"Strychnine interacts with chemical receptors on motor neurons, those that control movement. Electrical signals are sent along nerves but at the junctions between nerve cells, chemicals (neurotransmitters) are released to pass on the message. Two neurotransmitters are important in the case of strychnine: acetylcholine, which is the “go” message telling the adjoining nerve or muscle cell to fire, and glycine, the “stop” message, which tells the nerve not to fire. The balance of these two chemicals prevents false signals triggering nerves to fire and muscles to spasm. Strychnine attaches to glycine receptors and blocks the stop signals. The result is that the slightest stimulus can cause the nerve to fire or the muscle to contract."
And that is why we see this reaction in which Kennedy cannot release the contraction in his muscles. He was hit with a neurotoxin, one that ablated the inhibitory, releasing process in his muscles. He could not let go.
Jackie is grabbing him the way she is to try to get him to relax and lower his arm, but he couldn't do it. He is in spasm, and it is not from the physical trauma. There was no damage to JFK's spinal cord. It is from the poison in his system. This is Dr. Cinque telling you that you are looking at a neurologically impaired man, one who has been poisoned.
Now, let's move on to the Church Committee.
In 1975 a congressional hearing revealed the CIA had numerous top-secret weapons including a gun that became known as the “CIA heart attack gun.”