Q: In your recent article on plyometrics you stated, "The more force you can take in from one direction, the
more force you'll put out in the other direction - up to a certain point." What causes the the point in which force generation does not increase proportionally to the speed of the stretch?
Force output from a preceding stretch is going to be determined by #1. function, and #2. strength. You see what happens during a plyometric contraction, especially at high speeds, is the muscle fibers act largely as stabilizers and the tendons and other non-contractual elements act as movement generators. The muscle fibers lock up to stabilize and the tendons stretch back like a rubber band and generate the movement with the muscles contributing to this action but not dominating it. The stiffer the tendon the more forceful the reactive contraction. Think about it, a stiffer rubber band will put out more force then a not so stiff one. So, in order to gather force and use it to utilize in a contraction you have to first be able to stabilize the force by the strength of your muscles. However, your function also has to be correct otherwise your tendons (rubber bands) won't be gathering any of that energy and you won't be putting out much of anything with the force you stabilize.
Let me give you a few examples to illustrate. Imagine a 90 year old woman performing a depth jump off of a 36 inch box. What would happen? Likely she'd hit the ground and crumble without any chance to ever use that force to build up into a strong reactive contraction. Why? Because she's not strong enough. When the force from the stretch exceeds what the muscles and tendons are capable of absorbing proprioceptors kick in and shut the muscle down to avoid injury. Training will enhance the amount of force you can take in before proprioceptors shut you down.
Now imagine a champion bodybuilder performing the same depth jump. Likely he'd hit the ground and easily be able to absorb the shock......but - he wouldn't have the capacity to go with the flow and relax and absorb energy into the stretch and transfer that energy into a smooth contraction because he's too used to muscling everything. The harmony between his muscles and tendons (plyometric function) is compromised and this would be illustrated by a lack of energy utilization during the reactive contraction.
Now, imagine an elite triple jumper performing the same depth jump. They relax into the jump, stabilize and absorb effortlessly.....and then............. POW!!!....explode out of the hole just like a rubber band. So, once the proper function is there then the limit is how much force you can stabilize into a brief isometric during the transition from down to up or eccentric to concentric. Now this is where muscle strength comes into play. You can have the best movement efficiency in the world but if you're not strong enough to absorb the force the amplitude you can take in and put out will be limited. So it takes a proper balance. As you develop you can keep progressing from one side or the other - either stabilization or contraction. Once you have optimized the ability to deal with one level of force input and output then you can increase it to further your abilities. Optimization might mean adding some muscle mass in order to improve strength in order to improve stability at the transition. It also might mean enhancing what happens after the transition. It also might mean you have to teach proper muscle-tendon harmony and go back and work on basic plyometric functions with lower intensities. There is a time and place for everything but it should be prescribed on an individual basis.
Q: After reading your recent plyometric article a lot of things jumped out at me. I've been thinking I need to concentrate on just getting strong but now I'm not so sure. My movement efficiency tends not to be so great. I'm pretty heavy on my feet. Is there anything you do to determine basic plyometric function?
A: Yes you're right - Before you can build a house you have to lay the foundation and when you're talking about being good at sports - being able to move with ease and stay light on your feet is probably the most basic function and this ability gets more important the more advanced you become or the higher up you go. At the upper levels not only are people bigger and stronger but they're also often lighter on their feet and faster because they have better movement efficiency then others.
As far as determining basic plyometric function there are a host of things you can do. I usually just watch someone move but let me give you an example of a drill you can use to assess basic plyometric function yourself. This is a slightly less advanced version of a 1-legged speed box jump drill I picked up from Dietrich Buchenholz that I've also found works well as an evaluation tool. Stand on a box about mid-shin level high. Now, standing on one-leg bounce on and off the box in a smooth rhythmic fashion with as little effort as possible and without putting any muscle into the movement. As soon as your foot hits the ground you should reflexively and lightly bounce back up on the box like a basketball with no effort at all.
I have found a majority will be unable to perform this basic plyometric maneuver correctly without pausing or muscling the movement. Since I have seen 6 yr. olds perform it correctly I know it is not a strength issue it is just a movement pattern issue. The harmony between the muscles and tendons (plyometric function) is out of whack. Before you can run you gotta learn how to walk and before you can benefit from becoming as strong as an ox or as big as a house you gotta make sure basic muscle firing patterns are in place otherwise all the strength in the world will do you no good. Once you have the basic movement capabilities in place then you can often enhance them with added strength but not before. Use this drill along with some of the others I covered in previous articles and you should be able to cure this problem in no time at all.
Q: People are always saying that you should plan a program around eliminating your weaknesses. I am not very strong at anything so how do I know what they are and eliminate them?
A: Well I guess you could just assume you are weak at everything and train everything and see what happens. Just kidding! I would take a broader view of things. Depending on your goals your weaknesses will vary for a particular goal. Everybody has strengths and weaknesses even if they don't know it yet and the body will tend to adapt quickest to it's natural strengths. If you train for a goal your body will quickly show you its strengths if you look for them and for the most part you can assume the weaknesses are the complete opposite of the strengths.
To give you an idea, if you took 3 sixteen year olds and put them on an identical program that incorporated a nice blend of strength, power, and speed training you may have 3 separate outcomes. One of them may develop great power and become a shotputter or olympic lifter, one of them may develop great strength and become a powerlifter, while another may develop great speed and become a 100-meter runner.
But, what if you were the guy who was "naturally" more like a powerlifter but you wanted to be more like a sprinter?? Then you don't need to do anything that's going to favor your natural adaptation - you'll need to minimize anything telling your body to function slow and maximize everything signaling your body to function fast. Or, say for instance you want to become an explosive football player but your body naturally favors the endurance runner profile......weak and slow but with the endurance of a duracell battery. You have to minimize the natural tendencies to maximize an adaptation in the opposite direction. This means that other more gifted athletes might be able to do boatloads of endurance training and still maintain or develop speed, size, and explosiveness but you will not be so lucky and will have to focus your efforts.
To determine all this just take a look at your performance in various tasks. Are you stronger then you are fast or vice versa? Do you tend to have good endurance and poor speed or good speed and poor endurance? In a sprint, are you slow off the line and fast whenever you reach top speed or are you fast off the line and crater out at 20 yards? Whenever you lift, are you better at high reps or low reps? Are you smooth and fluid on your feet and weak, or are you strong as an ox and as heavy on your feet as an ox or somewhere in the middle? Ask yourself questions like these and the answers will become clearer. I hope this brief summary gives you some ideas. For more information check out my article:
Different Strokes For Different Folks