Isometrics: The Most Underrated Training Tool

Christian Thibaudeau

Co-founder of Thibarmy, Trainer

Articles, Muscle gain, Rehab, mobility & injury prevention, Strength and performance

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Isometrics: The Most Underrated Training Tool

Isometrics: The most Underrated Training Tool

Except for a few enlightened coaches, few people give isometrics the place it deserves in their training programs. This is really sad because it offers many benefits when it comes to getting stronger, bigger and healthier. Athletes in general also tend to lack isometric and eccentric strength relative to their concentric (lifting) strength. And as they say: “A chain is only as strong as it’s the weakest link”.

And even if you are more into building muscle, wouldn’t you want to use many different approaches to stimulate muscle growth? After all, once the body adapts to a type of stimulus it becomes increasingly hard to keep building more mass. The isometric methods presented in this article will allow you to breakthrough growth plateaus easily (but painfully!).

Interested? Read on!

What Are Isometrics

Simply put, isometrics refer to exercises where the muscles are producing force without movement. This can be achieved by either pushing/pulling against an immovable resistance or by holding a weight in a certain position.

In both cases, the intent is different but the external result is the same. Trying to move a resistance that can’t be moved is called overcoming isometrics (you are trying to overcome the resistance), whereas holding a weight in place, preventing it from dropping down is called yielding isometrics.

Although they look similar, they have slightly different training effects. Overcoming isometrics have more transfer to concentric strength and are more neurologically demanding. They are best suited for short, very intense efforts and have a greater impact on strength than size.

Yielding isometrics have more transfer to eccentric strength and are less neurologically draining. As such, they can be done for longer and work best to increase size than strength in a lift.

There are other subtypes of isometrics that we will explore but they are essentially variations of either overcoming or yielding isometrics.

Factors Affecting Strength

Being capable of displaying a high level of force in a specific movement depends on many factors: the amount of muscle mass you have (more muscle gives you a greater strength potential), your capacity to recruit muscle fibers, and to make the recruited fibers twitch faster (the more often they twitch per unit of time, the more force they produce), to better coordinate recruited fibers, to make the various muscles involved in a lift work more efficiently together and also, how active your own protective mechanisms are (they prevent you from using all the strength you have to protect you against yourself).

These are the modifiable mechanical factors involved in force production. Other elements come into play like leverage, fast-twitch fiber ratio, bone density, tendon length and the likes.  They also play a role, but these you can’t change.

From a practical standpoint, you can find yourself having other more specific issues leading to suboptimal performance on a lift. For example, you might be weaker at a specific point in the range of motion of a lift (sticking point) or be inefficient at recruiting one of the muscles involved in the lift, leading to a less efficient motor pattern.

As we will see, different isometric methods will be extremely effective at improving most of these factors.

Stimulating Muscle Growth

Just like there are plenty of factors affecting strength, there are many pathways to stimulating hypertrophy.

One of these pathways is the activation of mTor. To make things simple, mTor is the light switch and protein synthesis/muscle-building is the light. When mTor is turned on, protein synthesis is increased. And the more it’s turned on, the higher the rate of protein synthesis.

Another possible pathway is the release of local growth factors, specifically mechanical growth factor (MGF), which is a splice variant of insulin-like growth factor-1 (IGF-1). MGF has a direct impact on making a specific muscle grow. It is released through muscle damage caused by resistance training and by a combination of an accumulation of lactate inside a trained muscle and transient oxygen deprivation of that same muscle. These last two elements (lactate accumulation and lack of oxygen) are maximized when blood flow to a working muscle is reduced or prevented altogether.

Another way of stimulating muscle growth is achieving muscle fiber fatigue. As Zatsiorsky writes: “a muscle fiber that is recruited but not fatigued, is not being trained”. This is supported by a study by Mitchell et al. (2012) that found that if you go to muscle failure on an exercise, the muscle growth stimulated is the same regardless of how much weight was used, indicating that maximum muscle fiber fatigue is a powerful growth stimulus.

And at the root of all three of these pathways is the ability to maximally recruit or contract a specific muscle. If you are not efficient at contracting a specific muscle hard during an exercise, you will not be able to optimize any of the three pathways mentioned above. If a muscle is not contracting hard, you are not recruiting a maximum number of fibers (and especially not the most growth-prone fast-twitch fibers), and since you can’t fatigue fibers that were not recruited, and a fiber that is not fatigued is not being stimulated, the impact on growth will be limited.

Further, to release local growth factors you need to be able to cause a restriction in blood flow inside a muscle that is contracting long enough to result in a hypoxic state and an accumulation of lactic acid (about 20-40 seconds depending on contraction intensity). To occlude blood flow naturally you need to contract a muscle hard: the harder a muscle is contracting, the more blood flow inside that muscle is reduced. Not only that, you need to be able to sustain that contraction throughout the whole set (think about flexing your muscle while lifting weights), because the moment you release the tension, blood rushes back into the muscle and you are making it a lot harder to maximize growth factors. If you aren’t good at contracting a muscle hard and maintaining that contraction while moving the weight around, it will be hard to maximize growth factors.

As for mTor activation, it is maximized both by accentuating the eccentric portion and by reaching a stretched position while the muscle is contracting. Again, in both cases, you cannot optimize the process if you are not efficient at creating tension in a specific muscle: accentuating the eccentric means flexing the muscle hard while doing the lowering portion of the movement. And to reach a tensed stretched position you must be good at keeping a muscle contracting hard even in the stretched portion of an exercise. Again, in both cases, if you are not efficient at flexing, contracting a muscle there is no way of maximizing growth stimulation.

Muscle growth stimulation starts with the capacity to flex a specific muscle while lifting a weight.  Let’s see how isometric methods can be used for that purpose.

Movement And Recruitment Patterns

Performing optimally in an exercise is a function of movement pattern as well as the recruitment pattern.

What’s the difference?

A movement pattern refers to the technical execution of a movement or exercise: how well you are moving, are you in the proper position at all times during the exercise; are the joints changing angles with the proper coordination.

Recruitment patterns refer to the order and magnitude of the contraction of the muscles involved in the exercise. See, two people could have the same technical execution of a lift yet use a different recruitment strategy. For example, one might use the quads more to do a squat while the other one might rely more on glutes despite having a similar technique.

Movement patterns are easy to fix but recruitment patterns are much harder to correct. It much easier to put the body in the right position than to change how much each muscle is contributing to an exercise, especially when you are not good at contracting the muscle you want to involve more in the lift.

Isometrics is the best tool to work on changing the recruitment pattern/strategy used during the execution of a movement pattern, making these methods a very useful tool for improving performance.

With all that being said, let’s examine exactly how isometrics can be used the address the three objectives I just mentioned.

Isometrics To Increase Strength

Isometric exercises have some interesting properties when it comes to building strength.

  1. You can recruit up to 10% more muscle fibers during a maximal isometric action than during a maximal concentric or eccentric one. Since fiber recruitment is one of the key neural factors affecting strength, frequent isometric training can program your nervous system to be more efficient at recruiting more fibers. Once that is done, you will become stronger in your regular lifting exercises even without adding muscle mass.
  2. The firing rate of the recruited muscle fibers is higher during a maximal isometric action than during a maximal eccentric action and might be also higher than during maximal concentric actions. Again, over a certain length of time, this means that by using maximal isometric actions you can train your neuromuscular system to produce a higher firing rate during all types of muscle actions. This is another way of increasing strength production.
  3. During isometric exercises, strength is gained mostly at the trained joint angle. There is a carryover of about 15 degrees both sides (before and after the angle being trained) but the further away you are from the trained angle, the lesser the strength gains are. While this can be seen as a downside, it can also be beneficial since it allows you to target a specific portion of the range of motion. If you want to fix a sticking point or emphasize strength in a certain position, for example.
  4. A certain form of isometrics can be used to desensitize your body’s protective mechanisms: functional isometrics. Which are a super short-range partial lift (about 2 inches of movement) followed by a static hold for about 6-9 seconds? If you pick a strong point in the range of motion you can use 20-50% more than your full lift strength, getting your body used to handling such loads. Over time it will desensitize your protective mechanisms, allowing you to use more of your strength potential.

The two best forms of isometrics to increase strength are overcoming isometrics (pushing or pulling against an immovable resistance, like the safety pins in a power rack):

And functional isometrics that I just mentioned:

With these methods, I recommend sets of 6-9 seconds with maximal effort. Well, for the overcoming isometrics you gradually build up force output over the first 3-5 seconds of the set then push all out for the last 3-5 seconds. Normally, 3 work sets are done for a position during overcoming isometrics. They are a max effort method. And I recommend the Westside approach to max effort: 3-4 max effort lifts in a workout, max. That is the recommended volume if you are using only one position, specifically to strengthen a sticking point. If you are using 2 or 3 positions to strengthen the whole range of motion I recommend 2 sets per position.

An added benefit of overcoming isometrics is that they do not cause any muscle damage. As such they can be done very frequently which will allow you to develop the neural factors involved in strength production at a much faster rate. The lack of damage also makes this form of training interesting for in-season athletes who need to be able to easily recover from their workouts so that they can perform optimally during their games and practices.

For functional isometrics, I would recommend 2 or 3 work sets because you will need a few gradually heavier warm-ups sets to reach your working weights. While these do not max effort lifts, they still fatigue the nervous system slightly. On functional isometrics, I only recommend using one position: a position that allows you to use more weight than what you use for the full lift.

Isometrics To Increase Muscle Mass

While the effect of isometrics on strength is well researched and documented, few studies found a significant muscle mass increase via isometric training, especially in non-beginners.

The problem is, pretty much all studies on isometrics use overcoming isometrics (pushing/pulling against an immovable object) and normally a short duration (6-12 seconds bouts or even less).  It is not surprising that this type of training doesn’t lead to a significant amount of muscle growth. Think about it. You can stimulate muscle growth by:

  1. Thoroughly fatiguing many muscle fibers
  2. Creating muscle damage
  3. Maximally activating mTor
  4. Stimulating the release of local growth factors (MGF).

None of these occur during an overcoming isometric action lasting 6-12 seconds.

You don’t create muscle damage during overcoming isometrics.

The short duration doesn’t allow you to create maximal muscle fiber fatigue.

That same short duration will not lead to a significant deprivation of oxygen in the working muscle nor to an accumulation of lactate. So, the release of local growth factors is insignificant.

And mTor is activated mostly by accentuating the eccentric (which you don’t have in overcoming isometrics) or by having a muscle contract hard in the stretched position (most overcoming isometric protocols do not use the stretched position).

Let me be clear: overcoming isometrics is not effective at stimulating muscle growth. Unless you are using a duration of 30-45 seconds per set, which is very demanding with this form of isometrics.

So how do we use isometrics to stimulate muscle growth?

You have three options.

  1. Long-duration yielding isometrics (holding a weight or body weight at a certain point).

  1. Iso-dynamic methods (including holds during the set).

In the first two videos, there are holds during the set. Hold, reps, hold, reps. This is one of the most painful methods you can use and is amazing at maximizing the release of local growth factors and creating maximum muscle fatigue.

In the third video, the hold is placed at the end of the set. This allows you to maximize muscle fiber fatigue: when the fibers are too tired to be strong enough to continue lifting the weight, you continue to stimulate them by simply holding the weight in place.

In the fourth video, the isometric portion is done once you can’t do any more regular reps, again to continue fatiguing the muscle fibers even when you can’t lift the weight anymore. Then I added a twist by having the athlete perform eccentric-only actions afterwards to cause even more fatigue and stimulation.

  1. Loaded stretching (doing a long duration hold in the stretched position)

I wrote a full article detailing the benefits of loaded stretching here.

For loaded stretching you can use either your body weight (like in the video) or weights. If you are putting the target muscle under load, in a stretched position, it will work.

Note that we want active stretching: contract the target muscle do not just let your structure hold the weight up.

My friend Dr. John Rusin ( ) uses a variation that combines iso-dynamics and loaded stretching: at the end of a regular set you go down to the stretched position and hold there for as long as you can tolerate.

Loaded stretching is likely the most powerful growth-producing isometric variation. It stimulates hypertrophy via 3 of the 4 main pathways:

  • It’s very effective at activating mTor which triggers protein synthesis
  • It is (with occlusion training) the best way to increase the release of local growth factors because it combines muscle hypoxia (lack of oxygen) due to the constant tension and stretch (both reduce blood flow and oxygen entry into the muscle) and a large lactate accumulation.
  • When used for the proper duration (45-75 seconds) or at the end of a set it creates significant muscle fiber fatigue.

What training parameters should I use to stimulate growth?

Yielding isometrics: 2-3 sets of 45-75 seconds at the position where you can create the most tension in the target muscle. Don’t just hold the weight, flex the muscle as hard as you can.

Iso-dynamic 1 – Post-fatigue Normally I recommend doing this only on the last set of an exercise as the fatigue build-up could decrease performance on the subsequent sets too significantly. After performing 6-12 reps to failure or close to it on an exercise, hold your chosen position for as long as tolerable. You can use either the position where you can produce the most tension or the stretched position.

Iso-dynamic 2 – Multi-holds during a set: My favorite approach is to use three holds during a set, each lasting 10 to 20 seconds. Normally, I recommend a total 8-12 reps per set. So, a set could look like this: Hold 20 seconds / 3-4 reps / Hold 15 seconds / 3-4 reps / Hold 10 seconds / 3-4 reps. Of course, you can use a single or two holds in the set. I like the total time under isometric tension to be between 30 and 45 seconds and the reps to be between 8 and 12. Again, I like to do this on the last set of an exercise.

Iso-dynamic 3 – Pre-fatigue: This is a great method to improve mind-muscle connection. It may not be the best pure hypertrophy method, but it is very effective to learn to recruit and stimulate a lagging muscle group. You start an exercise by holding the position where you can feel the greatest tension in the target muscle. That can either be the peak contraction position or the mid-range, depending on the exercise. During that hold, you must focus on contracting the muscle as hard as you can, not just on holding the position. Hold for 20-30 seconds, then do 6-12 reps. You will feel the target muscle a lot more than usual. Since this method is more about motor learning than lifting big weights, you can do up to 3 sets on an exercise.

Loaded stretching: This is essentially a form of yielding isometrics so the same parameters can be used: 2-3 sets of 45-75 seconds.

Isometrics To Improve Motor And Recruitment Patterns

One thing I really like with isometrics is that they allow you to really focus on improving and strengthening lifting posture. Specifically, you can place an athlete in a key position in a lift and since he doesn’t have to move, you have the opportunity to easily adjust his position. The athlete can then focus on feeling the position so that he can program it in his nervous system and easily reproduce if when doing the full movement. Furthermore, since isometrics strengthen mostly the trained angle(s), doing isometrics at certain key points in the range of motion (where form tends to break down) will make these positions stronger and less likely to cause a form breakdown during a heavy set or when fatigue sets in.

You can also use isometrics to reprogram the proper muscle recruitment pattern. You do that by going to a key position and then focusing not only on the position itself but also on which muscle is contracting the most. Much easier to do that when you don’t have to move and overcome a resistance.

I personally prefer to use yielding isometrics for that purpose. I find that it has more technical transfer to the regular lift than overcoming isometrics. And it’s submaximal because you want a long duration to maximize motor learning. I use sets of 60-90 seconds with more advanced individuals and 30-45 seconds with lower level ones. However, if at any point during the set the position becomes less than optimal or if the individual cannot maintain tension in the correct muscle, we stop the set even if the time is not up.

I like to use this method at the beginning of a session as a specific muscle activation for the main exercise of the workout.

In the following video, we are using the Frankenstein squat to work on the back squat position and stability. As you can see the athlete lacks stability and rigidity in his position, which is the reason why we used that technique.

You can add weight of course. If 60-90 seconds is too easy, then add weight, but remember that even a light resistance should be challenging because you are trying to create a lot of internal tension (contracting the muscles hard to be solid as a rock) which is a maximal contraction even without the use of high resistance.


This is just a quick rundown of some cool isometric methods for various purposes. I highly recommend my second book Theory and Application of Modern Strength and Power Methods, which goes into great detail in the science and application of isometric, eccentric and concentric methods.

– CT