Dance Anatomy & Kinesiology

280 Dance Anatomy and Kinesiology

Closed kinematic chain exercises have gained

great popularity in the fitness and rehabilitation

arenas in recent years because they better replicate

functional movements in terms of the loads placed

upon the joints and the complex muscle contrac-

tion involved in coordinating multiple joints. It has

also been proposed that they place less stress on the

anterior cruciate ligament and are associated with

less patellofemoral compression force in the angles

of 0° to 53° of knee flexion (Hungerford and Barry,

1979). However, some of their theoretical advantages

have been questioned by recent research findings

(Irrgang and Neri, 2000); for example, it appears

that both open and closed kinematic chain exercises

can be effective in improving joint proprioception

(Perrin and Shultz, 2000). Furthermore, open kine-

matic chain exercises may offer advantages in terms

of producing effective overload with less resistance,

helping to correct muscle imbalances, and replicat-

ing dance demands of the gesture leg. So, one rec-

ommended approach is to include a combination

in a manner similar to that used with pliés and the

preparation for turns and jumps. It can be performed

with traditional weight apparatus (leg press machine)

or on a reformer with a large number of springs

offering resistance. The lunge (table 5.3I) and par-

ticularly the forward lunge (table 5.3J) are used to

develop lower body strength but can produce injury

if performed improperly, with too much overload,

or with underlying biomechanical problems. Thus,

such exercises should be reserved for adequately

skilled and conditioned dancers without a history of

knee problems and performed only with qualified

supervision.

With any of these closed kinematic chain exer-

cises, proper technique is particularly important.

In addition to stabilization and focus on proper

positioning of the torso, care must be taken to guide

the knee over the second toe, avoid letting the knee

fall inward, and lower only to a point at which cor-

rect form can be maintained and no knee pain is

experienced.

Controlling Hyperextended Knees

When the Foot Is Not Weight Bearing

Sit with one leg outstretched in front of you and the other knee bent with the foot on the floor. Practice

maintaining a straight but not hyperextended knee in the following exercises.

• Quad set (table 5.3A, variation 1). Place two fingertips about 1 1/2 inches (3.8 centimeters)
  above the patella and about 1/2 inch (1.3 centimeters) medial to the inner border of the patella. Focus
  on pulling the kneecap up toward your hip without pushing the knee back into hyperextension. A firm
  contraction should be felt in the muscle under your fingertips (vastus medialis). If you have difficulty
  avoiding pushing your knee back, place the fingertips of your other hand behind your outstretched
  knee to help prevent your knee from hyperextending. Co-contraction of the quadriceps and gastrocne-
  mius (knee flexor) may be necessary to establish a straight but not hyperextended position. For most
  dancers (depending on the size of the calf muscle), the heel of the outstretched leg should stay on
  the floor, and lifting of the heel off the floor indicates that the knee is being hyperextended.


• Straight leg raise (table 5.3B). Perform a quad set and then raise the leg off the ground, hold
  for four counts, and then lower the leg back to the starting position. Use your fingertips to check that
  the vastus medialis is staying contracted, and make sure the knee stays straight and not hyperex-
  tended throughout the movement. Avoid the common error of hamstring substitution. When the knee
  hyperextends, the line of pull of the hamstrings can switch from behind to in front of the axis of the
  knee joint, and thus the hamstrings can produce extension rather than its normal function of flexion
  of the knee. When raising the leg off the floor, some dancers will hyperextend the knee and then use
  the hamstrings (vs. the quadriceps) to maintain the hyperextension, while other hip flexors such as
  the iliopsoas are used to lift the leg. With this substitution, the vastus medialis will not be felt firmly
  contracting under the fingertips. This undesired substitution will not produce the desired strengthen-
  ing of the quadriceps or develop a desired muscle activation pattern.

CONCEPT DEMONSTRATION 5.3