From Ergo Log
Isolation exercises, trainers would still have you believe, help you to concentrate on a single muscle group. That way you can train the muscle group better. In the case of the peck-deck the theory doesn’t hold water, sports scientists from the Universidade de Brasilia write in Revista Brasileira de Medicina do Esporte.
The researchers tested the isolation theory on thirteen amateur bodybuilders who had been training for an average of seven years. The researchers attached electrodes to their subjects’ front shoulder muscles [AD], triceps [TB] and pectoralis major [PM] so that they could measure the muscle activity.
Other researchers used a similar method in an earlier study that compared bench presses with the peck-deck, but they didn’t attach electrodes to the triceps.
The test subjects did sets of ten reps, with enough weight to make it impossible for them to manage an eleventh rep. The subjects had to shift more weight with the peck-deck than with the bench press: 71 kg versus 66 kg. Despite the difference the amount of activity in the shoulder and chest muscles was the same for both the peck-deck [PD] and the bench press [BP] exercises. When the subjects did the bench presses the muscle activation was even a little higher, but the difference was not significant.
There was a clear difference though in the triceps activity. That’s not surprising – peck-deck exercises don’t work the triceps.
“Our findings go against the theory that you stimulate individual muscles better by doing isolation exercises than by doing complex exercises that use several muscle groups”, write the Brazilians. “If you want to develop your pectorals, you can just as well do bench presses as using the peck-deck. Of course you can use both types of exercise.”
The researchers don’t exclude the possibility that there are athletes who find they can isolate their chest muscles better on the peck-deck. An item for more research, they suggest.
Rev Bras Med Esporte vol.13 no.1 Niterói Jan./Feb. 2007.