G-force (gravitational force) is the force pulling an object toward the center of the earth. Normally, we are suffering a 1G when we are stationary. When a car is cornering or accelerating, the driver suffers more than 1G; a 10-pound human head will weigh 30 pounds under 3G acceleration.

1G = 9.8 m/sec², 1Gs = 9.8 m/sec

A golf swing is about 5000 Gs; therefore, do not wear an mechanical watch when playing golf.

According to the ISO 1413 standard, the shock resistance test is conducted by using a pendulum impact testing machine. The mechanism sets off a circular movement which brings the pendulum to hit the watch. When the watch is hit by the pendulum, the watch will "fly" at the presetted acceleration, e.g. 5000 Gs.

1^st shock is directed against the side of the case, parallel to the plane of the watch, on the 9 o'clock side.
2^nd shock is directed against the glass, perpendicular to the plane of the watch.