Dynamic vs Static
A dynamic contraction is one in which there is a change in muscle length, as it either lengthens (eccentric contraction), or shortens (concentric contraction), while producing force. A full range repetition consists of both, as the involved musculature produces enough force to shorten and ‘overcome’ the resistance, before reversing the motion, while still producing enough force to ‘yield’ the rate in which resistance lowers, as the muscles lengthen.
A static (isometric) contraction refers to a muscle generating force without physically seeing a change in its length – the fibers may actually shorten as they produce force, but the relative joint angle remains the same.
Overcoming / Yielding
Much like that are two types of dynamic contractions (concentric, and eccentric), there are two types of isometric actions:
· Overcoming – force is applied but is unable overcome the resistance, as it remains still. A practical example would be trying to press/pull a bar through the pins in a power rack.
· Yielding – the resistance unable to overcome the force being applied, and remains still. A practical example would be holding a weight and preventing it from succumbing to its gravitational pull.
Even though the physical action is identical, and the outcome is the same (no change in muscle length/joint angle), both techniques will not have the same effect because the neural pattern in both cases will be different. The intention to overcome may have a considerably larger impact on concentric strength, while the intension to yield may have a considerably larger impact on eccentric strength, and overall muscle mass.
While isometrics are likely not as effective at stimulating size or strength gains as concentric and/or eccentric training, they do come with their own distinct benefits which cannot be duplicated dynamically.
· Greater force production – Because isometrics (overcoming, in this case) require less motor skill, it’s possible to recruit almost all motor units when performing an isometric contraction. This simply isn’t possible when performing a dynamic movement because greater motor skill is needed to stabilize the load, and this affects the neural drive to the targeted muscles since the nervous system must coordinate the activation of other muscles to secure the body. Stability, which is a prerequisite to maximal force production, is all but eliminated when attempting to push/pull an immovable object, which facilitates maximal exertion.
· Improved neural drive – Because there is a greater level of activation when performing isometrics (overcoming, but yielding to some degree if supporting a supramaximal load), they can be used to acutely (performed at the beginning of the workout as a means of activating the muscles being trained that day), and chronically (by using them over a sustained period of time), improve the capacity to recruit more motor units during dynamic actions of the same nature, thus enhancing the quality of traditional training.
· Greater time under maximal tension – Because ‘strength’ is highly influenced by the total time under MAXIMAL tension, increasing the amount of time the muscles spend under maximal tension can increase strength gain potential. When performing a dynamic exercise, intramuscular tension is at its peak for roughly ¼ of a second, to a ½ of a second during the concentric repetition (due to improved leverages, and the fact that the velocity and acceleration imparted to the resistance limit the amount of force needed to move it – in fact, too much acceleration can result in the nervous system having to decelerate the load, which can hamper strength gain potential), but when attempting to push/pull an immovable object, or resist a supramaximal load from being lowered, maximal tension can be sustained for at least 3 full seconds, and up to anywhere between 6-12 seconds.
· Physical demand is low – Even with maximal exertion, the energy expended during isometrics is minimal at best, meaning it’s possible to reap their benefits without interfering with the rest of the workout, or hindering recovery.
· Specific ranges of motion can be overloaded – Because of the nature in which isometrics are performed, they can be used to overload specific ranges of motion, which otherwise wouldn’t happen, unless deliberately performing partials. Because the amount of weight that can be used for any exercise is limited by how strong you are at the weakest range of motion, the muscles are not fully stimulated for the majority of the range of motion. Isometrics can be set up to target specific ranges of motion so that the muscles are under maximal tension at ranges in which they wouldn’t be when performing the same pattern dynamically.
However, because strength is gained in the range it is trained, and muscle length does not change, the strength gained occurs chiefly at the joint angles in which the stress is applied, although 20-50% of the strength gained will carryover roughly 20 degrees each way. So even though isometrics can facilitate size and strength gains, without a concurrent dynamic program, progress will be suboptimal.
Like every other technique or method, the body adapts to the usage of isometrics, therefore they should only be used for short periods of time (gains may taper after 6-8 weeks) when progress has slowed down and a rapid improvement in strength is needed, or to prevent losing strength or size during periods when the volume needs to be reduced to allow for recovery, or are on a time constraint.
Practical Application – Time Under Tension Dictates The Training Effect
Since there are no actual reps performed when doing isometrics, the training effect is realized as a result of the time in which tension is applied.
For Strength – 3-6 seconds, 100-110% of max if yielding
Using isometrics to increase strength is similar in effect to dynamic methods consisting of 1-5 reps, with 85-100% of max. Isometrics for this purpose are better used as an activation/potentiation method prior to dynamic strength work, rather than a pure strength building method, because they can improve the capacity to recruit and synchronize motor-units (intramuscular coordination) in dynamic movements. Possibly the best way to incorporate isometrics for this purpose is with *contrast training.
*Contrast training consists of performing a ‘heavy’ set to activate the nervous system, so by ‘contrast’ the ‘light’ set feels lighter than it is, thus facilitating improved performance by way of allowing a slightly greater load to be used, or an extra rep to be performed than would otherwise be possible.
Because supramaximal loads are needed to get the same effect, isometrics of an overcoming nature (pushing or pulling against pins or an immovable resistance) are much more practical and safer, and thus is the preferred method, although both yielding, and overcoming, can be used effectively.
It’s important to remember to use multiple positions because the effect occurs specifically at the joint angle being trained, ex: 2 sets at bottom range, 2 sets at mid-range, 2 sets at top range, or vice versa.
For Size – 20-60 seconds, 50-80% of max if yielding
Using isometrics to increase size is similar in effect to dynamic methods consisting of 8-12 reps, with 70-80% of max. Isometrics for this purpose are better used as a means of extending the time under tension following dynamic strength work, rather than a pure muscle building method, because of the very significant growth stimulus placed on all of the muscle fibers. Possibly the best way to incorporate isometrics for this purpose is to pause during the final eccentric repetition for as long as possible – either at the mid-range, or stopping at 3 different ranges that are 20-40 degrees apart (bottom range, mid-range, top range).
This is a very taxing method and shouldn’t be performed for more than one exercise per muscle (if used for all sets) or for more than one set per exercise (if used for all exercises).
Because multiple pieces of equipment are needed (primarily a power rack) to get the same effect, isometrics of a yielding (holding the same weight used dynamically) nature are much more practical and effective, and thus is the preferred method, although both overcoming, and yielding, can be used effectively.
For Performance – (Ballistic) Dynamic/Isometric
*Not to be mistaken with iso-dynamic, in which an explosive action is preceded by an isometric pause to limit the force contribution from the stretch reflex, and any stored elastic energy from the eccentric repetition.
(Ballistic) dynamic-isometric refers to pushing/pulling against an immovable object for a very brief period of time (one or two seconds) while trying to reach peak force output as fast as possible to improve starting-strength, and the rate of force development. Due to the nature of the exercise, this can only be done with ‘overcoming’ isometrics — the nature being to produce maximum isometric tension in as little time as possible.
Aside from enhancing neural drive and potentiating the nervous system, or prolonging the time under tension, isometrics can also be used as a stand-alone method, in which they are not preceded or succeeded with a dynamic movement of the same pattern, or to pre-exhaust a muscle to enhance the mind-muscle connection during the succeeding dynamic movement, and thus enhance the quality of performance.
· Sets: 1-5 per position (perform all sets for each position before moving onto the next)
· Positions: 3 (mid-range, bottom range/full contraction, top range/near full stretch)
· Duration: 3-6 seconds for strength, 9-12 is also acceptable, 20-60 for size
· Yielding Load: 90-110% for strength, 70-80% for size
· Rest: 60 seconds, since isometrics are not energy expensive
Because of the limiting effect pre-exhaustion can have on strength gains, this method is best used as a tool to stimulate muscle growth only. Isolation exercises should be the only consideration, as they mechanically place the targeted muscle under the most tension, while limiting the force contribution of supporting muscle groups. This variation can produce rapid gains in muscle size and is especially useful in correcting specific aesthetic weaknesses.
· Sets: 1-3 per position (perform all sets for each position before moving onto the next)
· Positions: 3 (mid-range, bottom range/full contraction, top range/near full stretch)
· Duration: as long as possible (aiming for 45-60 seconds)
· Yielding Load: 90% (or 3 rep max)
· Rest: 60 seconds
Practical Example With Biceps
*The preacher bench is most practical for the iso since it provides the most stability, but any curl variation can be used for the dynamic portion of the superset.
A1) Isometric preacher - Elbows 90 degrees for max time
A2) Arm curl (barbell, dumbell, cable, etc.)
*No rest between A1 and A2, and 45-60 seconds rest between both rounds (2 sets only)
B1) Isometric preacher - Elbows almost fully flexed for max time
B2) Arm curl (barbell, dumbell, cable, etc.)
*No rest between B1 and B2, and 45-60 seconds rest between both rounds (2 sets only)
C1) Isometric preacher - Elbows almost fully extended for max time
C2) Arm curl (barbell, dumbell, cable, etc.)
*No rest between C1 and C2, and 45-60 seconds rest between both rounds (2 sets only)
If you have any questions about how to implement isometrics to increase size or strength, feel free to contact me at email@example.com. I'm available for online consulting and personalized program design, as well as one on one training if you are located in the Greater Toronto Area (GTA).