2)   Length of the Lever

Changing the length of the lever will affect the forces applied to the body during exercise. A lengthened lever will result in a higher force being exerted at the fulcrum of the movement, so more muscle work will be needed to produce or control the movement. This will also result in a higher force applied to structures during mobilizing exercises.

Levers may be shortened or lengthened by flexing or extending joints, most commonly the elbow or knee joints. They may also be lengthened by holding or attaching an object to the end of a limb such as holding a weight at arm's length.

The positioning of the application of resistance along the lever will affect the muscle work required. Resistance applied distally will require more effort and will reduce when the same resistance is applied more proximally.

3)  Speed of Movement

A change in the speed at which a movement is performed will change the nature of an exercise. When altering the speed, the physiotherapist must be clear as to the desired effect. An exercise performed slowly requires a great deal of precision and postural control. An exercise performed at higher velocities will produce a greater mobilizing effect at the end of range, but the client will require adequate neuromuscular control to perform this without risking further injury.


4)  Range of Movement

A change in the range through which an exercise is performed will alter its difficulty. Muscles are at their strongest in middle range and weakest in outer range (a more lengthened position).


5)  Resistance to Movement

The final way to progress an exercise is to apply resistance to strengthen a muscle resistance can be applied in a number of ways. These are related to the desired effect - whether the aim is to produce a change in power or in endurance.