Accommodating resistance is widely used in strength training (for more detail on accommodating resistance click here). However, not all accommodating resistances used (bands versus chains) will result in the same stimulus. Both bands and chains accomplish a similar goals (add resistance throughout the movement), but their influence on the kinematics of the movement are different.
Why use accommodating resistance (Short Answer)
Accommodating resistance can increase the time force is applied during a movement (increases time of acceleration) and total power of a movement (1). Accommodating resistance adds load to the bar as the athlete moves through the range of the motion of the movement, increasing from the bottom to the top. It does not make all movements “better”. However, when used properly it can add a unique stimulus to the athlete’s training.
Accommodating resistance with chains is pretty straight forward. As the the bar moves towards the end ranges of the movement, the chains will be picked up off the floor. Depending on how many chains you have attached to the bar and how high you have them hanging from the bar, the chains will increase the weight in a linear fashion from the point the are lifted.
Example, lets say you have a total of 120lbs of chains on the bar (60 each side). Also assume the chains don’t get picked up until the bar is one foot removed from the starting position and the total range of motion of the movement you are doing is two feet.
This means for every inch the bar moves above the halfway point (one foot above the bottom), the weight of the bar will increase by 5lbs each side (total of 10lbs). So, at the top of the movement (12 inches from the halfway point) the last links will be lifted and a total of 120lbs of chain will be off the ground (12inches X 10pounds per foot = 120lbs after one foot).
Bands are a little less straightforward than chains. They do not progress in load (tension) in a linear fashion. The greatest amount of change in tension will occur in the first portion of the lift and towards the end of the movement the change in resistance begins to lessen. Unlike chains, bands will be providing resistance throughout the entire range of motion. Obviously it will lessen towards the bottom, but there is no point where the bands get “picked up” off the floor.
Band Resisted Trap Bar
Bands and Nonlinear Tension
For example (just an example and not based on real numbers), lets say you have two bands attached to a bar. Also assume the range of motion of the movement is two feet. At the top of the movement there will be 75 pounds of band tension on the bar.
The first half of the movement (one foot) the bands might add 50 pounds of resistance each side and the second half of the movement the bands may only add 25 pounds of tension (plus the 50 pounds already there from the first half of the movement, total would be 75). As the bands got stretched, the amount of tension gained per-inch lessened. You can measure your band tension and tension drop off fairly easily with a fish scale or big game scale.
Scale link here
Bands and increased eccentric velocity
Bands also add an increase in eccentric velocity. Unlike chains, bands are actively pulling you down. They don’t actually weigh much, however they add resistance to the bar by adding tension, while chains add resistance via mass (weight). Because there is tension, the bands are going to be pulling you down to the ground faster than the speed of gravity (if you let them). This can allow for an eccentric velocity overload component. It might put a greater demand on the stretch shortening cycle (high velocity of stretch) and possibly utilize more elastic energy.
The faster eccentric velocity means that you will need to have a large change in momentum to move from an eccentric to concentric motion. This means we will have to produce more force at an equal load if the eccentric velocity is faster (its physics). It is all based on the impulse-momentum relationship. Feel free to click here to learn more about impulse
(Manipulating impulse:Link in bio) The above exercise is what some call a drop squat, a relax contract squat, or a reactive squat (whatever name works for you). Essentially the idea is to manipulate required impulse and the neural firing patterns. •••••••••••••••••••••••••••••••• The movement starts in an upright, contracted stated. You then slightly fire your hip flexors and knee flexors (brining your feet off the ground), this in then will force the relaxation of the monoatricutlate quad muscles (knee extensors) and hip extensors (glutes) via reciprocal inhibition. •••••••••••••••••••••••••••••••• The relaxation theoretically forces the the quads and gluteus to be first turned on then off and the back on rapidly to catch yourself at the bottom. Because there was no eccentric aid in slowing the weight down, the velocity will be quite high and require a high impulse (ideally on the force side) and encourage a fast RFD both eccentrically (the immediate absorption of the load) and concentrically (firing back up). This is all possible due to the understanding of impulse and requirements of stopping a large impulse.
Both bands and chains are forms of accommodating resistance. However, they are each a little different. Depending on your training goals and the level of athlete, one method may be more advantageous than the other.
How to set up bands
How to set up chains
- Siff, M.C. (2000). Supertraining. Denver: Supertraining Institute.