An isometric contraction occurs when the muscle tenses but does not change length (the affected joint angle will stay the same). Examples of this are bodybuilding poses or pushing against an immovable object such as a wall.
Probably the most common example of using isometrics in weight training is when a lifter holds the last rep of an exercise as long as possible. These are typically called iso-holds or static holds.
The claim is that Isometric Training can not only help you maintain the strength and muscle you currently have, but also build significant strength and muscle mass.
Some reports show where Isometric Training increased strength by 40% in as little as 10 weeks. Other studies support this by showing greater muscle fiber activation during isometric contractions than the other main contraction types (concentric and eccentric).
Russian strongman Alexander Zass credited much of his great strength to his Isometric Training as a prisoner during World War I. While imprisoned he pushed and pulled on the bars and chains to get stronger without weights.
However for muscle mass, NASA concluded that isometrics were not the best choice for stopping muscle loss in astronauts.
Ironically, the one athlete that relies significantly on isometrics AND has significant muscle mass is male gymnasts. They constantly use isometric contractions and have some of the best arm development you will see.
Every day we use isometrics during normal activities. Stabilizer muscles such as those in the core must use isometric contractions to hold the body in position so Isometric Training is important for strengthening these stabilizing muscles.
Like ALL training methods, isometrics have both potential benefits and shortcomings so you have to understand how best to use them in your training.
Benefits of Isometric Training
- One of the biggest benefits of isometric training is that the body is able to activate nearly all the available muscle motor units – something that is difficult to do unless you train for it.
- Isometric Training can improve our capacity to recruit more motor units during a maximal contraction. In the long run, this improved capacity could greatly increase one’s strength production potential.
- Maximum intramuscular (inside the muscle) tension is attained for only a brief period in dynamic (moving) exercises because of momentum while in isometric exercises you can sustain that maximal tension for a longer period of time. Strength is greatly influenced by the total time under maximal tension.
- Beginners especially have difficulty in producing high levels of intramuscular tension during normal contractions. Isometric Training can help to improve this so that normal training is even more productive.
- Isometric Training allows for strengthening those obvious sticking points in the full rep range. For example, if you find you’re weakest during the bench press with the barbell near the chest, you can use isometrics to strengthen that area specifically.
- Isometric exercises may also be useful to someone who has been injured or has a painful joint condition such as arthritis. For instance, if you injure your shoulder, isometric contractions and exercises may help to maintain strength during recovery without using joint movement.
- Isometric exercises aren’t energy expensive so you don’t expend much energy by doing Isometric Training. So, you can get the benefits of isometrics without interfering with the rest of your planned workout.
- When you have to decrease your training load either due to sickness, time constraints or vacation, Isometric Training may help prevent strength and possibly muscle losses.
Downsides of Isometric Training
- Because isometric exercises are done in one position without movement (no range of motion), they generally strengthen the muscle most in that one particular position.
- Normally isometrics are done in one position of an exercise but multiple points through the limb’s whole range of motion are needed for complete development.
- Since isometric exercises are done in a static (non-moving) position, they won’t help improve speed or athletic power and may even decrease muscle elasticity if additional stretching techniques are not used.
- You won’t be as tired and sore as with normal full range of motion training but you will still be fatiguing the central nervous system, which can take even longer to recover from.
Types of Isometric Training
There are two different ways to do isometrics:
Overcoming Isometrics – You push or pull against an immovable resistance. Although there’s no external movement, you try your hardest to move the resistance (even though it’s impossible). An example would be pushing against an overloaded barbell.
Yielding Isometrics – You hold a weight and prevent it from moving. Your goal is not to move the weight (even though you can) but hold it in place. An example would be holding a curl at mid-range for a certain amount of time (also called an iso-hold).
It’s important to understand that each technique uses different muscle and central nervous system (neural) patterns.
Overcoming isometrics are better at building concentric strength (where the muscle shortens under load) and yielding isometrics are better for eccentric strength (where the muscle lengthens under load).
How to Use Isometric Training
The only way most people have tried isometrics before is by using an iso-hold at the end of a set where the last rep is held as long as possible. Although useful, this is only one of many possible ways to do Isometric Training.
Most studies on Isometric Training seem to show it does work for strength gains but its use for muscle growth is less certain.
However, these studies were generally short term, often using too short a period of time to stimulate a significant increase in muscle mass but more than sufficient to cause neural adaptations leading to strength gains.
Many of the studies also used very short isometric contractions. As we know from time under tension, strength gains are greatest when the reps don’t last long (less than 30 seconds) but muscle growth generally happens beyond that time.
While Isometric Training can help to increase muscle strength and size, like all training methods, that doesn’t mean it will work forever or should completely replace regular training.
Isometric Training is best used as an addition to your regular training while still varying intensity and frequency.
One of the most effective uses of isometrics is to “activate” the muscle fibers and motor units before doing a regular full range of motion (dynamic) set.
If you want to sound less like a meathead, the principle behind this is called Post-Activation Potentiation (PAP). It basically means that a lighter set will be easier after a heavier (or explosive) set because of improved muscle activation.
By activating the muscle, more fibers will be used during the full dynamic set, which means more weight can be used allowing greater muscle stimulation.
The KEY is to activate the muscle but NOT fatigue it for this method to work.
To activate the muscle you will use overcoming isometrics and overload the exercise. Then perform several short reps (3 seconds or less) by pushing or pulling as hard as possible.
It’s important to overload the exercise, including bodyweight exercises like the pullup. Make sure to add extra weight such as with a backpack or weight belt if your bodyweight is not enough.
Since these isometric contractions create maximum muscle tension, they increase the neural drive through the central nervous system between the brain and the trained muscle.
Using the bench press as an example:
- Place the barbell on safety pins. Set the safety pins at a normal sticking point (such as right above the chest for most people).
- Load the barbell with a weight well above your maximum weight and get in position under the bar as with a normal bench press.
- Now press as hard as possible against the barbell for 3 seconds and then rest 30-60 seconds.
- Repeat 3-5 times.
- Now do a normal full range of motion bench press set.
Strength Training (Maximum Intensity) Isometrics
- These Isometrics are done similar to regular strength training which uses short but intense reps. Time under tension will be low but the muscle tension will be maximum. For this reason, overcoming isometrics are best used here.
- The basic idea is to complete multiple short sets with each lasting less than 30 seconds (generally 5-15 seconds is used). An example would be doing 5 sets of 1 rep each lasting 15 seconds.
- Longer rest periods (2-4 minutes) between sets are also used so that maximum effort can be applied on each rep/set.
- Since the muscle is strengthened most at the joint angle trained, strength isometrics are best used to strengthen obvious weak areas by shortening the range of motion.
- For example, if you are weakest in getting a deadlift started, overcoming isometrics would be used with an overloaded bar on the floor.
- If you want to strengthen an entire movement (exercise), then multiple positions would be used.
Pause Rep (In-set) Isometrics
In the powerlifting/strength community, isometrics are often used to strengthen the sticking areas in an exercise. The common way to do this is using strength training isometrics by themselves with overcoming isometrics as described above at each sticking point.
Another commonly used option is to instead use yielding isometrics and add pauses at the sticking points while still doing a full range of motion dynamic rep.
As an example, Pause Squats are widely used where the barbell is held briefly at the weakest spot during a full squat rep (typically near the bottom position of a squat).
During the full range of motion rep, you would pause at the bottom for say 5 seconds and then complete the squat by standing back up. You would do these pauses on each rep. You can also use multiple pauses at different locations.
The longer the pause, the longer the time under tension so short pauses should be used for strength goals and longer pauses for muscle building goals.
Muscle building (Maximum Time) Isometrics
With maximum time isometric exercises you will be pushing, pulling, or holding a submaximal load for as long as possible (going to muscle failure).
For the best effect you want to use sets ranging from 30 to 60 seconds in length to maximize time under tension for muscle growth.
With this method you can use both overcoming isometrics and yielding isometrics. However, yielding isometrics (holding a weight) seem to work better since the sets are longer in length.
Maximum effort is difficult to maintain for that long as you would if using overcoming isometrics.
Generally a weight you can do 6-12 full reps is used. You will hold the weight in position for 30 to 60 seconds (preferably to muscle failure). If failure takes longer/shorter than that, increase/decrease the weight as needed on other sets to get the 30-60 seconds.
Perform multiple sets (2-5) of 1 rep (30-60 seconds long) for each joint position. Generally three positions are used (full contraction, mid-range, right above full stretch).
Since muscle growth and fatigue are desired, keep rest periods around 1 minute between sets.
Pre-fatigue methods are not the best for strength gains but can be useful for muscle gains since the time under tension will be longer while also in a fatigued state.
Basically you will do a superset by combining yielding isometrics for maximum time along with regular full range of motion training.
This generally works best combining an isolation exercise with a compound one for the desired bodypart.
- For example, for chest you would first do yielding isometrics with dumbbell flyes held at the full stretch position for 30-60 seconds (best time under tension for muscle building).
- Then immediately do a set of full range of motion bench press for 6-12 reps.
- Now rest 1 minute and do another pre-fatigue isometric superset.
Post-Fatigue Isometrics (Iso-holds)
As with pre-fatigue, post-fatigue methods are not the best for strength gains but can be useful for muscle gains since the time under tension will be longer while in a fatigued state.
With this method you will use a yielding isometric at the end of a regular full range of motion set. These are essentially the iso-holds (static holds) most people are familiar with.
For example, for back you would do 10 chinups and then immediately hold the last rep for 30-60 seconds (or as long as possible). This is just one option.
You could INSTEAD:
- Hold the top position after the last full rep for the 5-30 seconds.
- Then drop halfway down and hold that position for 5-30 more seconds.
- Finally drop down to just above the bottom position for another 5-30 seconds.
The good thing about this method is that it will thoroughly exhaust all your muscle fibers through the full range of motion, which is one way to muscle growth.
However, it’s a very taxing method and should not be used all the time or for all sets (usually just the last one).