I'm just curious.  I haven't read much about Bucky until he took the mantle of Captain America.    I'm wondering what exactly enables him to perform as well as Steve Rogers?
 
I know he has a bionic army, so he has one arm that has super strength, but what else about him enables him to do what he does?
I realize he's been trained by Captain America.  I know that he must have received more training while he was the Winter Soldier.
But has he ever had some sort of Super Soldier Serum injection, or other physical enhancements?
 
Is he simply what he is purely through training and will power or is there more to it?

No, Bucky is all human with no superhuman abilities whatsoever. The only thing that grants him anything close to superhuman level abilities is his bionic arm which enhances his reflexes, gives him not super-strength but makes him stronger than your average person, and the arm has also been known to emit an electric shock. But all of those abilities are in that ONE arm, nothing more.

No, Bucky is all human with no superhuman abilities whatsoever. The only thing that grants him anything close to superhuman level abilities is his bionic arm which enhances his reflexes, gives him not super-strength but makes him stronger than your average person, and the arm has also been known to emit an electric shock. But all of those abilities are in that ONE arm, nothing more.

@Timandm: Agreed. But his arm is actually pretty strong. I would say as strong as a 10 tonner. This is because he can throw his shield into people, through metal guns and straight into super computers without a problem. 

@Timandm: Yeah, I didn't mean it makes him a 10 tonner, it's just like he has a 10 tonners arm.  Yes I did. But I know he is not dead for sure. There are too many hints that they will bring him back. 

No, Bucky is all human with no superhuman abilities whatsoever. The only thing that grants him anything close to superhuman level abilities is his bionic arm which enhances his reflexes, gives him not super-strength but makes him stronger than your average person, and the arm has also been known to emit an electric shock. But all of those abilities are in that ONE arm, nothing more.

In the movies was Bucky enhanced at all? He seemed like an average soldier in the First Avenger but all of the sudden he is competing physically (and winning much of the time) against Cap in the Winter Soldier. And he seems significantly stronger all around (not just his arm) than the rest of the humans sans Cap.

It was never stated in The Winter Soldier if Bucky was enhanced, though it was implied by Cap that Zola must have done something to Bucky when he was captured in The First Avenger and is the reason he was able to survive the fall off the train. This could have enhanced his body, but again it was never stated if this were the case or not

Even so, from the various feats Bucky displayed in TWS it does appear that he was enhanced to some extent, being able to leap down from that overpass without injuring himself as well as taking direct blows from Cap (which have been shown to send normal men flying) and brushing them off with ease.

So yes, it does appear that HYDRA apparently gave him some short of enhancements, but it is unclear what those enhancements were or to what extent Bucky's body was enhanced in terms of the Super-Soldier Serum that Cap was given.

Powers and Abilities

He's fast. Strong. Had a metal arm.

Captain America

Powers

Artificially Enhanced Physiology: After Bucky Barnes fell into a trench in an ice mountain, he was saved and given a metal arm, along with other enhanced abilities from a serum that had a similar effect on the human body as the Super Soldier Serum given to Steve Rogers.

Superhuman Strength: Winter Soldier has strength that is seemingly equal to that of Captain America. Barnes's physical strength is enhanced to the early levels of superhuman condition by a series of treatments performed on him by HYDRA scientists. He has used his legs and flesh arm to kick and punch others with a display of strength that far surpasses normal humans and closely resembles Captain America's own abilities.

Bionic Arm: HYDRA also removed the remnants of his severed left arm and replaced the missing limb with a cybernetic one. The bionic arm gives him superhuman strength superior to that of Captain America, though not quite on par with that of Spider-Man. Winter Soldier was able to rip open a S.H.I.E.L.D. armored SUV, rip apart Falcon's EXO-7 suit, and smash concrete by punching it. With his bionic arm supporting his already enhanced natural strength, the Winter Soldier was shown to overpower Captain America in a fight.

Enhanced Speed: Winter Soldier's speed is comparable to that of Captain America. It should be noted that Captain America can run at 26 miles per hour with relative ease, and still had trouble keeping up with Barnes.

Enhanced Durability: Winter Soldier's bones and muscles are apparently denser and more resilient than a normal human's. Arnim Zola's experiments fortified his form to the extent that he routinely leaps from significant heights onto hard surfaces and lands without any apparent injury.

Enhanced Stamina: Winter Soldier's musculature produces far less fatigue toxins during physical activity than the musculature of an ordinary human.

Enhanced Agility: Winter Soldier's agility is superior to that of an ordinary human. He has demonstrated the ability to leap on top of midsize cars in a single bound and do acrobatic flips avoiding gunfire into cover.

Enhanced Reflexes: Winter Soldier's reflexes are enhanced to extraordinary levels. His reflexes are responsive enough to catch Captain America's shield being thrown at him at a high velocity. He was also able to catch enemy grenades thrown at him, dodge fire from Falcon's Steyr SPPs, and leap on top of a moving car accelerating towards him with pinpoint accuracy.

Regenerative Healing Factor: Winter Soldier's biology has regenerative abilities, similar to Captain America. He can heal at high speeds, though he is unable to regenerate missing limbs. This may be one of the factors of his survival from the Swiss Alps.

@theblueangel93: Well at this point I'm guessing you've seen Civil War which confirms what most of us already knew. The Winter Soldiers are enhanced much in the same way Captain America is enhanced. Buckey's strength seems about on par with Captain America except his mechanical arm is pretty tough. You can see him overpower Iron Man's grip in the one fight scene. He was smashing Tony against the wall pretty hard.

616 Bucky is injected with Infinity Formula, but i dunno what kind of abilities did the formula grant him. MCU Bucky however is a super soldier / superhuman, this is a fact in the MCU ( this is stated multiple times in CW, and was implied in TWS, even the actors themselves have stated this) . He is way more OP than his 616 counterpart.