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Are weighted and unweighted underhand press ups safer than normal press ups? Some forums says underhand bench press has 30% more upper pectoral activation and since the bench press and the press up have pretty much the same motion I guess this applies to both.

But is it actually true? Also some forums says it safer while others say it's just a stupid way to get injured fast.

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    30% more upper pec activation is a lie. RHBP forces your elbows to come in closer to the body, which shifts emphasis from pecs to front deltoids and triceps as the primary movers. The front deltoid may feel like an upper chest activation, but I am in the camp of it's a good way to get injured quickly. – JohnP Oct 22 '18 at 18:39
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    I'd have to see a study proving this theory: wrist pronation/supination is pretty disconnected from the chest. – Dave Newton Oct 24 '18 at 20:53
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+50

An underhanded grip involves supination of the wrists, which is affected by ‘uncrossing’ the radius an ulna such that the entire length of the radius lies on the lateral side of the ulna. This is performed by the biceps brachii, brachioradialis, and supinator (longus)—only the first of which can act as an agonist in the pressing movement, being involved in flexion of the humerus. However, (because it is bi-articular), its change of length during the press is minimal. Supination may cause a very slight change in the angle of the ulna relative to the humerus, but since the elbow is a hinge joint, this is insignificant. The humerus is otherwise unchanged in direction and orientation, and as such, the supinated grip does not alter the bio-mechanics of the press other than altering the involvement of the biceps brachii.

Due to a physical limitation to the amount to which the wrist can be supinated relative to the humerus—according to Michael J. Alter in Science of Flexibility, around 0° (that is, normal to the frontal plane), but in practice, perhaps ±10° relative to that position—a supinated grip does limit the width by which we can grip the bar. Therefore, the underhanded grip does essentially enforce a narrow-grip press, which thereby activates the clavicular (‘upper’) portion of the pectoralis major significantly.

We can reasonably conclude that it is the width on the bar that the underhand grip enforces, and not the orientation of the wrists that has brought about the belief that the it activates the clavicular portion of the pectoralis major to a greater degree.

I hope that makes sense.

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    I believe the bicep is not antagonistic in pressing movements because it crosses the shoulder joint, therefore it can flex the shoulder. Also because my meat head tells me bench = bicep pump = good – user33278 Jun 14 at 5:34
  • Yes, @Kay, that is correct, but the combination of shoulder flexion and elbow extension means that the biceps brachii tend to contract isometrically rather than concentric/isotonically. – POD Jun 14 at 6:08
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Apparently yes, I suppose it is because a reverse grip forces external rotation of the shoulder which puts the pectorals into a stretched position.

reverse grip on the bench press – flat bench, not incline – increased subjects’ upper pec activity by 30%. And when you go from a flat bench to an incline, it’s supposed to hit the upper pecs even more, right? Yes, it does. But research has shown that it's only a 5%-10% increase. (However, the front delt activity increases by over 30%.)

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    Please quote relevant parts of articles. Link rot is real. – Dave Liepmann Jun 13 at 14:58
  • They are supposed to prevent injury The reverse grip forces shoulders into external rotation which makes it a good exercise if you have a shoulder injury... Or to prevent injury. Wrist placement is awkward enough to where I use dumbbells and do it at a slight angle. The barbell is possible though is you grip it the right way. I'd assume the press up also puts more activity on your anterior deltoids and takes away from lateral or rear. – Ace Cabbie Jun 13 at 18:32
  • I beg to differ, @AceCabbie. The reverse grip does not inherently alter the rotation of the humerus in any way. – POD Jun 14 at 1:25
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    @pod it's more a positioning which keeps the head of the humerus within the ball and socket joint – Ace Cabbie Jun 14 at 3:14
  • This is a good explanation as to why people think that an underhanded grip activates more ‘upper’ (clavicular) pectoral. But it is incorrect. Supination of the wrists does not force the rotation of the humerus. And even if it did, that would not activate more ‘upper’ pectoral, but simply more pectoral. In terms of the shoulder joint, an underhanded grip is indistinct from an overhanded grip taken at the same width. – POD Jun 17 at 12:47

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