Rules to forbid "spearing," or tackling with the head first, have sharply reduced the number of paralyzing injuries in high school and college football, according to a 14-year study.

The National Collegiate Athletic Association made it illegal in 1976 to "intentionally strike a runner with the crown or top of the helmet."

That rule, Dr. Joseph S. Torg wrote in the Journal of the American Medical Association, was the main reason the number of injuries leading to permanent quadriplegia fell from 34 in 1976 to five in 1984.

Defensive backs were most at risk of severely compressing their upper spine during such tackles. In high school, 52 percent of the victims were defensive backs; in college, 73 percent.

Torg, of the University of Pennsylvania, said this scientific study dispels any notion that the spinal injuries were "freak accidents," but were, in fact, clearly caused by this particular method of tackling.

In 1975, for example, six of the eight players paralyzed from the neck down "were playing defensive back and making a tackle. In each instance, the head was used as a battering ram . . ."

"Refutation of the 'freak accident' concept with the more logical principal of cause and effect has been most rewarding," Torg and several colleagues wrote.

Ironically, increased use of the head in tackling came after improved helmets were devel- oped in the 1960s and early 1970s, which provided better head and face protection.