-1.66) compared with the MTP. Results of this study demonstrate that the CMS may be a more advantageous exercise to perform to enhance force-time characteristics when compared with the MTP, due to the greater kinetics and kinematic values observed.

A Comparison of Kinetic and Kinematic Variables During the Pull From the Knee and Hang Pull, Across Loads

Meechan, D, McMahon, JJ, Suchomel, TJ, and Comfort, P. A comparison of kinetic and kinematic variables during the pull from the knee and hang pull, across loads. J Strength Cond Res 34(7): 1819-1829, 2020-Kinetic and kinematic variables during the pull from the knee (PFK) and hang pull (HP) were compared in this study. Eighteen men (age = 29.43 ± 3.95 years; height 1.77 ± 0.08 m; body mass 84.65 ± 18.79 kg) performed the PFK and HP with 40, 60, 80, 100, 120, and 140% of 1-repetition maximum (1RM) power clean, in a progressive manner. Peak force (PF), mean force (MF), peak system velocity (PSV), mean system velocity (MSV), peak power (PP), mean power (MP), and net impulse were calculated from force-time data during the propulsion phase. During the HP, small-to-moderate yet significantly greater MF was observed compared with the PFK, across all loads (p ≤ 0.001; Hedges g = 0.47-0.73). Hang pull PSV was moderately and significantly greater at 100-140% 1RM (p = 0.001; g = 0.64-0.94), whereas MSV was significantly greater and of a large-to-very large magnitude compared with PFK, across all loads (p < 0.001; g = 1.36-2.18). Hang pull exhibited small to moderate and significantly greater (p ≤ 0.011, g = 0.44-0.78) PP at 100-140%, with moderately and significantly greater (p ≤ 0.001, g = 0.64-0.98) MP across all loads, compared with the PFK. Hang pull resulted in a small to moderate and significantly greater net impulse between 100 and 140% 1RM (p = 0.001, g = 0.36-0.66), compared with PFK. The results of this study demonstrate that compared with the PFK, the HP may be a more beneficial exercise to enhance force-time characteristics, especially at loads of ≥1RM.

Differences in Utilization of Lower Limb Muscle Power in Squat Jump With Positive and Negative Load

Jump performance is related to the ability of lower limb muscles to produce power during the push-off phase. However, it is not known if the power associated with the action of active and passive elements of the lower limb muscles change significantly in jumps with positive and negative loads. In this study, the power associated with the action of passive and active components of lower limb muscles as a whole in squat jumps (SJ) with increase and decrease in the external load is analyzed Fourteen trained male subjects (22.5 ± 2.1 years; 176.5 ± 5.4 cm; 75.8 ± 5.8 kg; BMI 24.3 ± 1.8) performed SJ on a force plate. A functional electromechanical dynamometer (FEMD) system was used to change the external load in a range of -30 to +30% of the subject's body weight. A model comprising a mass, a spring, an active element, and a damper was used. We applied an optimization principle to determine power in center of mass (CoM) (ptot), the powers associated with active element (pact), damper (pƔ), and spring (pk) during the push-off phase. Significant differences between loading conditions for each variable were tested by repeated-measures one-way ANOVA with Bonferroni post hoc analysis, p < 0.05. Shapes of the average curves for instantaneous variation of pact, pƔ, pk, and ptot during push-off with positive loads were closer to 0% than with negative loads. As the load increased, maximum values of ptot, pƔ, and pk decreased. Only with a negative load of -30% did ptot increase significantly, this was not accompanied by changes in pact, pƔ, and pk. The load of one's own body provides conditions for develop high pact peaks, although the maximum ptot is not achieved in that condition. The increase in negative loads produces a significant increase in ptot, but not in pact and can be interpreted as a situation in which the power delivered to the system by the action of active components is better used. The SJ with positive load, although more similar to the instantaneous changes that occur to the SJ with body weight are not gestures where high power is developed.

Mechanical power production assessment during weightlifting exercises. A systematic review

The assessment of the mechanical power production is of great importance for researchers and practitioners. The purpose of this review was to compare the differences in ground reaction force (GRF), kinematic, and combined (bar velocity x GRF) methods to assess mechanical power production during weightlifting exercises. A search of electronic databases was conducted to identify all publications up to 31 May 2019. The peak power output (PPO) was selected as the key variable. The exercises included in this review were clean variations, which includes the hang power clean (HPC), power clean (PC) and clean. A total of 26 articles met the inclusion criteria with 53.9% using the GRF, 38.5% combined, and 30.8% the kinematic method. Articles were evaluated and descriptively analysed to enable comparison between methods. The three methods have inherent methodological differences in the data analysis and measurement systems, which suggests that these methods should not be used interchangeably to assess PPO in Watts during weightlifting exercises. In addition, this review provides evidence and rationale for the use of the GRF to assess power production applied to the system mass while the kinematic method may be more appropriate when looking to assess only the power applied to the barbell.

Magnitude and Reliability of Velocity and Power Variables During Deadlifts Performed With and Without Lifting Straps

Jukic, I, García-Ramos, A, Malecek, J, Omcirk, D, and Tufano, JJ. Magnitude and reliability of velocity and power variables during deadlifts performed with and without lifting straps. J Strength Cond Res XX(X): 000-000, 2020-This study aimed to compare the magnitude and reliability of mean velocity (MV), peak velocity (PV), mean power (MP), and peak power (PP) between deadlifts performed with (DLw) and without (DLn) lifting straps. Sixteen resistance-trained men performed a DLn 1-repetition maximum (1RM) session followed by 4 experimental sessions (2 with each deadlift variant in a randomized order). Each experimental session comprised lifts at 20, 40, 60, and 80% of the DLn 1RM. No significant differences were found between DLw and DLn for MV, MP, PV, and PP at any load (p = 0.309-1.00; g = 0.00-0.19). All mechanical variables showed an acceptable reliability for both deadlift conditions at each relative load (coefficient of variation [CV] <8%; intraclass correlation coefficient [ICC] > 0.70; g < 0.5) with the only exception of MV at 60% 1RM for DLw (ICC = 0.62) and at 40% 1RM for DLn (ICC = 0.65). Furthermore, MV and PV generally had lower within-subject CV (CV = 3.56-5.86%) than MP and PP (CV = 3.82-8.05%) during both deadlift conditions. Our findings suggest that sport professionals might not need to consider implementing lifting straps with the aim to maximize velocity and power outputs with submaximal loads in a deadlift exercise. Because all mechanical variables measured showed an acceptable level of reliability for both DLw and DLn, they can all be used to track changes in performance during the deadlift exercise. However, velocity variables were slightly more consistent (lower CV), which makes them more appropriate to track DLw and DLn performance changes.