Measuring upper body strength is common in high school, college and professional level sports. Arguments have been made for and against this practice, but that’s for another day. The prime movers in the bench press are the pectoralis major, triceps brachii, anterior deltoid and medial deltoid. However the medial deltoid acts more like a stabilizer than a prime mover. Just for the record, the deltoid is one muscle; Anterior, medial and posterior simply describe areas, they aren’t separate heads.

Two of many ways one can perform a bench press is with a free weight barbell or a smith machine. The free weight bench forces the lifter to balance while exerting force to lift the weight. This higher level of instability is essential for a lifter who wants to engage the stabilizing muscles while training. A smith machine guides the bar in a fixed path and requires almost no balance by the lifter. The almost total lack of instability is thought by many to allow for increased force production of the prime movers. If this were true, bodybuilders or powerlifters who want to concentrate on the development of the prime movers, would be able to accomplish this with the smith machine. More-over, a lifter involved in rehab, novice lifters and elderly lifters may find the smith machine fits there needs because of the lack of instability.

A study published in the Journal of Strength and Conditioning Research compared the muscle activation between the free weight bench and the smith machine. The purpose of the study was to compare the muscle activation of the pectoralis major, anterior deltoid and medial deltoid during both exercises.

14 experienced and 12 inexperienced subjects were used in the study. Testing took place in two visits one week apart from each other, each consisting of either smith machine or free weight benching. Electromyography was used during the concentric phase of each lift at a lower intensity (2 reps at 70% of 1 rep max) and higher intensity (2 reps at 90% of 1 rep max) to compare muscle activation.

The study found no difference in the activation of the pectoralis major and the anterior deltoid between exercises regardless of load or experience. If the lack of instability of the smith machine allows the lifter to create more force production in the prime movers compared to the free weight bench press, it was not supported in this study. The authors surmise this may be due to the unnatural bar path of the smith machine in contrast to the free weight bench. Also, activation of the medial deltoid was significantly greater during the free weight bench regardless of load and experience. The instability of the free weight bench causes a greater activation of the medial deltoid as a force producer and stabilizer.

(J Strength Cond Res 24(3): 779-784,2010)

From a practical standpoint, according to the findings of this study, the free weight bench press may lead to a greater requirement of stabilization of the glenohumeral joint (shoulder). Increased shoulder stabilization is not only important for athletes but anyone involved in weight training, which requires strength and stability about the glenohumeral joint.

Do the findings of this study suggest dropping the smith machine from your training program and concentrating on free weight bench pressing? Absolutely not. The best thing one can do in regards to exercise choice, is mix things up. There are many exercises one can use in order to build their chest and shoulders. Don’t get caught in a rut using the same exercise over and over.

Q: Mike,
I was told to do dumbbell flys on an incline bench (35-40 degrees). wrong? better? worse?

A: Better? No. Different? Yes.
As the angel of the incline starts to go beyond 30% the only difference is the degree to which the deltoids are used. And while we’re on the subject of angled benches, don’t even bother with decline bench. It is a myth that it stimulates the bottom portion of the pec muscles more than the flat bench.

Also, if you’re performing different angles to change the shape of your pecs, it’s not going to happen. Your shape is genetically predetermined. Train with 100% intensity and stick with the basics.

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