I know, you want to get stronger, that goal of increasing your squat 1RM by 50Lbs is all you can think about and it seems straight forward; squat more, do more dynamic movements with more weight. In the grand scheme of things this is true, after all go to any gym in any country on this rock we call earth and you will find people doing almost every form of dynamic movement known to man, because it works. When you move weight through a range of motion you gain strength throughout that range, some even use partials to get past weak points in a specific range. Seems like an open and shut case as to why we should use dynamic movements rather than isometrics doesn’t it?

Reinforcing this idea of dynamic movements over isometrics is the fact that you won’t often find much in the way of isometrics in most commercial gyms, sure the guy in the corner with the 200 Lb. dumbbells can’t seem to get them off the ground but it isn’t something that seems to be common or even a consideration in program design. Isometrics are a dinosaur in the fitness world but as you are about to learn, extinction isn’t warranted for this dinosaur.

What are Isometrics

If you are new to this whole fitness thing or maybe just new to lifting you may already be confused. Before we go any further we really should define how some of these terms are used so that you know exactly what is going on (and a little extra for future ease of understanding). We will start with tension and load. The force exerted by a contracting muscle on an object is called muscle tension. The opposing force exerted on the muscle by the weight of the object to be moved is called the load.

A contracting muscle does not always shorten and move the load. If muscle tension develops but the load is not moved, the contraction is called isometric (“same measure”)— think of trying to lift a 2000-lb car. If the muscle tension developed overcomes the load and muscle shortening occurs, the contraction is isotonic (“same tension”), as when you lift a 5-lb sack of sugar. 1 So in short if we take the definition at face value, isometrics are when a muscle is under tension and the muscle isn’t moving (length of the muscle doesn’t change) while isotonics are when a muscle is under tension and the tension doesn’t change. You may also notice the word isokinetic which means the amount of energy needed doesn’t change throughout the muscle contraction. Isometric contractions are static (no movement), all others are dynamic (movement). Also important is that concentric means the muscle is shortening while eccentric means it is lengthening.

Most movements we encounter in the gym, in sport and in life (such as lifting a sack of potatoes) are not truly isotonic but rather auxotonic. Auxotonic means that the length of the muscle changes as does the muscle tension. The same tension at every joint angle of a movement is a rare thing. Though not critical to know in practice as isotonic is often used in its place (such as in the above definition), knowing is better than not. The term dynamic constant external resistance (DCER) has also been used rather than isotonic 23 but I’m going to stick with what is already in wide use. To complicate matters some references may also only use isometric, concentric and eccentric 4 which although not incorrect, are speaking of only muscle length (no movement, shortening and lengthening respectively) and not energy used or amount of tension.

Below is a chart showing the organization of the terms used above (and a few others that aren’t being used here but are worth looking up). Click the image to enlarge.

Muscle Contraction Types

The simple answer: What it boils down to is this: Movements are isometric when the muscle does not lengthen or shorten, like the muscle is frozen in one spot, any movement or portion of a movement on the other hand is either lengthening or shortening the muscle and can be classified as something not isometric. The rest of the above information is important if you are trying to further understand the kinetics of the human body but in this case it is just there for the geek in you if you so wish to understand it.

Evidence in Favor of Isometrics

Although dynamic training does improve strength through the full range of motion many studies have shown that isometric training greatly improves strength at the joint angle used while training isometrically.5 6789 Also noted is that strength is increased at joint angles anywhere from +/-5 degrees of the angle trained 10 possibly at angles even greater than that. Further, when comparing strength gained using dynamic Vs. isometric training methods researchers have found that isometric training resulted in greater isometric strength gains at each joint angle and similar gains in isokinetic strength when using multiple angles to cover the full range of motion in training. 11 The groundwork for these findings can be found in research dating as far back as the 1950’s. Theodor Hettinger and others spent years (15 or so) researching the impact of isometrics on strength, in frogs and other animals as well as humans 12. Hettinger found that isometrics increased muscle strength and that training isometrics using 40%-50% of the current maximum strength of the muscle gives the maximum obtainable training effect 13 and a study in 2002 found that both maximal voluntary contraction (MVC) for 6 s per set with 12 sets per session (100%G) and 60% of MVC for 30 s per set with 4 sets per session (60%G) produced strength gains with no significant differences in relative gains between the 2 protocols but did show a difference in the ratio of muscle volume to torque in the 2 groups (the 60% group didn’t increase muscle volume as much). 14

The fact is that the evidence proves that isometrics have a measurable positive impact on strength and size but just in case the science doesn’t quite get your grey matter fired up and your blood pumping let’s take a step back and look at the application of isometric strength, who uses it and who should be using it.

Isometrics in Application

When looking at groups who would benefit from the implementation of isometrics the first is probably the group who most commonly uses them currently which consists of those involved in rehabilitation. Isometrics are one of the primary methods recommended along with closed kinetic chain exercises as an initial strengthening method for patients involved in rehabilitation due to safety concerns, the ability to treat the problem without introducing a large amount of pain and the overall effectiveness of the isometric contraction towards building strength at various joint angles.15

The injured are not the only people who benefit from isometrics however, anyone trying to better a personal best lift could benefit from this method of training. Remember from the evidence above that isometrics have been shown to be highly effective at increasing both isometric and dynamic strength but especially strength at the angles being trained. If you are stuck at a point in your deadlift isometric work with a load larger than you can lift in the rack at that sticking point may be just what you need.

Bodybuilders in preparation for a show are another population who already take advantage of isometric contractions even if for most they are but an afterthought. Posing routines consist of isometrics held for a long length of time, anecdotally the more these individuals pose, the better they become at muscle control and the better the mind/muscle connection becomes.

The Take Home

Given what we know, the advice provided by the late Mel Siff and supported by the previously mentioned 2002 study – 6 repetitions of 100% of one’s 1RM held for 6-8 seconds per repetition 16, is likely the best place to start if you are looking for both size and strength gains. If you wish to increase strength without an increase in mass it would be worth exploring the 60% MVC method. One important point worth making, and a point that Hettinger makes clear in his work is that every muscle has the ability to respond differently to those different values and many studies use methodologies which are not directly comparable. If one rep/set length doesn’t work it is worth trying another. What is known without a doubt though is that isometrics work so don’t be afraid give them a try as a supplement to your training routines even if it just means holding a position to better feel the muscle being worked during an exercise or pushing against a wall while waiting for the laundry to finish.

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  15. Brotzman, S. (2011). Clinical orthopaedic rehabilitation: An evidence-based approach (3rd ed., pp. 98-549).
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