DROP JUMPS--A MISUNDERSTOOD EXERCISE
    By Buck Blackwood, MS, CSCS

       Drop jumps are a commonly misunderstood exercise that can yield incredible power--if prescribed correctly.

    When drop jump training is mentioned, many coaches and athletes cringe at the thought of high-impact loading of the joints and the seemingly endless possibilities of injury. Yet the training benefits of drop jumps for developing explosive strength are very significant. 1,2,3,4,8,9,10,11 Unfortunately, there's also widespread misinformation about proper progression and techniques regarding drop jump training. So here are some general recommendations for developing lower-body power in a safe, progressive manner.

    WHY DROP JUMPS? -- Whether in sprinting, jumping, or throwing, it is crucial to overload the ability of the athlete to accelerate one's own body, an opponent, or an implement. Plyometric training is commonly used in the development of power.  Training plyometric exercises makes use of the stretch-shortening cycle (SSC).  In the SSC, an explosive concentric muscle action is preceded by an eccentric muscle action. This phenomenon has been shown to allow the muscle to produce higher force and power outputs.  One commonly trained plyometric exercise is the drop jump.  In performing a drop jump, the athlete steps off from a height and directly on landing executes an explosive vertical or horizontal jump.

    STRENGTH OF PROGRESSION -- An athlete should be able to squat at least 1.5 to 2 times their body weight before starting drop jump training. Sufficient strength and jumping technique are also a must before drop jumping. Follow the prescribed order of exercises during multi-cycle training--standard jumping exercises (e.g., broad and vertical jumps), weight training exercises (e.g., Olympic-style lifts and squats), and then drop jump training.  Drop jumps should not be trained by young athletes with weight training experience of less than 3-4 years.
              Unfortunately, when it comes to training, too many coaches and athletes follow the philosophy of "more is better." It's easy to fall into that trap, because only those who work hard achieve much, right? Wrong! Many repetitions of drop jumps frequently are prescribed for athletes because of the assumption that this sort of training will improve fatigue resistance in repeated actions, such as rebounding in basketball, yet research has shown this to be false.6
              Drop jump training is extremely taxing on the central nervous system and imposes significant stress on the tendons, in particular. 7 Drop jumps, like maximal weight training, involve single all-out repetitions separated by a few minutes of rest. It's the quality of the drop jumps, not the quantity that is necessary for developing explosive strength. Quality refers to the degree to which you use proper technique; which should actually always be high. However, quantity of training does play an important role early on in drop jump progression, when lower box heights are used with more jumps and emphasis on correct drop jump technique is coached.  
             

    DROP JUMP GUIDELINES

              Drop jump training is not inherently dangerous; however, like all types of exercise, the risk of injury can occur. Prepubescent children should not train drop jumps because the epiphyseal plates of the bones have yet to close. 8 Drop jumps aren't an exercise that you can "just do." Take the time to develop sufficient strength and conditioning levels, teach proper warm-up and progression of lead-up drills, prescribe appropriate volume and intensity for the phase of training, and suggest proper footwear and surface for drop jumps.

    1. Warm-up
              Drop jump training should always follow a sufficient warm-up of the lower-body muscles. Hopping in place for 3 sets of 20 repetitions followed by at least 6 sets of 15-yard dynamic stretches like walking lunges, broad jumps, and high-leg kicks are good activities to prepare the joints, tendons, and nervous system for the intensity of drop jumps.

    2. The jumps
              There are two main drop jumps:

    • A horizontal drop jump is done off a box with the goal of increasing the horizontal forward distance.
    • A vertical drop jump is also off a box but with the goal of increasing the upward height.

    Using athletic tape marked for measurement on either a wall or the floor, you can measure your progress.   Single-leg drop jumps may be used but should be trained only by those with adequate experience and ability as demonstrated in other types of the drop jump.

    3. Intensity
              The intensity of drop jumps is determined by the kinetic energy of the falling athlete.  The kinetic energy (E) is defined by the formula E=MV2 / 2, where
    M is mass and V is velocity.  In drop jumps, the intensity can be manipulated with different combinations of velocity (dropping distance) and mass. 
              The recommended height for drop jumps ranges from 12-42 in. (30-107 cm). 8 The optimal height of a drop jump doesn't result in a landing where your heel is forced to the floor by momentum.  If the height of the box is too high, the rebound velocity will decrease.  You should therefore begin with a height of 12in. and increase it slowly to the optimal height.
               An increase in mass can be achieved through the use of weighted vests.  However, an increase in mass always results in a decrease in rebound velocity.  Additionally, due to the high stress placed on involved muscles, connective tissues, and joints weighted drop jumps is not advisable.  It is important to note that the National Strength and Conditioning Association's position statement on plyometrics recommends that athletes weighing over 220 pounds should not drop jump from platforms higher than18 in. (46 cm) or less.5 

    4. Volume-Rest-Frequency
    The optimal prescribed volume of high-intensity drop jumps per workout shouldn't exceed 3 sets of 8 to 10 jumps for well-conditioned athletes and 2 to 3 sets of 5 to 7 jumps for lesser conditioned athletes. Recommended volume varies for athletes of different levels of experience so caution should be used in prescribing drop jump volume. Recovery between repetitions should be between 5 and 10 s and 2 to 3 min between sets. 8, 11 Throughout the preparatory cycles, seventy-two to 96 h between drop jump sessions is a typical recovery time guideline when prescribing drop jumps. 8 During the competition phase, drop jumps should be trained every 7 to 10 days, but no later than 10 days before an important competition. It's also not advisable to use drop jumps continuously for more than four weeks.11

    5. Technique
              Drop jumps require stepping off the box in an athletically relaxed state. Upon impact with the floor, you should push off as though the surface is a bed of red-hot coals. Propel yourself as high or as far as possible.  Pay careful attention to the degree of knee flexion and rotation of each athlete.  Too little knee flexion and increased internal/external rotation of the knee is directly related to increased impact forces which may result in anterior cruciate ligament (ACL) injury. 3
    Females, in particular, are prone to ACL injury during jump landings. 3 So jumping technique and strengthening exercises are all the more important for females prior to drop jump training.  

    6. Breathing
              Correct breathing is crucial during drop jump training. It's necessary that you hold your breath during the contact with the floor and the subsequent push-off. This helps to stabilize your body, which acts as a shock absorber, and to increase the rebound force. Right after push-off is when you can exhale.

    7. Surface and footwear
              The floor surface and footwear shouldn't be extremely soft or excessively shock absorbent since this may impede ankle stability and lessen the storage of elastic energy in the muscles and tendons. The best way to train drop jumps is on a grass field, suspended floor, or rubber mat with some type of court shoe. 8 Running shoes or other soft-soled shoes aren't advisable.
              For sand sports like beach volleyball, drop jumps should be performed on sand and without shoes to increase sport-specific jumping performance. Also, a sand surface is less stressful to the muscle-tendon complex when compared to a firm surface and doesn't induce as much muscle damage as a firm surface. 4,7 However, drop jumping height will typically be less on sand than on traditional surfaces because of longer contact time and energy lost due to foot slippage during the push-off phase of the jump.4

    8. Periodization
              Drop jump training has the most impact on athletic performance just before and during the competition phase of training. Build up to drop jumps by increasing strength levels through several months of training. For example, collegiate track and field competitive indoor season begins in January. Preparation for drop jump training by means of heavy squats, cleans, and proper jumping technique should begin early in the previous summer. In the fall, strength levels and jumping technique are sufficient enough to begin drop jump training.

    IN CONCLUSION

              When drop jump training is mentioned, a paranoid reaction by many coaches and athletes has more to do with inappropriate and ineffective prescription of drop jumps than the exercise itself. Follow the recommendations set out in this article and you'll be able to significantly increase your lower body power.

    References
    1. Bobbert, M.F., Huijing, P.A. and Van Ingen Schenau, G.J. (1987b). Drop jumping II: The influence of dropping height on the biomechanics of drop jumping. Medicine and Science in Sports and Exercise. 19, 339-346.
    2. Hakkinen, K., and P.V. Komi.  Effect of Explosive Type Strength Training on Electromyographic and Force Production Characteristics of Leg Extensor Muscles During Concentric and Various Stretch-Shortening Cycle Exercise.  Journal of Sport Sciences 7 pp. 65-75.
    3. Irmischer, B.S., Harris, C., Pfeiffer, R.P., DeBeliso, M.A., Kent, A.J., and Shea, K.G.  Effects of a Knee Ligament Injury Prevention Exercise Program on Impact Forces in Women.  Journal of Strength and Conditioning Research 18(4):703-707, 2004.
    4. Miyama, M., and K. Nosaka. Influence of surface on muscle damage and soreness induced by consecutive drop jumps. Journal of Strength and Conditioning Research 18(2):206-211, 2004.

    1. National Strength and Conditioning Association.Position statement: Explosive/plyometric exercises. National Strength and Conditioning Association Journal 15(3):16, 1993.
    2. Nicol, C., et al. Effects of repeated exhaustive stretch-shortening cycle exercises (SSC) on short latency reflex response. Medicine and Science in Sports and Exercise 29(5):1125, 1997.
    3. Nosaka, K., and T. Kuramata. Muscle soreness and serum enzyme activity following consecutive drop jumps. J. Sports Sci. 9:213-220. 1991.
    4. Potach, D.H., and D.A. Chu. Plyometric training.  In: Essentials of Strength Training and Conditioning (2nd ed.). T.R. Baechle and R.W. Earle, eds. Champaign, IL: Human Kinetics, 2000. pp. 427-470.
    5. Siff, M.C. Supertraining. Denver, CO: Supertraining Institute, 2000.
    6. Young, W. Specificity of strength development for improving the take-off ability in jumping events. Modern Athlete and Coach 33, 3-8.
    7. Zatsiorsky, V. Science and Practice of Strength Training. Champaign, IL: Human Kinetics, 1995.

     

    More Headlines