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THE COMPARISON OF MUSCLE ACTIVATION AND PERFORMANCE IN A NEUTRAL AND SUPINATED GRIP BICEP CURL
BACKGROUND: When performing a bicep curl, there are many muscles that must activate in order to achieve this motion much like any other body part. Changing the hand formation from a supinated to a neutral grip can change the biomechanics of the arm during elbow flexion. For this study, the brachioradialis was compared to determine whether or not it was more involved during the initial 40 degrees of elbow flexion during a neutral grip bicep curl compared to a supinated grip bicep curl. According to the literature, most studies found no significant difference in performance and muscle activity between a neutral grip and supinated grip. PURPOSE: The purpose of this study was to compare the muscle activity and performance of the brachioradialis during a supinated and neutral grip bicep curl. METHOD: A total of 5 male participants (Age 23.6 ±1.1 yrs) were chosen randomly at the University of Texas at Arlington. The participants performed physical activity at least3-5 times a week. Demographic data (height, weight, age) were recorded prior to the experiment. Two electromyographic (EMG) sensors as well as a ground electrode were placed on the participant’s bicep branchii and brachioradialis. Participant was stationed at the Biodex dynamometer and began warming up by performing bicep curls on the Biodex. The participant then performed 3 trials of an isometric and isokinetic elbow extension test on a neutral grip with a 2-minute rest period in between each trial. After these trials were completed, the participant performed the 3 trials of the same tests with a supinated grip instead of a neutral grip with the same number of trials and rest periods. Participant’s torque, power, and EMG activity were recorded. The data obtained during the experiment was converted to average torque, power, and EMG activity during the initial 0-40 degrees of elbow flexion. The maximum voluntary contraction percentage (MVC%) for the brachioradialis during the initial 40 degrees of elbow flexion was also calculated. RESULTS: According to the data the mean value of average during the initial 40 degrees of elbow flexion during a neutral grip was 34.22±6.14 N*m and 33.84 ±7.56 N*m during a supinated bicep curl which did not reach a significant difference (p>.05). The mean value for power during the initial 40 degrees of elbow flexion during a neutral grip bicep curl were 49.35 ±8.61 watts and 53.04 ±14.70 watts during a supinated bicep curl which also did not show a significant difference (p>.05). The mean value for MVC% for the brachioradialis during the first 40degrees was 67.70 ±9.08% during a neutral grip bicep curl and 63.84 ±8.19% during a supinated bicep curl which did have a significant difference (p>.05). The mean value for the average EMG activity for the brachioradialis during a neutral grip bicep curl was 565.17 ±163.80 μvolts and 541.80 ±165.46 μvolts during a supinated bicep curl was close in approaching significant difference (p=. 051). CONCLUSION: The results of this study indicated that there was not a significant difference in muscle activity and performance between a neutral grip and supinated grip bicep curl.