To most trainers choosing the right resistance is simply a matter of grabbing the right dumbbell. In reality the actual amount of a resistance is not that simple.
In every exercise the resistance varies throughout the range of motion. For most trainers this occurs unknowingly and haphazardly. This all happens whether you choose to be in charge of it or not!
Beneath the surface there are many hidden factors that affect the actual amount of resistance, and often have more influence than the number printed on the weight. These include numerous mechanical factors, the physic-al properties of the device, as well as user-related influences such as acceleration and tempo.
It is vital that we know all the ways that resistance is and can be manipulated. Strategic manipulation of the resistance at various points in the range of motion is paramount to altering the outcome of the exercise in terms of muscular challenge, motor recruitment, joint forces, and ultimately the exercise experience.