Introduction

In basketball, a free throw shot is a unique skill where every player uses a special component of technical preparation, which is based on an automation of movement where players are always performing the technique/skills in the same way (correct rhythm and speed) (Lenik, Krzeszowski, Przednowek & Lenik, 2019). The basketball free throw is an unopposed attempt to score a point from the free throw line on the basketball court. There are many rules about the free throws and many changes made to this skill which are controversial (Wood, 2019). For example, teams could decline shooting free throws and instead elect to inbound the ball at half court (in years between 1939-1952), and NCAA started to award 3 free throws if player is fouled during a 3-point shot (in 1990). The goal of the free throw is to throw the basketball from a line 4.25m in front of a basketball ring into the basket, with a diameter of 0.45m and height of 3.05. Jenkins (1977) states that “…the higher free throw percentage won 80% of the games”. To back this up, studies have shown that roughly one-half of the games played in a season is determined by free-throws (Hays & Krause, 1987; Walker, 1985). According to Hays & Krause (1987) and Mersky (1987), free throws make up 20 to 25% of all points scored in a game. Similar to other sports, optimal performance is determined by speed, direction, and height/angle of the basketball to successfully score. There are many factors affecting the acquisition of this skill, which includes the physical characteristics such as height, which can have an effect on the projectile motion and force applied to the ball for it to go through the hoop (Biomechanics and Physiology of Sport, 2017).  The basketball free throw will be broken down into the key movement stages and will be analysed using the biomechanical principles. This blog will discuss and analyse the biomechanical principles that optimize performance for the basketball free throw, with various sources and visual aids to back up our work and help to answer the research question.

Research Question

What is the biomechanically optimal technique for the basketball free throw?

Biomechanical Principles

The main biomechanical principles that are involved in the basketball free throw are:

• Base of Support
• Centre of Mass
• Levers
• Torque
• Potential energy and Kinetic energy
• Kinetic chain movements
• Magnus Effect
• Relative release height
• Angle of release
• Newton’s Laws

Main Movement Stages

Stage 1:

Preparation Phase

The first stage of the basketball free throw involves getting the body into the correct stance and positioning to prepare for the shot, holding the ball slightly above the head. In this stage it involves the athlete having the knees slightly bent and having the feet shoulder width apart.

Stage 2:

Flexion phase

The second stage is where the knee flexion is angled at almost 90 degrees, and flexion of the elbows and wrist is used to prepare to score (Gómez, M. Á., Kreivyte, R., & Sampaio, J, 2017). This phase involves the lower body angling towards the basketball ring, flexing the knees, hips and shoulders (the upper arm is raised upward) to the horizontal position so that the upper arm is almost parallel to the floor (Gómez, M. Á., Kreivyte, R., & Sampaio, J, 2017).

Stage 3a:

Lower Body Extension Phase

Trunk extension is used for loading the legs by increasing knee and hip flexion just prior to the extension for the shot. As trunk extension occurs while standing, associated postural adjustments include hip extension and knee flexion to help maintain balance (Oddsson, 1988). The legs store potential energy ready to be transferred to kinetic energy in the next phase.

Stage 3b:

Upper Body Extension Phase

This stage also involves the transfer of potential energy to kinetic energy. It transfers the potential energy in the arms when they move from flexion to extension, where the potential energy changes to kinetic energy. This happens where potential energy is stored as elastic energy in the tendons waiting to be released and transferred into kinetic energy to make the free throw.

Stage 4:

Release Phase

This stage of the skill involves the release of the ball with a push-like movement. A push-like movement is defined as extending all of the joints simultaneously in a single movement (Blazevich, 2017). This leads to the follow through of the arm once the ball has been thrown and also creates a backspin on the ball to assist in scoring.

Stage 5:

Landing Phase

The soft landing technique is essential for basketball players to prevent injuries, the ideal landing for basketball players is have their knees and hip slightly bent; this is to softly absorb the load, keeping their knees behind the toes, striking the ground toe to heel with ‘‘…the knee in a neutral position; the centre of the kneecap should be aligned with the second toe.” (Brizuela et al., 1997).

Analysis

The results of Table 1 and Table 2 show that the athlete accurately scored five times out of ten when standing on the free throw line, but only four out of ten at the 3 pointer line. This could be due to the difference in the distance of the throw, the optimal angle of release, the height of the athlete and the waiting time in between each shot. The difference in the distance between the free throw line and the 3 pointer line means that the range of the shot is much longer and the release angle will lower due to the increased distance that needs to be covered. To calculate the range of the shot it can be done manually by calculating the horizontal velocity and multiplying it by the flight time (Vh x t). The horizontal velocity can be calculated by using the cosine rule: Cos ϴ = adjacent side/hypotenuse (Blazevich, 2017); and the flight time can be calculated by timing the total amount of time the ball was in the air by adding the flight time part 1 and flight time part 2 (shown in Figure 1).

Figure 1. Calculating total flight time = Part 1 + Part 2.

The results for the release velocity and projectile angle in Table 1 and Table 2 were calculated by the apps we used while we were filming these videos which are called ‘Hudl Technique’ and ‘SpeedClock’. This means that the results may not be completely accurate due to possibility of technological error or human error when using the app to calculate the angle which then generated the release velocity. These problems will need to be considered when calculating these factors. The release height will be the same as we had the same athlete do each of the 10 attempts from both distances, and the distance in which we filmed from were the same each time because we placed cones to mark where to stand, so both of these helped to standardise the results. Furthermore, there was a small wait time between each attempt as the apps that were used could not be saved until the angle was calculated, which then calculated the release velocity, and were both needed in the results table. Only once these calculations were completed could the video then be saved to review later. This means that the athlete had to wait approximately 30 seconds to one minute in between each attempt. This affects the results because the athlete could lose their concentration, focus and their rhythm. Therefore the apps used will also need to be considered when wanting to calculate the release velocity and release angle and a more appropriate app or program may need to be used in the future to lead to more accurate results.

Basketball Free Throw Results – Table

We had an athlete try 10 attempts of a basketball free throw from the free throw line and then do another 10 attempts from the 3 pointer line. The reasoning behind this was to compare the difference in the biomechanical principles which will be discussed after the table of results. The results of this test are shown in Table 1 and Table 2 below.

Biomechanical Principles

Base of Support and COM:

In stage one, by having the correct stance and positioning it achieves a more stable base. It is more stable because the centre of mass (COM) is closer to the ground. The COM is described as the point of the body in which the mass is evenly distributed in every direction; and it moves out of the base of support the body is less stable and may cause the body to be unbalanced (Blazevich, 2017). So, by having the COM closer to the ground it results in a more stable base so the athlete is more balanced.

Levers

In stage two and stage three, they involve flexion and extension of the upper body and lower body muscles which relates to lever systems and lever length. Majority of the movements in the human body are classified as 3rd class lever systems. In the 3rd class lever system, the effort is the middle component which lies between the load and the fulcrum. One example of a 3rd class lever system is both flexion and extension of the knee joint and biceps brachii. A basketball free throw uses 2 types of 3rd class lever system to gain power and shoot the ball in the rim. A 3rd class lever is shown in Figure 2. The fulcrum is in the elbow joint, the effort is where the triceps muscle connects to the forearm and the load is where the ball is being held. The second type of 3rd class lever mainly focuses on accuracy of the shot. It is like the first type, however the effort is where the tendon from the forearm connects to the hand and its load is where the ball is held. The lever length is an important factor because depending on the lever length it can be either a biomechanical advantage or a biomechanical disadvantage. For a basketball free throw it would be more advantageous for the athlete to have longer levers so they can produce more height so the shot will be easier to make. On a side note, being taller in basketball is generally more advantageous as the additional height would help with defending positions when trying to intercept the ball and for attacking positions when trying to score.

Figure 2. 3rd class lever system.

Torque

Torque or momentum of force is the magnitude of the force causing the rotation of an object. Momentum of force refers to applying a force at a distance from the pivot point which are the force caused by the movement of the knees, arms and elbows. For example, biceps brachii is a muscle that produces forces during a free throw as the arm flexes and extends to apply force for the ball to travel a certain distance.

Potential Energy to Kinetic Energy

Potential energy is the energy that is associated with position and kinetic energy is the energy that is associated with motion. Within potential energy, elastic energy is stored within the tendons. So, in stage three, the elastic energy is stored in the tendons in the arms during the flexion phase in Stage 2 and is transferred into kinetic energy during the arm extension in this phase.

Kinetic Chain Movements

A kinetic chain describes the different body segments and the connected joints and muscles that work together to produce different movements (Sanchez, 2019). The kinetic chain can either be open or closed depending on whether the distal end of the body segment is fixed or if it can move without restrictions. In stage four the optimal technique is using a push-like movement rather than a throw. This is a closed kinetic chain because all joints are extended at the same time in a single movement. The push-like movement is easier to control and has a higher level of accuracy as the ball will be thrown using two hands. According to Blazevich (2017), it produces more force due to the torques that are generated at each joint resulting in the overall force being higher. The push-like movement generally results in a straight line (Blazevich, 2017) so this means that the ball being thrown will be straight and result in a more accurate score. On the other hand, a throw is much less accurate as the ball is thrown with one hand and it is faster than a push-like movement. A throw is an open kinetic chain which means that all of the joints are extended in a sequence one after the other (Blazevich, 2017) and is less accurate. A throw has a higher velocity due to the quick flexion of the wrist. Bartlet (2000) states that this type of throw is one of the quickest joint rotations in the human body. While a throw can reach higher velocities than a push-like movement, it is much less accurate to use for a basketball free-throw and therefore a push-like movement is the optimal technique to use when performing this skill. This type of movement also results in the ball having a backspin.

Magnus Effect

Magnus effect occur when the ball grabs the air that flows past it because of the friction between the air and the ball. The air particles start to spin the ball causing it to slow down or move faster and further (Blazevich, 2017). Slow-moving air is associated with higher pressure whereas faster-moving air is associated with lower pressure which is called pressure differential (Blazevich, 2017). A ball without a spin will continue to be at a high speed causing the ball to bounce back out over the front of the rim. However, a shot with a backspin will slow down as it hits the rim and will have a high chance of going in the rim (Orzel, 2017).

 

 

 Figure 3. Magnus Effect on the basketball free throw.

Figure 1 shows the pressure differential on the basketball free throw. The basketball is travelling through the air in the right direction towards the basketball with a weight vector going both up and down. The backspin producing force pushing the ball in the upwards direction, but the mass of the ball is heavier so gravity still pulls it in a downwards direction.

Relative Release Height

Relating to stage four, the relative release height is an important factor to consider when performing a basketball free throw. The relative release height is defined as “the vertical distance between the projection point of an object and the point at which it lands” (Blazevich, 2017). If the point in which the object is released is lower than the surface that the object will be landing on, then the relative height of projection is negative (shown in Figure 3.). If the height of the release point is higher than the point where the object will be landing, then the relative height of projection is positive (Shown in Figure 4.). For the basketball free throw, the relative height of projection is negative because the ball is being thrown into the basketball ring, which is much higher than the height of release when the ball is being thrown by the player. Figure 3 and Figure 4 model the two different relative release heights with the different landing positions. For our videos of an athlete doing 10 attempts from the free throw line and the 3 pointer line, the relative release height will be the same due to having the same athlete perform each attempt. The relative release height was calculated by measuring the athlete’s height (from feet to collarbone) and then added the arm length (shoulder to finger tips). This means that the optimal release and would stay the same. However, if the athlete was taller than the optimal release angle would slightly decrease and if they were shorter the optimal angle would slightly increase to improve their performance of this skill.

Figure 4. Negative relative release height.

Figure 5. Positive release height.

Angle of Release

This biomechanical principle relates to stage four where the ball is released with a push-like movement, with a negative relative release height. The optimal angle of release is determined by the range and the relative height of projection. The optimal release angle for a basketball free throw is generally 55 degrees. This is supported by (Blasevich, 2017) who states that the optimal angle for a negative release height is more than 45 degrees, but can be between 45 and 60 degrees. This is shown in Figure 6.

Figure 6. The effect of the release height on optimal projection angle (Blazevich, 2017).

In relation to the results in Table 1 for the free throw attempted from the free throw line, this optimal angle of release showed to be mostly accurate. For example, all of the attempts that had the ball land in the basketball ring ranged from the angles of 48 degrees to 58 degrees with the release velocity ranging from 4.78m/s and 5.60m/s. However there were 3 other attempts that were in between those optimal angles and yet did not score, and the release velocities were also in similar so that did not help with the explanation. Usually if the velocity was higher than it would affect scoring because the ball would have more force behind it and would most likely be thrown at a lower angle and would rebound off of the backboard; whereas if the ball was thrown softer, it would usually be thrown at a higher angle and go straight into the basketball ring. But, neither of these factors help to explain why some of the attempts from the free throw line went in and some did not even when the release angle and release velocities were similar. This also happened with the attempts from the 3 pointer line, where the attempts that scored had angles that ranged between 47 degrees and 51 degrees, with release velocities ranging between 4.84m/s ad 6.03m/s. This shows that the release angles were slightly lower and the velocities were slightly higher to make up for the longer distance that needed to be covered. There was no reason we could find that would explain these results.