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.

Notational Analysis

The key criteria within a notational analysis includes movement, work rate, positional play and distance covered. Movement is broken down into patterns which an individual makes through a football match, in any position, using a variety of techniques and skills to create these. By analysing these, you can break down certain patterns they are following and spot their weaknesses. For example, if the team always travel down the middle, but are stopped halfway down the pitch, you may say they should play wider, allowing the opposition to be spread out more, decreasing the chance of a tackle. When identified, these techniques should be work upon in training sessions to develop the team/individual to the next level. Certain movement patterns are in a team or seen to be individual, depending on the situation and position.

Positional Play is what a coach/manager will look at if they are interested in one player, or how a position is played. For example, we will be looking at a particular player in right midfield, therefore need to see her strengths/weaknesses and what she is contributing to the game from that position. This can be done in a number of scenarios such as choosing the right player to substitute on, talent identification and selection. They would check whether they suit the team’s style of play, or whether they can fulfill their role correctly. As a biomechanist, their role is to find information and assist the manager with this feedback. To help yourself in this, video analysis is the most reliable because you can rewatch and go back on certain movements in the position to correct or to highlight as a strength.

Assessing a performer’s work rate can be quite a difficult task due to each person having different fitness levels and different rates are required in different positions. For example, the work rate between a right midfielder and goalkeeper will be very different. A basic way to find their work rate is by using a heart rate monitor because by using a simple equation (220-age) can find an approximate maximum heart rate, and percentages can be seen from there. However, there are other factors to consider such as the outcome of the work, opposition influence, style of play and so on, therefore gets more difficult to assess.

 

In some sports, such as rugby union, it is important for a performer to cover as much distance as they can, however, like in any sport, this must be productive. In football, a midfielder is typically the one to run the furthest due to the roles of their position, so they need to monitor their runs, and before running they need to know whether it’ll be necessary or not, as they don’t want to tire too easily, especially in the long halves. Furthermore, they may substitute they running (dribbling with the ball) to a long pass instead. However this compares to a striker, who should be completing short sharp runs to lose their defender and short passes to accompany this. Simple ways to track their distance is by the use of a pedometer, and measuring their average stride length, then multiplying these together. As a bio mechanist, this would be your responsibility, as well as potentially monitoring a large spurt of distance covered in one go, and measuring its successfulness. If it is, then it should be maintained, but on the other hand, if it is unsuccessful, you should try and help the performer identify alongside the coach which opportunities should be chased and those which you should watch.

Data from Jamie's games

Positional Play: Jamie managed to stay in her position throughout the first game, and she made her position effective towards the game and the end result, therefore I am identifying this as one of her strengths. She ran up and down the line to support the wide passes out, and from this she contribute to scoring opportunities by crossing the ball into the penalty box. She did move out of her position 6 times, and these were for the Centre midfielder's responsibilities when she did not cover them, which is a weakness, so we need to look further into what in particular made these unsuccessful and then work to improve them. 

In the second game, which was an actual fixture, Jamie successful positional plays decreased whilst the unsuccessful one remained the same. This is therefore a weakness because she did not contribute to the game as much because her positioning was incorrect. This includes her being to high or low on the field to support a pass or cross in, and therefore resulting in the loss of possession or an awkward pass.

 www.football-coach.net/ says ‘’A good supporting angle with good body positioning allows your teammate to easily reach you with a pass that bypasses a defender and cannot be cut out easily. This is encouraged by staying in your position in order to create as much space as possible for you to receive the ball’’.  If Jamie had changed her positioning in the second game, she may have been more successful because she would be more easily available for a pass, and it would encourage positive play. This could've helped towards the team's overall score, and performance, just by changing positions.

 

Distance Covered: Jamie covered more distance in her second game by 0.5km than in the first, where she only covered 6.5km. By looking further into the statistics of the games she played, we can identify whether these were useful and effective runs or whether they were not needed, and we found that they were successful making it a good strength in her overall performance. As a right wing midfielder, her position expects her to run up and down the line quite a bit, therefore the distance covered being quite a high figure is accurate. When looking at her movement patterns, we can see that she performs more in the second game, showing that her extra movement is being put to good use and is successful in the vast majority of cases. 

footballscience.net/ states that if a footballer covers a distance of between 6-9km in a 90 minute game of football, their team will benefit and will most likely win the game due to a high work rate. This supports the fact that her distance covered is a strength.

Movement Patterns: Her movement patterns in game one were mostly successful, but over a third were unsuccessful, which is not a good statistic. Out of 22 patterns made, 15 were successful and 7 were unsuccessful, only giving a 68% success rate. This may have been because she was playing in training where the stakes aren't as high, however, this would be identified as a weakness. This includes her moving around players, losing her defender or dribbling with the ball to get free for a shot. In game two, she improves these massively where only approximately a sixth were unsuccessful, which is half the mistakes in the training game, showing she is improving and working towards changing the strength to a weakness. As we can see in the statistics, out of 26 patterns, 22 were successful and just 4 were not, showing an 84% success rate. They were effective though when successful as she made quick sharp runs away from the defender and dribbles up and down the line to create more scoring opportunities.

 

Movement patterns are essential because if you get them wrong, the consequences are apparent. Research into movement patterns conducted Hughes, Robertson and Nicholson (1988),  by examined that “The unsuccessful teams ran with the ball and dribbled the ball in their own defensive area in different patterns to the successful teams. The latter played up the middle in their own half, the former used the wings more”. This shows that the position in which the players move and play the ball are vital to the outcome of the game. Therefore, the first game’s results could’ve been due to the lack of successful movement patterns, and the win in the second game may also have been down to the 84% success rate.

If these were maintained and increased, then the results could be more consistent. More consistent results will potentially increase the chances of higher forms of success. These can include winning the cup, winning the league (or just moving up several places on the table) and when it comes down to it, score more goals.