Bench Press Arch Back Or Flat Back?
The flat barbell bench press is one exercise you'll see performed a multitude of ways in the gym...
The bro in the gym ensures his back is completely flat on the bench and lifts his legs up so they're off the bench, swearing it provides maximum isolation.
The powerlifting goes to the opposite extreme, with their back arched as far as can - with hardly any point of contact on the bench, allowing him to press 500lbs for reps.
What difference does a back arch make?
Is the traditional flat bodybuilding style bench press safer?
Let's take a look...
The Bench Press Arch Back
You'll Lift More
If your goal is to increase the numbers you're putting up on your bench you'll find that by switching from a traditional 'bodybuilder' style bench press to a 'powerlifter' style bench press with an arched back and retracted scapula you'll instantly be able to press more. We're not talking to the extreme of back arching here - simply enough to fit a fist in the gap between the bench and your lower back.
You're Actually REDUCING Your Risk of Injury
The #1 misconception I see and hear when it comes to the bench press arch back is that by using this form you're begging for an injury.
You'll find it's quite the opposite, and I speak from experience.
The majority of guys that've been lifting for a number of years have experienced some niggling shoulder issues from bench pressing with flared elbows or similiar.
By slightly arching your back you're able to contract your scapula (squeeze your shoulder blades together on the bench) which reduces the stress on your shoulder joints which are without a doubt the most vulnerable joint in your body.
You're Far More Stable
Utilizing a slight arch in your back while your feet are firmly planted on the ground and your scapula are contracted on the bench provides far more stability than the traditional flat back style bench press.
Not only does this physically help you add those extra pounds to the bar and squeeze out those few more reps, it also gives a big mental boost.
Even with a spotter, getting beyond certain numbers on the flat bench - be it 225lbs, 315lbs or whatever your number may be is more of a mental plateau than anything.
The Bench Press Flat Back
Ask a bodybuilder if they are their back and retract their shoulder blades while benching and they'll scoff at you "that's cheating!".
If your primary goal is building a big chest and strength is not a priority you'll likely prefer the flat back bench press, here's why...
You Have a Larger Range of Motion
When benching with your back flat on the bench press you'll find that your range of motion is substantially larger than that if you were to arch your back.
This is the equivelant to benching with a flat back and only bringing the bar part of the way down to your chest.
Limited range of motion = limited chest engagement.
Unless you're working through the entire range of motion of each repetition you're cutting yourself short in terms of chest activation.
You're Isolating The Chest
When benching with a flat back you're not utilizing other muscle groups to drive the barbell up on each repetition.
Your back, your shoulders and leg drive place a large part in the numbers some guys are putting up on their bench press - when these other muscle groups are coming into play that takes away from the chest.
You will not be able to achieve legitimate chest hypertrophy if you're lifting with an arched back and powerlifting style form as you're constantly going to be recruiting other muscle groups to aid.
My Take On The Bench Press Arch Back Vs. Flat Back
If your goal is 100% hypertrophy based and you're not concerned about strength then bench press with traditional flat back form.
If your goal is to build your pressing strength and you're not overly concerned about building a big chest then utilize an arched back and retracted scapula when pressing.
If you want to build a big chest AND put up numbers on your bench press then utilize a slight arch/scapula retraction when benching but focus on traditional flat back form on your other presses, be it incline barbell press, flat dumbbell press etc.