When you're using the Smith machine for chest, push ups probably aren't the first exercise that comes to mind. However, if you want to sculpt bigger, rounder pecs, then you shouldn't overlook Smith machine push ups because, when done right, they can build more mass than virtually any other chest exercise.
I'm not exaggerating.
This humble, bodyweight movement is one of the most prolific all-time mass builders known to man.
And I'm going to show you to perform this vastly underrated exercise for the fastest muscle gains possible.
Regular, off-the-floor push ups are generally performed with a neutral hand position, which naturally lends itself to a shoulder-friendly elbow tuck. However, since you perform the Smith machine press up with an overhand grip, it's tempting to flare your elbows way out to the sides in order to enjoy the extra chest stretch—avoid this.
While flaring your elbows excessively will indeed provide you with a satisfyingly deep chest stretch, it also severely compromises your shoulders if you add external resistance. Plus, you're weaker this way because your triceps are less engaged (which may actually lead to less chest stimulation overall).
Instead, tuck your elbows in at a 45-degree angle. If this positioning is hard to conceptualise, think of it as the halfway point in a lateral raise.
I'm sure that you've heard the "stay tight" or "brace your core" advice a million times.
But it bears repeating.
Much like powerlifters active their core and legs to increase their bench press strength (at no cost to their chest stimulation), you need to actively squeeze your whole body to maintain the proper tightness during incline push-ups.
If you don't, then your hips will sag, which drastically decreases the amount of tension that your pushing muscles receive.
Performing heavy push ups on Smith machine barbell attachments is a reliable method for adding serious size to your chest. But how do you actually burn the pecs out? And make sure that you've recruited every last muscle fibre?
Smith machine push up ladders, that's how.
These are a favourite of IFBB pro bodybuilder and all-around gentleman John Medows, and they work like gangbusters for finishing off your chest.
Essentially, you position the Smith bar on a low setting and bang out as many reps as possible. Then, you simply increase the bar height and smash out more repetitions unless your chest is fried once again. You might end up doing this 4-6 times (by which point even just resisting gravity will seem difficult).
What I like to do if I'm feeling particularly ballsy, is to perform one round in a weighted vest—to hit the fast-twitch muscle fibres—and then immediately take the vest off and crank out another round with just my bodyweight.
This training style provides the maximum amount of chest stimulation possible (presuming you also did an incline press) because you've successfully stimulated both the fast and slow-twitch muscle fibres in one exercise.
Nearly any gym-goer with an ounce common sense will wrap their wrists for bench presses. Yet virtually nobody but the elite lifters bother to wrap their wrists for push ups.
Now, if you're just doing bodyweight press ups, then this isn't much on an issue. Of course, if you do enough bodyweight push ups without wrist protection, then you will run into joint problems eventually.
However, if you attempt weighted push ups without first protecting your wrists, then you're in a for a whole world of pain. Your wrists simply cannot keep up with the strength of your chest and triceps, and if your force them to, then the damage will soon begin to show.
And while wrist wraps aren't a cure for poor form (bent wrists), they do encourage you to maintain straight wrists by offering a cast-like wrapping around your joints.
I use the RDX Wrist wraps, and I have no complaints.
I've paid for expensive powerlifting wraps before (3x the price), but honestly, I couldn't tell the difference. These particular Beast Gear wraps are made from cotton (for support) and elastic (for flexibility), so you get extremely heavy-duty protection without actually having to limit your range of motion.
Plus, you can completely customise the fit and tightness since they come in a generous 20" length. This built-in personalisation also means that you don't need to fiddle around with trying on different sizes and sending them back—because one size fits all.
When I first set up my home gym, I was too cheap to pay for a weighted vest. For some reason, I had the misconception that weighted vests were this really expensive piece of army-style fitness equipment that I couldn't afford.
But after getting frustrated by the weights constantly falling off my back during pushups (not to mention the chaffing of my dipping belt during pull ups), I decided to bite the bullet and invest in the Runfast Weight Vest.
For less than a meal for two at Nandos, this weighted vest is pretty much faultless. Ok, it doesn't come with a big brand name sewed onto it, but the quality is on point. It's equally as sturdy as any of the fancy weighted vests that I've tried, which is what counts.
It's also extremely breathable thanks to the moisture-wicking material, which prevents your skin from becoming irritated by sweat-soaked fabric. I definitely realised the benefits of this when I did two full rounds of ladder push ups!
No program, supplement or training tool has done as much for my bench press strength as the Sling Shot Original.
I kid you not: this thing increased my one-rep max by 7.5kg in a matter of weeks. And that's just as a result of training in it—not while wearing it. While wearing the Sling Shot, my bench press was actually 22.5kg higher. Not bad, eh?
Anyway. I was playing around with my Sling Shot and then realised that it's a remarkable tool for assisted push ups. You can effectively lower the full weight of your body down to the ground and then have the Sling Shot help you back up.
It's basically like having your very own assisted push up machine. Yet it costs about 50x less.
Moreover, you can use the Sling Shot as an advanced push up tool.
I love to start with weighted push ups. Then I drop down to bodyweight. And then, when even bodyweight becomes too challenging, I shock my chest into new growth by strapping myself into my Sling Shot and pushing my pecs beyond failure.
No other training tool besides the Sling Shot Original lets you overload your pecs with such ease and intensity. Highly recommended if you want to build a bigger chest or increase your pressing strength.
These "incline push-ups" are actually equal to a decline press in terms of your arm position relative to your torso. Of course, this doesn't prevent them from being effective.
However, by elevating your feet on a step-up platform or bench and then setting the bar to the same height, you effectively turn the movement into a flat press. Which, in the case of push ups, provides a much more intense chest stretch than the so-called "incline" variation
Your front delts get hammered during the Smith machine incline push up because they receive a deeper stretch than in regular bodyweight press ups. However, you can increase shoulder activation even further by elevating your feet.
As a rule of thumb, the higher your feet are in relation to your hand position; the more active your front delts will be.
Ladder push ups, in particular, are great for the triceps because they make them more resistant to fatigue. And while the triceps are mainly a fast-twitch muscle that responds best heavy weight, if you can make them more fatigue-resistant, then you can naturally train them with higher volume. And it's volume—not max strength—that's the primary driver behind muscle growth .
The core abdominal muscles are reasonably active during the Smith machine incline pushup because they have to stabilise your body mass. Yet, by elevating your feet by even just a small amount, you can significantly increase ab activation because your core simply has to stabilise a higher percentage of your bodyweight.
Add a weighted vest into the mix, and you suddenly turn the push up into one of the ultimate full-body exercises.
Smith machine exercises are excellent for adding mass because they enable you to focus purely on the working muscles without needing to waste your energy stabilising the bar.
However, they're a double-edged sword.
While you will indeed develop a strong mind-muscle connection on machine-based chest exercises, these kinds of movements don't typically carry over that well to free weight bench presses. This is simply because you're working your prime movers (chest, triceps, shoulders) much more intensely than you're training your stabiliser muscles.
But Smith machine push ups are different. In fact, they require greater core strength than the barbell bench press.
As a result, getting strong at push ups is a surefire way to increase your bench press because you're simultaneously developing your pressing muscles and your stabiliser muscles .
Did you know that weighted push ups are one of the all-time best mass builders for the chest?
Weighted push ups enable you to overload your pecs with near limitless resistance—all without the worry of dropping the weight on yourself. However, if you do them off the floor, then your wrists might feel like you've just punched a rock.
This pain is simply because your wrists aren't straight during standard pushups, which is fine until you add 20kg or more.
However, by performing your weighted push ups on the Smith machine barbell, you can keep your wrists completely straight. Not only does this eliminate the common joint pain, but it also makes you stronger (thereby building a bigger chest) because you can generate far more pressing power with straight wrists than you can with bent wrists.
Don't get me wrong. I love performing chest flys as much as the next guy. However, nothing sets my chest on fire like the push up ladder 
And it's the perfect two-for-one exercise.
Not only do you get an unrivalled pec pump, but you also get to sneak in some extra push up practise while you're burning out your chest muscles. In other words, you're training your stabilisers and improving your weighted push up strength while enjoying what's likely to be the most intense chest pump you've ever experienced (or subjected your body to!).
Just make sure to actively think about squeezing your elbows together as you push yourself up. Doing this will light up your inner chest because one of the main functions of the pecs is transverse shoulder abduction (bringing your arms across your body).
As mentioned, regular push ups can hurt your wrists if you do enough of them (or do them weighted).
However, because the Smith bar naturally allows you to maintain straight wrists, you increase your pressing power while also protecting your joints from unnecessary stress.
That said, I always recommend wearing some supportive wrist wraps just to be on the safe side.
Performing the Smith machine assisted bench press is a great way to bulk up your pushing muscles quickly. Since you don't have to put any effort into stabilising the weight, you can focus 100% of your attention towards stretching and squeezing your pecs. This naturally leads to faster muscle growth because your main muscles are getting a larger majority of the tension.
If I could do only one chest exercise, it would 100% be weighted push ups. Not only are they one of the best mass builders for your chest, but they're also one of the safest. Unlike with a barbell bench press, you can train to complete failure without a hint of worry because there's no risk of dropping a weight on yourself and potentially crushing your chest .
I originally used to load my push ups with weight discs. However, if I performed my reps even somewhat explosively, the plates would inevitably fall off my back and ruin my set. So I decided to stop being so cheap, and I eventually stepped up my push game by ordering a sturdy weighted vest .
Ahh, the chest fly. Is there any better feeling than watching your pecs swell to epic proportions?
I think not.
Dumbbells flys were one of Arnold's favourite exercise for pumping up his pecs because the movement allowed him to focus purely on stretching and squeezing the muscle. If you want an isolation exercise to complement your heavy Smith machine pushups, then grab some dumbbells, lay on a bench and hug that tree! 
Then just watch your chest grow.