Source: jonsturdevant.com
Slam dunks are found commonly in highlight reals and are an exciting part of basketball. Michael Jordan was not the only NBA player with incredible athleticism, there was and still is numerous others. As it is now becoming more and more important for basketballers to be athletic most young basketballers try to train themselves to be able to jump higher but generally don’t now where to start. By understanding some simple biomechanical principles young athletes would be able to increase their vertical leap and improve their chances of being able to slam dunk.
I find it hard to believe that Jordan could fly but to fully determine whether or not
The Slam Dunk
Here we will take a closer look at the slam dunk by analysing video footage of some of the most impressive dunks in history. The slam dunk has no set technique, as athletes create their own 'works of art' from it. From the dunks below we will be able to see how different scenarios call for force to be produced in a different way and through different trajectories.Michael Jordan's final dunk from the free throw line in 1988 was easily his most memorable as it not only had the added difficulty of the double clutch but he also got his head in line with the rim and beat Dominique Wilkins to claim the title of dunk champion.
Source: YouTube
Vince Carter was one of the most athletic basketballers of the 2000's. His 'honey dip' dunk required incredible athleticism to get his forearm above and into the rim. To view the dunk in question skip to 1.52 of the video or enjoy the whole clip!
Source: YouTube
Blake Griffin is one of the most exciting athletes of the present. In the 2011 dunk competition he jumped over a car! To view the dunk skip to 0.48, the start of the clip is just presentation.
Source: YouTube
This gives us an idea of what is required for different slam dunks, when looking at height, distance and body control. What we must now do is determine what is involved in the skill of the slam dunk.BIOMECHANICAL PRINCIPLES
Burkett (2010) suggests that when analysing a skill it can be separated into four different phases and that within each phase there are key elements of the skill. Below we will identify these four stages and their key elements.- Phase 1: Preparation
- Get into run-up position (opposite end of the court in Jordan's case)
- Observe surroundings, including; rim, ball, takeoff point and landing area
- Phase 2: Takeoff
- Lower centre of gravity and move it behind takeoff leg
- Force production
- Phase 3: Flight/dunk
- The flight stage is based around projectile motion – remembering that all objects (or athletes) projected into the air are under the laws of projectile motion
- During the flight phase the athlete must focus on what their body is doing, what the ball is doing, where the rim is and if there are any outside forces that will potentially act upon them
- Phase 4: Recovery
- During the recovery phase the athlete must land softly to absorb the landing impact and slow themselves down to decrease the risk of injury
Probably the most important element in these phases is the 'force production' one. Force production is what lifts an athlete into the air. To better understand force production we will refer to Newton's laws of motion.
Newton's Laws of Motion
Newton's first law of motion states that
"an object will remain at rest or continue to move with constant velocity as long as the net force equals zero". (Blazevich, 2012, p. 44)
Therefore for the athlete to move from rest (or from a horizontal motion to a vertical motion) they must apply a force in a different direction. So now we need a way to apply this force which comes from Newton's third law of action-reaction. This states that
"for every action, there is an equal and opposite reaction".
(Blazevich, 2012, p.45)
(Blazevich, 2012, p.45)
Therefore for the athlete to apply a force to themselves, they must first apply a force to something else in the opposite direction in which they want to travel. In this case the athlete needs to apply a downwards force on the Earth and the Earth will apply an upwards force to their body. The greater the force they can apply to the Earth the greater the force that will be applied to them. Some wonder why the athlete moves but the Earth does not. Well the Earth does move but only very slightly because of it's incredibly large mass. Therefore, for an athlete to create greater lift they must be able to apply a greater force to the ground. What an athlete could also do is become lighter as Newton's second law states that
A simple diagram of Newton's 3rd Law
"the acceleration of an object is proportional to the net force acting on it and inversely proportional to the mass of an object" (Blazevich, 2012, p. 45)
This means that an 85kg athlete producing as much force as a 95kg athlete would jump higher as they would be accelerating faster at the release point. Not only this but gravity has less influence on a lighter person than it does on a heavier person.
There are many other elements surrounding force production. In the preparation phase we see an athlete must get into their run-up position. The run-up varies between slam dunks. If we look at the footage from Jordan's slam dunk from the free throw line we see he backs up all the way to the end of the court, but why does he do this? Blazevich (2012) suggests that range (or horizontal distance) of flight is directly proportional to horizontal velocity. This means for Jordan
We can also see from the takeoff phase that the athlete lowers their centre of gravity and brings it behind them. This is because the athlete needs to change his direction from almost directly horizontal to something more vertical. To do this they must change their inertia or apply an impulse. Impulse equals Force multiplied by time. Therefore by lowering their centre of gravity and getting it behind their takeoff foot they are increasing the time with which force is applied. This extra time increases their impulse which can also be thought of as the change in inertia. Another way they can increase the impulse is to increase the force which we found out how to do using Newton's laws of motion.
Projectile Motion
Another of the underlying biomechanical principles is projectile motion.
Once the force production phase
is over the rest of the skill is based around projectile motion.
Projectile motion can be described as the motion of an object or athlete projected at an angle into the air (Blazevich, 2012). There are certain factors that will influence an athletes flight path.
Projectile motion can be described as the motion of an object or athlete projected at an angle into the air (Blazevich, 2012). There are certain factors that will influence an athletes flight path.
These major factors influencing
the athletes flight path are:
-
speed of release (takeoff speed)
-
angle of release (angle athlete jumps at)
-
relative height of release (the difference between height of rim and
athletes standing reach)
-
gravity (9.81 m/s/s)
-
spin (in this case none)
-
air resistance (in this case none)
Speed of Release
-
is used to measure range and height
-
range is the horizontal distance covered
-
range equals the horizontal velocity multiplied
by the time of flight
- horizontal velocity is constant throughout the flight
The diagram shows that horizontal velocity remains constant throughout the run-up, takeoff and flight elements
-
height is the vertical distance covered
- height is related to vertical velocity and gravity
- vertical velocity will change throughout flight because of the gravitational force
- height can be found using s=vit+(at^2)/2
(Blazevich, 2012)- vertical velocity will change throughout flight because of the gravitational force
- height can be found using s=vit+(at^2)/2
Angle of Release
-
the optimum angle of release for distance when
projecting an object to a level height is 45 degrees
-
For the slam dunk however the athlete needs to
project themselves to a point higher than their takeoff point, for this we must
look at how the relative height of release influences angle of release
Relative height of release
-
If the release point is higher than where the
projectile or athlete lands the relative height is positive and visa-versa
-
In this case the relative height is negative as
the release point is lower than the basketball ring
-
To maximise distance for a negative release point the angle of
release should be higher than 45 degrees
-
To maximise distance for a positive release point the angle of
release should be lower than 45 degrees
(Blazevich, 2012)
Gravity
-
gravity is the attraction force between two objects (Nelson, 2004), for example the Earth and an athlete
- when there are no other outside forces like air resistance and spin, gravity will cause projectiles to travel
in a parabolic path
THE ANSWER
What does all this tell us. Using these factors of projectile motion separately we can find things like, range, height, flight time and velocity at a given point. Once all these have been found we can sketch a diagram to illustrate flight path. However, Sport Science (2007) used special motion capture technology to analyse the footage and gave us this picture of Jordan's flight path:
Source: Sports Science
So to answer the question 'Could Michael Jordan Really Fly' we need to understand the term flying. Many dictionaries (Oxford, Macmillan, Merriam-Webster and more) define it as moving through the air by the use of wings. However, I understand flying as being able to defer from the flight path put forward by gravity, or in simpler terms to be able to move through the air in any direction at will. So when we ask whether Michael Jordan could fly we can refer to the picture of his flight path. We can see that although his head and hand can defer from the general flight path his centre of gravity continues along the parabola. The lift his head gets comes from his stretching body and this creates the illusion of prolonged hang time or flying. However, instead of him flying it is purely a contortion of the body and thus we can conclude that Jordan could not fly.Now that we have shown that Jordan was unable to fly we must identify how he and other athletes can jump high enough to be able to create the illusion of flight. We looked at Newton's Laws of motion earlier and saw that for an athlete to overcome their body's inertia they must apply a force against themselves. They do this by applying a force against the earth which then responds by applying a force equal in magnitude but in the opposite direction. This is what creates lift. An athlete can also lengthen the time the force is applied (increasing the impulse) to create a greater change in momentum which in turn will give the athlete a greater initial velocity.
Along with this incredible force production an athlete must also understand projectile motion and how there speed, angle and height of release affect their trajectory. In Jordan's case he needed to jump further than a more common dunk so his horizontal velocity at release would have needed to be greater. Also as we noted before, when the relative height of release is negative the optimum release angle is higher than 45 degrees. So for Jordan's dunk from the free throw line his angle of release should have been somewhere between 55 and 65 degrees. However for a dunk like Vince Carter's honey dip the angle would have needed to be closer to 90 degrees because he needed to go higher than Jordan did. Therefore, we can conclude that for every dunk, force will need to be applied in a different direction and with different magnitude depending on the situation. There is no set trajectory for each dunk as each athlete puts there own mark on the skill.
HOW ELSE CAN WE USE THIS INFORMATION
The slam dunk is one of the more exciting plays in basketball so young athletes are always trying to increase their vertical jump to be able to perform such plays.There are many ways to increase vertical leap. The first and most common way is resistance training. Resistance training is popular because all it takes is effort, there is very little understanding needed. However to increase vertical jump through the use biomechanics there is a deeper understanding required. Something as simple as losing weight can increase vertical jump. We see this from Newton's second law where acceleration is inversely proportional to ones mass so if an athlete decreases their mass they will increase their acceleration. Similarly decreasing there mass will also decrease their inertia as inertia is the product of mass and velocity.
Something else we noticed is that understanding projectile motion can help an athlete increase their chances of being able to dunk. Choosing the correct trajectory based on speed and relative height of release can improve the length and height of an athletes jump. This requires the athlete to apply the force in the correct direction.
The kinetic chain is also part of force production. Although we did not explain it before, athletes with greater co-ordination will be ale to jump higher as they can get there muscles firing in unison to apply a greater amount of force to the ground.
It is best not to forget that technique plays a huge role in vertical leap and that strength is not all that's required. Small changes can be the difference between a game winner and falling just short.
REFERENCES
Blazevich, A. (2010). Sports biomechanics, the basics: Optimising human performance. A&C Black.
Burkett, B. (2010). Sport mechanics for coaches. Champaign , IL
Nelson,
G. (2004). What is Gravity. Science and Children. 42(1). ProQuest Central pp. 22-23
sportsfan50. (2007, October 23). FSN Sport Science. Episode 1 - Hang Time - Jordan Farmar [video file]. Retrieved from http://www.youtube.com/watch?v=vZqVq5LrdQQ
