WarriorFX

New trainees frequently enter a resistance training routine understanding one basic principle: push or pull a load for a predetermined amount of repetitions. However, there is a lot more to understand about each repetition and how it affects muscular failure and subsequent growth.

Muscle contractions are often confused with muscle shortening due to the nature of the word “contract.” Muscular contractions are involved whenever the muscle produces tension - its sole purpose. Skeletal muscle can raise, lower or resist a load; classified as concentric, eccentric or isometric, respectfully. The type of muscle contraction is determined by the motion of the associated joints and how the muscle transforms in response to the load.

Concentric

Concentric, positive-range, contractions occur when a load is pushed or pulled. The muscle shortens as it contracts. It overcomes an external torque by opposing gravity using muscular momentum and a decreasing joint angle. The force generated by the muscle is less than its maximum. Continued repetitions can be completed until the muscle reaches its maximum contraction velocity. At this point, the load can no longer be pulled or pushed through the same range of motion. Concentric failure is reached.

In bodybuilding and powerlifting, concentric force is measured using limit or relative strength performance by an athlete in a movement. Powerlifters train for maximal concentric strength in the flat bench press, squat and deadlift.

Isometric

Isometric, sometimes called static, contractions occur when a muscle is activated at a constant length. The force generated is dependent on the length of the muscle while under tension. Maximal isometric tension is dependent on its length-tension curve.

Although not considered absolute failure, being able to resist a load is no easy feat. This can be accomplished by either holding a load in place or by acting upon an immovable object - muscular tension and length remains constant. Shaking results as increased muscle fibers are recruited; it takes discipline for a bodybuilder to not break proper form. Isometric failure is reached when a load can no longer be suspended.

Isometric exercise is frequently used to produce muscle growth, modest strength gains, as well as rehabilitation. Sometimes sports-specific training introduces a functional need for static strength.

Eccentric

Eccentric, negative-range, contractions occur when a load is resisted while descending. Gravity is controlled as the muscle lengthens and joint angle increases. Eccentric failure transpires as the external force on the muscle becomes greater than the force the muscle can generate. This type of stimulation is considered absolute and remains a very popular area of study for growth of skeletal muscle.

Lengthening muscle contractions have been shown to produce ultra structural damage in the form of microscopic tears. This muscle damage produces a cascade of metabolic events and an increase in muscle protein synthesis and degradation. The events associated with muscle hypertrophy are more apparent following eccentric than concentric resistance exercise.

A tempo pattern is written in resistance literature using a series four numbers (X-X-X-X). The first number is the eccentric phase, second is the fully-stretched position, third is concentric and fourth is the fully contracted position. Many trainers suggest large limb movements stick to a 4-0-2-0 tempo: squats, rows, leg curls, dips and bench press. Shorter limb movements using a 2-0-2-0 tempo: flyes, lateral raises, barbell curls, wrist curls, calve raises, sit-ups and back extensions. The following tempos are a generally accepted way to keep continuous tension on the muscle to promote growth. The actual tempos used should be tailored to an athlete’s requirements and remain goal-orientated.

Example of a 4-0-2-0 Bench Press tempo:

1. Lower the weight using a four-second count
2. Immediately change direction without a pause
3. List the weight using a two-second count
4. Immediately repeating the next repetition.