Who said all muscle growth is created equally?
Research has shown that not all muscle growth is equal. The type of growth a muscle sees is directly related to the type of stimulus a muscle gets during weight training. So I thought we’d take a look at the growth in muscle tissue stimulated by conventional training versus static contraction training and see what differences there are.
Before we talk about stimulating muscle growth, we need to understand the anatomy of a muscle.
Here is a diagram that shows how a muscle is arranged (courtesy of Wikipedia):
This diagram shows you that the basic contractile unit inside a muscle cell is the myofibril. Actin and myosin fibers make up a myofibril. These fibers overlap one another and, when a stimulus is received from the nervous system, act together to cause the myofibril to contract. As the individual myofibrils contract, it causes the whole muscle to contract and shorten. The more myofibrils there are in a muscle, the more force is produced from their contraction.
Myofibrils are bundled together to form muscle fibers. The individual muscle fibers are bundled together to form a muscle.
The diagram also shows you the space surrounding the myofibrils is called sarcoplasm. Sarcoplasm is basically the cytoplasm, or cellular fluid, surrounding the myofibrils and contains enzymes, non contractile proteins and cellular machinery needed for the muscle to produce the energy for contraction. However, these proteins do not contribute to the production of force.
When you train using static contraction, you stimulate myofibril growth. The number of myofibrils in each muscle fiber will grow as an adaptation to the stimulus provided by a static hold. Ask the muscle to generate more force to lift the heaviest weight possible that it can lift and it will adapt by generating more myofibrils which will help it contract with more force. This is called myofibril hypertrophy. The reason muscles have this adaptive response simply has to do with the intensity of the contraction. Think of it this way. A suntan is a way for the body to adapt to sun exposure. You go out in the sun during the wintertime and the summertime but usually you get a suntan during the summertime? Why? Because the intensity of the sun is greater during the summer than it is in the winter. This causes the body to create melanin (suntan) to counteract this intensity. Well, during a static contraction workout, the intensity of the lift is greater than during a conventional workout and hence the body adapts by building up myofibrils to better adapt to this intensity.
As the number of myofibrils increase in each muscle fiber, so does the diameter of the muscle fiber. As the diameter of each muscle fibers increase, so does the diameter of the whole muscle itself. Hence by training using static contraction, you develop strong, dense muscle with more force generating myofibrils.
Conventional training on the other hand stimulates a different type of muscle growth. During the course of a conventional workout set your muscle is under tension for much longer than the 5 seconds used in static contraction. We all know that the longer a workout goes, the lower the intensity. What this stimulus triggers is a different energy system to supply energy for the muscle to contract. Without going into great detail on muscle energy systems, this energy system requires more enzymes to generate an energy molecule that the muscle uses during the contraction. The stimulus your muscle gets from the conventional contraction hence triggers your body to improve these energy systems. As I mentioned above, the sarcoplasm surrounding the myofibril is full of enzymes, non contractile proteins and cellular machinery that provides energy to the muscles. To adapt to a conventional lift where more energy is needed to complete the set, the body builds more of these enzymes, proteins and machinery in the sarcoplasm. The result is sarcoplasmic hypertrophy which is a growth of the sarcoplasm surrounding the muscle fiber. While this growth does result in an increase in muscle diameter, it does nothing for increasing the force production that the muscle can generate.
We’ve now looked at two different types of muscle growth that a muscle can undergo depending on the stimulus it receives. So which type of muscle growth is better? Stay tuned for that discussion…..