Box Jumps for Height Don’t Stack Up

The Sandlot is one of the greatest sports movies of all time – no question. The hero of the story, Benny “The Jet” Rodriguez, amazes his friends several times throughout the movie, in ways that no other kid could ever dream of.  He gets out of a pickle in the opening scene by being able to change direction and outmaneuver his opponents; he joins the maybe two or three other guys in history who ever busted the guts out of a ball; and he finally jumps old man Mertle’s fence to escape The Beast. The movie would have us believe that Benny pulled these feats off because he wore PF Flyers, but he was actually able to pull of these moves as a result of his power.

Power shows itself in all kinds of athletic actions – rotation of a home run swing, throwing a Heater, sprint speed, change of direction, jumping, and so on. Every athlete, and every person for that matter, benefits from improved power.  The popularity of some classic power training techniques has seen a reemergence lately in the fitness world, but as trainers and athletes jump on new trends as quickly as possible, they have a tendency to overlook or under-appreciate the fundamentals.

Power, in the most basic sense, is the combination of strength (the ability to produce force) and speed (the ability to move at a high velocity). If an athlete learns to produce that force quickly, especially with a submaximal load (like bodyweight), the athlete becomes explosive. Common logic would tell us that if we want to jump higher, we just need to practice jumping. If we want to sprint faster, we just need to practice sprinting.  To an extent, that’s true. You may see improvements in power from remedial tasks like jumping and sprinting, especially for relatively untrained athletes, but there is a lot more going on with power development than meets the eye. To continue to see improvements, or to maximize improvements, we’ll have to dig a little deeper.

Power is really a function of the nervous system, so we really need to focus on how the nerves interact with the muscles.  The nervous system is sensitive – it doesn’t need to be beaten down to grow like our muscles, and it doesn’t need to be pushed to exhaustion to improve like our metabolic systems.  It requires a few really specific overloads, then it needs time to recover.  It also remembers things.  It remembers how you performed your perfect reps, but, more importantly, it remembers how you did your ugly reps.  Since those ugly reps most likely came at the end of your workout, when you had to cut corners because you were exhausted, your nervous system will try to repeat those patterns in the future.

Training power should teach motor units to work more efficiently.  More of them need to fire, they need to fire more rapidly, and they need to learn to fire in sync. Plyometric movements, for instance, happen in less than a quarter of a second, so your body has to learn how to create as much force as possible in a very short amount of time. To make this process quicker, power relies on reflexes – meaning the signal that says “Jump!” never even reaches your brain to be processed. As you land from a jump the muscles stretch rapidly, that signal makes its way to your spinal cord, then a signal is sent back to make those stretched muscles contract.  This is what happens when a doctor hits a patellar tendon with a little mallet: the quadriceps stretch rapidly, that signal goes to the spinal cord, then the signal is sent back that tells the quadriceps to forcefully contract.  That’s why your leg kicks up without you making the conscious decision to do it. To improve our power output, we want to take full advantage of these reflexes and enhanced motor unit function.  Ultimately, these adaptations allow an athlete to develop force more rapidly and impart more force into the ground.

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Another source of force – perhaps the most important source for maximizing power – is the connective tissue surrounding muscles and connecting them to bone.  The elastic properties of this connective tissue act like a rubber band, so when these tissues are stretched rapidly they will rebound forcefully.  To maximize power output, we also need to harness the energy generated by this stretch and snap. To stretch these tissues adequately, the body needs to be moving forcefully into the ground (or other immovable object) before it decelerates and launches in the opposite direction. This is the true definition of plyometrics – the forceful eccentric load (landing) before moving into a brief isometric contraction and stretch of elastic tissues (amortization phase) and finally a concentric contraction (muscles shortening) to move the body back into space.  This method allows an athlete to create a ton of force, and to create it quickly, so that the force can be imparted into the ground. Since the ground doesn’t move, that force launches the athlete into the air.

To reiterate:

  • Maximum power utilizes elastic energy, the stretch reflex, and triple extension
  • To improve force production, we have to overload these systems (more than what we’d see from a standard jump)
  • Plyometric work involves a body moving in one direction, stopping forcefully, then exploding in the opposite direction

Let’s take a look at box jumps.  The real purpose of jumping on top of a box is to remove the impact of landing on the ground. It’s like being caught in midair before you start to fall back to earth.  As a coaching tool, this can be useful to teach proper takeoff from the ground while removing the impact or intensity of landing.  Box jumps, in this case, would be a valuable tool for teaching a beginner to jump or for bringing an athlete back to competition shape after rehabbing an injury. To teach jump technique with plyo boxes, we also need to consider the landing position on top of the box.  Hip and knee angles should be similar to what we’d see in an athlete who is about to take off for a jump – this looks similar to a quarter squat. We definitely should not see the hips dropping below the knees.  There’s no way to repeat a jump from that position. Let’s be clear – jumping onto a box is, without question, less intense than jumping into the air and landing back on the ground. The counter-movement used to initiate the jump (throwing your arms down as you lower your body just before extending into the jump) is the most intense part of this drill. For a beginner this may be enough of a stimulus to improve power, but it will not continue to elicit adaptations for long.

 

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Countermovement/Loading – Notice Hip & Knee Angles

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Takeoff – Triple Extension

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Landing – Proper Hip & Knee Angles

 

Stacking up boxes to see how high you can land does nothing to improve power.  Power is generated when you react with the ground, so what happens in the air is inconsequential.  The best way I’ve heard this explained is that “anyone listing box jump heights is usually showcasing the ability to create triple flexion in the air rather than triple extension through the ground” -Carl Valle. Increasing your power will improve your potential to land on higher boxes, but landing on higher boxes will not improve your power.  We could create another analogous test to illustrate this point – see how many times an athlete can clap his hands in the air.  If the athlete keeps practicing, he will first learn how to clap his hands faster and faster, ultimately increasing the number of claps he can achieve mid-air, but he still hasn’t increased the force he’s imparting into the ground. If the athlete did improve his power, he would be able to jump higher and give himself more time to clap in the air, but it should be obvious that what he’s doing in the air is not going to affect his ability to generate force through triple extension. Similarly, an athlete who is testing his box jump height will simply figure out a way to land with his feet tucked higher and higher, without ever really enhancing his takeoff. Plus, we’re not drilling in a proper landing position as noted earlier (hips should not drop below knees). 

 

Power production, in the case of jumps, happens on the ground. One way to test power is with a vertical jump.  This is very similar to a box jump when we look at the takeoff, but what we’re measuring is much different.  In a vertical jump test, we want to measure the vertical displacement of the center of mass.  You would measure the height of an outstretched hand while standing on the ground, then see how high that outstretched hand can reach during a jump. This test shows how far the center of mass moved.  Getting your feet up on top of a tall box and measuring that box does not indicate vertical displacement.  In this scenario, the feet have been brought up close to the hips, with knees tucked into the chest. It’s an indication of how high you can get your feet, not how far you displaced your center of mass.  To really tap into the elastic and reflexive contributions to power, we want to progress athletes toward true plyometric exercises like repeated jumps or depth jumps. 

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Proper Landing Height

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Added Height – Hips Too Low

Along the same lines, but with a different misguided goal, using repeated box jumps for conditioning (10+ reps per set) is not a great option. Jumping up on the box simply pauses your jump for a second or two as you land.  It doesn’t make jumping any harder, and in fact it probably reduces the intensity of your takeoff since you’ll start tapping your toes on the edge of the box with bent knees and hips. What repeated box jumps will do is provide a nice tripping hazard, and often a sharp edge to remove skin from your shin bone. Again, let’s be clear on this point – jumping onto a box is less intense than jumping into the air and landing back on the ground. Tuck jumps, for example, would be a much safer and more effective method for conditioning.

 

This is not to say that plyo boxes don’t have any value.  Proper landing height is a great teaching tool for beginners. Removing the impact of landing can be beneficial for easing back into more intense jumps after injury. Boxes are great to use for drilling perfect takeoff technique, and there are several ways to use them for strength (step ups, box squats, etc.). Admittedly, seeing someone jump onto a box that’s as tall as they are looks pretty impressive. However, we have to keep in mind what our ultimate goal is – do we want to do things that look cool in the weight room, or do we want to become better, more explosive athletes outside of the weight room?

 

*A special thanks to Chris and Gary for agreeing to be in the photos. They are both incredible athletes and have advanced abilities way beyond box jumps. They would never make any of these mistakes had I not asked them to demonstrate for illustration’s sake.

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