You are working with a patient diagnosed with an anterior cruciate ligament (ACL) insufficiency. The physician's referral specifies closed kinematic chain rehabilitation only. Which of the following exercises would NOT be appropriate based on the physician's order?
1. Exercising on a stair machine
2. Limiting squats to 45°
3. Walking backward on a treadmill
4. Isokinetic knee extension and flexion
The correct answer will be posted in a few days.