Factors Affecting the Speed of Interior Linemen
For players in positions requiring considerable body weight, mass, and strength, such as interior linemen, some slowing in the “first three steps” and in short sprints of 5-15 yards or more may occur following planned off-season weight gain. The trend toward larger linemen continues at both the college and professional level as teams recruit or develop 300-375 pound athletes to enhance blocking, rushing, and tackling skills. From a health standpoint, it is desirable that most of these extra pounds be added in the form of muscle mass over a longer period of time without the use of steroids or growth
hormones. Unfortunately, athletes often add large amounts of adipose tissue and exceed the recommended percent of body fat for optimum speed and health. Regardless of whether the added weight is muscle or fat, it places increased demands on the body and requires more force production to maintain pre-weight gain speed.
According to the findings of researcher, Ralph Mann, the act of sprinting in football, baseball, and other sports requires the athlete to produce powerful vertical and horizontal ground contact forces. The propulsive force for an interior lineman during the initial two-foot push off the ground to initiate a pass rush, for example, requires slightly more force in a vertical direction than horizontal. With each step during this early acceleration phase of a short sprint (3-10 steps, about 5-20 yards), additional vertical force and less horizontal force is needed as the body makes the transition from front side mechanics to back side mechanics. Ground contact force must equal the athlete’s weight just to stand and support the body. The total vertical force needed in sprinting to stop downward velocity, counter breaking forces, produce upward velocity, and overcome the force of gravity is approximately 2.15 X body weight. A 275 pound athlete needs to exert a ground contact force with each step of approximately 591 pounds during the sprinting action; even more during the start and first 5-10 yards of a short sprint.
During the initial push off both feet (the Start), 100 percent of a player’s available force can be applied to the ground. The main limiting factor in determining how fast an interior lineman accelerates during the pass rush is his speed-strength in the muscles involved in this pushing action. As speed increases, less and less of one’s available force can be applied to the ground due to the rapid movement of body segments and the short period of time the foot is in contact with the ground. At maximum speed, the amount of force that can be applied may be as little as 50% of available force. At this “zero” acceleration phase, nearly 100 percent of the force is in a vertical direction. Training programs that improve an athlete’s maximum available ground contact force obviously also increase the amount of force that can be applied to the ground ((50% of a maximum available force of 500 pounds, for example, is greater than 50% of 450 available pounds of maximum force). Gifted sprinters and athletes are able to apply a somewhat higher percentage of maximum available force.
For each pound of weight a football player adds, ground contact force requirements increase. A 275 pound lineman who adds 25 pounds of muscle and fat to reach 300 pounds now may need an additional push-off force of approximately 53 pounds to maintain pre weight gain speed. While some improvement in ground contact force will occur as muscle and fat are added, the increase may not keep pace with the weight gain and some slowing will occur. Sprinting is a demanding, intense activity requiring a force close to the limit of every athlete’s capability on each step.
Keep in mind also that the ratio between body weight and ground contact force is a key factor affecting speed that can be altered in a number of ways. Adding too much weight and not improving the strength of the pushing action away from the ground negatively changes this ratio. Losing body weight and merely maintaining present ground contact force has a positive effect on this ratio and will improve speed in short sprints. A 10-25 pound weight loss (body fat) with no reduction in ground contact force is a desirable goal for over fat football players in any position. Weight loss in combination with increases in ground contact force provides a “double “hit” and has the greatest effect on the ratio of ground contact force to body weight and speed in short sprints. Ground contact force affects the start (first two steps), stride rate, stride length, acceleration, and maximum speed. If linemen are to maintain their pre weight gain speed or improve current speed in short sprints, training must focus on increasing the force of the pushing against against the ground in both a horizontal and vertical direction. Several of many available specific exercises for three modes of strength training to increase propulsive force in both directions are shown in Table 1.
Summary of Speed-strength Exercises to Increase Horizontal and Vertical Force
|STRENGTH TRAINING PROGRAM||HORIZONTAL DIRECTION||VERTICAL DIRECTION|
|Free Weights and Weight Machines||Barbell hip thrust
Lunge Single reverse leg press
|Olympic Lifts: clean, jerk, snatch
Front and back squat
Standing broad jump
Standing triple jump
|Sport Loading: Resistance Training||Austin leg drive machine
Harness and release
Rubber band sprint movements
Rubber band sprint movements
To execute a fast, short sprint, the amount of force, timing, and the speed which force is applied plays a major role. This requires athletes to generate very high levels of static, dynamic, and elastic strength. In addition, mastering proper form and technique in the start (three-point, four-point, or standing) and acceleration phase of a short sprint makes certain that all forces are applied at exactly the right time, in the right manner, and in the right direction with no interference from sideward or other unnecessary movement. A coach with an expertise in sprint mechanics can be a valuable asset to football players in every position. An accurate, practical and inexpensive test is still needed to measure the ground contact force of athletes and the resulting changes following participation in a wide variety of training programs.