A common question for many strength trainers is whether exercise with free weights or with machines is best. The advantage with free weights and machines is a popular debate among both athletes, coaches and scientists, but there is still no definite answer. Therefore, the purpose with this study was to examine the differences in muscle activity in the dominant and the non dominant side of Pectoralis major and Deltoideus anterior, in bench press with barbell and in a Smith machine.

Participants consisted of 13 male students at Halmstad University with a mean age of 25,2 ± 3,0 years. All participants had at least 1 year experience from bench press. They performed three tests. At first one test to get their 1 repetition maximum (1RM), then two tests with 6 repetitions on 60 % of their 1RM, one with barbell and the other one in a Smith machine. The muscle activity was measured with surface electromyography (sEMG).

All participants turned out to be right handed. The result shows that Deltoideus anterior had a significant higher muscle activity bilateral when using a barbell then a Smith machine (p≤0,05). Deltoideus anterior had higher muscle activity than Pectoralis major, both with a barbell (p≤0,05) and in the Smith machine. Pectoralis major had higher muscle activity bilateral in the Smith machine than with a barbell. The dominant side of Pectoralis major had higher muscle activity than the non dominant side in bench press with both barbell and Smith machine. The non dominant side of Deltoideus anterior had higher muscle activity than the dominant side in bench press with both barbell and Smith machine.

Working out with a barbell and in a Smith machine has its advantages and disadvantages. There is no answer to which one is the best, it depends on both experience and the goal with the training. If the purpose is to train the middle part of the breast, it is according to our study better to do the bench press in a Smith machine. For novices, it can be a good idea to use machines in the beginning, to give the body time to adapt without stressing the muscles and the joints unnecessarily. Persons with more experience can benefit greatly from the additional benefits, as greater variation in exercises, and the similarity to daily and sport movements that exercising with free weights can give. For most people, the combination of free weights and machines gives an effective variation in the training.