Methodology & Numerical Model

Methodology

Firstly, we set up the camera on a block, which stood about 1.4m upright, in order to get a ‘straight on’ angle of the athlete’s movement. When setting up the camera, we stood it upon a tripod for stability and support, to make sure our camera would not shift mid-action. The lens of the camera was pointing in the same direction as the front tripod leg, so when we angle the camera, we have something to determine the prime angle of the camera, so the whole action is in the shot. Whilst setting up the camera, we also needed to consider the background. This should be as blank and non-distracting as possible in order to view the markers and the action more clearly when brought up on the screen, ready to be analysed. This would ensure more perfect representations on the angles and height because their figure would be much more obvious compared to a background moving or busy backgrounds.

Secondly, we set up the scalers, which would show a certain distance, e.g. a metre stick, in the field of interest, which would be used for measurements when on the computer, such as seeing how high they jump or the arm extensions.

After we have set up the scalers, we place markers on the main anatomical landmarks. These include: shoulder, hip, knee, ankle elbow and wrist joints. To make sure these were correct, we recorded the actions 3 times each to find the clearest video to analyse. However, to reduce perspective error, we had to make sure the performer did not move at all otherwise our focus would be shifted when viewing the videos back.

 

When positioning the camera, we should aim to maximise camera-subject distance while also maximising size of subject within field of view. We can do this by situating the camera at a perpendicular angle towards the athlete, but far away. The camera should zoom in from this distance, and the athlete should or move any closer to the camera. This should reduce the effect of perspective error. By reducing perspective error, we are keeping the results accurate; if the athlete moved closer or further away when completing the action, the measurements would change.

 

Parallax error occurs when you don’t use the correct measurements, and the athlete looks closer or further away, which will affect the overall data. In order to reduce this effect, the athlete should be positioned in the middle of the plane of view, to prevent the incorrect results being used. Another step we can complete to make the results more accurate would be to repeat the process. By asking the athlete to complete the motion three times through, we will increase the internal validity of the results

What is deterministic modelling?

A deterministic model describes the biomechanical factors that determine a movement or an action. This starts with the primary factors of performance, such as race time, and then progresses to the secondary factors and so on through different levels, of which the deterministic model has many. As we go further into each level, we start to look at the finer details. For example, if we look at race time as a primary factor, the second level would be involved in the average speed and distance; the third stride length and frequency, the fourth landing distance etc. Therefore we can use this to break down a skill and try and work on more specific components that make up the bigger picture.

Why would a Deterministic Model (DM) be used?

We would use a Deterministic model to meticulously plan a skill in its finer details to analyse movement. This could be through qualitative analysis, by looking at the rhythm and posture of the motion, or by quantitatively looking into the sprint, watching the speed, stride count/length and distance covered.

How would a DM be used?

In a training session, these individual components would be developed. The coach and athlete would look at the relationship between their motion and the skill.

Which three numerical components may you consider?

1. Linear velocity of the ball
2. Joint Angle of the knee
3. Angular velocity of the ball

Numerical Model

Linear Velocity

Velocity (m/s-1) = displacement (change in position) ÷ time

19.3 m/s-1 = 0.58m ÷ 0.3s

Angular Velocity

Angular velocity (ω) = angular displacement (θ) ÷ time (t)

7,000 degrees per second

Start-Finish Joint Angle of knee:
Starting Angle of the Knee: 86 Degrees
Finishing Angle of the Knee: 156 Degrees.

The starting angle of the knee joint was 86 degrees, however, research- The Effects of Approach Angle on Penalty Kicking Accuracy and Kick Kinematics with Recreational Soccer Players- states that “the kicking leg at preparation should be 100 degrees” (http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3761486/). This shows that Charlotte needs to improve her body position in order to become more successful at kicking. She needs to therefore reduce the extension of her leg during this stage of the penalty in order to increase the accuracy of the ball's flight. The coach and other athletes will also be able to analyse the athlete’s performance to enhance their chances of scoring more penalty kicks during a competition event. The coach can then advance the situation once the ideal kicking angles have been created, and start to implement more real life scenarios, such as a defender, to make it more realistic. This will force the athlete to think about the angle more whilst trying to keep possession etc, so she can overcome any barriers faced that try to prevent her from achieving the perfect shot.

The finishing angle of the shot was 156 degrees. This angle is similar to the starting angle because it is a similar distance away from the literature recommendation. The journal Angle-specific hamstring-to-quadriceps ratio: a comparison of football players and recreationally active males, stated that the ideal finishing knee joint angle for a penalty kick should be “115-145 degrees”, (http://www.ncbi.nlm.nih.gov/pubmed/25073098). Charlotte had evidently over extended her knee, which decreased the possible leverage for the shot, causing the velocity and efficiency to also decline with it. However, on the positive side, she is only 11 degrees away from the recommendation, therefore the coach is more than capable of correcting this in a short amount of time.

Through the equation of 0.58m÷ 0.3s, we discovered the linear velocity of the ball was 19.3m/s-1,

This is the perfect linear velocity for a penalty kick, according to Biomechanical Characteristics and Determinants of Instep Soccer Kick, (http//www.ncbi.nlm.nih.gov/pmc/articles/PMC3786235/) because it should measure up to “18-25m/s-1, “. Even though this is ideal for the pace of the shot, it could also be improved, to further decrease the chances of the goalkeeper saving the shot. This can be done through coach referrals and tips, so that they can combine all elements, such as the knee angles, to create a more powerful shot. This will also have to coincide with ball contact point for example, so the placement is correct. If the placement isn’t correct but the power is perfect, then the shot will not be successful.

The angular velocity from Charlotte’s penalty kick was 700 degrees per second, which again is very close to the ‘perfect’ degree of “745-800” (www.jssm.org/vol6/n2/1/v62n-1text.php). Although she isn’t far off, further coaching would increase her velocity, forcing the shot to be more successful. COmbining the linear and angular velocity of her shot, alongside keeping the knee joint angles correct, the perfect penalty can be formed.