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Depth Jumps: A Closer LookDepth jumps are what most people (incorrectly) think of when you mention plyometrics and vertical jump training. In training circles many coaches remain unsure about whether the risks outweigh the benefits. In this article I will take a closer look at this often mis-understood exercise and hopefully provide you with some good ideas about how to appropriately use them in your jump training. WHAT IS A DEPTH JUMPDepth jumps are an excellent exercise to help improve reactive/eccentric strength. One of the great things about them is that often they provide immediate and noticeable gains in jump height. The down side is that these short term results often lead to them being abused as a training tool (see below).Depth jumps are simply a jump that is performed after the athlete has dropped to the ground off a platform or box. The jump should be both immediate and rapid. As the goal of depth jumps is to improve an athlete’s reactive strength, the less bending of the knees and the less time the feet are in contact with the ground, the more effective it is.
A Depth Jump One of the more commonly heard myths about this exercise is that you should land on your toes and that your heels should not touch the ground. The rationale for this is that your heels touching the ground increases contact time. This myth is half true. Yes your heels touching the ground may increase contact time, but the landing and jumping can still be performed sufficiently fast so that they provide plenty of reactive stimulation. The other upside to a bit of heel contact is that it helps reduce the pressure on your joints by increasing the surface area over which forces can be dissipated. Another quick point about performing depth jumps is that they are very hard on your CNS. In order to get the most out f them you should make sure you have plenty of rest between sets (2-3 minutes at least. The more reps you perform per set, the more rest you need between sets). You should also get plenty of rest between training sessions. Even with advanced athletes I would still only recommend their use up to twice per week. SAFETY CONCERNSBefore I continue I wanted to address one of the biggest issues that coaches have with depth jumps – safety. Over the years the abuse of them in an athletes training program has lead to many reporting injuries from their use. Due to this there are a lot of coaches who feel that only advanced athletes should use them (often quoted is the need for a minimum of a 1.5x BW squat).This however is something that to I do not entirely agree with. Why? I believe it has more to do with the volume and the drop height causing the injuries, not the exercise itself. After all you only have to look around the various athletic chat rooms to see that there are plenty of athletes will lots of strength and training experience who have still had problems from depth jumps. Another way to look at it is that no one argues that squats are a great way to build strength in the legs. If you have never squatted before the chances are that you would be pretty bad at it. The squat is also a reasonably advanced exercise. It requires balance, core strength, decent range of motion etc as well as strength. Does this mean that you wouldn’t have a beginner squat? No of course not. What it does mean however is that instead of loading up the bar with 2x your bodyweight you would pick a very light weight to start with and work up from there. The same approach should be applied to depth jumps. They are a great way to develop reactive strength. Just because you are not great at them to begin with doesn’t mean you cannot do them, it just means you have to start nice and easy. In this case nice and easy means starting with a low box and with low number of jumps until you have found a height and volume that allows you to perform the movement quickly, correctly, and most important of all, safely. One final comment about depth jumps and training experience that I would like to make is that it is my experience that stronger, more experience athletes definitely get more out of this exercise. However it is also the case the stronger athletes generally get more out of all jumping exercises. Why? Stronger athletes have the potential to generate more force and performing plyometrics such as depth jumps and other jumping drills helps reduce the explosive strength deficit (ESD). Less experienced and weaker athletes do not have the ability to generate much force to begin with so there ESD is generally going to be much smaller meaning they have less to gain from plyometric activities. What is the ESD you ask? The ESD is the difference between how much force you can develop if you have an unlimited amount of time against how much force you can develop when our time is limited. A powerlifter might be able to squat 4 times his bodyweight but if he can’t jump high it just means he cannot access his strength quick enough and he has a high ESD. A sprinter might squat only 2.5 times his bodyweight but he can access that strength much more rapidly which allows him to run so fast and often jump quite high. What does this mean to you? It basically means that if you are inexperienced and not very strong and you are going to use this exercise in your program, you would be well advised to also be doing plenty of strength work as well. DETERMINING DROP HEIGHTThe intensity of the exercise is largely determined by the height from which you drop, and as such the box height (in conjunction with training volume) must be carefully monitored to ensure both safety and effectiveness.If you use a box height that is too high the obvious problem is as already covered, the increased chance of injury.
 Figure 1 and 2: Choosing the right drop height. When performing depth jumps you need to know your limits. Jumping from too high up can result in some bad crash landings - even for somome as strong as the Hulk! The other issue related to excessive drop height is that it can create an eccentric (downward) force that is too great for the athlete’s reactive strength to handle. So even though the athlete might not injure themselves on that jump, the downward force might still be too great for them to rebound straight back up off the ground quick enough for there to be a decent training effect. So what is an appropriate height? The most commonly prescribed method is to identify the drop height that allows you to jump the highest when performing a depth jump. The process of determining what this height is might take a bit of trial and error. A number of authors (Chu, Baggett) suggest the following method. Step 1. Perform a standing vertical jump (SVJ) and mark the height you touched. Step 2. Stand on an 18 inch box and perform a depth jump trying to beat your SVJ. Step 3. If you did not reach the same height as your SVJ, keep lowering the box in 6 inch intervals until you can reach the same or a higher point. Step 4. If you did reach a same or higher point than your standing vertical you keep raising the height of the box in 6 inch intervals until your performance declines. An example might be:
Standing Vertical Jump Height Touched: 290cm Optimal drop height therefore would be a 24 inch box. The alternatively the situation might look like this:
Standing Vertical Jump Height Touched: 290cm Recommendation – Insufficient strength, do not do this exercise. This is generally accepted as very a good way to determine your optimal drop height but I don’t believe it is the best way. Comparing depth jump height to standing vertical jump height really only indicates how reactively strong you are. If you can’t match your standing vertical jump from a 12 inch box this doesn’t mean you should not do depth jumps (as suggested by Chu), it just means you are low in reactive strength The better way for determining the optimal depth jump height is to start on a 6 inch box and work your way up in 6 inch increments until you find the drop height that results in the highest touch. For example:
Test 1 - Height Touched Off 6 inch box: 290cm Optimal drop height in this case is 12 inches. What about drop height for single leg depth jumps? The logical answer that comes to mind is to use a box half the height of your two foot depth jump. However, it isn’t quite so simple. Landing and jumping with two feet is much easier as two legs make it much easier to balance and minimize the amortization phase. When you land on a single leg it is much harder for your joints and muscles to absorb the eccentric forces. For single leg depth jumps I would use exactly the same method I just outlined but I would start with a 6 inch box and move up from there in 3 inch increments instead. You will be surprised how dramatically your performance drops off when using the single leg version.
Single Leg Depth Jumps - Much Harder Speaking of drop height the next question is when should you start to increase it? Whilst progression is the key to achieving your vertical jump goals, you don’t want to do it too quickly, particularly with high impact plyometrics. You should start increasing the box height only after you have made noticeable improvements in your jump height without sacrificing the speed of the jump.
WHEN NOT TO DO DEPTH JUMPSIf regardless of what box height you use on a two legged depth jump you cannot touch a higher point than your maximum standing vertical jump DO NOT DO DEPTH JUMPS. If your reactivity is not up to depth jumps it is better to start off with moderate height altitude landings.What is an altitude landing? An altitude landing is like a depth jump in that you step off an elevated platform or box, but instead of rebounding quickly back off the ground you try and stick the landing in a controlled manner. Altitude landings help to not only build eccentric strength, but also to teach your body how to absorb force. By starting out with these instead of the depth jumps you will build a stronger base for later plyometric work. So what box height do you use for altitude landings? Again start low. I suggest starting with an 18 inch box. If you can comfortably stick and hold the landing at that height with minimum knee bend, then move up to a 24 inch box. When you can comfortably stick and control the landing at that height move up another 6 inches again. Altitude landings are a great exercise for which to build up your reactive strength – especially when you are a beginner. I regularly see athletes who are lacking the reactivity to perform depth jumps correctly will do altitude landings for a month or so and see excellent improvements in force absorption. If they re-test for their appropriate depth jump height again they often find that they are now able to touch higher from low boxes than from a standing position. The reason for this is not that they have necessarily gotten really reactively strong but they have trained their body to reduce what is known as Golgi tendon inhibition (GTI). Basically this is a nervous system response to the higher landing forces that you experience when dropping from a height. The effect that GTI has is like a brake being applied to your muscles which prevents you from executing a powerful concentric contraction after the drop which is why your heights are lower than your standing vertical jump. After a few weeks of altitude landings your body gets used to the higher forces on the drops and as you are not injuring yourself it gradually releases the break which allows you to take advantage of the stretch shorten response and spring back up with greater force. The other thing that altitude landings do which is very important is that they help teach good landing mechanics. This helps has longer term ramifications as landing properly minimizes the impact forces on your joints, tendons and muscles which in turn reduces your chances of injury. SHOULD DEPTH JUMPS BE USED ALL THE TIMEThe short answer to this is no. One of the great things about this exercise is that often they provide very good gains in a short space of time. However the rate of these gains also tapers off quite quickly. What this leads to is athletes thinking that more is better so they end up doing way too much volume for too long a period of time.It is this overuse of depth jumps that I believe has contributed to so many injuries in the past. The length of time you should use them for will once again depend on the height of the box, the volume of jumps performed, and the training experience of the athlete. Once your gains taper off take a break from them for a few months and when you come back you will be ready once again to take advantage of this exercise. POWER JUMPER DEPTH JUMPSBefore I sign off on this article I would like to mention one other way to perform depth jumps and that is with the Lifeline USA Power Jumper. As is already mentioned the main reason this exerise has caused so much controversy is due to the high rate of injury athletes have had. This injury rate is partially due to the high impact nature of the jump.One simle and easy way to reduce the impact is to perform them from a slightly lower box whilst wearing the Power Jumper. The over-speed nature of the Power Jumper cords offset the reduction of downward forces that comes from using a lower box. The very large upside to this is that you get the same training result but with a much reduced level of impact to the joints.
Power Jumper Depth Jumps - A Joint Friendly Alternative If you do own a Power Jumper and are thinking of using it, only use the one cord so that you do not add too much resistance on the concentric/upward jumping motion. You still want to be able to get off the ground quickly and excessive resistance caused by too many cords may have an adverse effect. CONCLUSIONDepth jumps can be a very beneficial exercise for improving your vertical jump. They often rate in many coaches top 10 jumping exercises lists. However abuse of them has often resulted in injuries leaving them with a bad reputation with many coaches.Hopefully in this article I have given you some good ideas about how to safely incorporate this interesting exercise into your vertical jump training. The key points are to start conservatively, and to use low boxes and low volume until you start to get a feel for what you can handle. One final thing, depth jumps are just one exercise out of many you can perform to help you jump higher. If you are worried about getting injured, or that you are not sufficiently prepared to use them – then don’t. There are plenty of vertical jump exercises you can do besides this one. Special Thanks to Alek for letting me use his pictures of the Hulk!. If you click on the appropriately green Hulk link just above there are plenty more adventures to see of him getting up to things you might not normally see a giant green monster doing. RELATED ARTICLESPlyometrics Introduction - Plyometrics is to many uninformed people almost another way of saying vertical jump training. Here is the introductory section of our 3 part article on the topic that may enlighten your knowledge of this often misunderstood form of training.Injury Prevention - No one likes getting hurt. By taking a few precautionary steps you can reduce your chances of getting injured significantly. Fast Twitch Muscle Fiber - Fast twitch muscle fibers! What are they and how do you develop them. Ground Contact Time - An analysis of the role ground contact time has in plyometrics. |
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