Mechanical tension is the main mechanisms of muscle hypertrophy… but what regulates mechanical tension?
In this post, we’ll review what mechanical tension is, and the main factors affecting this mechanism!
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What is Mechanical Tension?
Mechanical tension is the force created when a muscle contracts isotonically against a load. The tension produced by force generation and stretch is essential for muscle growth (source).
In your daily life you are continuously exposed to the natural force of gravity. When a different force is applied (i.e lifting weights), a cascade of molecular and cellular responses happen in your muscle.
Sufficient mechanical force will send a signaling cascade to your body to build muscle and adapt to the new situation. This process is called mechanotransduction.
Although mechanical tension alone can produce muscle hypertrophy, it needs of metabolic stress and muscle damage to fully produce muscle gains.
Mechanotransduction
When an overload force is opposed, your central nervous system gets into play to activate the muscle fibers.
In this process, mechanical stress is translated into chemical signals. The chemical signals will trigger a signaling cascade to produce muscle growth.
Mechanotransduction is the basic principle of mechanical tension. A load is opposed, and your body works to activate muscle fibers, exert force to lift the load, and send a signal to build muscle.
The transmission of the force is caused by many different systems. After the muscle has contracted, the forces are transmitted from end to end of the muscle fibers, and laterally from the sarcomere to the extracellular matrix.
This way, the force generated by the muscle fiber can be sensed by the rest of your body, resulting in muscle hypertrophy.
Regulation of Mechanical Tension
If you want to build muscle, you need to know what mechanical tension is, and what are the factors regulating this mechanism.
In the next 3min, we talk about regulation of mechanical tension!
Regulation of Mechanical Tension
- Force-velocity
- Passive tension
- Eccentric loading
- Incremental loading
- Range of motion
Force-Velocity
The force-velocity profile is the best way to determine and induce mechanical tension. The force-velocity curve tells us how much force a muscle can produce at a given velocity (source).
For mechanical tension to have some kind of effect, the muscle fibers need to activate.
When the muscle is contracted and/or stretched, the motor units are recruited and the muscle fiber is ultimately activated
A lower velocity curve will activate more muscle fibers, as more force is needed. On the other end, a higher velocity curve will not need as much force, and the activation extent will not be as great (study)
Lower velocities increase the extent of mechanical tension and muscle adaptations (study). The force-velocity profile is, then, one of the main regulators of mechanical tension.
Passive Tension
Passive tension is created when a two-joint muscle is stretched at one joint while it is forced to contract at the other joint (source).
It develops because of the lengthening of elements out of the muscle cell, especially collagen and titin, two regulators of muscle hypertrophy.
At higher extents of stretch, there will be more passive tension. This mechanism produces fiber-type specific muscle hypertrophy, with an effect only in fast-twitch muscle fibers (source)
Passive tension produces a favourable length-tension relationship on your muscle, being able to produce more force. It increases the amount of mechanical tension, and muscle hypertrophy.
As passive tension is fiber-specific, it can be used to target specific groups of fibers within a muscle.
Eccentric Loading
During eccentric loading, the muscle lengthens as the resistance becomes greater than the force the muscle is producing (source)
As the resistance overcomes the force produced by the muscle, eccentric loading activates muscle fibers to a great extent, being one of the main regulators of mechanical tension.
The ability ton produce greater forces during eccentric actions induces muscle hypertrophy (source)
Eccentric loading can, however, create large amounts of muscle damage as well.
Incremental Loading
Using progressively heavier weights can help you increase and optimize mechanical tension during an exercise.
As the load on the bar increases, the force required to overcome the resistance increases. This produces great amounts of mechanical tension, which will translate in later muscle gains.
Heavy loads will lower the velocity curve of the exercise, and more muscle fibers will activate.
Incremental loading can help you regulate and optimize mechanical tension by creating an appropriate resistance to overcome.
Range of Motion
The range of motion refers to the maximum amount of movement available at a joint during an exercise.
Exercising your muscles through the full range of motion forces them to contract at the same time they are being stretched.
Larger range of motion will create greater biomechanical stress on a given muscle. This will lead to an increase on mechanical tension, and muscle hypertrophy.
Introducing exercises with full range of motion can be beneficial as, compared to partial range of motion, a larger range will bring greater muscle gains (study)
Conclusion
Mechanical tension is one of the main drivers of muscle hypertrophy. It is regulated by the range of motion, eccentric loading, passive tension, incremental loading, and the force-velocity curve.
To optimize mechanical tension, work through an extended range of motion applying incremental loads, and include exercises involving passive tension and/or eccentric contractions.
