This document discusses different types of knee strengthening exercises and their effects on force generation in the quadriceps muscles. It states that free weight exercises generate the greatest force at the end range of knee extension, while pulley or cam systems produce less force in the end range. Closed chain exercises increase the force requirement of the quads as knee flexion increases. The document recommends closed chain exercises in slight knee flexion for strengthening without stressing the patellofemoral joint.

2.  OPEN CHAIN STRENGTHENING WITH FREE
WEIGHTS –
The shorter M.A of quads causes greater force to be
generated by muscles in end range extension.

3.  WITH PULLEY OR CAM SYSTEM –
A pulley system exerts a perpendicular resistance throughout the
range
Therefore, force required to be generated by quads in the end
range is lesser.

4.  ISOKINETIC DYNAMOMETER –
Therefore, peak force is generated in midrange.

5.  CLOSED CHAIN –
The force required of quads increases
as flexion increases.

6.  Different strengthening exercises target different
ranges i.e
a. Strengthening with free weights maximum
strengthening forces occur at end range extension.
b. With pulley or cam system at initial half range.
c. With dynamometer at midrange.
d. In closed chain exercises as flexion angle increases.
 Normal extensor moment
a. Normal locomotion – 30Nm
b. Kicking a ball – 260Nm
c. Rising from chair- 200Nm

7.  Joint reaction forces consists of axial (compressive) and
shear stresses (anteroposterior and medial-lateral).
 Compressive forces are greater than shear forces.

9. Closed chain exercises in slight knee flexion are recommended for
strengthening without stressing PFJ

11.  Kinesiology mechanics and pathomechanics; 2nd edition.
Carol.A. Oatis.