By: John De Witt, Ph.D., C.S.C.S Provided by: Amplified Soccer Acceleration/Deceleration Exposure Required to Recreate Match-Like Loading Article Objectives:
It is well known that players perform a variety of activities in the course of a soccer game. There is now plenty of research that shows that senior players tend to cover distances of over 10 km during a match, with about 500-1500 m of that being high speed running. Because of the emphasis being able to complete repeated sprints throughout the match, interval training is the best method to improve match fitness. During training sessions, interval training is often set up as a linear activity. In other words, the exercises completed by the players tend to be in straight lines. This is not necessarily a problem, given that it takes about 30m of distance for an athlete to achieve maximum velocity. The 30m issue is the heart of a trade-off that must be made when selecting training activities. Change of directions play a large role in matches as players must consistently adjust to the rapidly changing situations they encounter. However, it is probable that at some time during the match they will also be required to perform linear actions at top speed, such as when attacking or defending a counterattack. For that reason, it is important to include both linear and change of direction activities in your player preparation planning. A change of direction is simply an adjustment in an athlete's movement. Some changes of direction occur with little change in speed, depending upon the amount of change in direction and the speed of movement before and after the change. Stopping and starting while maintaining the direction of movement, such as when a player looks to deceive a defender, may not be an angular change of direction, for the purposes of this article, it will be considered a direction change. The important aspect of the change of direction that we want to focus on is the deceleration (stop), followed by the acceleration (start). In physiological terms, muscles create force by shortening, or absorb force by lengthening. The shortening, called a concentric contraction, is an active production of force that results in angular accelerations of the joints that the muscle cross. When starting a run, a majority of the muscular actions are concentric, producing the forces across the lower leg joints that result in the gain of running speed. During force production while lengthening, called eccentric force production, the muscle creates a resistance force to decelerate the joint motion that the muscle crossed. It is during the eccentric activation that micro-damage occurs in the muscle. This micro-damage can be 'good' in that it results in muscle growth, but it can also be 'bad' by resulting in injury. One of the things that coaches should strive for in their training program and periodization is the elimination of soft tissue non-contact injury. Nothing can be done about a contact injury in terms of the external forces that are applied to the injured body part. In the case of a soft tissue non-contact injury, like a muscle pull, there is a different story. A muscle pull will occur when the muscle is attempting to decelerate the joint, but the force necessary is greater than the muscle is capable of producing. For example, hamstring pulls rarely occur when an athlete is accelerating. These injuries typically occur when an athlete is already at top speed. Often times, the hamstring pull occurs because of the following scenario. During the running stride as the athlete brings their leg forward prior to their heel hitting the ground,the knee extends and the lower leg moves forward rapidly due to the lower leg's momentum. The hamstrings act eccentrically to slow the knee extension to protect against hyperextension. The lower leg momentum, however, it too large, and the hamstrings tear. Hamstring tears and similar injuries are avoidable. The key is to include force production (start) and force absorption (stop) activities in your training. These activities, which should be a part of your training program and could be incorporated into your warmup routine, can help your players' bodies to become more accustomed to both aspects of the speed generation. Coaches often focus on the acceleration aspect; we need to remember to also address the force absorption aspect. Suggested activities - make these activities a part of your fitness program to help decrease your player's injury risk.
|