Parma Rod & Gun Club IDPA --Inter-Limb Interaction--

Inter-Limb Interaction

The Golden Rule:

Of the four firearms safety rules, rule #3 is the golden rule.

Keep your finger out of the trigger guard and off the trigger until your sights are on the target. The reason we make an issue out of this in the beginning of training and practice is a phenomenon called Inter-Limb Interaction.

This term is used to describe the involuntary contraction of an individual's hand and finger muscles under stressful conditions. The following are three factors which all shooters should be aware of.

1) Sympathetic Squeeze Response:

This can occur when the shooting hand is holding a weapon. The non-shooting hand must be employed in some forceful or violent action. An example: a typical law enforcement situation, a suspect is taken into custody at gun point, but cooperatively. The suspect then violently resists when the officer attempts to search or make a physical arrest. With weapon still in hand and the finger inside the trigger guard the officer securely grabs the suspect with the non-weapon hand. He inadvertently squeezes the trigger on with the gun hand, wounding or killing the suspect. Both hands grip at the same time.

2) Startle Response:

This can occur when holding a weapon improperly and a sudden unexpected stimulus takes place. An example: a homeowner is investigating a suspicious noise at home while armed. The homeowner is suddenly startled by a loud scream, lights coming on, or encountering a family pet in the dark. Once again with the finger inside the trigger guard the startle response causes pressure on the trigger, BANG! This easily leads to an unintended round being discharged.

3) Loss of Balance Response:

This can occur any time one unexpectedly stumbles or experiences an unanticipated loss of balance. An example: again a homeowner investigating a suspicious noise, miss counting steps, or stepping on an unseen object on the floor or ground. In each of these situations a response is tensing of the hand and other muscle groups in an attempt to recover one's balance. If the finger is allowed inside the trigger guard, an unintended round will likely be fired.

Interaction Is Stronger Than You Think:

Medical tests of this phenomenon show that it is present for all humans. Further the involuntary squeeze is very powerful, measured in the 30 to 50 lbs force range. For this reason, do not expect a heavy trigger spring or long trigger pull to change the outcome of these involuntary squeezes.
IF YOU DO NOT SEE YOUR FRONT SIGHT, YOU SHOULD NOT FEEL YOUR TRIGGER WITH YOUR FINGER. THE SOLUTION IS AS SIMPLE AS IT IS CRUCIAL. TEACH, ENFORCE and LIVE RULE NUMBER THREE ! ! !