This principle is essential for developing maximum strength, power and muscle mass, for getting a better sense of feel and control and shaping each muscle, and for getting the best possible pump. It helps increase the safety of any exercise and the effectiveness of other training principles. And, like the rest of the bodybuilding training principles, the Continuous Tension Training Principle is based on decades of experience and results in bodybuilding and lifting champions.

Tension

To understand why constant tension is so important and use it most effectively, it's necessary to understand what tension is. You probably remember from your science or biology classes that there is always a little tension in the muscle. This is what we call muscle tone. It's due to a constant low level stimulation of our muscles by the nervous system. Without it, your muscle metabolism would slow to a crawl and your muscles would shrink and lose their strength.

Physiologically, tension refers to the cross bridges or chemical bonds that form between strands of the contractile proteins (actin and myosin) in muscle. When the chemistry of the muscle fiber is in order (not too acidic or depleted of any key elements like calcium, potassium, magnesium, etc.) and energy (ATP) is available, these bridges can pivot in a ratchet like fashion, pulling or sliding the myofilaments across one another, resulting in muscle shortening. The more cross bridges you can form, the more tension you can develop and the more force you can exert and the stronger you are. And, depending upon your diet and other aspects of your training, increased strength and tone can mean a larger, thicker, denser, more vascular muscle.

Using the Continuous Tension Training Principle correctly can help you develop more cross bridges. By concentrating specifically on controlling the weight and on the feeling (of tension) in the muscle, constantly trying to feel more rather than to lift more, you will be learning to form more cross bridges in each fiber and using more muscle fibers. The result of this is that more myofilaments are added to each fiber so each fiber can make more cross bridges, develop more tension, and exert more force. The end result is more strength, more density, more mass.

Speed of Movement

Although faster movements provide less time for cross bridge formation and tension and force development, the rate of cross bridge formation may be more of a stimulus for the muscle to add contractile proteins and cross bridges than the slower contractions (in which absolute force and tension are actually higher). And, in fact, true power (high speed) training seems to result in larger individual fast twitch muscle fibers.

Actual power production is generally highest when you're using 60 - 70% of your one rep max and attempting to move the resistance as fast as possible. That just happens to be about the 15 - 20 rep max range for most people for most exercises. And that's probably one of the main reasons that rep range is used so much by so many champions.

Exercise performed at slower speeds provides more time for cross bridges to form and allows for development of more tension. I'm talking about heavier movements in the 5 - 6 rep range. This type of training enlarges both fast and slow twitch fibers and, particularly when used in a cycle training program and combined with some faster, lighter weight movements, its still the most common method of adding mass.

Eccentric Contractions

Eccentric contractions play a unique role in muscle growth. Eccentric, or negative training has been a controversial topic for 40 years, ever since early research indicated that it might be a more effective stimulus for strength increase than concentric training. Heavily promoted by heavy duty advocates, it never quite lived up to its promise of accelerating and improving mass and strength gains.

Recent research on exercise machines further underscores the importance of the eccentric portion of contractions. Exercise machines that provide resistance only in the concentric mode can enable a normal (non-atrophied) muscle to increase in strength. However, without the eccentric portion, muscle growth does not occur.

The reason the eccentric portion of a movement is so important is that the capacity for tension (force) development is actually highest then. When you keep maximum tension on the muscle and resist as much as possible during the eccentric portion of a movement, the cross bridges are forcibly broken, reforms as the muscle lengthens and re-broken until the movement is completed. This effect is particularly important when the resistance is high enough to cause the muscle to be lengthened forcibly (such as your partner giving you extra resistance).

You can visualize this as if you were sliding down the edge of a cliff with a lot of weight attached to your waist. You'd be grasping handhold after handhold but would eventually slide further and further down until you reach the bottom. You can easily imagine the damage this would do to your hands.

Well, it seems that something similar happens to the cross bridges and actin and myosin filaments in muscle when it's stretched by some load. That's why the weight and speed of contraction must be carefully controlled during eccentric-accentuated or eccentric-only sets. If they're not, you don't have time to form the cross bridges, you can't control the weight, and you greatly increase your risk of injury.

These shearing effects on the contractile proteins, plus the stretching of the connective tissue that covers the muscle fibers, bundles of fibers and the entire muscle, are probably responsible for the soreness that follows more or harder eccentric work than you're accustomed to. Soreness, incidentally, as well as hypertrophy, occurs only when there is an eccentric component to a movement.

But more importantly for the bodybuilder, the forced stretching that occurs during a controlled eccentric portion of a movement seems to be the reason it's so critical for growth. I'm talking about staying as tight as possible during the negative portion whether you have a partner add resistance or not.

Stretching Under Load

Research closely shows that the most forceful contraction occurs when the muscle is stretched by a load to 10% beyond its normal internal resting length. This stretching is an internal phenomenon and has nothing to do with going through the full range of joint motion. And a controlled eccentric contraction causes that kind of internal stretching and makes for a significantly better, more forceful concentric contraction. This is one aspect of what 'staying tight' during a lift means.

The 'loaded' stretching that occurs to varying extent during the eccentric part of weight training or other movements is in fact the most powerful of all known growth stimulators. It is so important and powerful that, when combined with an increase in intensity and particularly the volume of work, it can literally cause a doubling of muscle size within a matter of days.

Range of Motion

Just going through the full range of motion is far less important for stimulating growth than many experts seem to think. It's certainly less important than keeping maximum tension on the muscle during the eccentric portion of contraction. Again, that's why having a partner add resistance to increase the tension and work during the eccentric portion of the rep can be so beneficial if it's performed correctly. This is not to say that you shouldn't go through the full range of motion, but you can keep the muscle tightest if you only move through a small range at a time (really concentrating intensely on maintaining maximal tension). You can certainly get an incredible pump of the whole muscle that way.

Partial Reps

Try this partial reps program someday and see for yourself. Select an exercise. Divide the range of motion for that exercise onto two or three parts. Adjust your body position to maximize stress on the intended muscle for one portion of the range of motion for each set. Then perform a set or two to the desired point of fatigue for each position and see how your muscles feel, concentrating on keeping the muscle as tight as possible throughout the range of motion.

It'll help if you have a partner add just enough resistance to make the eccentric part hard. Not impossible, just hard - hard enough that you fight it all the way down for 4 - 5 seconds. With effort and experience, you will be able to keep the muscle so tight and the resistance under such control, particularly in the middle and upper portions of the range of motion, that you can let the weight accelerate slight during the eccentric portion and then use a plyometric rebound to intensify the concentric portion of the contraction. Remember, these are for partial reps, and for safety and effectiveness, the weight must be under complete control.

You should also try working each portion of an exercise for a specified number of reps or to the point of fatigue and then, in the same set, work the other part or parts of the range of motion. Finally, you would complete the body part by doing a set or two of an exercise that takes you through the whole range. This is what the Partial Reps Training Principle is all about. The above example shows how all the Training Principles are inter-related. They're all based on ways to alter the rate and amount of tension.

Balance

Every movement, not just exercise, has an eccentric as well as a concentric portion. Consider running. Your hamstrings are contracting concentrically as they pull each leg rearward. They're contracting eccentrically and being rapidly and forcible stretched as the quads and hip flexors pull the upper and lower legs forward. That kind of stretching can lead to pulled and torn hamstrings. This occurs especially when there is a strength imbalance between the quads and hamstrings. If the quads are much more than three times as strong as the hams, when the quads are pulling the legs forward, the relatively weaker hams can't handle the force - much the same way that any muscle group would react to repeated eccentrics with weights that are too heavy and beyond the capacity of that muscle to control.

Inadequate flexibility as well as strength imbalances can also contribute to muscle pulls as described above. Flexibility is nothing more than the ability to control the tension in a muscle - to be able to reduce it and relax the muscle to the extent that the muscle can be stretched beyond its resting length. That's why stretching, which breaks cross bridges that are formed, reduces tension and more or less forces a muscle to relax - is used to stop cramps and muscle spasms.

But control of the tension in the muscle is the name of the game. If you can release it, you can increase it. And increased tension allows you to lift more and grow. Stretching - during warm up, cool down, and as part of off day recovery or active rest - also promotes increased blood flow and increased uptake of amino acids from the blood. And this is exactly what's required for protein synthesis and muscle growth.

Back to Continuous Tension

Enough about stretching and eccentrics. What else is important about continuous tension? Continuous tension means trying to squeeze the muscle as hard as possible all the way through the range of motion, in both directions, no matter how fast you're performing the movement and not just at the end in a peak contraction.

As noted, this virtually eliminates bouncing, swinging and hyperextension of joints, maximizing joint and body stability and making any exercise about as safe as it can possibly be. The Continuous Tension Training Principle can save your joints and connective tissue, and it's absolutely critical for those working through or rehabilitating an injury.

Tension in the muscle tends to reduce blood flow and when the tension, actually the force exerted, is 50% of maximum, blood flow through a muscle is completely stopped due to compression of blood vessels by the contracted muscle. As a result of being deprived of blood and oxygen and other nutrients and of heat and various metabolic wastes flushed away during the set, the body develops the capacity to function more effectively under such anaerobic conditions. This is one of the effects of weight training that makes it such a fundamental and important part of conditioning for so many sports.

From the perspective of the bodybuilder, this temporary disruption of the blood supply to the working muscle has one of the most important of all training effects. It produces such an incredible demand for oxygen, nutrients and waste removal that, as soon as the tension is taken off the muscle, there occurs what is called in physiology a 'reactive hyperemia.' All the blood vessels are wide open and the blood is almost sucked into the muscle, with flow increasing 10 - 20 times or more above normal.

The Pump

With that kind of flow, and the leakage of fluid out of the bloodstream and into the area between the cells that occurs due to the high volume and pressure of blood flowing through the muscle, one of the primary goals and sensations of bodybuilding is achieved - the muscle pump. And the more tension, the more energy is used, the more work is done, the greater the demand for blood, and the greater the pump. That's why you hear knowledgeable bodybuilders taking the tension off the muscle by relaxing or locking out at the completion of a repetition.

Maximizing tension in the flexing muscles will also help squeeze the veins, so that they're visible just below the skin. That huge volume of blood flowing through those veins can also over months and years of training enlarge and expand into those pipelines you see running across the bodies of the more intense bodybuilders and lifters.

Focusing on the tension in the muscle will help you think in terms of the feeling in the muscle instead of just getting the weight up. And it should also help you more because of necessarily perform the movement stricter and slower, as a result of which you can't help but feel more and pump better. The usual tendency is for athletes to get into this principle by using lighter weights - that they can feel and control better. Once you get the hang of it, though, you'll obviously need to keep adding resistance to push the muscles to new levels of quality. But you'll get a lot more out of it. Whether it's simply a better toned, more symmetrical body or thicker, denser, more vascular physique with better overall muscularity, the end result will be more than worth the effort.

That about sums up how you can use the Continuous Tension Training Principle.