Flat Bench Press vs. Smith Machine Bench

A popular question many trainees have is “what are the differences between these two exercises?” First and foremost, the movement is different. In regards to flat bench press (i.e. using free weights) there’s a natural arc that happens when lifting and lowering the weight. When benching on the smith machine there is no arc, you’re following a fixed movement pattern. Basically, you’re moving the bar straight up and down. This is important to note because the natural arc that happens when benching on a flat bench requires more muscles to stabilize the movement, whereas with the smith machine – not so much. So your body has to work a little harder during flat bench press when compared to benching on the smith machine.

Ok, so what about the chest muscles? Are they being worked any harder during either exercise? Well, to answer that we have to look at the research.

In a 2010 study published in the Journal of Strength and Conditioning Research a research team compared the effects of performing smith machine bench against flat bench press. They had experienced and inexperienced lifters perform each exercise using 70% and 90% of their one-rep max (1RM). The researchers found that muscle activation in the pectoralis major (one of the chest muscles – the big one) was not much different when subjects used the barbell or the smith machine – regardless of their experience level or weight used. What was significantly different was the activation of the medial deltoid (side delt). There was far greater activation when a barbell was used.

Therefore, while we don’t often have trainees perform smith machine bench they may have a place in your training, such as rehabbing a shoulder injury or used in combination with other exercises in a superset format to continue working the chest muscles even if the delts have fatigued. Of course any exercise, even machine work, can be used to apply progressive tension overload on the target muscle (see the link below for more info on the benefits of maintaining constant tension). However, in light of this, it’s generally recommended to stick with flat bench press if just looking at these two movements head to head.