STUDY ON EVALUATION FOR MUSCULAR STRENGTH OF KNEE JOINT MOVEMENT BY CYBEX II

Traditionally there have been two types of muscular exercise, isometric and isotonic. Recently, isokinetic exercise, developed to incorporate the advantages of the previous two types of exercise and overcome their disadvantages, has found application in sport and rehabilitation medicine, although it still has many aspects to be clarified clinically. We measured muscular strength of top-ranking athletes, and used an isokinetic machine to study characterisitics of their muscular strength in various events. W e also used isokinetic exercise for rehabilitation of top-ranking professional and amateur athletes who had injured knee joints, and observed their muscular strength for certain elements, such as muscle power, work volume and peak torque acceleration energy, to assess the possibility of using these elements for objective evaluation of progress in muscle strength recovery and on return to sport and ADL. Studies were carried out on : (1) 39 top-ranking track and field athletes engaged in various events, (2) five amateur athletes with knee joint injuries, and (3) 9 top-ranking skiers with knee joint injuries. Results were as follows : (1) Measurement and analysis of the track and field athletes revealed maximum muscle strength differences for knee extension and power endurance depending on the characteristics of their events. This necessitated grouping them into two types : Quick muscle fiber dominance was found in athletes such as throwers, short-distance runners and jumpers, who had strong explosive power but poor endurance. Slow muscle fiber dominance was found in athletes such as long- and middle-distance runners, who showed poor explosive power, but strong endurance. These results encouraged application of isokinetic exercise to sports medicine. (2) Application of isokinetic exercise for rehabilitation of amateurs with knee joint injuries increased the maximum absolute values of muscular strength for knee extension and flexion with increasing exercise duration. Muscular strength elements, such as muscle power, work volume and power endurance also increased with increasing muscle volume. In addition, results of the study suggested that recovery of the maximum muscle strength of the affected side to 30 to 50 % of that of the unaffected side could indicate possible return to ADL. (3) Application of isokinetic exercise for rehabilitation of atheletes with knee joint injuries also revealed that recovery of muscle strength on the affected side compared to that on the unaffected side is a more effective indicator than the absolute value of muscular strength for return to sport and ADL. It is important for skiers to recover muscle strength to 70 % of normal before returning to sking, and increase in muscle strength recovery should be more marked in muscular strength for knee extension than that for knee flexion.