Minggu, 09 September 2012

Motion Analysis in Football


Nowadays, many coaches start using notational analysis by pen and paper to help their coaching. For example, they count the number of passes, shots and crosses etc to see how the team performed and which area can be improved. Apart from notational analysis, the coaches can improve their coaching by knowing more about motion analysis in football as well. In my previous article (here), I discussed about what motion analysis is. In short, motion analysis is the process of classifying activities according to intensity of movements (Strudwick and Reilly 2001). The three elements that should be considered are intensity (or quality), duration (or distance) and frequency (Carling et al 2005). The activities were coded according to intensity of movement, e.g. walking, jogging, cruising and sprinting. By using the information, the coaches can design specific drills to fit the football players in different levels and positions in order to achieve higher efficiency of improving performance.

Work rate activity profiles

One of the early researches about motion analysis in football was from Reilly and Thomas (1976). They found that the overall distance covered by outfield player during a match consists of 24% walking, 36% jogging, 20% cruising, 11% sprinting, 7% moving backwards and 2% moving in possession of the ball. The below figure visualises the above finding.

Figure 1 Relative distances covered in different categories of activity for outfield players during soccer match-play
They found two things about the ratio of low-high intensity exercise. The ratio is 2.2 to 1 in terms of distance covered and 7 to 1 in terms of time. Different researchers have different activity profiles. For example, Bradley et al (2009) classified players’ activities into standing, walking, jogging, running, high-speed running and sprinting. Generally, the activities would be classified into two categories: low to moderate intensity activity and high intensity activity and different researches had similar results. Bradley et al (2009) found that low-intensity activity represented 85.4% of total time. Bloomfield et al (2007) had a similar finding that 80-90% of performance is spent in low to moderate intensity activity whereas the remaining 10-20% are high intensity activities. From the above figure, you may realize that only 2% of the total distance covered by top players is with the ball, that means vast majority of actions are “off the ball”, for instance, running into space, support teammates, tracking opposing players. If you are a coach, try to ask yourself “Should I put more effort and time coaching players without the ball rather than just coaching the player with the ball?”. Some other findings such as player has a short rest pause of only 3s every 2 minutes and players generally have to run with effort (cruise or sprint) every 30s (Reilly and Williams 2003) may be useful for the coaches as well.
For the mean distance covered, Strudwick and Reilly (2001) stated that the top division players in the 1970s covered a mean distance of 8680m. In contemporary premier league the figure became 11264m. They suggested that it was because there are more passes, runs with the ball, dribbles and crosses which lead to the increase in the tempo of games. In the research of Bradley et al (2009), the result is 10714m. If you are a coach of adult’s team, the information can be a benchmark for your reference about distance covered for your players.

Does work rate and movement vary by the different positional roles?

Some coaches may realize there should be some differences but they may not realize what the differences are. There are positional differences in work rate and fitness levels. In terms of distance covered, midfield players have the greatest distance covered which is reasonable because they acts as links between defence and attack (Reilly and Thomas 1976)(Ekblom 1986)(Bangsbo et al 1991). This finding was supported by other research. For example, midfielders were engaged in a significantly less amount of time standing still and shuffling and the most time running and sprinting (Bloomfield et al 2007). Greatest distance covered sprinting were found in strikers and midfield players (Reilly and Williams 2003). In terms of the difference between full backs and centre backs, full backs covered more overall distance than the centre backs, but less distance sprinting (Strudwick and Reilly 2001)(Reilly and Williams 2003).
Apart from work rate, motion analysis analyse movement as well. There are different movement characteristics for different positions. Here is the list of findings from different researchers.
Defenders:

  • Perform the highest amount of jogging, skipping  and shuffling movements and spend a significantly less amount of time sprinting and running than the other positions (Bloomfield et al 2007)
  •  More body strength in order to compete with the strikers
  •  Highest amount of backwards and lateral movements (Rienze et al 2000)
  • More turns of 0-90 degree(Bloomfield et al 2007)
  • Ability to move backwards and sideways is important for defenders (Carling et al2005)
  •  To be heavier and with higher BMI, although only slightly taller, than midfielders (Bloomfield et al 2005)


Midfielders:

  • Were engaged in a significantly less amount of time standing still and shuffling and the most time running and sprinting (Bloomfield et al 2007)
  • Perform the most directly forward movements (Rienze et al 2000)
  •  More diagonal and arc movements (Bloomfield et al 2007)
  • More turns of 270-360 degree (Bloomfield et al 2007)


Strikers/Forwards:


  •  Perform the most of the other types movements (jumping, landing, diving, sliding slowing downing, falling and getting up)
  • Perform the most physical contact at high intensity
  • More stopping, these activities produce shearing forces on the lower limbs and Besier et al (2001) suggested that strength training and prehabilitation practices must be adopted and emphasised
  • More diagonal and arc movements (Bloomfield et al 2007)
  • More turns of 270-360 degree (Bloomfield et al 2007)
  • Forwards tend to receive the ball when sprinting (Carling et al 2005)
  • To be heavier and with higher BMI, although only slightly taller, than midfielders (Bloomfield et al 2005)




I hope these are useful for the coaches to know more about different requirements in different positions in terms of work rate, movement and even body strength.

Does work rate vary by the styles of play?

Although all the work rate research done by different researchers are facts, we should think about whether it is ‘all of the facts’. Are they always 100% right and can be applied to all situations? I think style of play is a factor which can affect the work rate of a team. Some researchers had the same view also (Bradley et al 2009)(Reilly and Williams 2003). In possession play, the pace of the game is slowed down, the attacking moves are delayed and the players will wait until opportunities rises. In direct play, the team tries to raise the pace of the game by passing the ball quickly in order to transfer the ball quickly from defence to attack to create opportunities. Therefore, the team would prefer long passes rather than a sequence of short passes. Apart from possession play and direct play which are the most discussed styles of play, we shouldn’t ignore Total football and South American style. I don’t know much about these two styles but I think the work rate requirement of Total football would be similar to direct play as they exchanges positions frequently. South American style is more rhythmic and the overall distance covered is 1.5km less than in the English Premier League (Rienze et al 2000).

Summary

In the 90-minute match time, 80-90% of performance is spent in low to moderate intensity activity whereas the remaining 10-20% are high intensity activities. However, we must remember that most of the key incidents of the game are happened within those 10-20% high intensity activities. There are significant differences existing between strikers, midfield players and defenders in terms of work rate, activity profiles and movements. For example, defenders have the most of backwards and lateral movements. Midfielders covered the greatest distance. Strikers/ forwards tend to receive the ball when sprinting. I hope this article would be useful for the coaches to know more about different requirements of different positions in order to design more specific conditioning programs for the players. Defenders and strikers need speed and agility type drills while midfielders need interval running over longer distances.


References


BANGSBO, J., L. NORREGAARD  and F. THORSO, 1991. Activity profile of professional soccer. Canadian Journal of Sports Science, 16, 110-16

BESIER, T.F., D.G. LLOYD, J.L. COCHRANE and T.R. ACKLAND, 2001. External loading of the knee joint during running and cutting manoeuvres. Medicine and Science in Sport and Exercise, 33, 1168-1175

BLOOMFIELD, J., R.C.J. POLMAN, R. BUTTERLY and P.G. O’DONOGHUE, 2005. An analysis of quality and body composition of four European soccer leagues. Journal of Sports Medicine and Physical Fitness, 45, 58-67

BLOOMFIELD, J., R. POLMAN and P. O’DONOGHUE, 2007. Physical demands of different positions in FA Premier League Soccer. Journal of Sports Science and Medicine, 6, 63-70

BRADLEY, P.S., W. SHELDON, B. WOOSTER, P.OLSEN, P.BOANAS and P. KRUSTRUP, 2009. High-intensity running in English FA Premier League soccer matches. Journal of Sports Sciences, 27(2), 159-168

CARLING, C. et al., 2005. Handbook of Soccer Match Analysis.Oxon:  Routledge

EKBLOM, B., 1986. Applied physiology of soccer. Sports Medicine, 3, 50-60

REILLY, T. and A., M. WILLIAMS, 2003. Science and Soccer. 2nd ed. Oxon:  Routledge

REILLY, T. and V. THOMAS, 1976. A motion analysis of work-rate in different positional roles in professional football match-play. Journal of Human Movement Studies, 2, 87-97

RIENZE, E., B. DRUST, T. REILLY, J.E.L. CARTER and A. MARTIN, 2000. Investigation of anthropometric and work-rate profiles of elite South American international players. Journal of Sports Medicine and Physical Fitness, 40, 162-9

STRUDWICK, T. and T. REILLY, 2001. Work-rate Profiles of Elite Premier League Football Players. Journal of Exercise Science, 4(2) 

Rabu, 05 September 2012

What are Performance Analysis and Match Analysis?


Fifteen years ago, there may be only a few big Premier League football clubs had a performance analysis department. Nowadays, even a League 2 club like Aldershot for which I am working have set up a Performance Analysis department this season. It is a fast growing industry and I firmly believe it will keep growing for the next ten years at least.
Where does it come from?
If we want to know where it came from, sports science has to be mentioned. The first academic programmes in sports science were studied in the UK in 1975. Initially, it included biology, biochemistry, physiology, biomechanics, mathematics, psychology and sociology. Nowadays, the sports science programmes may include economics, recreation sport development, coaching and computer science also (Reilly and Williams 2003). The first Bachelor of Science degree which combined science and football together was offered at Liverpool John Moores University in 1997. Performance analysis in football was one of the core modules.
Difference between Performance Analysis and Match Analysis
You may realize both terms are used in books and articles as they are very similar. In my opinion, match analysis focuses everything about the matches, e.g. post-match analysis, opposition analysis (tactics and strategies). Performance analysis has a wider coverage and includes more disciplines. In short, match analysis is part of the performance analysis. Apart from match analysis, performance analysis includes player recruitment, player evaluation, training analysis, trend analysis and even referees analysis (Prozone 2009). However, you may realize that some of these disciplines are just the further development of match analysis, e.g. player evaluation and trend analysis. Therefore, I think match analysis is the core part of performance analysis. I will focuses on match analysis in the following paragraphs.
Why match analysis is undertaken?
Some people may argue that soccer is an art, especially if you watch the Zinadine Zidane played. I won’t deny that as I agree playing and coaching soccer are arts but I think science can be a part of soccer as well. In terms of preparation, science information is helpful for coaches and trainers to make decisions and judgement. For one’s own team, the information can be used to identify strengths and weaknesses. For opposition, we can use data to counter opposing strengths and exploit weaknesses. Moreover, match analysis can be used to evaluate whether the training programmes improve the match performance or not (Carling et al.2005). The information is a big set of data and coach can’t remember all of it during the game. Franks and Miller (1986) found that international level soccer coaches could only recollect 30% of the key elements that determined successful soccer performance observed. Another research indicated that coaches are able to recall fewer than half of the key incidents (Carling et al. 2005). Another reason is that the coach may not be able to get the information objectively. Neisser (1982) found that the accuracy of memories of events I greatly influenced by many factors, e.g. the beliefs of the observer. In other words, coaches are active observers rather than passive perceivers of information. Their perception of events would not be a copying process but rather a selective and constructive one (Reilly 1996). Then coaches can’t provide an objective and unbiased information. Therefore, match analysis/ performance analysis is needed to provide such information and analysis.
What does match analysis include?
In my opinion, match analysis can be divided into two categories: Notational analysis and Motion analysis.
Notational analysis is a means of recording events so that there is an accurate and objective record of what actually took place (Carling et al. 2005). There should be at least five elements which should be recorded: the position (where?), the players involved (who?), the action concerned (what?), the time (when?) and the outcome of the activity (e.g. successful or unsuccessful, or on target or off target. Generally there are two ways to do it: by hand/manual or by computer. Reep and Benjamin (1968) were the early researchers in hand notation system. They collected data from 3213 matches between 1953 and 1968 and recorded actions such as passing and shooting. Their conclusions were that 80% of goals were resulted from a sequence of three passes or less and 50% of all goals came from possession gained in the final attacking quarter of the pitch. In terms of computerized notation system, Matchviewer of Prozone is a good example which provides the data of passing, heading, shooting, tackling etc. Both systems have their strengths and weaknesses. The following table summarizes part of it.
Hand/ Manual notational system
Computerized notational system
Strength
·         Cheap
·         Accurate (fully defined and used correctly)
·         Game is represented in its entirely and store in ROM which forms a database
·         Immediate feedback (i.e. short time)
·         Lead to the development of  predictive models
·         Indication of areas requiring improvement
·         Search video recording
·         Learning time required can be reduced considerably (e.g. keyboards, pads, graphical user interfaces, voice interactive systems)
·         Good presentation because of computer graphics, word-processing, database and multi-media  packages
Weakness
·         Time required for data processing can be very long
·         For complex game such as soccer, learning and training time is long in order to ensure accuracy and reliability of the operator
·         Expensive
·         Less accurate unless very carefully designed and validated

Table 1: Summary of the strengths and weaknesses of hand and computerized notation system
Another category of match analysis is motion analysis which focuses on raw features of an individual’s activity and movement (Carling et al. 2005). It can specify work rates of the players in different positions and distances covered in a game (Reilly and Williams 2003). This analysis is useful in identifying fatigue and differentiating between positional differences in work rate and fitness levels (e.g. ability to move backwards and sideways is important for defenders) (Carling et al. 2005). There are three elements which should be measured: intensity (walking, jogging, cruising and sprinting), duration (or distance) and frequency. Prozone3 is software of Prozone which provides this sort of data. Nowadays, most of the motion analysis would be done by computer as it is difficult for people to record how many metres a player ran in a match. However, in the old days, researchers had to do it by hand. Reilly and Thomas (1976) recorded and analyzed the intensity and extent of discrete activities. They combined hand notation with tape to analyse the movement of the players. They found that a player is in possession of the ball for less than 2% of the game.
Conclusion
Performance analysis is becoming more popular in lower leagues and more football clubs will set up the performance analysis department in future. There is still much room for the development of performance analysis. Match analysis is different from performance analysis but it is the core part of performance analysis. The aim of doing analysis is to provide objective information and analysis for the coach about past performance (either team or individual). The analysis can be done by hand/manual and computer as well. Both systems have their own strengths and weaknesses.

References

CARLING, C. et al., 2005. Handbook of Soccer Match Analysis.Oxon:  Routledge
FRANKS, I.M. and MILLER, G., 1986. Eyewitness testimony in sport. Journal of Sport Behavior, 9, 38-45
NEISSER, U., 1982. Memory Observed. San Francisco: CA
PROZONE, 2009. Services [online][viewed 5 September 2012]. Available from: http://www.prozonesports.com/services.html
REEP, C., & BENJAMIN, B., 1968. Skill and chance in association football. Journal of the Royal Statistical Society A, 131, 581-585

REILLY, T., 1996. Science and Soccer. E & FN Spon
REILLY, T. and THOMAS, V., 1976. A motion analysis of work-rate in different positional roles in professional football match-play. Journal of Human Movement Studies, 2, 87-97
REILLY, T. and A., M. WILLIAMS, 2003. Science and Soccer. 2nd ed. Oxon:  Routledge