Free weights always produce force downward
. To load muscles in various locations along the joint's range of motion
the body has to be reoriented using different exercises. Force always stays the same, downward.
Triceps Exercises -examples of changing body position to emphasize different portions of the joint's Range of Motion for triceps.
Cables with Weights.
Cables & pulleys always produce force in the direction of the cable which often changes during the exercise. Force magnitude stays the same, but direction changes.
Resistance bands, like cables always pull in the direction of the resistance band. Resistance bands change force magnitude significantly with length/stretch. I believe the force associated with a resistance band is usually listed for 100% lengthening or doubling of the band length. For example, a '25lb' resistance band will pull with 25 lbs force when its length is doubled (100% elongation). Force magnitude varies with length and direction changes. A short elastic band will vary force more than a long band as length is varied.
For all exercises the muscle does no work when it shortens in a direction perpendicular to the resistance force (for free weights & cables there's no work when the exercise does not move the weight up
in gravity). For example, if you stand and curl a dumbbell at the very beginning when the arm is straight down at the side there is no resistance to flexing the arm - the weight moves forward
but not up
. For the curl also at the top there is little force required to finish flexing the arm. This is why certain body exercises are done with the body in different positions. For example, curling on a 45 d. bench
causes the muscles to work much harder at the beginning of the curl, etc.
There are some hip exercises that I do with resistance band loops
because they are idea. Clamshells, etc.
BTW, I think that I sometimes nick Therabands with my fingernails and a short length will soon break off the end.
I have a long Theraband tied near the microwave and do external shoulder rotation exercises while heating stuff. First, there's a light set to warm up and then a heavier set for conditioning. [Very heavy resistance is not recommended for rotator cuff conditioning.]
Another TW thread