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The Science of the High-Jump

Figure One. Muscles are like springs in that they both respond to a mechanical load with elastic rebound. The more the load the more the rebound, until the strength of the spring or muscle fails.

Authors

Aaron Shunk, PhD; Adam Shunk, PhD

Abstract

High-Jump is an event in track and field that requires an athlete to jump off of one leg and clear a horizontal bar held at a certain height in the air before landing onto a mat. The winner is the athlete whom clears the highest bar with the fewest attempts. Our survey of experts indicate the key to clearing maximum heights is the ability for an athlete to run an effective approach that allows them to take off with optimal speed. Understanding the science of the high jump incorporates biology, anatomy, physics, and even neurobiology. In this article, we break down a successful high jump with  a relatively simple set of key scientific principles that can help  athletes and coaches better understand the event.

We start with the physiology of muscles and training strategies before covering the technique of the approach. A simple spring analogy illustrates the importance of speed and muscle strength during this conversion process. We emphasize 3 critical phases of an approach including: the linear phase where the athlete starts the approach by running a straight line and gaining speed towards the bar. Then discuss the importance of running an efficient curve that lowers center of gravity and places  the athlete in an optimal take off position. We then discuss how muscles convert horizontal speed into vertical lift at the take-off. The article then concludes with the final phase of  clearing the bar in the air and land safely on the mat.

Content

Muscles Like Springs: Muscle Physiology

•Muscles convert energy into motion (mechanical work). In general, skeletal muscles do mechanical work when they contract (muscles shorten) and [AS1] pull on tendons that move the skeleton. The brain coordinates electrical signals to initiate a synchronized physiological contraction of muscle fibers that control motion. This muscular contraction can convert an external force onto the muscle (like a foot striking the ground) into a counter movement. A muscles response to an external force can be simply modeled as a spring (Schultz et. al) because both muscles and springs shorten when activated and the shortening loads each elastic system with kinetic energy (Fig 1). The load of stored kinetic energy can then be converted into desired motion. So the more you load a muscle, the more mechanical work can occur. In the simplified case of a stationary vertical jump the muscles fibers are loaded from bending at the hips, knees and ankles into a takeoff position and then the muscles convert the elastic mechanical energy into vertical lift like a spring. Therefore, the more you load muscles, and the stronger the muscles response to the loading, the higher the jump. The muscle fibers of each part of the body behave independently like a spring and together generate mechanical work to convert the load into vertical lift during take-off. Interestingly, about half the total mechanical energy of the large hip muscles is transferred to the smaller muscles in the knee and ankle to help them contribute to the jump. So most of high jumping originates from the large muscles in the hips rather than the calf or knee area.

•Communications between your brain and muscles are important, and this is why repetitive practice of specific movements is critical to ‘learn’ to efficiently convert muscle loading from an external force into mechanical work. So a critical part of high jump success is to repetitively high jumping through drills and full jumps in order to train the brain to coordinate the motion. In addition, a muscle contraction performs differently under elastic strain, which occurs when a force on the muscle exceeds the strength of the muscle. The damage from this strain is what creates muscle soreness. In response to ongoing elastic strain, the individual muscle fibers strengthen and adapt, and the body learns to improve muscle coordination by adapting and optimizing the physiology of the muscle itself. The muscle improvement relates to a spring-like mega-protein called Titin that develops in athletes during training. Titin has been shown to fine-tune muscles to effectively handle an external force. So jumping practice not only trains the brain to communicate efficiently with the muscles but also adapts the muscles themselves to jump more efficiently.

Mechanics of High Jumping:

•The high jump is more complex than a stationary vertical jump because it relies on a one legged take-off and there is the addition of horizontal speed (mechanical energy) that requires a quick conversion (take-off) into upward energy (lift).  The loading of muscles in high jump uses the combination of gravity and velocity from the approach run up (Fig 2). Thus, the process involves a complex timing and coordination of specific anatomical positions that allow an efficient transfer of energy from speed to lift.  Basically, if an athlete is able to run fast, get into the correct position, and execute a quick take-off, then an efficient jump occurs.  Just like a stationary jump, as an athlete plants their foot to high jump, the ankle, then knee, then large hip muscles are loaded. The amount of loading force is proportional to the approach velocity and the mass of the jumper. During take-off the energy from the loading force is converted to mechanical work in reverse from the hips to the ground. The more velocity gained during the approach the more muscle fiber is activated for conversion  into lift. In other words, the faster an athlete runs the more energy is available and loaded into the  muscles for jumping potential. However, there is one other important detail to consider. Just like a spring can fail if it is loaded with too much force, a muscle can fail with too much loading from excessive speed (Fig. 1). The solution is to utilize as much speed as possible without overloading the muscles.  This illustrates the importance of strength training and optimizing neuromuscular activation and coordination through training. Increasing strength and neuromuscular activation efficiency allow more available force/potential to be converted into lift.  Using the spring as an analogy, a stronger muscle would be like using a stronger spring made out of thicker wire. So think about a car suspension spring that can handle more load than the spring in a writing pen.

The 3-parts of an approach: Linear, Curve, and Take-off

 The Expert Opinion:

•Our panel of four elite high jumpers (all clearing 2.30m or higher) and the scientist who once squeaked over 2.19m, collectively indicate that the approach represents an overwhelming majority of a successful jump (estimated to be around 75% of a successful jump). Many beginner, intermediate, and even advanced high jumpers never learn to take off from a curve properly. The goal of this section is to elaborate of the importance of  the approach. The modern high jump approach can be divided into 3 components (Fig. 3A): The linear phase, curve, and take-off.

The Linear Approach:

•The linear approach is the initiation of an approach where an athlete is often running in a straight line while accelerating to  build up speed from a standing position. The critical part of the linear approach is that the athlete is consistent with regard to body position (running in an upright position) and velocity. This is important for consistency and to assure a smooth transition into a curved path. It is easier to maintain consistency by running a straight line than running other geometries- such as a C shape. Many young high jumpers are irregular during acceleration at the beginning of the approach, especially when excited during a big competition, and throw off their entire approach. Relaxation and a consistent build-up is critical for the approach.

•Running a curve requires a jumper running a roughly semicircular path as they maintain a vertical body position aligning  the upper body (spine and head) with the lower body (hips, knee and ankles) (Fig. 3C). However, and athlete will lean their entire body towards the center of the circle as they run. Running an appropriate curve  is important for  several reasons: I. It allows the athlete to get into an ideal leaning position for jumping. When an athlete runs upright with a lean such that their body is at an angle into the center of the circular path, the athlete builds centripetal force, which is a force acting on the athlete towards the center of the circle.  (Fig. 3B). After the body leaves the ground it is set into motion and will follow the path established at take-off.  After take-off this force helps rotate the athlete into a back-to-bar position (Fig. 2). Although the parabola and path are established at take-off, the athlete can make minor changes in body position in the air to facilitate effective timing over the bar, but the lean and take-off position are the most important factor. II. The lean forces the position of the inside hip joint to lower, which causes the knee to bend (Fig. 3D). This body position prepares the athlete for the jump by pre-loading the leg into a powerful take-off position.  As previously mentioned in the ‘Mechanics of Jumping’ section, an athlete must significantly bend the ankles, knees, and hips to load the body into a take-off position to jump, and running a curve is a cheat to increase the bend of the take-off leg and pre-load for take-off. III. A proper curved approach maintains speed. Pre-loading the leg is critical because it allows the jumper to maintain speed by reducing the leg strength to load into a jumping position. Lowering the body using mostly the legs essentially puts the breaks onto speed and consumes energy. The lost energy results in less vertical force and less lift. So a curve increases the loading and ability to jump high by maintaining more speed.   

The Take Off:

•In order to jump high, an athlete must convert speed or velocity into vertical lift at a sufficient angle to have both: I. the vertical height to clear the bar, and II. the penetration distance into the pit to maintain clearance over the bar with the entire length of his or her body. In order to do this the athlete “plants” their foot onto the track, “loads” their leg and hip muscles, then use elastic force of the muscle to create lift at the proper angle. Just like a spring, the more the athlete lowers by bending the leg and loads at take-off, the more elastic force and lift can be generated. Unfortunately, there is a trade-off because the more the athlete loads by bending the more the speed is lost and the jump fails because of insufficient penetration distance. If an athlete does not load enough, then the take-off trajectory is too horizontal (like a long jump trajectory). They will not have the height to get the center of mass over the bar. Fortunately, as discussed in the ‘Running the Curve’ section there is a cheat that allows the athlete to load the takeoff leg without losing speed by leaning. Thus, the optimal take-off is dependent on the speed and height of the athlete. A shorter athlete can successfully jump more vertical with less penetration than a taller athlete whom must penetrate further in order to clear their entire body. A tall jumper certainly has advantage in regards to a higher center of mass to start with, but it can be more difficult in regards to over the bar clearance and timing. The taller a jumper, the more penetration required and typically a wider curve is required to establish appropriate take-off position. So there does not seem to be an ideal height of a high jumper.

Clearing the Bar:

 •The take-off position is also critical for enabling the athlete's body to obtain the back-to-bar technique “Fosbury flop” for clearing the bar. A common misunderstanding is that high jumpers twist their body during the take-off to rotate over the bar. Actually, for an experienced high jumper the rotation occurs because the curve phase where the athlete stores centripetal force that creates rotation after the athlete leaves the ground. The resulting momentum continues on that set path in the air. A twisting motion during take-off would waste energy and potentially increase the risk of injury. In theory, it is possible for the high jumper’s body to clear a bar while his or her center of gravity passes below the bar as pointed out in multiple articles on the subject (Scientific American), but this is actually rare to achieve, and not that critical for success even amongst elite jumpers. So we don’t recommend focusing much effort on this aspect of the jump. What is critical is that the timing of the different body segments from the head, shoulders, torso, hips, then calves and feet is coordinated with the jump. This requires a high-level of muscle memory and coordination.  It is also very important to understand that when changes occur to an approach or take-off speed, there will also be resulting changes in timing over the bar. Often a break-through in technique will result in faster approach speed that cause an athlete to initially miss the bar. So an athlete should be aware and not get frustrated. A coachable athlete will realize that it takes time and numerous repetitions of practice to coordinate  timing and bar clearance in order to achieve higher heights.

Training and Drills:

Umberger, suggests that the ideal strength training works similar muscles to jumping such as power clean and snatch, hang clean, and plyometrics, but he also emphasizes the importance of building the hips with controlled squats and calf presses to support the muscle loading.  In general, weight training should focus on full body recruitment exercises such as Olympic style lifting.  Explosive movements are preferential over slow strengthening movements and combination of strengthening exercises with explosive movements is ideal. Any lower body exercises should incorporate core stabilization to teach the body how to correctly sequence anatomical positions and muscle activation patterns together.  If part of the spring is weak, it doesn’t matter how strong the rest of the spring is, a breakdown occurs at the weakest point. The body core is the link between the upper and lower body and is necessary for an optimal body position. 

It is critical to jump at higher heights in practice and with significant speed in order to establish timing and coordination.  Lower heights, short approach drills with less speed are also important to training the body appropriate techniques.  It is easier to learn and develop specific skills, like running a proper curve with lead, when things are slowed down.  Ideally, technical changes occur initially at lower heights with less speed that progress into full jumps over time and as skills improve.  

Core strengthening is critical strength for a high jumper that allows correct body position and strength to run an effective curve and be able to full body firing at take-off position.  Athletes are only as strong as their weakest link so if any breakdown in strength occurs, the whole body will fail at take-off position.

Speed development and neuromuscular activation is critical as the primary variable in high jump is the transfer of force gathered by speed at the take-off position. Drills that emphasize running on a curve and training the body to comfortably get into desired position is critical.

Over the bar coordination drills are critical for a jumper to develop coordination and timing.

Strength and plyometric training is quintessential to improve the body’s strength index and explosiveness.  Exercises that emphasize quick, explosive firing of muscles and develop strength specific to the loading position described in this article are most important. Considering the unnatural body positions and demands that high jump places on the body, injury prevention through conditioning, strengthening and recovery are also important.

 

 

 

Data/ Methods

•Spring Analogy. A strong magnet was substituted for a mechanical spring. A cluster of 4 magnets with a fixed mass of counter polarized magnets was dropped down the length of a transparent plastic tube (Fig. 4). The distance of the initial height (Hi) drop was used for velocity since height and velocity are linear relationship in this configuration. The rebound height ((Hr) was measured using a high speed camera in slow motion.

 

•Athlete body positions were evaluated using time-lapse photographs that were digitized into figures that could be measured using simple graphical software.

REFERENCES

Mechanics of the Vertical Jump and Two-Joint Muscles: Implications for Training. Brian R. Umberger. University of Rochester Medical Center. The muscles fibers, and then converting the mechanical energy into vertical lift. In a Strength and Conditioning Oct, 1998.



Figure Two. In the high-jump the faster an athlete runs, the more mechanical load on the muscles, and ultimately the more the lift. At take-off the body is like a series of connected springs that load and then rebound.
Figure Three: A. The approach is comprised of the approach, curve, and take-off. B. The curve lowers hip height pre-loading the leg for takeoff. C. A cartoon for a successful high-jump at 2.40 m. D. Data showing hip-height graphically for same jump.
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