In the lower extremity

1. Open- and closed-kinetic chain exercises have different biomechanical effects … the lower extremity and … particular … the knee joint. 2. It is essential … the sports therapist to understand forces that occur … the knee joint. 3. Palmitier et al. have proposed a biomechanical model … the lower extremity that quantifies two critical forces … the knee joint. 4. Ashear force occurs … a posterior direction that would cause the tibia to translate anteriorly if not checked … soft tissue constraints (primarily the anterior cruciate ligament). 5. The second force is a compressive force directed … a longitudinal axis … the tibia. 6. Weight-bearing exercises increase joint compression, which enhances joint stability.

6.10. Open the brackets and use a verb in a proper tense and voice form.

1. In an open-kinetic chain seated knee joint exercise, as a resistive force

(apply) to the distal tibia, the shear and compressive forces (would, maximize). 2. When a resistive force (apply) more proximally, shear force (reduce) significantly, as (be) the compressive force. 4. If the resistive force (apply) in a more axial direction, the shear force (be) also smaller. 5. If a hamstring co-contraction (occur), the shear force (minimize).

LATERAL STEP-UP EXERCISE Lateral step-ups are another widely used closed-kinetic chain exercise. Lateral step-ups seem to be used more often clinically than do forward step-ups. Step height can be adjusted to patient capabilities and generally progress up to about 8 inches. Heights greater than 8 inches create a large flexion moment at the knee, increasing anterior shear force and making hamstring co-contraction more difficult.

6.11. Make the sentences below negative.

1. Closed-kinetic chain exercises induce hamstring contraction by creating a flexion moment at both the hip and knee with the contracting hamstrings stabilizing the hip and the quadriceps stabilizing the knee. 2. A moment is the product of force and distance from the axis of rotation. 3. Also referred to as torque, it describes the turning effect produced when a force is exerted on the body that is pivoted about some fixed point. 4. Co-contraction of the hamstring muscles helps to counteract the tendency of the quadriceps to cause anterior tibial translation. 5. Co-contraction of the hamstrings is most efficient in reducing shear force when the resistive force is directed in an axial orientation relative to the tibia, as is the case in a weight-bearing exercise. 6. Several studies have shown that co-contraction is useful in stabilizing the knee joint and decreasing shear forces.

6.12. Put general questions to the following sentences.

1. The tension in the hamstrings can be further enhanced with slight anterior flexion of the trunk. 2. Trunk flexion moves the centre of gravity anteriorly, decreasing the knee flexion moment and thus reducing knee shear force and decreasing patellofemoral compression forces. 3. Closed-kinetic chain exercises try to minimize the flexion moment at the knee while increasing the flexion moment at the hip. 4. A flexion moment is also created at the ankle when the resistive force is applied to the bottom of the foot. 5. The soleus stabilizes ankle flexion and creates a knee extension moment, which again helps to neutralize anterior shear force. 6. Thus the entire lower extremity kinetic chain is recruited by applying an axial force at the distal segment.

Terminal knee extensions using rubber tubing.	Closed-kinetic chain isokinetic testing. Closed-kinetic chain isokinetic testing attachment from Biodex.
Closed-kinetic chain exercises for upper extremity. A, Seated push-ups. B, Weight-shifting exercises.

6 .13. Use the sentences below in one of the Past Tenses.

1. In an open-kinetic chain exercise involving seated leg extensions, the resistive force is applied to the distal tibia, creating a flexion moment at the knee only. 2. This negates the effects of a hamstring co-contraction and thus produces maximal shear forceatthe knee joint. 3. Shear forces created by isometric open-kinetic chain knee flexion and extension at 30 and 60 degrees of knee flexion are greater than with closed-kinetic chain exercises. 4. Decreased anterior tibial displacement during isometric closed-kinetic chain knee flexion at 30 degrees when measured by knee arthrometry has also been demonstrated.

6 .14. Put disjunctive questions to the sentences below.

1. The effects of open- vs. closed-kinetic chain exercises on the patellofemoral joint must also be considered. 2. In open-kinetic chain knee extension exercise, the flexion moment increases as the knee tends from 90 degrees of flexion to full extension increasing tension in the quadriceps and patellar tendon. 3. Thus the patellofemoral joint reaction forces are increased with peak force occurring at 36 degree joint flexion. 4. As the knee moves toward full extension, the patellofemoral contact area decreases, causing increased contact stress per unit area.

6.15. Give a talk on the text “Closed-Kinetic Chain Exercise”.