Buckle up; this one is going to be long and exhaustive.
Everyone wants to go fast. I work with a lot of high school athletes, and they all want to do speed work. Nearly every parent I've ever talked to has mentioned in one way or another that their kid needs to "get faster" or "needs speed work". For reasons we will discuss, this is often a case of putting the cart a mile before the horse. Who can blame them though? In sports, speed is arguably the biggest physical advantage an athlete can have.
Unfortunately, speed is a pain to develop. If you aren't born with it, then getting fast is messy business. It's not a simple roadmap like, say, building strength. You need to be stronger? Lift big, eat big, sleep big, repeat. Conversely, there's a LOT of pieces to the speed puzzle. The margin of potential improvement is also much more limited by genetic factors.
The purpose of this article is to outline the factors of game speed, debunk many of the myths surrounding speed development, and examine some methods of squeezing out every last drop of potential speed. It is not intended to be an algorithm or specific guide for making an athlete faster, but rather as an eye opener as to what actually dictates game speed. I'm hoping it will also change the way some coaches approach speed training. I die a little inside each time I see coaches making athletes run gassers with 10 second rest periods in the name of "speed work".
*note: I'm just going to say up front that none of this applies to long distance events so I don't have to keep doing it in text.
"Game Speed" Vs "Top Speed"
One of the reasons this topic is so argued is that "speed" is a butchered term. We've got the physics definitions, but how does that translate in the sports world? Does it mean top linear sprint speed? Time around a track? Top running speed? A 40 yard dash? How fast an athlete changes direction? How fast a powerlifter achieves a six plate pull?
Speed is defined as the rate of change of position, expressed in distance divided by time. In plain terms, it's the rate that something goes from point A to point B. Acceleration is defined as the rate of change of velocity, expressed in distance/time². Acceleration expresses how fast an object attains/loses it's speed. Power is defined as the rate of doing work, where work is how much force is applied in relationship to the distance and direction it moves.
I'll assert that when people use the term "speed", what they usually mean is acceleration or power. But so what - why should we care?
Let's use a timed mile as an example. We generally examine the mile purely in the time it took that person to finish. If we were to look at the acceleration of that run, we'd measure how fast the runner got up to his cruising speed (or slowed down). If we measured power, we'd see that it peaked when the athlete was moving their body at the fastest rate possible while covering the most linear distance. Picture one runner running a normal mile at a steady pace, and one doing it by sprinting 100m and walking 100m 8 times - they might finish at the same time, but graphs of their acceleration and power would be wildly different.
For me personally, I make the differentiation by calling acceleration/power/explosiveness "game speed"
Here's the game changer: almost every sport is determined by acceleration/power, not max speed. Max speed has little to no impact on the outcome of most games.
This assertion becomes absolutely evident when we examine the performance of elite athletes. Acceleration phases of elite sprinters lasts for about the first 60m; you can see it come to an end once the sprinter achieves a fully erect torso. This pace can be maintained for, at most, 10m. Deceleration begins immediately after this point.
|Graph of Usain Bolt's Record 100m. Note that "speed" peaks at 70m then falls off. "Acceleration" is maximal at starting moments of the race, decreases as speed increases. "Power" peaks at ~3 seconds.|
It's been long established that elite sprinters accelerate up to 70 meters, with better sprinters generally prolonging the acceleration phase for longer distances (knowing that they will only maintain top speed for a few meters). Less skilled sprinters (read: all other athletes) will hit that peak earlier on, but no halfway decent sprinter will ever hit it before the 30-40m marks.
In my last article on conditioning, we examined a comprehensive review by Spencer et al. 2005. The vast majority of research shows that for field sports, the average sprint is 2-3 seconds or 20-30 meters, the average max sprint lasts 4.1 +/- 2.1 seconds, that athletes get an average of 20-60 seconds to actively recover from sprinting, and that a major factor of what separates good from elite players is how well they perform in repeat bouts of these short sprints. The important of acceleration goes double for football; the average play time is right around 5.5-7 seconds from snap to whistle, with up to 40 seconds of inactive rest between plays.
The questions become evident: how often does an athlete travel for 60+ uninterrupted meters in a game? How often are they ever actually reaching top speed? Practically never. The data implies that what counts is how fast we GET to speed, not how fast we are when we REACH speed.
Forces At Play
Ground Reaction Forces
According to Newton, for every action there is an equal and opposite reaction. Because most sports occur with feet on the ground, "ground force" is used often to describe the amount of force driven into the ground by the athlete (which, by way of the ground "pushing back", drives the athlete). When you stand on the ground, you exert a force equal to your body weight. When you attempt to sprint, jump, or otherwise be athletic, you do so by delivering work to the ground within a short time period. That work, divided by the time it took to deliver it, equals your power in a specific direction. The ground then graciously delivers the power right back at you in the opposite direction, propelling your body in direct proportion to the amount and rate of force you delivered. Ground force is what ties athletics to physics in a practical sense. It is the connecting element which makes it possible to understand in real life terms that to be more quick/powerful, we must increase either the amount or the rate of force we jam down into the ground. WE don't move our bodies through space, the GROUND does.
|Illustration of the action-reaction relationship between an athlete and the ground.|
The body abides the laws of physics just the same as any other object. The problem is that sports science started borrowing all these kinematics terms from physics in a very loose manner. People say force when they mean work, acceleration when they mean power, speed when they mean acceleration, power when they mean strength, and so on. This makes it nearly impossible to have a useful discussion about sports performance while staying true to physics. Here's how we're going to handle it all:
ΣForce = Mass x Acceleration, or Acceleration = ΣForce / Mass
Force, mass, and acceleration are interrelated. The key point is that acceleration is increased by either increasing force, or reducing mass. As force to the object increases, acceleration increases directly. As mass increases, acceleration decreases inversely. If you push an object twice as hard, it accelerates twice as much. If you double the object's mass, it accelerates half as much.
It is also extremely important to understand that the formula accounts for net force on the object. In other words, it accounts only for the force being applied in one vector, NOT the total amount of force being applied to the object. What does this mean in real life terms? Let's say you have an athlete performing a vertical leap. Ideal form would direct every little bit of force directly in a purely upward direction. If the athlete jumps with faulty form and leans back, leans forward, or otherwise directs force anywhere other than straight upward, force will be lost to another vector, which means less force applied to the jump (thus, less acceleration).
Acceleration = Power/(mass x speed) would be ideal, but we must assume that mass is relatively constant,
Power = Force x cos(theta) x (distance/time)
In most cases, this is the equation that makes the most practical sense in terms of sports performance. The only confusing term in the equation is cos(theta), which describes the angle between force applied and actual displacement of the object.
Here's how it all boils down in plain english:
Being Quick/Powerful (All Game) = Generating Tons Of Force Solely In the Intended Direction At The Fastest Rate Possible (As Many Times As Necessary)
Generating Tons Of Force...
Amount of force production is more or less synonymous with amount of strength. Stronger athletes always produce more force. A stronger athlete will always out-produce the force of a weaker athlete, and since practically every sport revolves around force production in some form, it behooves athletes to get strong. Simply put, an athlete can't generate a ton of force rapidly/efficiently unless they can generate a ton of force.
A common argument against the need for high levels of maximal strength is that we never come anywhere close to actually using that much strength in a game. This is absolutely true - explosive movements only use a fraction of maximal force potential. However, the larger the pool of maximal force, the more can be utilized at any one time. Let's say that a vertical leap utilizes 40% of maximal triple extension force production. If we can increase an athlete's maximal triple extension force production from 10,000 newtons to 12,000, that still adds 800 newtons of force to his vertical leap.
Keep in mind that for most sports, strength is a requisite and not an end goal. There's been a huge surge of powerlifting for athletic performance in recent years, and that's fantastic - every athlete should pursue strength. That being said, it's definitely a huge case of the pendulum swinging too far in the other direction. There's now a huge population believing that adding lbs to their powerlifts will make everything fall into place, and that's simply not true. Being strong is bullet point on a long checklist of achieving athletic performance.
There's no upper limit to levels of strength, but there is certainly a threshold where an athlete is much better off maintaining what they have and aggressively pursuing form/reactivity/other sports skills versus getting stronger. Where this threshold lies depends on the player and the needs of the sport, but when you have a slow guy who can squat 2.5x his body weight, it should be clear that his time should be spent elsewhere.
Optimal Strength/Weight Ratio
Optimal strength/weight ratio is another term borrowed from physics to describe the "sweet spot" an athlete should be at to express maximum acceleration/power. Because acceleration = force/mass, the higher the mass, the lower the acceleration. If force production/rate of production are equal, then the lighter the athlete will produce greater power.
Obviously there's a lot more to think about in the context of a sport. You might not have the luxury of letting your 350 lbs offensive lineman drop weight just to be quicker. The mass and potential loss in strength makes it a poor tradeoff. For fairly lean to lean athletes, it's not worth devoting much effort here. It's worth considering if you have an athlete pushing high body fat percentage if they don't need the extra mass. For weight class restricted athletes, it's definitely worth trying to hone in on their ideal strength/weight ratio, as that's the weight class they will be the most powerful at.
...Solely In The Intended Direction...
The entire point of training sprint/jump mechanics is to allow the body to generate force in the most directly applicable manner. Mechanics don't make a person generate more force or do it in less time, rather they allow an athlete to direct forces in the most efficient manner. Mechanical flaws equate to force skittering off in an unproductive vector, resulting in loss of net force to the object. Sometimes you'll hear this called a "power leak".
Example: Athlete A sprints with proper mechanics, while athlete B runs with excess vertical motion or "bobbing". They may demonstrate the exact same force production, and they may generate it in same period of time, but athlete B is directing some of his force towards unproductive directions. Athlete B's net force towards the intended direction will be lower than athlete A's, and therefore athlete B's acceleration/power will be lower.
A requisite level of flexibility/mobility is needed to perform a given athletic motion. For instance, elite sprinters reach something approaching 90 degrees of hip flexion. If an athlete can't move their limbs through the required range of motion (hamstring length/tightness prohibits 90 degrees of hip flexion), or they can't do it without compensating (IE, leaning back to get the knee higher) in some way, then they have a performance roadblock. If it gets in the way of executing proper form fluidly, then it must be fixed ASAP before compensations become bad habits or career ending injuries.
...At The Fastest Rate Possible
Rate of force production is what separates strong athletes from quick/powerful athletes. We all know at least one guy that pulls six plates and has traps so big he can't turn his head, yet can't run a 40 in under six seconds. Even though bear-man can generate massive amounts of force, he cannot do it rapidly.
This is where "speed work" (in the common sense of the term) comes into play. Plyos such as depth jumps are all done in an effort to increase rate of force production, not amount of force generated. This is also where you train an athlete to utilize the stretch reflex. Quality sprint/jump work falls under this category, so long they are done fresh, with long rest periods, never to significant fatigue. You'll hear good coaches harping on minimal ground contact time, because the faster an athlete can deliver force into the ground, the more powerful/quick they will be.
When muscle tissue is rapidly stretched, sensors called muscle spindles detect and counteract the potentially damaging movement. The muscle spindle signals a reflexive contraction of the stretched muscle and all synergists which produce similar motion. It simultaneously reduces tone of the opposing muscles through reciprocal inhibition. When the target muscle is recruited immediately after this stretch reflex, force is actually increased beyond normal output.
|Illustration of the stretch-shortening cycle during a sprint.|
The dynamic stretch reflex makes use of a very small window of opportunity in which our muscles act more elastically than they would at rest. This occurs directly after a rapid stretch, starts decreasing immediately, and fully dissipates within . We can utilize this window to increase the amount of force a muscle would produce - more than it possibly could without the reflex. This is easily demonstrated in real life terms - trying benching a load with no pause at the bottom versus a pin press of the same weight, and you'll see exactly how powerful the stretch reflex is.
This phenomenon is the basis of plyometric training. Making use of it is a teachable skill, and getting better at utilizing it is a trainable parameter. More on this later in the article.
...As Many Times As Necessary
This is an athlete's ability to endure at high to maximal intensity given the parameters of the game. How an athlete conditions depends entirely on the unique demands of the sport. My last article covered this topic in depth, so check out Conditioning For Athletes for more info.
Apart from how we condition, one major factor is that endurance actually ties in directly with skill. You can see this show up in slow motion with elite sprinters; they all run with relaxed shoulders, "jelly jaw", floppy tongues, and no signs of wasted effort. Hands are either opened straight, or in a relaxed "gently holding an egg" position - never clenched.
|Asafa Powell showing a relaxed upper body and jelly jaw. Probably frothing spit all over his competitors too.|
|Allyson Felix demonstrating the same techniques mid stride.|
Okay, this one's not necessarily about increasing stimulation/arousal, but rather honing in on the appropriate levels for the individual athlete.
Stimulation - I'm talking about the chemical kind here. Stimulants have proven to be very effective at increasing performance, up to a point where they will acutely disrupt it. Caffeine is a proven performance enhancer that can be safely used by most. Anything more potent is up to the athlete and their sport's governing bodies.
Arousal - deals with the level of emotional excitement an athlete has for an event. Coaches often believe that it's in their player's best interest to GET HYPE GET AMP GET PUMPED 2THEMAX. Years of sports psychology research has indicated that there's an optimal level of arousal for each athlete, and that it's rarely achieved by cranking the energy up to 11.
As an aside, Radcliffe et al, 2013 did an interesting study on A) Psychological factors key to success and B) methods of psychological management used by athletes, organized by how many years they've been competing:
As much as psychology can be "confirmed", it's been shown that too much arousal causes jitters, lack of concentration, reduction in sports skills, loss of performance, adrenaline dumping, etc. Over-arousal basically pushes kids into an artificial fight-or-flight, which will absolutely wreck endurance. You see this happen all the time with combat athletes in their first few fights - no matter how well-conditioned, the "first fight jitters" destroys their gas tank. I don't want to go too far in depth here because I can't do it justice, but a coach should always attempt to match up the excitement to the individual athlete whenever possible. Athletes should attempt to manage their excitement levels, and routines/pre-event rituals have proven to be very helpful in doing so.
Tying It To A Training Plan
When we're dealing with real athletes, we need to determine what component they're weakest in - that will offer the biggest gains. Do you have an athlete who is can generate tons of force and has great technique, but moves slowly? Work his rate of production with plyos etc. Got a kid who is super reactive ball of fast twitch and moves fluidly, yet can't generate tons of force? Get him powerlifting. The amazing natural athlete who has the natural gifts of being crazy strong and super quick, has horrific movement patterns? Emphasize technique. Can you put 30 athletes on the same "speed" program and see some improvement? Sure, but definitely not as much as an individual program tailored to fix their flaws. Speed training is NOT one size fits all.
If an athlete improves in any of the areas previously discussed without a negative impact to other areas, acceleration and power will increase. That being said, we always need to consider the best use of training time and energy. To that end, consider the population or the individual athlete and make a priority list of the following components:
Go for the low hanging fruit. Get athletes lifting heavy compounds with appropriate assistance exercises under quality instruction, and magic will happen. Here's a basic sample template I run with beginner high school athletes to prep them for more advanced strength work. I tailor it from here depending on the group. There's a million quality programs to choose from out there.
Bench Press 3x8
Overhead Press 3x8
Glute Bridge 3x8
Landmine Row 3x8
Clock Lunge x3
Chin Up/Inv Row 3x12
Single Leg Split Squat 3x8
Asym. Farmer’s Walk x3
DB Reverse Lunge 3x12
DB Hamstring Curl 3x12
It's important to understand that while heavy bilateral compounds are crucial, they do not adequately prepare an athlete for the dynamic demands of most sports. Classic powerlifting programs leave many ab/adductors, internal/external rotators, and deep core musculature underdeveloped.
There's a number of global skills that apply to most every sport. These include sprinting techniques such as learning the proper drive phase mechanics, triple extending into the ground, stride recovery, etc. It also includes change in direction technique such as crossover/wedge steps.
A proper sprint is a lot like a proper punch - to the untrained eye, they seem like innate abilities we all instinctually know how to perform. In reality, they're some of the most difficult, most counterintuitive skills to master. A proper sprint is weird. If an athlete does not make a concerted effort to learn it, they will not perform it. This entails tons and tons of drilling on each and every little cog of the sprint.
Taylor Mays 4.24 40. This is not an innate skill.
Detailing the finer points of a proper sprint is beyond this article - just understand that it is absolutely something that needs to taught. There are tons of excellent web and text resources on sprint technique; you can take your pick, as long as you prioritize the importance of sprint technique.
Get More Reactive
Plyometric training is the go-to here. The focus has to be on shortening the amortization phase (the ground contact time), utilizing the stretch reflex, ensuring proper arm rip mechanics, learning proper landing mechanics, etc.
Training to generate force more rapidly can be tricky and requires excellent coaching. The emphasis should always be on appropriate amounts of deceleration forces for the population. The weaker the athlete, the more the coach has to mitigate the effects of gravity. Here's a good snippet of Mike Boyle discussing this consideration with his staff:
It's also key to understand that plyometrics are NOT conditioning. They require the absolute avoidance of fatigue to be useful. Plyos can also beat the hell out of the body and require careful programming to avoid injury.
Speed lifting utilizes classic weighted exercises, performed at a much lower load, done in an explosive/jump fashion. Loaded jump squats, speed deadlifts, Heavy KB swings, etc. These are usually performed as explosively as possible with loads around 30-40% of 1RM. Here's a good clip of Eric Cressey performing some speed deads:
These exercises can be extremely useful for improving the connection between big force production and power. That being said, they are not for beginners. Performing them safely requires immaculate form and an athlete smart enough to know they aren't supposed to be done to fatigue.
Improve Strength To Weight Ratio
This one is obvious, but the key point here is that the athlete loses weight without losing lean tissue. If it's in season/preseason, this must be done carefully or performance will go down the toilet. Proper fat loss methods are beyond the scope of this article, but it's certainly something worth considering for some athletes.
Get More Mobile
Common problems such as upper/lower crossed syndrome, neurologically inactivated glutes/hamstrings, super tight hip flexors, etc. will not only make a sprint suck, they will make it a dangerous activity.
Improving mobility is going to depend on an athlete's specific limitations. It also requires an understanding that "mobility" does not equal "laxity", "instability", or "lack of good tension". There are plenty of landmarks in the body that an athlete wants to keep rigid, such as the core or lumbar region.
There's a lot of material out there on mobility. DeFranco's limber 11 isn't a bad place to start, but there's plenty to dig into.
Stimulants are a sensitive subject. I would obviously never recommend anything illegal, but there's plenty of potent stimulants that are well within the law. Tolerance to these compounds needs to be assessed on an athlete-to-athlete basis, and all of the risk factors need to be weighed against the benefits.
On the coaches' end, this is accomplished by modifying their arousal techniques to best suit the crowd or the individual. This is more art than science.
For the individual athlete, mastering relaxation techniques and having a sound pre-game ritual can be immensely beneficial in managing the psychological stresses of sports. These techniques can include exercises such as positive imagery, motivational self-talking, and so on. Here's a nice little summary from USA Swimming:
|Arousal Management - USAswimming.org|
Speed endurance is absolutely critical to game performance. Developing this comes down to training programs, nutrition, hydration, supplementation, etc. Again, I will refer you to my Conditioning For Athletes article.
One thing worth mentioning here is that a major distinction between a poor coach and a good coach is the understanding that conditioning DOES NOT improve speed. Well, okay, if you take a doughy, out of shape athlete and condition them hard, then yeah, they'll probably pick up a bit of speed just by virtue of being able to sustain the pace. Past that though, conditioning and speed work really need to be kept separate for sustained improvements, and they need to be handled completely differently.
Speed endurance requires an adequate pool of substrates. Maximal speed implies anaerobic conditions, which necessitates adequate glycogen. Hydration status is also critical to endurance. I covered this as well in the Conditioning For Athletes article.
Nothing cripples performance like a lack of sleep. Burn out can be as bad or worse. One of my favorite S&C quotes (that I blatantly ripped off from Eric Cressey) is "fatigue masks fitness". In other words, we may have amazing potential for performance, but is often depressed by some measure of fatigue. How we manage that fatigue directly impacts how well we perform.
Unfortunately, avoiding burn out is not always within an athlete's control. I have known many, many coaches over the years that try to compensate for their complete and utter lack of training knowledge by just throwing insane amounts of work at kids. This is poor coaching at its finest. It is a coaches' JOB to make sure athletes are given appropriately difficult physical and mental stress that they can adequately recover from. Nothing irritates me more than coaches who beat kids into the ground to "toughen them up".
Sleep, however, is entirely within an athlete's control. Nothing complicated here, just commit to 8-9 hours of sleep per night. This is one of those training directives that is so easy on paper, yet so hard in life. That being said, it is absolutely worth the effort needed to consistently sleep enough.
Most supplements either offer very little in the way increases to acceleration and power. Ones that are worth considering:
Creatine: this is far and away the best choice for improving power and endurance in the PCr energy system, AKA for max effort, short duration performance. Read more here: What Is Creatine and How Does It Work?
Beta Alanine: from my previous article, An In Depth Look At Pre Workout Supplement Effectiveness And Safety:
Beta alanine is an amino acid which serves as a precursor to carnosine production. Carnosine is a dipeptide which has a prominent role in buffering H+ ions/pH during intense activity...
...Somewhat similar to creatine, beta alanine supplementation allows for a bit more work output during all out activity, potentially letting you get that extra rep or that couple more seconds of hard sprinting. Whereas creatine allows for a prolonged stay in the ATP-PC energy pathway, carnosine staves off muscle acidity from all out activity.Beta Vulgaris (beet root extract): I'm planning on doing a large article on beet root/nitrates soon, so I will save discussion for that. More on this in the future.
Since fatigue from muscle acidity tends to set in a bit after the switch from the ATP-PC energy system to the glycolytic energy system, you can expect beta alanine supplementation to come into play just after creatine. In terms of resistance training, you might have creatine supplementation exerting its effects on the 1-3 rep range, and carnosine doing so on a higher rep range.
Edit: I have so much faith in these ingredients that I made a product including all of them (as sell as vitamin D3 and LCLT). Check it out here: Optimum Apex, or on Amazon: Optimum Apex
Great, But How Do I Know What's Needed The Most?
Certain components are easy to assess - it's apparent when an athlete needs to lose 50 lbs of flub or when they show up to practice after an all night bender. Where to direct their training efforts is a bit trickier.
The best course of action is to consider what we call a force/velocity curve, or a strength/speed continuum. We've beaten the force production/rate of production horse to death at this point - what should be crystal clear is that maximal power is expressed when large force is developed rapidly. High velocity with low force production, and high force production with low velocity both have absolutely terrible transfer to sports performance. We gotta' work 'em toward the middle.
Address the strength-speed continuum. If an athlete can produce massive force but does so slowly, they need to train at becoming more reactive/applying force more rapidly. This seems to be done best at the 30-40% of 1RM range with jump squats, cleans, med balls, etc. For many athletes, especially younger ones who haven't been exposed to resistance training, they need to get stronger, plain and simple. This is also true of the rare athlete who has exceptional sprint technique, but poor force production.
Prioritizing strength vs reactive vs technique training will dictate most of the training program. Apart from that, just answer some obvious questions about the athlete. If they're gassing out hard, assess their conditioning. If they aren't enduring as well as they should be, take a good look at their diet, or refer them. Same goes for rest and recovery. Losing focus or technique breaks down over an event? Investigate some new motivational/focusing strategies.
Physiological and metabolic responses of repeated-sprint activities:specific to field-based team sports. Spencer M, Bishop D, Dawson B, Goodman C. Sports Med. 2005;35(12):1025-44. Retrieved from http://www.google.com/url?
THE PERCEPTION OF PSYCHOLOGY AND THE
FREQUENCY OF PSYCHOLOGICAL STRATEGIES USED
BY STRENGTH AND CONDITIONING PRACTITIONERS.
JON N. RADCLIFFE, PAUL COMFORT, AND TOM FAWCETT. Journal of Strength & Conditioning Research: April 2013 - Volume 27 - Issue 4 - p 1136-1146doi: 10.1519/JSC.0b013e3182606ddc. Retrieved from http://journals.lww.com/nsca-jscr/Fulltext/2013/04000/The_Perception_of_Psychology_and_the_Frequency_of.35.aspx.
http://journals.lww.com/nsca-jscr/Fulltext/2010/04000/Kinematic_and_Kinetic_Comparisons_of_Elite_and.2.aspx greater rate of force development
Med Sci Sports Exerc. 2012 Apr;44(4):647-58. doi: 10.1249/MSS.0b013e318236a3d2.
Mechanics of the human hamstring muscles during sprinting.
Schache AG1, Dorn TW, Blanch PD, Brown NA, Pandy MG.
J Biomech Eng. 2013 Aug;135(8):81008. doi: 10.1115/1.4024577.
Simulation of aperiodic bipedal sprinting. Celik H1, Piazza SJ.
J Strength Cond Res. 2014 Oct;28(10):2954-60. doi: 10.1519/JSC.0000000000000492.
Effects of resisted sprint training on acceleration with three different loads accounting for 5, 12.5, and 20% of body mass. Bachero-Mena B1, González-Badillo JJ.
J Sports Sci. 2014;32(18):1722-8. doi: 10.1080/02640414.2014.915423. Epub 2014 May 19.
Mechanics of the muscles crossing the hip joint during sprint running.
Nagano Y1, Higashihara A, Takahashi K, Fukubayashi T.
Int J Sports Physiol Perform. 2014 Aug 22. [Epub ahead of print]
Caffeinated Energy Drinks Enhance Physical Performance in Elite Junior Tennis Players.
Gallo-Salazar C1, Areces F, Abián-Vicén J, Lara B, Salinero JJ, Gonzalez-Millán C, Portillo J, Muñoz V, Juarez D, Del Coso J.
Int J Sports Physiol Perform. 2014 Sep 5. [Epub ahead of print]
Prior Heavy-Intensity Exercise Enhances VO2 Kinetics and Short-Term High-Intensity Exercise Performance Independently of Aerobic Training Status.
Caritá RA1, Greco CC, Denadai BS.