A Comparison of Onset Time and Muscle Activation of Hip Extensors During Dead-lift, Squat and Kettlebell Swing Exercises

The purpose of this study was to find out the muscle activation depending on the intensity of Dead-lift, Squat, Kettlebell swing exercises that are widely used in the field for hip extensor exercise, and provide appropriated exercise types for strengthening hip extensors by identifying the onset time of extensor muscle contraction which appears in extension pre, during, and post exercise. The subjects were men in 20s living in Seoul, and the result was derived targeting on 29 persons using random sampling method among persons with one year or longer experience of weight training. After attaching surface EMG (sEMG) on both erector spinae, gluteus maximus, and semitendinous muscles, the onset time was measured using prone hip extension test to find out the changes in the hip extensors pre and post exercise. Also, the muscle activation and onset time were measured. By summarizing results, the three types of exercises are considered to be effective in strengthening hip extensor muscles as the muscle activation of hip extensors increased when the intensity as increased from 1RM 50% to 75%. However, it is thought to be effective to select Dead-lift and Kettlebell Swing exercises to intensively strengthen gluteus maximus and semitendinous muscles, and select Kettlebell Swing exercise to enhance the power of the two muscles. In addition, to normalize the onset time between the hip extensors, selecting Dead-lift and Kettlebell Swing exercise is thought to be effective, and since Dead-lift exercise, which is identified to have no difference in onset time even during exercise, can be widely used in rehabilitation, retraining of hip movements, and etc., it is thought to be effective in prevention and preventing relapse without having interfered by movement patterns