Muscle Hypertrophy is known as an increase in muscle mass, through addition of sarcomeres in parallel or increase on their size. Mechanical tension, on the other hand, is the main mechanism by which we can achieve muscle hypertrophy. In this post we'll give an insight on what mechanical tension is, the factors to consider and practical applications to optimize it and boost your trainings.
Bodybuilding started a century ago. However, the well known 'bro-lifters' didn't really know how to induce muscle hypertrophy and the mechanisms behind it. They probably didn't even know what 'muscle hypertrophy' was. They knew that going to the gym to lift weights until the muscle was sore gave nice results and the muscle looked bigger over time.
Now, with the help of science, we can now the mechanisms behind muscle hypertrophy to optimize our training and induce higher muscle gains.
When we talk about muscle hypertrophy there are three main mechanisms by which we can induce muscle hypertrophy. Of course, citing these three mechanisms as the main and only cause of muscle hypertrophy is not correct. In fact, muscle hypertrophy is a result of different mechanical and biochemical cascades leading to muscle growth (source).
But for now, we'll introduce muscle hypertrophy as the result of the combination of the following mechanisms:
Out of the three mentioned, mechanical tension is considered the most important one. While metabolic stress and mechanical tension have been proved to induce muscle hypertrophy, muscle damage is a result of the other two mechanisms, and it is not known at the date of this post wether it's essentially necessary for muscle hypertrophy.
What is Mechanical Tension?
Mechanical tension is the force created when a muscle contracts isotonically against a load (isotonically refers to when the force remains constant throughout the movement).
This force is received by mechanosensors, detecting the external stimulus and activating signal cascades. These signal cascades converts the mechanical process into a biochemical process. This phenomenon is called mechanotransduction (definition).
When we execute an exercise and induce mechanical tension, the signal cascades activated lead to further increased muscle protein synthesis, and consequent muscle hypertrophy. In other words, your metabolism "wakes up" when you give it a reason for it (lifting weights) and activates various pathways with a final destination; increasing muscle protein synthesis and hypertrophy
Why is Mechanical Tension Important?
As we have said earlier, mechanical tension is the king factor for muscle hypertrophy.
Mechanical tension is simply putting some force to induce the contraction and elongation of the muscle. This stimulus will tell our body to adapt to the 'new' situation, and our body will give us more muscle.
If we cut out the first step of this chain reaction (taking the weight), the muscle won't contract, and our body will stay as it was five seconds before that happened.
Muscle fibers are the structural units taking action during muscular contraction. If no sufficient force is used, muscle fibers will not activate. If muscle fibers are not activated, there's no mechanotransduction, and no mechanical signal can be translated into biochemical signals. In other words, we need to use an external force to contract and activate muscle fibers.
- The main mechanisms driving muscle hypertrophy are (from higher to lower importance): mechanical tension, metabolic stress, and muscle damage.
- Mechanical tension is the force created when the muscle contracts against an external load
- Mechanical tension is essential for muscle hypertrophy to happen
Force-Velocity Relationship for Mechanical Tension
The force-velocity profile of an exercise is the best way to determine and induce mechanical tension.
Our organism contains biostructures called motor units, formed by a motoneuron and the fibers connected to it (picture shown below). Each motoneuron may be connected from dozens to thousands of muscle fibers.
When the muscle is contracted and stretched by an external force (e.g lifting a weight), motor units are recruited from small to big. The first motor units recruited are those with less fibers connected. When those start to be fatigued, larger motor units are activated.
Force-velocity can help us estimating how much mechanical tension we put into our trainings. When muscle fibers shorten slowly, they exert a high force. On the other hand, when they shorten quickly, low forces are exerted (source).
This study performed in 1981 showed that by doing a test at different velocities, lower velocities showed higher muscle adaptations when compared to higher velocities (study).
Don’t Fake the Slow Velocity
The force-velocity is the main cause of mechanical tension. But it can't be faked. Your body is wise, and knows exactly the amount of fibres needed to lift the load. Even if you do fake it, your body won't activate all muscle fibres.
This relationship is based on the load being lifted. The higher the load, the more effort and lower velocity. If you are using a light load and faking the velocity, your body will notice because mecanical tension will not be high enough to induce adaptations.
Factors Affecting Mechanical Tension
Mechanical tension is a multifactorial phenomenon, and there are several factors we can consider when trying to optimize our training sessions. Since it's such an important phenomenon in muscle hypertrophy, it is of your interest to know about them and tell your buddies how you train to get those big biceps.
Train with Heavy Loads
Mechanical tension and high loads are directly correlated. The higher the load, the higher the force our muscle has to support, and therefore the tension. When we use heavy loads, the force-velocity ratio is higher.
High loads have been shown to activate more muscle fibers than lighter loads doing the same amount of reps. The higher load will take you closer to muscle failure, and more motor units will be activated, leading to more muscle fibers working.
Time Under Tension
The duration of the exercise and the mechanical tension are correlated. The longer we keep our muscle resisting the force, the higher the mechanical tension produced.
Results correlating time under tension (TUT) and mechanical tension are poor, and we may need more studies to conclude a positive and consistent effect. But it may be a potential variable to induce mechanical tension.
In this study, it was observed that TUT and volume affect muscle adaptations and hypertrophy (study). Using three different protocols in where one factor (volume load or TUT) changed while the other was kept constant, it was observed that either higher volume load or TUT led to higher adaptations.
Your body is able to adapt to the external stimuli (lifting weights), and muscle grows as the final result. You should be able to lift more weight and go for higher reps as the time moves on (if you are constant and train fairly often).
To keep inducing and optimizing mechanical tension, we need to give our body new reasons to keep building more muscle. But how do we do it?
There are many ways by which we can progressively overload and keep inducing muscle hypertrophy (and mechanical tension). These are, among others:
To make sure you are inducing progressive overload, it's important to keep track of your trainings, wether using pen and notebook (old school) or taking notes on your phone. This way, during your session you can go back to your last session and know what to do.
Your goal during each session is to do AT LEAST what you did the last session. This is extremely important to keep building adaptations.
- Force-velocity relationship is the main factor to determine mechanical tension
- High loads and lower reps may help achieving a better force-velocity relationship and neuronal adaptations.
- Time under tension and the cadence of the exercise determines the mechanical tension during your session.
- Progressive overload is essential to keep building adaptations and mechanical tension over time.
How to Optimize Mechanical Tension
There are many ways to achieve mechanical tension, and adherence to training is the most important of all. If you try these applications and you don't get good feelings, maybe they are not meant for you, and you'll have to try something else.
High Loads at the Beginning of the Session
Try to put the exercises with higher loads at the beginning of your session. Without being fatigued yet, the muscle mind connection will be greater and easier to achieve.
Focus on training with high loads, proper technique and between 4-8 reps. If you are a beginner, you should be seeking for the higher range of reps, while if you are more advanced can play around with the range.
Exercises with a Good Resistance Profile
Not all the exercises are the same, and the resistance profile differs between exercises.
We can differentiate between assisted exercises and free-weight exercises. Each of them bring us some advatantatges. While free-weight enable us to get some work done on our stabilizing muscles and induce a more general hypertrophy, assisted exercises are better to isolate the muscle of interest, and the exercise itself is easier to perform.
When we are trying to optimize mechanical tension, we want to choose those exercises with higher ROM (range of motion) and a better resistance profile. By doing this, we ensure that the muscle of interest is the limiting factor, inducing higher mechanical tension.
Advanced Training Techniques
Advanced hypertrophy techniques are a great tool to add some more volume load and intensity to our trainings. However, they should only be used during strategic moments of our periodized program or if you are an advanced athlete. In this systematic review it was observed that these techniques may provide a higher stimulus for muscle hypertrophy when compared to traditional approaches (systematic review)
Focus on the Eccentric Phase
During an exercise there are two phases; concentric (muscle being contracted) and eccentric (muscle being stretched). Eccentric phase induces higher muscle damage and mechanical tension (study). Although the complete mechanisms behind this are not known yet, it may be due to higher neuronal adaptations and muscle fibers activation, maximizing mechanical tension.
Do the Proper Technique
A good technique is the base of the pyramid. If we don't do the exercise with the technique meant, we are losing so much on each exercise, and we'll have to spend more time to achieve the same results. Focus on good technique, controlled and with good feelings.
Each person may have a different technique. Because we don't have exactly the same structures and dimensions, we'll need to adapt each exercises to our body levers to maximize the stimulus and make the exercise as efficient as possible.
Mechanical Tension to Build Muscle
We do need of mechanical tension in our trainings to build muscle. As we have seen in this post, it's the main mechanism underlying muscle hypertrophy.
If you want to build muscle, you need mechanical tension. To achieve and optimize mechanical tension, you must:
- Use heavy loads and low repetition ranges (4-8)
- Prioritize a good technique on each exercise
- Use loads to perform a low velocity-force profile
- Include eccentric exercises
- Use compound exercises at the beginning of the session and focus on going 'heavy'
All this and the other mechanisms of muscle building are explained in the new course available on TBS!! All you need to know to understand mechanical tension, muscle hypertrophy, and optimize the process of muscle building. It also includes modules about sports nutrition, sleep and recovery, and how to optimize your training program. Go get it now!!
HOW TO START CHANGING YOUR PHYSIQUE
In this post, we have seen that there are three main mechanisms driving muscle hypertrophy, being mechanical tension the main one. To induce mechanical tension we have to take into account the force-velocity relationship, in where slow movements induced by high loads lead to more muscle fibers activated. Other factors to take into consideration are the external load, time under tension and progressive overload.
Knowing what mechanical tension is and the main factors that determine the level of mechanical tension created during the session, we can put it into practice and program our session to get better results. Some of these applications are:
- Do high-load exercises first
- Prioritize technique on each exercise
- Use advanced hypertrophy techniques if necessary
- Choose exercises with a good resistance profile
- Control the eccentric phase on each exercise