The externally-applied force can either vary across the whole joint angle range of motion, or it can remain constant.
In the gym, it is actually quite rare for an externally-applied force to remain completely constant during an exercise, as we will see shortly.
The weight on the bar is the same wherever you measure it.
However, the externally-applied force is not constant, because this force is not solely attributable to weight, but equals .
External load types include pneumatic resistance, elastic resistance, weights (including free weights, chains, and machines), and dynamometers (which use magnets).