There was a research study conducted when I worked at the Steadman Hawkins Sports Medicine Clinic in Vail, Colorado to quantify muscle activation levels, knee joint angles and applied forces during five elastic resistance knee rehabilitation exercises.
Based on the muscles activation patterns, a progressive continuum of rehabilitation exercises that can be applied to nonoperative injuries as well as anterior cruciate ligament reconstruction was developed.
Single Knee Dip
Anchor one end of the elastic resistance device to the back of a chair. The subject should stand on their injured leg, with the resistance device anchored underneath the foot.
The subject should balance themselves with one hand on the back of the chair, hold the other end of the elastic device with their opposite hand, and stretch the elastic resistance device so that it is at waist level. The subject should lower their body to a one-third knee bend and return to a position of slight knee flexion.
Double Knee Dip
This exercise is performed in the same manner as the single knee dip, but the subject places both feet on the middle of the elastic resistance device. The exercise consists of a two-legged knee dip with both ends of the elastic resistance device held at waist level.
The subject should sit in a chair with the elastic resistance device handle placed over the ball of their foot on their injured side. The subject holds the other end of the elastic resistance device to provide resistance (which can be varied), but should start such that the device is taut with the subject's knee and hip at maximal flexion. The subject should perform a leg press, not a leg extension, with the knee returning towards the subject's chest during the knee and hip flexion phase.
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The elastic resistance device should be anchored to a wall at a height of approximately 30 cm and the other end attached around the subject's heel on the injured side, with an accessory strap. The subject should be seated in a chair with his/her foot (on the injured side) on the ground, knee flexed to approximately 20°, and the elastic resistance device taut. Subjects should drag their foot back along the floor as far as they can and lift it slightly while returning it to the initial position.
The elastic resistance device should be anchored to a wall at a height of about 120 cm, and the other end attached to belt (on the subject's injured sided) which is around the subject's waist. The subject should begin from a position where the elastic resistance device is just taut. The exercise involves a lateral jump of approximately 1 m with the subjects supporting themselves on only on foot at a time. The subject should initially push off on their injured leg, against the resistance of the elastic cord, then land on and push off with their opposite leg, with assistance of the stretched cord, and complete the cycle by landing on their injured leg.
Progression Of Exercise
The EMG data from the study suggest a progression of exercise for knee rehabilitation. This can be accomplished through an exercise progression that increases muscle activity or within an exercise by increasing the resistance.
Patients begin the immediate postoperative stage (days 1-3) by performing the double knee dip while wearing a brace that limits knee range of motion from 10 to 90° of flexion.
The leg press and hamstring pull are included in addition to the double knee dip during the early rehabilitative phase (day 3 to week 8).
The intermediate (weeks 8 to 12) and late (weeks 12 to 20) build progressively from the immediate postoperative phase. The intermediate rehabilitative phase include the exercises from the preceding phases and adds single knee dips to fatigue. The late rehabilitative phase adds the side-to-side jump exercise.
Return To Activity
Upon completion of the late rehabilitative phase, patients should perform a functional test using the elastic resistance device. The test involves 3 minutes of double knee dips, 3 minutes of single knee dips with each leg, and 50 repetitions of side-to-side jumps on each side.
Successful and pain free completion of the test means patients can progress to other functional activities, such as jogging, tennis, and inline skating.
"Paradox of Exercise"
Please be cautious of a "paradox of exercise" where the patient risks excessive anterior cruciate ligament strain if quadriceps strengthening exercises are performed at less than 30° of knee flexion, but patellofemoral joint complications are possible of the exercises are performed at greater than 60° of knee flexion.
About The Author
Scott Colby is a biomechanical specialist and the President, SC Fitness, located in the Dallas/Ft. Worth Area. Visit his website at http://www.scfitness.com.
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