The left foot is pressed backward against the right foot and, with both feet extended, toes down, a nail is driven through the arch of each, leaving the knees flexed a bit. This will allow the victim to try to lift himself up in order to breathe and to relieve the pressure on his arms. As he slowly sags down, this causes more weight on the nails in the wrists; excruciating pain shoots along the fingers and up the arms to explode in the brain. The nails in the wrists are putting pressure on the median nerves (veins) as well. As he pushes himself upward to avoid his stretching/pulling torment, he places the full weight on the nail through his feet. Again, he feels the searing agony of the nail tearing through the nerves between the bones of the feet.
As the arms fatigue, cramps sweep through the muscles, knotting them in throbbing pain. With these cramps comes the inability to push himself upward anymore, in order to breathe. Air can be drawn into the lungs, but not exhaled. He fights and struggles to pull himself up in order to get even one small breath. Finally carbon dioxide builds up in the lungs and in the blood stream, and the cramps partially subside, due to his near-death state. Spasmodically he is able to push himself upward to exhale and bring in life-giving oxygen. Hours of this limitless pain, cycles of twisting, joint-rending cramps, intermittent partial asphyxiation, searing pain as tissue is torn from his lacerated back as he moves himself up and down against the rough timber of the cross. Then another agony begins; a deep, crushing pain, deep in the chest as the pericardium, (a cavity or space that contains the heart), slowly fills with serum and begins to compress, or squeeze, the heart.
It is now almost over. The loss of tissue fluids has reached a critical level — the compressed heart is struggling to pump sluggish blood into the tissues — the tortured lungs are making a frantic effort to gasp in small gulps of air. He can feel the chill of death creeping through his tissues — finally, he cannot fight or struggle anymore. He can finally allow his body to die. – Taken from SilverCreekChurch.net
“Do you understand what I have done for you?” - NIV