An exercise theorist by the name of Ken Hutchins developed RenEx for use in a research project on osteoporosis conducted by Nautilus Sports/Medical Industries and the University of Florida. Since elderly women with frail bones were the research subjects, special care had to be taken to reduce the risk of injury. If not done cautiously, lifting weights might cause fractures in the thinned bones of these women. Fractures would occur if the weakened bones encountered any force that exceeded their structural integrity. However, for reasons discussed in the previous chapter, enough weight had to be used to produce a rate of fatigue that would result in meaningful inroading. Mr. Hutchins had to find a way to use enough weight to be meaningful, yet still keep forces low enough to not cause injury to very frail subjects.
Ken and his co-researcher/wife, Brenda, turned to simple physics for the answer to their problem. The formula which describes for is F = M x A. Which means force equals mass times acceleration. Since the mass used could only be reduced so much without compromising inroading, force would have to be decreased by reducing acceleration. Acceleration is defined as the change in speed per unit of time. When you move a weight quickly, you go from a dead stop, to a given speed in a short period of time… ie. you accelerate. When you change directions, you must stop and begin movement in the opposite direction, which again is acceleration. If you move more slowly the difference in speed from a dead stop to any point in the range of motion is less, therefore the change in speed per unit of time is less and, therefore, acceleration is decreased.
Exactly how slow to go becomes important. The average person can only move a weight so slow and be able to do it smoothly. If you lift the weight over 8-12 seconds, most people can produce smooth movement. If you try to lift it over 15-20 seconds, the weight cannot be moved smoothly. At this speed of movement, you actually have a series of stops and starts. When you stop and start like this, you simply have multiple little accelerations. So you want to use the slowest speed that produces the smoothest movement possible, because smooth movement indicates a constant speed. At a constant speed, there is no change in speed over a given unit of time, and thus acceleration is close to eliminated. With acceleration greatly reduced in the equation F = M x A, we can see that the force will be greatly reduced. Furthermore, at this speed, changes in direction can occur smoothly and continuously, which almost eliminates the acceleration at the point where you change direction from lifting and lowering and lowering to lifting.
You can now see one of the major reasons why I recommend Mr. Hutchins’ RenEx protocol. It makes exercise safer. Stimulating physical improvements would not be worthwhile if you got hurt in the process.
Another reason I recommend RenEx is because it makes exercise harder. This was noted serendipitously in the osteoporosis study. The subjects seemed to gain strength faster than had previously been seen. The answer as to why became evident when they looked at the protocol in the context of inroading.
The process of inroading is not just dependent on correct resistance selection. For inroading to occur, the muscle must be continuously exposed to the resistance. If the muscle gets a respite from the resistance, then some of the slow twitch motor units can recover and thwart the inroading process. If you watch most people working out in a commercial gym, you will see that they are not lifting weights, they are throwing weights. We have a natural tendency to accelerate when we lift weights. The reason we accelerate is because we are trying to use momentum to make the task easier. Momentum is defined by the tendency of any object that is put into motion to remain in motion. An object is put into motion by an acceleration force. If the weight you are using to work out with is moving under its own momentum, then it is not loading the muscle. We instinctually accelerate the weight because the resultant momentum spares us of muscular loading and the consequent muscular fatigue. The less we use acceleration, the less the weight can move under its own momentum, and therefore the muscle is more continuously loaded. When the muscle is continuously loaded, inroading is increased.
Returning again to our safety discussion, we should note that we also decrease force by decreasing mass in our equation, F = M x A. The amount of weight we can use when we can’t invoke acceleration and momentum to help us out is decreased. You simply can’t lift as much weight as you can throw. So by using the RenEx protocol, you decrease force by decreasing both mass and acceleration.
So you can see why I recommend RenEx. It makes the exercise both harder and safer. Most importantly, it makes exercise harder and safer at the same time. While it may seem trivial at first glance, this characteristic is revolutionary in the field of exercise. In any other form of exercise, as you increase the difficulty of the exercise, you must also increase the forces involved. In order to make other forms of exercise more challenging, you have to make them more dangerous. When you start an aerobics class, you will usually begin in the low impact class. When you get in better shape and need more challenge, you graduate to the high impact class. Finally, when you are really moving up, you graduate to the step class. By the time you make it to this level, you may have to drop out because your knees, hips, and back are hurting. How many times have you seen a substitute instructor in an aerobics class because the regular instructor is out with an overuse injury? If you go from walking, to jogging, to running wind sprints, the forces go up with intensity…and disproportionately so. RenEx exercise will get you in great shape, and it won’t get you hurt in the process.
By M. Doug McGuff, MD