The goalkeeper is the last line of defence and can decide the outcome of a match! Despite this there is little research specific to this position, which results in a lack of understanding of the game demands and therefore specific training methods. From the little amount of research it is suggested that the goalkeepers actions are very short term, explosive and technically demanding (1). Physiologically, walking dominants a goalkeepers actions but if they do need to make a sprint the distance covered most frequently is between 0-5m as can be seen in figure 1 below.
Match analysis research investigating 34 goalkeepers participating in the 2002 World Cup (54 matches) found goalkeepers perform on average 23.4 defensive actions per match (minimum of 9 and maximum of 46) and the actions most often used are the save (lateral) followed by foot control and clear out (hand, foot and head) (3). On average there was 6.2 lateral saves and 3.8 jumps (high save and punch) per match, highlighting the importance of the lateral save over the vertical save. As the lateral save is the most frequent action performed by the goalkeeper, it is imperative this action is trained with specificity. In order to design training exercises that are specific to the lateral dive, a biomechanical analysis is required.
The lateral dive is a combination of both technical-tactical and physical components. It is the goalkeepers’ skill of tactical understanding, perception and anticipation followed by the strength/power of the lower body and the arm span that determines the efficiency of this critically important action (4). Biomechanically the lateral dive can be categorised into a near or far dive. Into different heights from the ground – upper, middle and lower (ground). Into three different stages of movement – initiation, transition and take-off and finally each leg can be described as the ball side (BS) or the contralateral side (CS). Figure 2 provides a visual breakdown of both the near and far dive and the three different stages of movement.
Research by Matsukura, Asai & Sakamoto (2014) investigating the magnitude of force (ground reaction force) and the direction of this force (force vectors) of the lateral dive found that both legs exerted high magnitudes of force via a triple extension moment. Further, the CS leg exerted a high magnitude of force during the initiation phase and the BS leg exerted a high magnitude of force during the take-off phase. It was also found that the direction of force in the CS leg was approximately the same for all three-ball heights however, for the BS leg the direction of force was different for all three-ball heights. The authors suggested that during the lateral dive the CS leg contributes a counter-movement to shift the center of gravity towards the ball and the BS leg contributes high magnitudes of force and dictates the direction of this force in response to the ball height. It was also mentioned the BS leg requires considerable force production to propel the goalkeepers center of gravity upon ground contact immediately towards the flight of the ball.
This information should be used to organize goalkeeper specific training and specific strength training exercises to induce transfer to a match. The principles of strength training specificity emphasize the biomechanical and motor qualities for a specific action in the context of the sport. Siff (2003) proposes the concept of dynamic correspondence (DC) to achieve specificity, where exercise selection is governed by five principles; 1) the amplitude and direction of movement, 2) the accentuated region of force production, 3) the dynamics of effort, 4) the rate and time of maximum force production and 5) the regime of muscular work. As mentioned earlier there is a lack of biomechanical research for goalkeepers so to perform an in-depth DC analysis of the lateral dive is difficult. However, this is the case for most team sport actions due the complexity of performing in a highly unpredictable environment. Despite this we can still aim to get as close to specificity as possible with the limited amount of information we do have.
Here is an example of just one of the exercises I use to induce the principle of specificity in strength training for goalkeepers. The aim of this exercise is to specifically improve the magnitude and velocity of force expression in the BS leg, as this is the leg that contributes more force towards the flight of the ball, which in theory increases the probability of a save.
- The magnitude and direction of force emphasizes the range of movement or amplitude and the direction in which force is expressed (6). As described above the BS leg contributes large forces in the horizontal and vertical vectors. Therefore, we are required to design an exercise that produces force in both the horizontal and vertical vectors at the same time. Traditionally these vectors are isolated into either vertical or horizontal force production.
- The accentuated region of force production identifies the specific joint angle within a given movement where the maximal amount of dynamic force is produced (6). As the lateral dive is a reactive action identifying a specific joint angle is difficult. Therefore it is important to train with variation and the freedom of “task completion” to cover this principle.
- The dynamics of effort emphasizes that the selected training stimulus should correspond to the type of strength needed, based on the amount of force and the velocity of the movement. It is also proposed the intensity used should not be less than but greater then the sporting skill (6). Without force-velocity profiles it can be assumed the lateral dive requires maximal power produced in the shortest amount of time. Therefore it is plyometric in nature and a plyometric exercise has been selected, specifically a drop jump to increase the intensity beyond that of the lateral dive.
- The rate and time of maximum force production emphasizes the need to produce large forces within a certain time limit, thus using a high rate of force development (RFD) (6). Again the selection of a plyometric exercise covers this principle. What could be improved is the utilisation of a jump mat to monitor ground contact times, making sure large lateral jumps are not achieved at the expense of a long amortisation phase.
- The regime of muscular work determines the type of musculature contractions that are undertaken during the sporting skill (6). As highlighted earlier it was suggested that the BS leg requires a considerable amount of force to propel the center of gravity towards the ball upon ground contact, suggesting there is a counter-movement jump involved. Again this principle will be covered with a counter-movement biased plyometric exercise.
So as you can see we require an exercise that is plyometric in nature (counter-movement jump), this plyometric needs to be advanced to increase intensity beyond the sporting action (plyometric drop jump), and the direction of this force needs to be produced in both the horizontal and vertical vectors. Below is a video that I feel represents an exercise specific to the requirements of the BS leg in the lateral dive for goalkeepers.
References
1. Bangsbo, J. (1993) The physiology of soccer – with special reference to intense intermittent exercise. Doctoral Thesis, August Krogh Institute, University of Copenhagen.
2. Di Salvo, V., Benito, P.J., Calderon, F.J., Di Salvo, M., & Pigozzi, F. (2008). Activity profile of elite goalkeepers during football match-play. The Journal of Sports Medicine & Physical Fitness, 48, 443-445.
3. De Baranda, P.S., Ortega, E., & Palao, J.M. (2008). Analysis of goalkeepers’ defence in the World Cup in Korea and Japan in 2002. European Journal of Sports Science, 8, 127-134.
4. Hoff, J. (2005). Training and testing physical capacities for elite soccer players. Journal of Sports Sciences, 23, 573-582.
5. Matsukura, K., Asai. T., & Sakamoto, K. (2014). Characteristics of movement and force exerted by soccer goalkeepers during diving motion. Procedia Engineering, 72, 44-49.