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A knee to the groin is perfectly acceptable. Pulling hair is actually encouraged. Gouging someone's eyes with your car keys? Hey, whatever works.

It's no surprise that people use the phrase "anything goes" to describe Krav Maga, the official self-defense course that has been taught to Israeli soldiers for decades.

And now, direct from the Israel Defense Force to a martial arts studio near you, Krav Maga is emerging as the new self-defense, urban-fitness craze in the United States.

Krav Maga — which is pronounced krahv muh-GAH and means "contact combat" in Hebrew — is already wildly popular in New York City and especially Los Angeles, where law enforcement officials and trendy Hollywood types are battling for mat time.

Now, it's looking to put a stranglehold on the Bay Area. An academy in San Francisco began teaching classes in October, joining a martial arts school in Fremont that has been teaching it for more than two years.

"It's just starting to blossom," said Dave Moeller of Fremont's Self Defense Institute, which offers seven Krav Maga classes per week. "I have no doubt it's going to be big."

Krav Maga combines self-defense with hand-to-hand combat, encouraging participants to use their fists, arms, elbows and knees as weapons against an assailant. Instructors tout it as formalized street fighting and easy to learn.

"Anything goes — anything that works for you in the streets," said Roger D'Onofrio, who runs 20 weekly Krav Maga classes at the San Quan Dao Academy, a Chinese boxing school in San Francisco. "The primary targets are the eyes, ears, throat, instep and groin — things that even a small person can attack."

A typical training session might go like this: The instructor barks at one of his students, "Choke me! Choke me!" As the student tries to make his move, the instructor delivers a kick to the groin, and follows up with a knee jab to the face as the student is doubling over in pain.

It's only a simulation, but the students in the class get the point.

Another main tactic is to pluck an attacker's hands from one's neck while simultaneously kicking the groin.

"Sometimes people call Krav Maga fighters 'dirty fighters.' But if a fight is fair and you're not a professional fighter, you're going to lose," said Barny Foland, an instructor at D'Onofrio's school. "So why not pick up a broom handle or whatever is nearby if it's going to help you win?"

Of the approximately 100 students who have learned Krav Maga from Moeller in the past two years, none has ever told him about using Krav Maga in real life.

In fact, what many people like most about Krav Maga is that it provides an excellent cardiovascular workout. Encouraged to keep going when they are tired, D'Onofrio said, participants are sweating from head to toe after an hour session, and their arms and shoulders feel like jelly.

As for a connection to Judaism, D'Onofrio estimated that 50 percent of his students are Jews, although neither he nor his top instructor are. Moeller isn't Jewish, either.

"Most of the high-ranking people down in L.A. are all Jewish, and they all trained in Israel," said D'Onofrio, referring to the Krav Maga National Training Center in West Los Angeles, which is run by Darren Levine. Most Krav Maga instructors in the United States must go there to get certified.

Estimating that 40 percent of his students are Jews from southern Alameda County, Moeller said, "People that hear about it in the Jewish community are really interested. They think, 'This is part of my heritage,' and they want to try it."

Krav Maga was created in the streets of Slovakia by Imrich "Imi" Lichtenfeld, who often found himself defending Jews against fascists in the late 1930s.

He learned much of his technique from his father, a police chief who taught the officers his own system of self-defense. Lichtenfeld also incorporated his own style, which was more along the lines of neutralize your opponent by any means possible.

After emigrating to Palestine in 1942, Lichtenfeld joined pre-state Israel's Haganah fighters. Enhancing what his father had taught him and what he had learned on the streets of Slovakia, he was recruited to teach self-defense to the soldiers.

He later became the IDF's chief instructor of physical training and Krav Maga. For 20 years, he continued to develop his system, training instructors and soldiers in the IDF's elite units. A basic course in Krav Maga remains a standard part of basic training, with those in combat units receiving more advanced instruction.

In the United States, more than 100 police departments receive Krav Maga training, according to a 1998 article in Time. SWAT teams and the FBI's Chicago office do too.

"The American army is being taught Krav Maga — the elite forces and the Delta fighters," Foland said. "You don't teach civilians the same things you teach the elite."

D'Onofrio's San Francisco institute is one of 10 centers in the United States currently licensed by Krav Maga Worldwide Enterprises Inc. in Los Angeles; another 50, including Fremont's, are waiting to come aboard.

"It's a new fad we think is going to grow for quite some time," D'Onofrio said. "A lot of people will try it out."