Eccentric Versus Concentric Velocity And Electromyographic Activity In The Bench Press Exercise Against Different Loads

Previous studies measured kinematics and surface electromyographic activity (sEMG) during either the concentric (CON) or the eccentric (ECC) phase of muscle contractions in non-fatiguing and fatiguing conditions. However, data are sparse on the combined effects of fatigue and load during resistance exercise comprising multiple consecutive CON and ECC movements. PURPOSE: To compare movement velocity and sEMG of prime mover muscles during the CON and ECC phase of the bench press exercise to failure against different loads. METHODS: Ten healthy men performed a set to failure with maximum intended velocity, against a light (40% of 1 repetition maximum-RM) and a heavy load (80%1RM) in a Smith Machine, one week apart. Mean eccentric and concentric velocity were measured with a linear position transducer, and sEMG of the pectoralis major and triceps brachii muscles were recorded at the initial and the last repetitions of each set and expressed as a percentage of sEMG during maximum isometric bench press effort (MVIC). RESULTS: CON velocity loss was greater in 40%1RM (-78.4%; from 1.07 ± 0.11 to 0.23 ± 0.09 m.s-1; p < 0.001) than 80%1RM (-65.4%; from 0.51 ± 0.06 to 0.18 ± 0.06 m.s-1 p < 0.001). However, ECC velocity loss was less than CON for both loads (40%1RM: -58.5%; from 1.18 ± 0.12 to 0.48 ± 0.13 m.s-1; p < 0.0001; 80%1RM: -34.4%; from 0.70 ± 0.12 to 0.46 ± 0.15 m.s-1; p < 0.001). sEMG during CON and ECC was higher during 80%1RM than 40%1RM (p < 0.01) in both muscles. sEMG of pectoralis major during CON was increased by 48.6% (from 84.7 ± 23.0% to 122.1 ± 30.8% MVIC; p < 0.001) and by 24.8% (from 111.2 ± 20.0% to 138.4 ± 33.0% MVIC; p = 0.0014) in 40% vs. 80%1RM, respectively. sEMG of triceps brachii during CON was increased by 15.7% (from 62.4% ± 8.9% to 72.2 ± 13.9%MVIC; p = 0.0205) and by 21.0% (from 98.3 ± 25.4% to 117.1 ± 26.7% MVIC; p < 0.001) in 40% vs. 80%1RM, respectively. However, there was no increase in sEMG during ECC for both muscles and loads (p = 0.107 to 0.262). CONCLUSIONS: During the bench press exercise performed to failure with maximum intended velocity, CON velocity loss and sEMG increase in pectoralis major are greater when using a light vs. heavy load. Velocity loss is lower for both loads in the ECC phase, and there is no change in sEMG. These results indicate that fatigue during bench press is lower in the ECC phase of the movement, irrespective of load.