November 6, 2011

Strength Curves - How To Use Variable Resistance To Make An Exercise More Complete, And Maximize Results

Constant vs. Variable Resistance

When resistance remains constant, muscular tension is greatest at the range in which the resistance's line of pull is perpendicular (90 degrees) to body's lever arm, as relative continuous muscular tension is not required throughout the full range of motion of an exercise. As a result, there ends up being a relatively large difference in terms of muscle tension that takes place throughout the range of motion, the degree of which can vary depending on the length of range.


The relationship between muscular tension and length of range of motion is inversely proportionate:

The shorter the range of motion – the greater percentage of the range in which the muscle tension is relatively continuous, ex: calf raise, wrist curl – the muscles remain under very high levels of tension throughout the range of motion as a result of the minimal range

The greater the range of motion – the lesser percentage of the range in which the muscle tension is relatively continuous, ex: squat, deadlift, bench press, pull-up – the muscles are not under very high levels of tension through the majority of the range of motion as a result of the extended range

Variable resistance requires relative continuous muscular tension throughout the full range of motion, as long as the resistance matches the exercise’s strength profile.

Strength Profiles

Gravity dependent, free weight exercises have their own specific strength profile (AKA resistance curve), which describe their characteristic change of force throughout the range of motion, and can be classified under one of three categories – ascending, descending, concave/bell-shaped.

Ascending Strength Curve

The tension curve in which the muscular tension required decreases as leverage increases, and the movement becomes progressively easier throughout the range of motion until the end of concentric range (most compound extension oriented movements fall under this category, as they generally place the targeted muscle under the greatest amount of tension at the beginning of concentric range: ex, bench press, squat, deadlift)

Descending Strength Curve

The tension curve in which the muscular tension required increases as leverage decreases, and the movement becomes progressively harder throughout the range of motion until the end of concentric range (most compound flexion oriented movements fall under this category, as they generally place the targeted muscle under the greatest amount of tension at the end of concentric range: ex, pull-up, chin-up, rows)

Concave/Bell-Shaped Strength Curve

The tension curve in which the muscular tension required increases then decreases, as leverage decreases then increases, and the movement becomes progressively harder and then easier. Many gravity dependent exercises tend to have a bell shaped resistance curve where muscular tension is greatest in middle of the range (most free weight isolation movements fall under this category, as they generally place the targeted muscle under the greatest amount of tension in the middle of the range of motion: ex, arm curls/extensions w/barbells or dumbells)

And Why Is This Important?

In a perfect world, the resistance would increase, decrease, or both, throughout the range of motion to match the strength profile of the exercise being performed, and effectively overload the entire strength curve by gradually increasing for movements with an ascending strength profile, gradually decreasing for movements with a descending strength curve, and gradually decreasing then increasing for movements with a concave/bell-shaped strength curve. Since we don’t live in such a world, muscles are undertrained under normal conditions, as the amount of resistance needed to overload the entire strength curve is limited by how much force can be generated in the most disadvantageous range of the movement.

Bands And Chains

Variable resistance can be applied with the use of resistance bands, or lifting chains, to match the strength profile of movements which follow an ascending strength curve, to create a more complete movement, so that relative continuous muscular tension is required throughout the range of motion. Unfortunately, movements which follow a descending, or concave/bell-shaped strength profile, don’t have this luxury, therefore the only opportunity to perform movements in which the resistance matches the strength profile of the exercise is to use variable resistance machines specifically designed for this purpose.

Aside from creating a more complete movement by overloading the entire strength curve so that relative continuous muscular tension is required throughout the range of motion, the variable resistance provided by bands and chains offers a few other significant benefits:

·         Chains, and bands, are valuable tools for teaching the nervous system the concept of acceleration. Under normal conditions the amount of force needed to overcome the resistance decreases as leverage improves, and even if the intent is to lift with maximal acceleration, because more force can be produced with improved leverage, the weight is relatively lighter at the end of concentric range resulting in a phase of deceleration as range comes to an end. In fact, the deceleration phase during an explosive lift can be as long, if not longer, than the acceleration phase, as greater acceleration requires greater deceleration, and this can have adverse effects by essentially teaching and reinforcing the concept of deceleration. Chains, and bands, all but eliminate the deceleration phase at end range because the amount of force needed to overcome the resistance increases in direct proportion to one another. And how does the nervous system respond to the variable demand? By relying on the high threshold motor units! Do this enough times and over time the nervous system will begin to preferentially recruit those motor units, thus increasing the quality of the rest of your training because of the carryover effect.

·         Chains, and bands, increase the average load per set, and increase the time under maximal tension. Because chains, and bands, overload the entire strength curve, the resistance at the end of concentric range is generally far greater than would otherwise be possible under normal conditions.

Chains vs. Bands

The differences between chains and bands are minimal, but each ultimately provides a much different stimulus. While chains and bands similarly increase the amount of resistance felt, bands require greater eccentric demands, as they attempt to rapidly pull the bar down into the floor. Because of this, chains are generally preferred over bands when training for power, as they are much easier to control when lifting explosively, while bands may positively influence strength development to a slightly greater degree because of the enhanced eccentric component.

Loading

The whole purpose of matching the resistance to the strength curve is to ensure the heaviest weight possible is being applied throughout the range of motion, since generally much greater loads can be handled at the end of concentric range. Therefore, as far as loading is concerned, the resistance at the end range should represent over 100% of full range max. This is perhaps the greatest benefit which chains, and bands, can offer – the use of supramaximal weights, albeit through a limited range. Generally a 20-30% discrepancy between top range, and bottom range, loading is ideal: ex. bottom range loading is equivalent to 80% of 1RM, top range loading is equivalent to 105% of 1RM. If the discrepancy is either too great, or too little, much of the training effect is lost.

Reverse Bands

The greatest difference between chains and bands is that bands offer far greater versatility. While chains are only capable of opposing gravitational forces, bands can oppose force from virtually any angle – even from above. While bands increase eccentric stress, reverse bands decrease it, so even with the same relative load at the top and bottom range of motion, the eccentric stress is drastically different. For this reason, reverse bands are preferred for those with tender shoulders when pressing, as they provide the most assistance in the most vulnerable range, which allows for the movement to continue being trained (with maximal loads), to prevent gains from being lost by removing it from the program all together.

A Word Of Caution

The variable resistance provided by chains, and bands, is very neurologically demanding, as the nervous system doesn’t have the opportunity to put things on ‘cruise control’ for much of the range of motion that would otherwise be possible when resistance remains constant. Because of this, it’s best to cycle the usage of these highly intensive tools in, and out, of a training program, to prevent overworking the body’s capacity to recover from the workload, an example of a workout-to-workout progression looking like this:

Workout 1: 4 x 6-8 – NO CHAINS OR BANDS ADDED
Workout 2: 3-4 x 4-6 – WITH CHAINS
Workout 3: 3-4 x 4-6 – WITH BANDS

Cycle can be repeated 2-3 times, then it’s best to cycle off chains and bands for a few weeks because of the increased neural demand.

BEST EXERCISES TO IMPLEMENT THE USE OF CHAINS, BANDS, AND REVERSE BANDS

Squats (front squat, back squat)

Deadlifts (standard, sumo, Romanian)

Good Mornings

Bench Press (All forms of presses can be used very effectively with chains/bands/reverse bands)

*Decline Triceps Extension

Chains, and bands, are best implemented with exercises in which the bar path is as close to vertical as possible. If the bar path shifts, the resistance applied by the chains or bands can negatively affect the motor pattern, thus reducing the effectiveness of the movement, as well as the ability to carry over the gains made using the chains and bands. Bands however, can be effectively implemented with many machines because their line of pull can vary in a way that is not possible with chains, due to gravity.

*With a decline bench, the bar basically travels vertically as the arms are extended and flexed, as opposed to the flat angle which has more of an ‘arc’ path which, as described above, can negatively affect motor pattern development.


If you have any questions about strength curves, and how to use chains and bands to increase strength, feel free to contact me at ben@paramounttraining.ca. 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).

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