SquattingTo Be Explosive, Train Explosive.
Kenny Croxdale, B.A., C.S.C.S. and Tom Morris, M.S., C.S.C.S.
Plyometric Bench Press Training for More Strength and Power
Kenny Croxdale, BA, CSCS and Tom Morris MS, CSCS
Reprinted with the permission of the author and Mike Lambert - Powerlifting USA Magazine - August/03. Powerlifting USA subscriptions- Call 1-800-448-7693 to order
In any field of endeavor, you want to use the right tool when completing a task. The best choice is a hammer and not a screwdriver when driving a nail into the wall. The same thing applies to training. You want to use the right training tool to invoke the desired results. Powerlifters should consider the tool of plyometric training to improve their power, which, in turn, will improve their 1RM.
To fully appreciate the value of plyometric training in the development of power, one must understand what power is and why it is important to powerlifters. As discussed in a previous article (Croxdale & Morris, 2002), power can be defined as force multiplied by distance divided by time. Since force is sometimes referred to as strength and distance divided20by time is the same as speed, power , for the purpose of this article, can be defined as follows:
Power = Strength x Speed
Since strength and speed are components of power, increasing one while neglecting the other limits total power development. Unfortunately, many resistance trained athletes focus on strength because they are familiar with this traditional and well-established mode of training. Because strength and speed have a multiplicative impact on power, athletes can make greater gains if they develop both components. For example, if an arbitrary strength score for an athlete was 2, and the athlete's arbitrary speed score also was 2, the hypothetical power rating would be:
2 x 2 = 4
Doubling strength without altering speed would double power:
4 x 2 = 8
If the same athlete made only a 50 percent gain in strength and an equal gain in speed, the power rating would be:
3 x 3 = 9 (Brittenham, 1997)
All powerlifters understand what strength is. Strength is the ability to generate the maximal amount of force against an external resistance. The amount of time it takes to exert a maximal force in a strength movement like the squat is greater than one second. While the "movement time during explosive activities is typically less than 300ms" (Robberds, 2001). Due to the time it takes to generate, apply and fully complete a maximal effort against a heavy object, typical strength movements are not considered speed movements. Resea rch indicates that a heavy squat, even when performed in an explosive manner "is an insufficient stimulus for improvements in muscle power…" (McBride et. al., 2002).
The gap between one's maximum power (developed in milliseconds) and maximum strength (developed in a second or longer) is called the Explosive Strength Deficit (ESD). "ESD shows the percentage of an athlete's strength potential that was not used in a given attempt." (Zatsiorsky, 1995). Think of the Explosive Strength Deficit as a car race. Both cars have top speeds of 100 mph (1RM). In a quarter mile race, car A is able to reach 65 mph (65% of 1RM). Car B is only able to reach 55 mph (55% of 1RM). Car A is able to generate more power than car B. Therefore, Car A's deficit is 35 % (100-65=35). Car B's deficit is 45% (100-55=45). Consequently, 35% of car A's potential was not used compared to 45% of car B's. The smaller the gap in one's Explosive Strength Deficit percentage, the greater one's explosive power.
The strength part of the power equation is where powerlifters excel. However, the majority of powerlifters lack speed. To close the Explosive Strength Deficit percentage gap, powerlifters need to implement more speed training…specifically plyometrics.
Plyometric exercises are characterized by a powerful, explosive muscular contraction in response to a prior, immediate, rapid dynamic loading of the involved muscles. Rapid loading of the20muscles using either ones body weight and/or light load causes that muscle to undergo an aggressive stretch. In order to protect the stretched muscle from injury, that stretched muscle
undergoes a reflexive contraction. This stretch reflex causes a proportional contraction of the stretched muscle thereby eliciting a more powerful contraction of that muscle compared to any contraction it could have generated had it not been previously stretched. It is the goal of plyometric exercise to utilize this stretch reflex in order to cause an even more powerful, explosive movement of the muscle…a form of sprint-assisted training.
Sprint assisted training involves overloading a muscle to cause a training effect by forcing the muscle to contract more powerfully than it would normally be capable of without the prior stretch. This pre-stretching produces a sling shot reaction. One has more firepower out of the hole, greater starting-strength.
As with all components of strength, the foundation of one strength level is built on another. "Starting strength is the underlying mechanism crucial for the display of acceleration-strength." (Siff and Verhoshansky, 1998)."The higher the level to which starting-strength is developed, the faster acceleration-strength can be realized." (Verhoshansky, 1977). In other words, the faster one moves from one part of the strength curve to the next, the faster one reaches the finish line or in this case locks the weight out. One might consider starting -strength as first gear on a car and acceleration-strength as second gear.
In order to generate a hypercontraction of the muscle, one must convert the eccentric movement of the loaded muscle to a concentric contraction as soon as possible. The time between the eccentric movement and the concentric contraction is referred to as the amortization phase. By decreasing the amortization phase, a more powerful, explosive movement is generated.
The amount of time spent in the amortization phase is the determining factor in a movement being plyometric or not. Research by Wilson et. al. (1990) examined different delay times in the bench press and showed that the benefits of prior stretch may endure for as long as 4 seconds, at which point it is suggested that all stored elastic energy is lost. This could lead one to believe that there is full retention of a stretch reflex if the amortization phase is 4 seconds or less. However, the stretch reflex begins to dissolve immediately. Even a short pause will negate the stretch reflex. Additional research indicates that "delays as short as .02 seconds are sufficient to dissipate the benefits of prior stretch", with up to 50% of the stretch reflex being lost in
one second. (Siff and Verkhoshansky, 1998). Therefore, it can be concluded that the longer the pause, the less powerful the contraction. To put it simply, the longer it sits, the heavier it gets.
Plyometric training has the added benefit of allo wing explosive power to be generated throughout the entire range of motion of a movement. Traditional barbell and dumbbell training actually causes one to actively decelerate the load during the later portion of the movement. The National Strength and Conditioning Association (2002) indicates that "performing speed repetitions
as fast as possible with light weights (e.g., 30-44% of 1RM) in exercises in which the bar is held on to and must be decelerated at the end of the joint's range of motion (e.g., squat) to protect the joint does not produce power or speed training but rather teaches the body how to decelerate, or slow down. If the load can be released into the air (i.e., the bar can be let go at the
end of the range of motion, making it ballistic), the negative effects are eliminated."
With this information in hand, the various method of developing squatting speed will be explored with the ultimate goal of increasing ones 1RM. The order in which the following methods are presented are from "easiest' to "hardest". The authors suggest that the athlete work his/her way sequentially from #1 to #4 over the course of their squat training program (based on Chu's periodization of plyometric training (1992). This will allow the lifter to establish a base of plyometric conditioning and then progress up through the more difficult activities while minimizing the chance of injury and maximizing power. Care should be taken when performing these activities.
1)=2 0Plyometric Bouncing Box Squa ts: Plyometric bouncing box squats involve performing loaded squats to a box placed under the lifter's mid hamstring-glute area. By allowing the legs to hit in this area, it reduces the loading on the spine, the legs absorbing the majority of the impact. As the lifter eccentrically lowers him/herself down to the box, they quickly reverse the movement by bouncing off the box and forcefully exploding upward completing the squat.
2) Jump Squats: Jump squats involve performing a typical squat with the only difference being that the individual aggressively explodes up during the concentric phase of the lift. The powerful extension of the hips and knees should propel the lifter into the air as if s/he were performing a vertical jump. Initially, the lifter should perform the exercise without weight just utilizing their body weight. As one's tolerance improves, external weight may be added. When performing non-resisted jump squats, the authors suggest using an aggressive arm swing as a form of sprint assisted training (over speed training) to more fully exploit power output.
3) Load Release Jumps. Load release jumps are similar in nature to jump squats. Two of the methods that can be utilized are dumbbell release jumps squats and barbell jump squats with weight releasers attached to the bar.
Dumbbell release jumps squats involve a bench or box and a dumbbell. Place the Bench or box in front of you. You will be jumping up on it.
Get a dumbbell and hold it in front of you. Quickly drop into a squat. As you drop into a squat; the dumbbell will end up between your legs.
Just prior to exploding up onto the bench, release the dumbbell. Wearing a weight vest can provide additional loading to this movement.
The second form of load release jumps is barbell jump squats with weight releasers. Weight Releasers are attached to the barbell. The weight releasers can be set to fall off the bar at a selected height, thus a load release effect is achieved. Once the load is released, the lifter explodes into the air in essence performing a vertical jump.
4) Depth Jumps: Depth jumps involve stepping off boxes of various heights and upon landing on the floor with both legs simultaneously, exploding vertically into he air…again aggressively using the arms the added power. "The average
heights for depth jumps are 0.75-0.8 meters (27-30 inches). Athletes over 220 pounds should use heights of 0.5-0.75 meters (18-27 inches)." (Dassie, 1999).
If one wishes to add external weight, the recommended plyometric jump squat training percentages are 10-40% of 1RM of the squat (Lamont & Stone, 2001). Within this training range, 30% of 1RM of the squat has been indicated to be the most productive plyometric training percentage to increase force and power (Kaneko, et. al., 1983). Performing jump squats with 10-40% of one's squat 1RM is a potentially dangerous activity especially considering the load absorbed by the spine upon landing from the jump.
Since speed is not typically considered an important component of a strength program, the majority of powerlifters ignore this facet of training. Powerlifters need to appreciate the vital part speed plays in the quest for strength. Yes, strength is the most important component of powerlifting. However, in moving a heavy object up a mountain, power is essential. Power creates the momentum needed to slide through one's sticking point, outrunning gravity. Increasing speed through plyometrics magnifies one's power and strength. In a nutshell, you lift like you train. To be explosive, train explosive.
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