Resistance Bands Tension Calculations
Updated: Jun 3, 2020
One common question that we receive at Bodylastics USA Inc. is "how much resistance is the band generating for certain exercises?"
In other words, if you are standing on a 19 lbs. band with a handle in each hand how much will each arm be feeling/working against?
The easy explanation is that a resistance band will generate the rated amount of tension as you stretch each single band from an anchor point.
So in the example from above, each arm will be curling against 19 lbs. of tension.
Wait! it can't be a steady 19 lbs. throughout the range of motion, right? Don't Resistance Bands Create Variable Progressive Resistance?
Yes. True! Since it's a Resistance Band, the resistance will not be a consistent 19 lbs. throughout the range of motion. It will progress as you contract and shorten each muscle for each exercise. Remember, the tension that the bands generate naturally increases as they are elongated/stretched. So, for the Arm Curl, the amount of tension may only be at 4 lbs. at the start of the exercise, and then increase to 28 lbs. as you curl your arm. This may seem significant, but it isn't. The variance in the band resistance doesn't erase the fact that you must choose enough resistance to challenge your muscles and force them to struggle. If your muscle struggles in every set, it will be forced to change.
Tension With Multiple Bands
In the case that you have "Stacked" your bands (see the picture above) you simply need to add up the tension rating for each band from the anchor point (in this case your foot). For example if you are standing on a combination of an 3, 5 and 8 lbs. band, you will working against 16 lbs. of tension, since you add the resistance rating for each single band.
Double The Resistance For A Single Band
This also means that for certain exercises, you can double the resistance and the rating of a single band by anchoring it and clipping both ends onto a handle or ankle strap. In this case there will be 2 single strands of the band from the anchor point.