Assessing the effect of weight implement used, Saeterbekken et al. (2011) explored the differences in biceps brachii muscle activity between the free - weight barbell, dumbbell and smith machine bench press. (strengthandconditioningresearch.com)
Using a barbell is superior to using dumbbells but there are no differences in triceps brachii muscle activity between a barbell and a machine bench press. (strengthandconditioningresearch.com)
Assessing the effect of load, McCaw & Friday (1994) found a main difference in biceps brachii muscle activity between 60 % and 80 % of 1RM when performing the free - weight and smith machine bench press. (strengthandconditioningresearch.com)