Isokinetic exercise refers to a movement in which a limb moves around a fixed joint while maintaining a constant speed throughout the entire motion, also known as “constant velocity training.” The human body can hardly produce such a movement in its natural state and requires the assistance of special equipment. Evaluating muscle function at a certain movement speed is called isokinetic strength testing, which is currently the best method for assessing muscle function and mechanical properties.
Clinical applications of isokinetic strength testing technology include:
① assessing the degree of impairment in joint, muscle, or nerve function;
② determining the baseline values of the healthy side as the expected values for the therapeutic effect of the affected side;
③ evaluating the efficacy of rehabilitation treatment plans and monitoring the rehabilitation process in real-time to adjust the rehabilitation plan timely.
Muscle Strength Evaluation
Currently, manual muscle testing is widely used in clinical practice to assess muscle strength. Although it is easy to perform, it has drawbacks such as relying on the examiner’s subjective judgment and not being quantifiable. Isokinetic strength testing, on the other hand, can accurately quantify the muscle strength of the muscles surrounding the tested joint. Peak torque (PT) at low angular velocities (30°/s-60°/s) is typically used for maximum strength assessment, while total work (TW) at high angular velocities (180°/s-300°/s) is used for muscle endurance assessment. PT decreases with increasing angular velocity. 
Joint Stability Assessment
Knee joint stability assessment mainly adopts the hamstring/quadriceps (H/Q) ratio of peak torque. The H/Q ratio is an important indicator of whether the flexion and extension muscle strength of the knee joint is balanced. Research has shown that the normal H/Q standard value is 60%-69% at a knee joint angular velocity of 60°/s. The H/Q ratio increases with increasing angular velocity. An excessively high or low H/Q ratio can affect the coordination and stability of muscle movement, leading to knee joint injuries. 
Bilateral Limb Symmetry Assessment
Bilateral limb symmetry assessment mainly adopts the muscle strength differences of bilateral homonymous muscle groups. When the ratio of homonymous muscle groups on both sides of the human body is less than 0.8, injuries are more likely to occur, especially when both sides generate maximum explosive force simultaneously. Research generally believes that the difference in peak torque between homonymous muscles on both sides should be within 10% to ensure a balance of muscle strength.
Auxiliary Diagnosis
By analyzing the notches, fluctuations, plateaus, asymmetries, or other deformations in the isokinetic torque curve, as well as the interruption or shortening of the curve, possible joint lesions can be determined, such as the “M”-shaped curve of knee osteoarthritis (KOA) and the “W”-shaped curve of meniscal injury. Analyzing abnormal torque curves can provide objective information about muscle and joint pathological changes. However, the abnormal torque curves measured by isokinetic technology are usually nonspecific and can only be used as auxiliary information, requiring further confirmation in conjunction with other clinical methods.
Isokinetic strength testing is an important practical technology for muscle assessment and has extensive applications in clinical practice. Isokinetic equipment can be used for isokinetic strength training while testing, which is also a primary method for muscle training.
Article source: Liu Gongliang, Department of Rehabilitation Medicine, Shanghai Sixth People’s Hospital
For product details, please click: Multi-Joint Isokinetic Strength Testing & Training System
Post time: Jul-17-2023