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Jean-Benoît Morin and Pierre Samozino

Recent studies have brought new insights into the evaluation of power-force-velocity profiles in both ballistic push-offs (eg, jumps) and sprint movements. These are major physical components of performance in many sports, and the methods the authors developed and validated are based on data that are now rather simple to obtain in field conditions (eg, body mass, jump height, sprint times, or velocity). The promising aspect of these approaches is that they allow for more individualized and accurate evaluation, monitoring, and training practices, the success of which is highly dependent on the correct collection, generation, and interpretation of athletes’ mechanical outputs. The authors therefore wanted to provide a practical vade mecum to sports practitioners interested in implementing these power-force-velocity–profiling approaches. After providing a summary of theoretical and practical definitions for the main variables, the authors first detail how vertical profiling can be used to manage ballistic push-off performance, with emphasis on the concept of optimal force–velocity profile and the associated force–velocity imbalance. Furthermore, they discuss these same concepts with regard to horizontal profiling in the management of sprinting performance. These sections are illustrated by typical examples from the authors’ practice. Finally, they provide a practical and operational synthesis and outline future challenges that will help further develop these approaches.

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Guillaume P. Ducrocq, Thomas J. Hureau, Olivier Meste and Grégory M. Blain

V ˙ T O 2 max , a key determinant of V ˙ O 2 max improvement with training, 12 , 13 , 38 , 39 was found between IT DJ9 and IT run . Our findings, therefore, indicate that the repetition of 192 drop jumps, a training method commonly used during physical training to improve explosive performance

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Akinori Nagano, Taku Komura and Senshi Fukashiro

The two goals of this study were (a) to evaluate the effects of the series elasticity of the muscle tendon complex on an explosive performance that allows a counter movement, and (b) to determine whether or not a counter movement is automatically generated in the optimal explosive activity, using computer simulation. A computer simulation model of the Hill-type muscle tendon complex, which is composed of a contractile element (CE) and a series elastic element (SEE), was constructed. The proximal end of the CE was affixed to a point in the gravitational field, and a massless supporting object was affixed to the distal end of the SEE. An inertia was held on the supporting object. The goal of the explosive activity was to maximize the height reached by the inertia. A variation of the SEE elasticity was examined within the natural range. The optimal pattern of neural activation input was sought through numerical optimization for each value of the SEE elasticity. Two major findings were obtained: (a) As the SEE elasticity increased, the maximal height reached by the inertia increased. This was primarily due to the enhanced force development of the CE. (b) A counter movement was automatically generated for all values of the SEE elasticity through the numerical optimization. It is suggested that it is beneficial to make a counter movement in order to reach a greater jump height, and the effect of making a counter movement increases as the elasticity of the muscle tendon complex increases.

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Randy J. Schmitz, John C. Cone, Timothy J. Copple, Robert A. Henson and Sandra J. Shultz

Context:

Potential biomechanical compensations allowing for maintenance of maximal explosive performance during prolonged intermittent exercise, with respect to the corresponding rise in injury rates during the later stages of exercise or competition, are relatively unknown.

Objective:

To identify lower-extremity countermovement-jump (CMJ) biomechanical factors using a principal-components approach and then examine how these factors changed during a 90-min intermittent-exercise protocol (IEP) while maintaining maximal jump height.

Design:

Mixed-model design.

Setting:

Laboratory.

Participants:

Fifty-nine intermittent-sport athletes (30 male, 29 female) participated in experimental and control conditions.

Interventions:

Before and after a dynamic warm-up and every 15 min during the 1st and 2nd halves of an individually prescribed 90-min IEP, participants were assessed on rating of perceived exertion, sprint/cut speed, and 3-dimensional CMJ biomechanics (experimental). On a separate day, the same measures were obtained every 15 min during 90 min of quiet rest (control).

Main Outcome Measures:

Univariate piecewise growth models analyzed progressive changes in CMJ performance and biomechanical factors extracted from a principal-components analysis of the individual biomechanical dependent variables.

Results:

While CMJ height was maintained during the 1st and 2nd halves, the body descended less and knee kinetic and energetic magnitudes decreased as the IEP progressed.

Conclusions:

The results indicate that vertical-jump performance is maintained along with progressive biomechanical changes commonly associated with decreased performance. A better understanding of lower-extremity biomechanics during explosive actions in response to IEP allows us to further develop and individualize performance training programs.

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Lynda B. Ransdell and Christine L. Wells

Do women out-perform men in endurance sports? Are women as strong, pound for pound, as men? Many questions have been raised about the ability of women and men to perform physical tasks equally well. The issue of sex differences and similarities in performance has considerable significance today as women seek physically demanding careers in police-work, fire-fighting, the military, industry, and athletics. As more women participate in recreational and career opportunities formerly open only to men, knowledge about sex differences in response to physical exertion and training becomes increasingly important. In this paper we describes differences between the sexes in athletic performance.

Most performance differences are due to variations in morphological (structural) or physiological characteristics typical of women and men (Wells, 1991). Nevertheless, variations in these characteristics are often as large or larger within each sex as they are between the sexes. The same is true of physical performance. Thus, when the entire population is considered, there are extensive differences in performance within each sex, and considerable overlap in performance between the sexes.

We will base our examination of performance differences on the most outstanding performances of each sex: those exemplified by World Records in athletic events. We seek to answer such questions as: How large are sex differences in world record performances? Can existing performance differences be explained entirely by biological differences between the sexes? Or, are a large portion of these performance differ-ences attributable to sociocultural factors?

We will analyze sex differences in performance relative to the human energy system. This system allows an extraordinary range of mechanisms for neuromuscular coordination and metabolism. Because of this, the human has a virtually unlimited movement repertoire and is capable of movements requiring large bursts of energy over very brief periods of time, as well as movements requiring low levels of energy production over very long periods of time. We will progress from sports that require very high intensity and explosive quality movements such as jumping and power lifting, through the “energy spectrum” to feats of endurance such as marathon running, ultra-distance triathlon, and open-water distance swimming.

Due to our desire to focus this paper on a reasonable amount of data, our analysis will be limited as follows:

1) for sex differences in high intensity-brief duration, explosive per-formance, we will discuss the high jump, long jump, and various mea-sures of strength (powerlifting),

2) for sex differences in high intensity-short duration performance, we will present data on sprint running (100m, 400m) and swimming (100m),

3) for sex differences in moderate intensity-moderate duration performance, we will discuss middle-distance running (1500m, 5000m, 10,000m), and swimming (1500m), and

4) for differences in low intensity-long duration performance, we will discuss the marathon, the "Ironman Triathlon," and open ocean distance swimming.

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Antonio Dello Iacono, Stephanie Valentin, Mark Sanderson and Israel Halperin

-jump protocols on explosive performances of elite handball players . J Strength Cond Res . 2016 ; 30 ( 11 ): 3122 – 3133 . PubMed ID: 26958786 doi: 10.1519/JSC.0000000000001393 10. Morin J-B , Slawinski J , Dorel S , et al . Acceleration capability in elite sprinters and ground impulse: push more

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Manuel Terraza-Rebollo and Ernest Baiget

of prior dynamic resistance exercise using different loads on subsequent upper-body explosive performance in resistance-trained men . J Strength Cond Res . 2005 ; 19 ( 2 ): 427 – 432 . PubMed ID: 15903386 15903386 14. Till KA , Cooke C . The effects of postactivation potentiation on sprint

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João Ribeiro, Luís Teixeira, Rui Lemos, Anderson S. Teixeira, Vitor Moreira, Pedro Silva and Fábio Y. Nakamura

-Skok O , Sanudo B , et al. Comparative effects of in-season full-back squat, resisted sprint training, and plyometric training on explosive performance in U-19 elite soccer players . J Strength Cond Res . 2016 ; 30 ( 2 ): 368 – 377 . PubMed ID: 26813630 doi: 10.1519/JSC.0000000000001094 22

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Mark G.L. Sayers and Stephen Bishop

), 20 – 24 . PubMed 11708701 5. Brandenburg JP . The acute effects of prior dynamic resistance exercise using different loads on subsequent upper-body explosive performance in resistance-trained men . J Strength Cond Res. 2005 ; 19 ( 2 ), 427 – 432 . PubMed doi: 10.1519/R-15074.1 15903386 6

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Jason Lake, Peter Mundy, Paul Comfort, John J. McMahon, Timothy J. Suchomel and Patrick Carden

.0000000000001226 10.1519/JSC.0000000000001226 26439787 9. Suchomel TJ , Bailey CA , Sole CJ , Grazer JL , Beckham GK . Using reactive strength index-modified as an explosive performance measurement tool in Division I athletes . J Strength Cond Res . 2015 ; 29 ( 4 ): 899 – 904 . PubMed ID: 25426515