Muscle Growth Explained

Muscle Growth Explained

When muscles are worked harder than normal they will be forced to do extra work to overcome the load. This process is called overloading and leads to increases in strength through the following process.

When the muscle contracts against a resistance it stimulates a breakdown of muscle proteins and the formation of very small (micro) tears in the muscle fibers and connective tissue. This occurs primarily during the eccentric phase of the motion. After a period of rest and recovery, new proteins are build-up, the connective tissue is repaired, the muscle fibers enlarge, and the muscle increases in diameter and strength.

This is not due to an increase in the number of muscle fibers ( which remains the same ) but to an increase in the size of filaments in the fibers. Thus each fiber becomes denser and denser the fibers the more force they can generate against a resistance. The greater the size of the muscle and the density of fibers within it, the stronger the muscle.

Also, regular training causes an increase in the number of blood vessels in the muscle ( capillarization ). This means that more oxygen, fuel, and nutrients can be delivered to the muscles, and metabolic waste products can be removed more readily. The overall result is one of increased efficiency, strength, and size.
The attached tendons, ligaments, and bones also increase in strength and so the whole surrounding structural framework becomes stronger.

The nerve pathways serving the muscle improve, allowing the muscle fibers to be used more efficiently at any one time. This accounts for the relatively rapid improvements in strength when beginning a training programme. Muscle size remains the same initially as the muscle can lift the weight more efficiently and strength improves.


  • Anabolic-the building of muscle tissue-a net increase in muscle protein.

  • Catabolic-breakdown of muscle tissue-a net decrease in muscle protein.

  • Concentric-shortening of muscle during contraction.

  • Eccentric-lengthening of a muscle under tension.


Muscle strength is the amount of force a muscle can produce, for example, the amount of weight can be lifted. The greater the size of a muscle the greater the strength. Strength is acquired through progressive resistance training, that is, lifting heavier and heavier weights over some time.

Muscle endurance is the ability of a muscle to continue contracting against resistance. This is developed by maintaining a constant workload for increasing periods of time-lifting a weight for 12 or more repetitions then building up to say 15, 20, 25, and so on as endurance improves.

Strength training will develop both muscle strength and endurance, but the amount of weight lifted and the number of repetitions will determine which aspect is developed most. In general, using heavy weights for lower repetitions (less than 12) develops strength, using lighter weights for more repetitions develops endurance.

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