Muscle Activation Patterns And Repetitions-to-failure Performance In The Bench Press Exercise

Abstract

The bench press (BP) exercise is used to determine and develop upper-body muscular strength and work capacity. PURPOSE: To examine the muscle activation pattern during performance of a bench press repetitions-to-failure (RTF) test. METHODS: Subjects (n=16; Age: 21+2 yr; ht: 179+6 cm; wt: 78+7 kg) performed BP one-repetition maximum (1-RM) and RTF (60% 1-RM) test. Surface EMG was collected during each repetition of both tests from the pectoralis major (PM), triceps brachii (TB), anterior (AD) and posterior (PD) deltoid, latissimus dorsi (LD), and biceps brachii (BB) muscle groups. The concentric phase EMG signals were integrated (iEMG) and normalized to muscle group specific EMG activity collected during a maximal voluntary isometric contraction (EMGMVC) performed at the mid-range of the BP exercise and prior to initiating testing. Mean power frequency (MPF) was also determined for the concentric phase. RESULTS: 1-RM BP (92.2+24.3 kg) was moderately correlated with body mass (r=0.74), fat-free mass (r=0.64) and fat mass (r=0.71). Subjects performed 23.4+2.5 reps during RTF. Although 1-RM was highly correlated with work capacity (load.reps; 1388+330 kg. reps; r=0.89) the relationship with RTF was negative and low (r=-0.22). During RTF concentric contraction time increased (0.69 +0.21 to 1.81 +0.83 sec), while range of motion (242+8° to 254+19°) and excentric contraction time (0.640-.900 sec) did not change from the first to the last repetition. iEMG/ EMGMVC increased progressively from the beginning (∼0.16-0.30) to the end (∼0.21-0.51) of each concentric contraction in PM, TB, AD and LD during RTF. At failure iEMG/ EMGMVC increased at the beginning (∼0.21-0.46) and end (∼0.39-0.83) of the concentric contraction; the latter activity was equal to iEMG/ EMGMVC activity observed during 1-RM. MPF decreased in PM (55.2+8.1 to 47.1+5.6 Hz) and TB (55.7+5.3 to 49.4+6.8 Hz), while AD (54.2+4.4 to 53.5+3.5 Hz) and LD (50.8+8.1 to 47.4+6.8 Hz) remained unchanged. CONCLUSION: There was a progressive increase in concentric contraction time and EMG activity and a decrease in MPF associated with muscle failure during RTF testing. The pattern and magnitude of EMG activity relative to EMGMVC was similar in PM, TB, AD and LD muscle groups. Supported in part by PEO Soldier Grant # AHS1131