CYBEX VR2 Owner's And Service Manual page 45

The Hamstring
• Knee Flexion - The hamstring group is respon-
sible for flexion of the knee joint. The ham-
strings also cross the hip joint and are responsi-
ble for hip extension. Altering the stabilized
position of the hip creates variety for resisted
knee flexion exercises. It should be noted that
any movement of the hip joint (loss of stabi-
lization) that occurs during resisted knee flex-
ion usually decreases the effectiveness of the
exercise by allowing unresisted change in the
hamstring's length.
• Range of Motion - The normal range of knee
motion is generally considered to be -10 to 135
degrees. The hamstring is limited by mechani-
cal disadvantage near full extension (eccentric
"lowering of the weight"). Due to the direction
of resistance and the availability of hyperexten
sion at the knee, it is advised to limit the
eccentric movement just short of full extension. Due to the position of hip flexion near 90
degrees, many users will not be able to achieve even this degree of extension eccentrically
due to poor hamstring flexibility. Resisted knee flexion is limited only by concentric
control.
• Associated Muscles - The gastrocnemius is an assistant mover for knee flexion. It can be
discouraged from use by attempting to completely relax the ankle muscles or by planter
flexing the ankle. Plantar flexion shortens the gastroc and as knee flexion occurs the muscle
will achieve a condition of active insufficiency. However, the fact that the gastroc is
involved in plantar flexion can further its involvement through much of the knee motion.
Dorsiflexion encourages gastroc contraction. The gracilis, sartorius, and plantaris are also
assistant movers for knee flexion.
Exercise
Page 3-14
CYBEX VR2 Owner's Manual
MUSCLES TRAINED