The guillotine press was made famous by the Iron Guru, Vince Gironda, who was well-known in the fitness industry for his unconventional training methods.
He felt that the regular bench was inferior for chest development. So instead, he prescribed a "neck press", in which trainees were instructed to literally bring the bar down to their neck.
Now, this form makes perfect sense for chest development from an anatomical perspective—maximum chest stretch, minimum shoulder involvement. So surely it should take pride of balance in your Smith machine chest workout, right?
Well, there is one problem—the guillotine press is absolute suicide for your rotator cuffs. And oh yeah, it can decapitate you if you're not too careful. So what's not to like?
Here's how to do a Smith machine guillotine press (if you dare):
Don't be the plonker that actually brings the bar down to his neck.
Instead, lower the bar to your collarbone.
This way, if the worst does happen, then you'll only shatter a clavicle—and not your windpipe.
Plus, do you really think that bringing the bar a few centimetres higher up on your body—to your neck—works your chest more?
I hope you don't. And if you do, you're a muppet.
"Yeh but that bloke from U-tuuube says that any exercise is dangerous with crap form."
"Big Darren does em' an he's proper massive."
Listen, I don't care what those gormless geeks have to say—everyone's hardcore until they get injured.
Plus, all exercises come with different levels of danger.
When was the last time you heard about someone dying from cable curls?
What's that? Never?
And yet. Every. Single. Bloody. Year, people still die from regular bench presses!
You know as well as I do that the only reason why the Smith machine guillotine press doesn't claim more lives is that it's so unheard of. At least you were smart enough to research the exercise before doing it!
Fact: the incline bench press has built more upper chests than any other pec exercise in history.
I can cite a disgusting number of cases where lads have died from regular bench presses. Now, just imagine how many more deaths we'd have if everyone stared bringing the bar to their necks!
Some bloke got his throat crushed by a 220lb loaded barbell and died .
A 15-year old boy died after getting his neck trapped under a 98kg bar. 
Another poor fella dropped 50kg on his chest while using a Smith machine! 
Sadly, Smith machines lure people into a false sense of security. You must ALWAYS set the safety catches before you load the bar.
And DO NOT EVER just lie under the bar without gripping it. You have a duty to control that bar like you have a duty to protect your children. Your life is too important to perish at the hands of a gym machine or barbell.
The Smith machine guillotine press activates more chest muscle fibres than a regular bench press because it places the pecs under an extreme stretch. However, as you'll discover in just a second, muscle activation and actual muscle growth are two very different things.
The guillotine press places your front delts in a very weak position. As such, they're hardly active during the exercise.
Your triceps are less active during a guillotine press than in a regular bench press simply because your chest is taking more of the load.
A grand total of one study shows that guillotine presses activate more chest muscle fibres than regular bench presses .
And get this, muscle activation doesn't even equate to real muscle growth. It's just a vague estimate that gives us an idea of what exercises could work in theory.
For example, if I squeeze my chest as hard as possible, I bet my muscle activation levels would be off the bloody chart.
But would I build any size by just squeezing my chest?
The guillotine press works the same way. Just because it registers a high EMG reading doesn't mean that it's better for muscle growth than the likes of incline or reverse-grip bench presses.
The Smith machine flat bench press is a great alternative to the guillotine press because it enables you to overload your chest with more weight. Plus, if you use the proper form, then it's much easier on your shoulders, too.
Performing the Smith machine incline bench press is a brilliant way to build a bigger upper chest safely. And, since there's no need to waste energy stabilising the bar, you can often see faster gains than with the barbell version. Overall, it's an excellent Smith machine neck press alternative.
Since the free weight version of this exercise is a bit risky due to the unorthodox underhand grip, which most people aren't accustomed to using, it's a smart idea to always perform the reverse grip bench press on the Smith machine. It's much safer than the Smith machine guillotine press, too.
Oh, and if there's EVER an article of mine that you share, please let it be this one.
I know it sounds dramatic. But learning the truth about guillotine presses could literally mean the difference between life and death for another human being—one who's just trying to better themselves like we all are.
Thanks for reading. And I hope that you learned a thing or two about this deadly exercise.