Inroad Theory of Exercise

by Dr. Doug McGuff

The most time-efficient and productive exercise program is one based upon the principles of High-Intensity Training (H.I.T.). Productive exercise must be of a threshold level of intensity, as any level below this threshold will not stimulate maximal results. As a result, H.I.T. exercise sessions will be comparatively brief and infrequently performed (as opposed to conventional exercise sessions).

The degree to which you have been weakened, and the amount of time it took to do so (approximately 2 minutes), represents a threat that from the body’s perspective must be addressed. The positive adaptive response to effective resistance training is the building of bigger, stronger muscles so that there will be more strength left over the next time such a stimulus is encountered. As you repeat the process, you will increase the resistance that your muscles will be made to contract against to produce a similar response each time, but doing so is metabolically expensive. By performing more intense exercise you must reduce the volume and frequency of that exercise, and vise versa.

To get the best results from high-intensity session, it is referred to as the Inroad Theory of Exercise. Inroad is the momentary weakening of muscle. Here is how the phenomenon of inroading is achieved:

STAGE 1: Set begins.
At the beginning of the set, you are fresh with 100 units of strength. For inroad to occur, the resistance must be meaningful, i.e. 75-80 percent of your existing strength level. If the resistance selected is too light, the muscle will recover at a faster rate then it fatigues, with the result that no inroad will occur. Using a slow, controlled speed of contraction and extension, move the weight for 6-10 seconds during the lifting (or positive) phase, and 6-10 seconds during the lowering (or negative) phase.

STAGE 2: Strength diminishes.
With each passing second of exercise your initial strength level diminishes and your level of fatigue increases. Your respiration increases, and you begin to feel the burning sensation of lactic acid in your muscles. You have now lost some degree of your initial 100 units of strength, but you are still stronger than 75 units of resistance on the machine.

STAGE 3: Muscles fail.
Your muscles are now so weakened that it may take 15, 20, or even 30 seconds to complete the lifting portion of the repetition, and it is getting very difficult to control the lowering portion of the repetition. Your strength and resistance are at virtually the same level, but your strength continues to drop until it is just below the resistance.

This is where inroading begins.

STAGE 4: Inroad.
You attempt to move the resistance but fail to do so. You continue to do for 10 seconds as your strength dips well below the resistance level of the machine. At the end of the countdown you unload from the machine. By the time the set is finished, your strength has been reduced to approximately 60 units, and you have inroaded your muscles by 40 percent. (You will develop an almost instinctual sense of panic, a feeling that you are not strong enough to meet the resistance you are under. This is “make-or break” point in the set. If you understand that are you trying to do is achieve a deep level of muscular fatigue, you can override the instinct to attempt to escape. Just keep pushing in the same manner that you did in the beginning, and if it stops moving, do not panic: just keep pushing. After all, the purpose of the exercise is not to make the weight go up and down; it is to achieve a deep level of inroad.)

Inroading consumes resources that must be replenished. If you bring the inroading stimulus back to your muscles before your body has the response, it will either interfere with response or prevent it from occurring. Providing a sufficient stimulus is only 50 percent of the process, sufficient recovery time makes up the other 50 percent. This is why you should not perform more than one workout per week.

When inroading is successfully achieved from exercise, not only is muscle growth promoted, but some secondary events take place as well:

• Cardio-respiratory stimulation: Your cardio-respiratory system serves the mechanical functioning of the muscles. The higher the intensity of the muscular work, the higher the quality of the cardiovascular and respiratory stimulus will be.

• Metabolic stimulation: During inroading, metabolic wastes (mostly lactic acid) accumulate faster than they can be eliminated. This creates an environment where growth factors are released and the first stage of muscle growth are stimulated.

• Muscle and bone increases: As you get stronger, heavier weights are necessary to challenge you enough for inroading to occur. Exposure to heavier weight causes microscopic cellular damage that initiates the muscular adaptation and is viewed as essential for stimulating increases in bone mineral density.