This means that each of His arms was supporting about 71% of His body weight.
This may seem odd: how can this be?
It's a principle of physics that if an object is hanging from two supports, perhaps on two strings or ropes, the farther apart the supports are, the greater the tension on the supporting ropes.
Naturally, the heavier the object, the greater the tension.
(A side fact is that no rope, for instance a clothesline, can be pulled so tight that there will be no sag at all in it. It will sag from its own weight.)
Dr. Barbet estimates Jesus' weight to have been about 175-180 pounds. This means that the "pull" on each of His arms would have been about 124-128 pounds.
One may think that a healthy, fit, and strong man could lift 125 pounds in each hand without too much trouble. This may be so.
However, Jesus was neither healthy nor fit at the time. He had had nothing to eat since supper the night before. He had sweat blood in the Garden, which besides causing great pain to His whole body, lowered his resistance. He had been brutally scourged with Roman whips. He had to carry the Cross until (as Scripture mentions) the Roman soldiers made Simon carry it; because Jesus might have died on the way to Golgotha, and Pilate's orders were that Jesus be crucified.
To make matters worse, when Jesus was hanging supported only by His arms, He could not breathe. He could inhale but not exhale. To exhale, He would have had to rest his weight on the nail through His feet. The whole point of crucifixion was a gradual increase pain and weakness to cause asphyxiation.
(When I was about 16 or 17, I jumped up and hung from the high bar in the school gym. I indeed found that the farther apart I moved my hands, the greater was the pull on my arms. I also found, as Dr. Barbet had predicted, that I could inhale but not exhale. I would not recommend trying this.)
You will notice that Jesus' thumbs are not visible. This is so because when the nails were driven -- through the little hollow spot between the wrist bones called Destot's Space -- they greatly injured the median nerve, this creating more pain and pulling the thumbs in across the palms.
That said ---
All this physical pain was, I'm speculating, far far less than the mental and emotional agony He endured. I myself can become very saddened by thinking of even one nasty thing that someone did to me, even if it was long ago; or even one nasty thing I did to someone else.
Now Jesus was sinless, of course; but at least from the Garden to the Cross, He carried in Himself the "evil residue" of all the sins committed by every person, in the entire world, from the creation to the end of time. No wonder that towards the end He cried out in agony to His Father.
