An advanced method using dynamometers such as Cybex/Biodex to measure and rehabilitate muscle strength, balance and endurance with variable resistance at a constant angular velocity.
Indication
- Knee rehabilitation after anterior cruciate ligament (ACL) reconstruction
- Muscle strengthening after meniscus surgery or rotator cuff repair
- Assessment of muscle strength in injuries of the knee, hip, shoulder, elbow and ankle
- Return-to-play testing after sports injuries
- Measurement of trunk muscle balance in chronic low back and neck pain
- Quantitative assessment of muscle weakness in neurological conditions (stroke, MS)
- Objective measurement of muscle capacity in occupational and forensic cases
Preparation
- Avoid heavy exercise for 24 hours before the test
- Do not test on an empty stomach; eat lightly and stay well hydrated
- Wear sportswear and appropriate footwear
- Testing should not be performed before acute pain, swelling or post-operative healing has resolved
- Physician clearance: no cardiac disease, uncontrolled hypertension or acute musculoskeletal pathology
How it's performed
- The patient is positioned appropriately on the dynamometer (Cybex, Biodex or similar); trunk and limb are stabilized
- A 5-10 minute warm-up is performed; the device is calibrated
- The test is performed at different angular velocities (e.g., 60 deg/s, 180 deg/s, 240 deg/s)
- Muscle groups (quadriceps/hamstrings, agonist/antagonist) are measured with concentric and eccentric contractions
- Peak torque, work capacity, endurance and the difference between the involved and uninvolved sides are reported
- When used for rehabilitation, the same device is used for progressive resistance strengthening exercises
Post-procedure
- A single test session lasts 30-45 minutes; rehabilitation programs are recommended 2-3 days per week
- Results are compared with reference values and reported in writing
- Return-to-play decisions are typically made when strength reaches 85-90% or more of the uninvolved side
- The treatment plan may last 6-12 weeks and is updated according to clinical progress
- With regular follow-up, gradual loading and functional exercises are progressed
Risks
- Muscle strain or delayed-onset muscle soreness with overexertion
- Joint pain or transient swelling (especially after eccentric testing)
- Cardiovascular strain in patients with uncontrolled blood pressure
- Delayed healing if testing is performed too early after acute injury
- Misleading results due to incorrect calibration or positioning
FAQ
What is the difference between isokinetic testing and MRI/EMG?
MRI and EMG are structural and electrical assessments, whereas isokinetic testing quantifies the actual force and endurance the muscle can generate.
How often should athletes be tested?
It is recommended at the start of the season and after returning from injury. Assessment is essential before return-to-play following an injury.
Is the test painful?
Brief muscle fatigue and mild soreness may occur during maximal contractions; significant pain is not expected.
When is it performed after ACL reconstruction?
An initial assessment is generally performed 4-6 months after surgery, with return-to-play testing between 6-9 months; the decision is made jointly with the surgeon and physiotherapist.
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