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What is Resisted Sprinting?

Resisted sprinting training is a relatively new method of training for improving sprinting speed involving sprint running with additional resistance.

Resistance can be either vertically directed (for example, using a weighted vest) or horizontally directed (for example, using elastic bands or towing a weighted sled).

The most commonly-investigated form of resisted sprint training is the weighted sled, which has been explored in many acute and chronic trials, although other types of resistance have also been assessed, such as parachutes, pulley systems, elastic resistance bands, and weighted belts or vests.

Can very heavy sled towing improve sprinting performance more than unresisted sprinting?

The study: Very-Heavy Sled Training for Improving Horizontal Force Output in Soccer Players. Morin, J. B., Petrakos, G., Jimenez-Reyes, P., Brown, S. R., Samozino, P., & Cross, M. R. (2016). International Journal of Sports Physiology and Performance, 1-13.

What did the researchers do?

The researchers investigated whether resisted sprint running using a weighted sled with a very heavy load would lead to increased sprinting performance and increased horizontal ground reaction force (and related mechanical variables) in male amateur soccer players. The athletes were randomly allocated into either a very heavy sled training group (VHS) or an unresisted control group (CON).

They measured sprinting velocity over the whole of a 20m sprint using a radar device, and instantaneous velocity was subsequently derived to calculate:

• net horizontal ground reaction force
• horizontal power
• theoretical maximum horizontal force (HF-MAX)
• theoretical maximum horizontal velocity (HV-MAX)
• the ratio of HGRF to resultant ground reaction force (RATIO-F)
• the rate of decrease in the RATIO-F (DRF)

All subjects trained 2 times per week for 8 weeks. CON performed 2 blocks of 5 sets of 20m unresisted sprints, with 2 minutes of rest between sprints, and 5 minutes of rest between blocks. VHS performed the same protocol but including some resisted sprints, towing a sled loaded with 80% of bodyweight. The number of the sprints that were resisted increased over the course of the program, from 5 – 8 out of 10 total sprints.

What happened?

Using magnitude-based inferences, sprint running times at 5m improved by more in the VHS group than in CON (moderate vs. small ES), as well as at 20m (small vs. trivial ES). The changes in mechanical variables were unclear or trivial in CON. In VHS, HF-MAX increased (moderate ES), RATIO-F increased (moderate ES), and DRF became more negative (moderate ES). The researchers concluded that (1) very heavy sled towing improves sprint running ability in amateur soccer players, (2) the improvement is likely greater than the change after unresisted sprinting training, and (3) the increases in sprinting ability after very heavy sled towing were accompanied by increases in HF-MAX and RATIO-F, indicating an increased ability to produce force in the horizontal direction.

Can weighted vest sprinting improve sprinting performance more than unresisted sprinting?

The study: Effects of Sprint Training With and Without Weighted Vest on Speed and Repeated Sprint Ability in Male Soccer Players. Rey, E., Padrón-Cabo, A., & Fernández-Penedo, D. (2016). The Journal of Strength & Conditioning Research.

What did the researchers do?

The researchers compared the effects of resisted sprint training with weighted vests and unresisted sprint running training on changes in jumping, sprinting, and repeated sprinting ability (RSA) in amateur male soccer players. RSA measurements included average sprint time (AT), fastest sprint time (FT), total sprint time (TT), as well as the percentage increase in sprint times as a measure of fatigue. The athletes were randomly assigned to either a group who did resisted sprint training using a weighted vest (VEST) or a group who trained using unresisted sprinting (CON).

All subject trained 2 times a week for 6 weeks, with a very similar program involving 1 – 4 sets of 3 – 7 reps of 20m sprints with 2 minutes of rest between reps and 5 minutes of rest between sets. VEST performed all sprints with an additional weight of 18.9% ± 2.1% of body mass.

What happened?

Both VEST and CON improved 10m sprint times and 30m sprint times by a similar amount, but neither group improved vertical jump height. RSA as measured by AT, FT, and TT improved similarly in both VEST and CON groups (7.3 – 7.5% vs. 8.3 – 9.3%). Although neither group improved the percentage increase in sprint times during the RSA, there was a trend for the improvement to be greater in CON than in VEST (3.3% vs. 0.4%). The researchers therefore concluded that sprint running training using a weighted vest was not superior to a similar but unresisted sprint running training program for either sprinting or RSA.

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When instructing the non-Olympic Weightlifting athlete who has never performed Olympic Style Weightlifting (OSW) exercises or exercise alternatives (i.e. pulls), one error often observed occurs during the athlete’s upper extremity involvement during the exercise execution. Inexperienced athletes will often excessively pull the barbell with their arms instead of allowing a proper lower extremity contribution for vertical barbell velocity and successful exercise performance. This instructional exercise offered to me years ago by my good friend Al Vermeil will provide feedback to the athlete and assist in ensuring an appropriate lower extremity contribution for proper technical exercise performance.

The Exercise Starting Position

The athlete assumes a “hang” position exercise posture while holding a wooden dowel positioned against the popliteal fossa at the posterior aspect of the knee. A clean or snatch grip is incorporated upon the dowel depending upon the specific exercise of instruction (Figure 1).

The Exercise Execution

The athlete slowly extends their body vertically while allowing the wooden dowel to rise against the posterior aspect of their legs, concluding in a position of triple extension on the balls of their feet with their shoulders shrugged (Figure 2). The exercise is then repeated at faster tempos to generate a greater exercise velocity performance via the lower extremities.

Figure 1 The Starting Position                    Figure 2 The Exercise Execution

The position of the wooden dowel offers a “bar pathway” posterior to the body thus eliminating the upper extremities from the exercise equation. Since the arms are not a contributing factor to the exercise performance, the athlete is now provided with feedback as they sense the lower extremity involvement during the exercise performance. This is the same lower extremity sensation that should occur during the actual OSW exercise performance with a barbell positioned anterior to the body.

The post A Simple Tip for Olympic Weightlifting Training appeared first on Bret Contreras.

Building Multi-Directional Strength and Power
By: Eric Cressey

Sagittal-plane dominant exercises like squats, deadlifts, bench presses, and chin-ups get all the love in the world of strength training, but the truth is that both everyday activities and all levels of athletics require individuals to be strong and powerful in both the frontal and transverse planes, too. This knowledge gave rise to a central tenet of the functional training era: multi-planar training.

Unfortunately, it’s just not as simple as telling folks to train in all three planes, as there is a progression one must go through to stay healthy while reaping the benefits of these new exercises.  Otherwise, baseball players (as an example) wouldn’t need hitting and pitching coaches any more than basketball players would need “vertical jump coaches.” Getting outside the sagittal plane is challenging to learn, and complex to train. With that in mind, I thought I’d use today’s post to outline some of my favorite training progressions in this regard. We’ll start with actual “strength movements.”

Building Usable Strength

1. Single-leg Exercises

To the casual observer to exercise science, single-leg drills are sagittal plane exercises.  However, what you must appreciate is that while you’re training in the sagittal plane, you’re actually stabilizing in the frontal and transverse planes.  It’s important that you master these drills in the sagittal plane before you start experimenting with strength work in the frontal and transverse planes.

In terms of progression, one can start with either dumbbell-at-the-side movements or the goblet position, and then move to scenarios where the center of mass raised by using barbells or holding weights overhead. You could also wrap a band around the lower thigh and pull the knee into adduction/internal rotation to increase the challenge in the frontal and transverse planes.

2. Alternating Lateral Lunge with Overhead Reach

Also at the basic level, you can work unloaded lateral lunge variations into your warm-up. They might be in place, or alternating. As soon as folks can handle them, though, I like to progress to including an overhead reach in order to challenge anterior core stability and raise the center of mass up away from the base of support a bit.  This also gives folks a chance to work on their shoulder mobility and scapulohumeral rhythm.

Bowler squats are also an awesome exercise to begin to challenge control outside the pure sagittal plane:

3. Plate-Loaded Slideboard Lateral Lunge

I like this as a starter progression because the plate out in front serves as a great counterbalance to allow folks to work on their hip hinge. Additionally, there isn’t a big deceleration challenge on the leg that’s going through the most abduction range of motion; rather, the load is predominantly on the fixed leg, which is resisting excessive adduction (knee in).

Worthy of note: I never load this beyond 10 pounds, as folks tend to become kyphotic if the counterbalance is too heavy.  You’re better off loading with #3…

3. Dumbbell or Kettlebell Goblet Slideboard Lateral Lunge

By keeping the weight closer to the axis of rotation (hips) and minimizing the load the arms have to take on, we can load this up a bit without unfavorable compensations.

4. 1-arm Kettlebell Slideboard Lateral Lunges

This exercise builds on our previous example by adding an element of rotary stability.  You’d hold it in the rack position (or go bottoms-up, if you want variety and an increased stability challenge at the shoulder girdle). I’ve tried this with the KB held on both sides, and it’s a trivial difference in terms of the challenge created – so you can just use rotate them for variety.

5. Dumbbell (or Kettlebell) Goblet Lateral Lunge

You can load this sucker up pretty well once you’re good at it. Just be cognizant of not getting too rounded over at the upper back.

6. In-Place Lateral Lunge with Band Overload

This is variation that we use sparingly, but it does always come in handy when you have a post-op elbow or shoulder athlete who can’t hold weights in the affected upper extremity. The band increases eccentric overload in the frontal (and, to a lesser degree, transverse) plane, effectively pulling you “into” the hip.  You have to fight against excessive adduction/internal rotation, and then “get out” of the hip against resistance.  This is something every athlete encounters, whether it’s in rotational power development or basic change-of-direction work.

As an added bonus, using a band actually creates a scenario of accommodating resistance.  Assuming the partner stays in the same position throughout the drill, the tension on the band is lightest when you’re the weakest, and it’s more challenging where you’re stronger.

7. Side Sled Drags

Side sled drags are a great option for integrating some work outside the sagittal plane for folks who either a) aren’t coordinated enough for lateral lunge variations or b) have some knee or hip issues that don’t handle deceleration stress well.  As you can see, the exercise is pretty much purely concentric.  We’ll usually use it as a third exercise on a lower body strength training day – and as you can see, it can offer some metabolic conditioning benefits as well.

Keep in mind that these are just strength development progressions, and they don’t guarantee that anything will transfer over to aggressive power training in the frontal and transverse planes. That’s where the following exercises come in.

Building Usable Power

1. 1-leg Rotational Med Ball Taps to Wall and Split-Stance Anti-Rotation Scoop Tosses

These are two med ball exercises you have to dominate before I’ll allow you to go to the next level. The 1-leg rotational med ball tap verifies that you have enough static balance to be able to even train dynamic balance. It’s low-level and can be practiced every day. Every single one of our baseball players does this early on in their programs – and there is actually some research to suggest that static balance proficiency is associated with improved pitching performance.

The split-stance anti-rotation scoop toss is key because it introduces the concept of hip/trunk separation through good thoracic mobility (as opposed to excessive lower back motion).

Additionally it teaches athletes to have a firm front side to help accept force.

2. Rotational Med Ball Scoop Tosses and Rotational Med Ball Shotputs

These are the two “cornerstones” of any rotational power training program. The “separation” sequencing is comparable for the two, as efficient rotation is efficient rotation. However, what is different between the two is the demands on the upper body. Generally speaking, a scoop toss (when done correctly) will be easier on the elbow and shoulder.

3. Scoop Toss and Shotput Progressions

The progressions of these two “core” drills is primarly focused on playing with rhythm, tinkering with momentum, and increasing eccentric preloading (respectively).

4. Lateral Hops

Hops are done on one leg, and jumps are on two legs. However, just to give athletes constant reminders, I always call them 1-leg hops. It’s like saying “side laterals,” but whatever! You’ve got to be able to both produce and reduce force in the frontal plane before taking the next step. I like this drill without a hurdle to start, with a progression to using low hurdles and ultimately a short-response (no pause on the ground between each rep).

5. Heidens (Skaters)

Named after speed skater Eric Heiden, these are a great way to build on hopping initiatives in the frontal plane. The most important component is to emphasize good hip force production/reduction and appropriate shin angles.

6. Heiden Progressions

To progress heidens, you can do a few different things:

a. Change landing positions:

b. Add resistance:

c. Minimize ground contact time: just do a regular heiden, but spring back quickly. We call this a reactive heiden.

d. Increase eccentric pre-loading: Step off a low (12”) box, and go directly into a heiden.

7. Sprint and Agility Drills

You won’t get a greater plyometric training effect – most of which occurs in single-leg stance – than with sprinting at top speeds and doing change-of-direction training. Beyond the carryover you’ll get to power in the frontal and transverse planes, you’ll also reduce the likelihood that an athlete will get injured during the actual “movement” portions of his/her athletic endeavors.

Wrap-up 

This certainly isn’t an exhaustive list of our strength and power progressions, but it does offer a glimpse into some of the thought processes of how we bring rotational sport athletes along over the course of time. Hopefully you’ve acquired some new exercises and programming strategies you can apply yourself or with the athletes you coach. 

Bret: As you can see, Eric puts a lot of time and energy into creating detailed programs that are both backed by science and molded by anecdotal experience. The High Performance Handbook is one such example, and is a versatile program that can be used to accomplish a variety of different athletic and fitness goals. It’s also on sale this week for $50 off; click here to check it out.

The post Building Multi-Directional Strength and Power appeared first on Bret Contreras.

I’m very excited to present to you some incredible brand new technology. Imagine an iPhone app that allows athletes and coaches to:

1. Calculate jump height based on the iPhone’s video capture capabilities
2. Create a force-velocity profile by performing several jumps with varying loads
3. Compare the force-velocity profile to an ideal force-velocity profile, thus providing individualized training recommendations

Previously, this required expensive equipment, but now it’s available for mass usage if you have an iPhone or iPad. The app is called My Jump, and it can be yours today for only $6. Yes, you read that properly – just six dollars! In addition, My Jump:

1. Is highly valid and reliable when compared to data obtained on a $12,000 force plate
2. Provides individualized training recommendations, which will expedite your progress

Reason why? Until now, the vast majority of strength coaches prescribe the same power training programs to every athlete. This is due to the fact that they have not been privy to the athlete’s unique force-velocity profile. Knowing how the athlete’s force-velocity profile compares to the ideal force-velocity profile allow for individualized training. Recently, this individualization has been found to lead to better performance results than traditional power training methods that are not individualized (publication in progress).

I’ve longed for an invention like this for many years. Heck, I’d pay $6 for an app that simply calculated jump height, but this app goes the extra mile and tells me exactly how I should be training in order to best improve my vertical jump performance. How freakin’ cool is that?! You can use this app with your clients and athletes if you’re a personal training or strength coach, or to conduce experiments if you’re a sports science researcher.

Click HERE to purchase My Jump for $6 (not an affiliate link)

Below is a guest article from the inventors of the app.

From the Lab to Your Pocket: Groundbreaking Lower-Limbs Power Measurement With Your iPhone 

by Carlos Balsalobre, Pierre Samozino and Jean-Benoit Morin

Introduction: Jump height as a measure of lower-limbs explosive performance

Explosive movements such as vertical jumps, change of direction, and the first few steps of running, are some of the most frequent activities in a wide range of sports (4,6,11). Basketball, soccer, volleyball, martial arts, and gymnastics each require explosive push-offs in order to succeed in several specific tasks in competition. Vertical jump performance has been used to assess these lower limb explosive capabilities. Many studies show that vertical jumping ability is a good indicator of lower-limbs strength, power or short sprint times (10,12). So, in fact, every athlete involved in any power/explosive sport would need to perform great jumps as a measure of his/her lower limbs explosive capabilities.

But vertical jumping ability not only represents the athletes’ explosive capabilities, it is also a great tool to know the levels of fatigue induced by training and practice (17). For example, it was demonstrated that the jump height decrease observed between the beginning and the end of a back squat training session is very highly correlated to the levels of blood lactate produced (a metabolite associated fatigue); thus, the higher the jump decreases, the higher the blood lactate concentrations.

For those reasons, many researchers have studied and designed different jumping tests to evaluate athletes’ lower limbs performance during the last decades (1,3,13). French scientist and pioneer of motion analysis Etienne-Jules Marey made one of the first attempts in history before 1900.

More recently, based on an equation derived from the Newtonian laws of motion, and used by Asmussen and Bonde-Petersen (1), Bosco designed a widespread battery of tests to assess jumping abilities. These tests included squat jumps, countermovement jumps, drop-jumps or repeated jumps.

However, the most popular tests focusing on explosive capabilities (i.e. squat jump and counter movement jump) have the main limitations of not providing power values or information about their force and velocity components. This is mainly because they do not account for the length of leg push-off distance during the push-off phase, which significantly influences power output. Even if mechanical power output is often estimated via regression equations based on jump height, this approach provides only an indirect estimation associated to a very poor accuracy.

To tackle these issues, Samozino and colleagues published a simple method allowing for simple and accurate computations of force, velocity and power outputs during a vertical jump, on the basis of body mass, lower limbs length and jump height (15). 

Force-Velocity profile and power output in squat jump for a 75kg male subject who jumped 30.8, 26.5, 23.5, 17.1 and 14.9 cm while carrying additional loads of 0, 10, 20, 40 and 50 kg, respectively.

Then, in order to know the full range of force and velocity capabilities of an athlete, these authors proposed, on the basis of several jumps with various additional loads, to draw the linear “force-velocity profile”. This relationship basically describes, for each individual, the entire profile of his/her force and velocity capability, from the theoretical maximal force “usually called F₀”, to the theoretical maximal velocity (V₀) the lower limbs neuromuscular system can produce. The slope of this relationship, i.e. the F-V profile describes the orientation of the athlete’s system towards force or velocity qualities, and which of these mostly determine its power output (14).

The optimal Force-Velocity Profile approach to optimize your performance

Many studies have analyzed the effects of different training programs to improve vertical jump performance (6,8,18). However there is no consensus about what kind of loads and exercises should be used to improve explosive performance, since both heavy resistance training exercises (i.e. back squat with 85%RM) and light/ballistic exercises (i.e., 30%RM, plyometrics) have been probed to increase vertical jumping abilities. It is well known that power output depends on both the force and velocity produced in a certain exercise (15); therefore, increasing velocity (via high-speed, light exercises) or force (or maximal strength, via low-speed, heavy exercises) capabilities might increase vertical jump performance. The question is: in what proportion should we train force and velocity capabilities to best increase our athletes’ vertical jump height?

Samozino and colleagues recently showed, on the basis of a mathematical modeling of jump performance, that there is, for each individual, an optimal value of F-V profile (slope of the linear relationship) that maximizes (all other things, including maximal power, being equal) jump height (16). In other words, for a given maximal power, among the various force and velocity capabilities combinations that lead to these power qualities, only one will result in a maximized jump performance. This optimal combination, called “optimal force-velocity profile” is individual and can be easily determined using the simple method described above. Should your profile be too much force- or velocity-oriented compared to your optimal profile, your jump performance (and more in general, your explosive performance) is lower than what it could be. This analysis led to the concept of individual “force-velocity imbalance” and was shown to be directly related to jump performance (14). Research in progress will show how to “re-orient” athletes’ individual profile via individualized, optimized training regimen, and that this results in better improvements of jump height than traditional strength training not taking account of the individual F-V imbalance of the athletes (publication in process).

The F-V profile of the subject presented in the previous figure (black line) compared to his individual optimal profile computed from Samozino et al.’s 2012 equation (blue dashed line). The F-V imbalance (% difference between actual and optimal profiles) for this subject is 30%. This means that, for a same given maximal power output, should this subject train to increase his force capabilities in jumping, he will decrease his F-V imbalance, shift his profile towards his optimal value, and in turn increase his jump height. If, at the same time, he does not decrease his velocity capabilities, he would also increase his Pmax, and in turn increase his jump height to an even larger extent

My Jump app: Powerful & accurate jump measurements with your iPhone

As stated above, the measurement of the vertical jump height of the athletes is a simple input variable that can be used to provide great information about their lower-limb force-velocity-power capabilities and explosive performance ability, and in turn it helps optimize training programs to maximize gains. Thus, vertical jump assessment is a must for many S&C coaches. Sport scientists have been using different technologies, such as force, contact or infrared systems to accurately measure jump height (5,7,9). These technologies calculate the height of vertical jumps from the measurement of flight time, since fundamental laws of physics establish that the height reached by the center of mass of the subject depends on the time he/she is able to stay in the air during the jump (1).

This approach is highly accurate and it is widely used by sport scientists, researchers and coaches around the world; however, jump systems have a major drawback that prevent their use out of laboratories, Universities or big sports centers: they are still too expensive for regular coaches (for example, one of the most popular system, the Optojump, costs about $2,000). To avoid this great limitation and bring accurate vertical jump measurements to many sport coaches and field practitioners, Carlos Balsalobre, a Spanish sport scientist, designed an app for iPhone & iPad (named My Jump) that accurately calculates vertical jump height, as shown in the validation paper recently published in Journal of Sports Sciences (2).

To do this, My Jump uses the high-speed video recording on the iPhone 5s, iPhone 6/6 Plus or iPad Air 2 to record the vertical jumps (120 or 240 frames per second depending on the model). Measuring the height of a vertical jump with My Jump is quite simple: you have to record a video of the feet of the athlete while jumping, and then you just need to select the frame in which the subject leaves the ground and the frame in which he/she lands, and the app calculates the jump height through the flight time.

User interface of My Jump app. After a jump has been recorded, the user can navigate the video frame by frame to select the take-off and landing moments

To test its validity and reliability, Carlos and his colleagues measured 100 jumps in different subjects using My Jump and a $10,000 force platform simultaneously, and then compared the results. We are going to skip advanced statistics stuff but, basically, they showed that My Jump on an iPhone 5s (which records videos at 120 frames per second) provides jump height values with the same reliability as the force platform and a mean difference between these two systems of just 12mm. Moreover, the recent iPhone 6/6 Plus incorporates an enhanced high-speed camera of 240fps, so the accuracy is even better with these devices.

Recently, Pierre Samozino and JB Morin (see our recent interview of JB here) – the sport scientists and fathers of the optimal F-V profile method described above, collaborated with Carlos Balsalobre to incorporate the published F-V profile calculations (14–16) in the updated version of his app. After several weeks of design and validation testing, Carlos and the French iOS developer he works with, Francis Bonnin, were able to release the new version of My Jump that includes Pierre’s and JB’s Optimal F-V profile calculation. Therefore, My Jump can now be used to perform an advanced evaluation of the lower limbs explosive capabilities using just an iPhone or iPad. And that is how technology met science to simplify and improve field practice, packing the theory with several recent scientific publications and validated equations in an accurate <6$ mobile device app.

F-v profile results screen of My Jump. Optimal and actual F-v profiles, as well as F0, v0, Pmax and F-v imbalance are calculated.

Practical implications 

The optimal F-V profile method is an excellent approach to evaluate your athletes’ lower-limbs explosive performance and can help to optimize your training programs taking into account the specific individual f-v capabilities of each subject.

This advanced lower-limbs evaluation can now be performed in an accurate, reliable, non-expensive way using My Jump in your iPhone or iPad. My Jump is available on the Appstore for just $5.99 – click HERE for the link. You can find more information about My Jump in its Twitter, Facebook or YouTube accounts.

References

1. Asmussen, E and Bonde-Petersen, F. Storage of elastic energy in skeletal muscles in man. Acta Physiol Scand 91: 385–92, 1974.
2. Balsalobre-Fernández, C, Glaister, M, and Lockey, RA. The validity and reliability of an iPhone app for measuring vertical jump performance. J Sports Sci , 2015.
3. Bosco, C, Luhtanen, P, and Komi, P V. Simple method for measurement of mechanical power in jumping. Eur J Appl Physiol 50: 273–282, 1983.
4. Buchheit, M, Spencer, M, and Ahmaidi, S. Reliability, Usefulness, and Validity of a Repeated Sprint and Jump Ability Test. Int J Sport Physiol Perform 5: 3–17, 2010.
5. Caireallain, AO and Kenny, IC. Validation of an electronic jump mat. Int Symp Biomech Sport Conf Proc Arch 28: 1–4, 2010.
6. Chaudhary, C and Jhajharia, B. Effects of plyometric exercises on selected motor abilities of university level female basketball players. Br J Sports Med 44: i23–i23, 2010.
7. Glatthorn, JF, Gouge, S, Nussbaumer, S, Stauffacher, S, Impellizzeri, FM, and Maffiuletti, NA. Validity and reliability of Optojump photoelectric cells for estimating vertical jump height. J Strength Cond Res 25: 556–560, 2011.
8. Hartmann, H, Wirth, K, Klusemann, M, Dalic, J, Matuschek, C, and Schmidtbleicher, D. Influence of squatting depth on jumping performance. J Strength Cond Res 26: 3243–3261, 2012.
9. Hertogh, C and Hue, O. Jump evaluation of elite volleyball players using two methods: jump power equations and force platform. J Sport Med Phys Fit 42: 300–303, 2002.
10. Kale, M, Asci, A, Bayrak, CI, and Acikada, C. Relationships among jumping performances and sprint parameters during maximum speed phase in sprinters. J Strength Cond Res 23: 2272–2279, 2009.
11. López-Segovia, M, Marques, MC, Vam den Tillaar, R, and González-Badillo, JJ. Relationships Between Vertical Jump and Full Squat Power Outputs With Sprint Times in U21 Soccer Players. J Hum Kinet 30: 135–144, 2011.
12. Loturco, I, D’Angelo, RA, Fernandes, V, Gil, S, Kobal, R, Cal Abad, CC, et al. Relationship between sprint ability and loaded/unloaded jump tests in elite sprinters. J Strength Cond Res , 2014.
13. Marey, E. Le Mouvement. Paris: Ed. Masson, 1984.
14. Samozino, P, Edouard, P, Sangnier, S, Brughelli, M, Gimenez, P, and Morin, JB. Force-velocity profile: imbalance determination and effect on lower limb ballistic performance. Int J Sport Med 35: 505–510, 2014.
15. Samozino, P, Morin, JB, Hintzy, F, and Belli, A. A simple method for measuring force, velocity and power output during squat jump. J Biomech 41: 2940–2945, 2008.
16. Samozino, P, Rejc, E, Di Prampero, PE, Belli, A, and Morin, JB. Optimal force-velocity profile in ballistic movements–altius: citius or fortius? Med Sci Sport Exerc 44: 313–322, 2012.
17. Sanchez-Medina, L and González-Badillo, JJ. Velocity Loss as an Indicator of Neuromuscular Fatigue during Resistance Training. Med Sci Sport Exerc 43: 1725–1734, 2011.
18. Thompson, BJ, Stock, MS, Shields, JE, Luera, MJ, Munayer, IK, Mota, JA, et al. Barbell deadlift training increases the rate of torque development and vertical jump performance in novices. J Strength Cond Res 29: 1–10, 2015.

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