Danville, Calif.

Ivan Abadjiev knows a thing or two about heavy lifting.

Bulgaria's most renowned weightlifting coach led his tiny country to a stunning Olympic victory over the Soviet Union in 1972. By the 1980s his country's strongmen completely dominated world competitions, hoisting more than three times their body weight—a feat that has rarely been matched. He's produced champions in Turkey and Qatar—and he even turned around his country's junior national badminton team.

Now, at age 79, the soft-spoken, silver-haired legend who speaks little English is taking on his most difficult challenge to date: Convincing American athletes they can do better. If only, that is, they would only adopt "the Bulgarian method."

Under the Bulgarian method, which Mr. Abadjiev invented, there is no danger of overtraining. The body, if pushed gradually and consistently, will adapt to any level of stress. Practice should ideally consume nearly half of one's waking hours and, most important, there are no days off. The theory is that injury and fatigue are less likely while adrenaline is coursing through the body, stimulating protein synthesis. Junk food is fair game.

By contrast, most American fitness trainers believe peak performance results only from an expertly plotted combination of exercises to build things like endurance, core strength and cardiovascular health—while including periods of stretching and rest. A healthy, balanced diet is essential.

For the past six months, Mr. Abadjiev has been spending nearly every morning and afternoon training competitive weightlifters at a new academy here, missing work only when he heads out of town to lecture. A former student hired Mr. Abadjiev to spread his message: Never attempt less than the maximum.

So far, there are only four Americans and one Mexican training at the Danville academy, which hopes to produce several Olympic medalists in the 2016 Summer Games in Rio de Janeiro.

"It goes against everything you were ever taught," says Jacqueline Janet, a 48-year-old personal trainer who swore off jogging, sit-ups and yoga in order to do a monotonous series of lifts, up to five hours a day, with Mr. Abadjiev. She says she's now a believer after recently breaking a national record for her age group in an amateur weightlifting competition. Still, she disagrees with Mr. Abadjiev's "horrible diet" and tosses out his candy and soda.

Last month, Mr. Abadjiev delivered a 90-minute lecture at a collegiate strength-coach convention in Kansas City, Mo., explaining how the Bulgarian method could be applied to college sports. The concept was met with hearty skepticism.

One coach doubted he could "get the guys to buy in" to such a taxing, time-consuming program. (Mr. Abadjiev suggested revoking their personal possessions, like cellphones.) Southern Illinois University's strength coach, Jared Nessland, said after the presentation, "You can't beat the snot out of these kids—they don't have the mental toughness."

But Tommy Lee Barnes, an associate strength coach from the University of Tennessee, was intrigued.

"It kind of made me think, 'Gosh, am I loading my athletes enough?' " said Mr. Barnes, adding that American coaches tend to "lean on the side of undertraining" to account for other stresses in their athletes' lives, like classwork and relationships. "We tend to be on the reserved side, but then again, the American [men] haven't won a gold medal in 40 years."

Bulgaria held its first weightlifting competition in 1946, but the country lost miserably year after year. Then, Mr. Abadjiev, who had spent his childhood working in a basket-weaving factory, earned the country's first weightlifting medal—a silver—in the Tehran World Championships in 1957. Mr. Abadjiev says he began experimenting with his own physical limits in his free time. Reading up on biological research confirmed his suspicions: "You lift more, train more, you get higher results."

Mr. Abadjiev and his followers say the Bulgarian method decreases the risk of injury, since these lifters are acclimated to weights that opponents would attempt only in competition. But some U.S. coaches say Bulgarian-trained lifters have had shorter Olympic careers, on average, than lifters from other countries. There are no comparative statistical data to verify either claim.

Over the years, Mr. Abadjiev's credibility has been undercut as Bulgarians have repeatedly been caught using banned substances, both under his watch and his successors'. The International Weightlifting Federation has warned its member federations against hiring Mr. Abadjiev because of his links to doping scandals, though Mr. Abadjiev says the only drug he ever tried giving his athletes was Albuterol, a medicine asthmatics inhale to clear their airways that wasn't banned at the time.

In 1989, Mr. Abadjiev, resigned from coaching the national team as communism fell. He worked as a locksmith and a security guard to make ends meet. He also coached national teams in Turkey and Qatar and even Bulgaria's junior badminton players before returning to coach the Bulgarian weightlifters for the 2000 Sydney Olympics. There, three lifters returned their medals after testing positive for trace amounts of a diuretic. A Bulgarian court later found Mr. Abadjiev and the athletes not guilty because a Bulgarian drug maker hadn't disclosed the presence of the diuretic in a supplement the team was taking. Nonetheless, the IWF stopped recommending him for coaching positions.

Mr. Abadjiev had been living on his small pension in the Bulgarian capital of Sofia with his wife when he got a call last year from one of his first students, Alex Krychev. A one-time silver medalist, Mr. Krychev had founded a supplement company called CSA Nuitrition and partnered with Swedish barbell maker Eleiko to open its first Olympic training academy. Mr. Krychev hired Mr. Abadjiev to consult.

Mr. Krychev says the Danville academy, which opened in January has two American Olympic hopefuls, Kris Pavlov, a 20-year-old former Monte Vista, Calif., football player who speaks Bulgarian and serves as Mr. Abadjiev's translator, and Sina Abadi, an Iranian high-school sophomore from Concord, Calif., who's ranked No. 1 in the U.S. in his weight class among lifters born in 1995.

In the meantime, Arthur Drechsler, chairman of USA Weightlifting's board of directors, says the Olympics organization is seeking a middle ground. Many American coaches have attended Mr. Abadjiev's seminars, read his articles and even traveled to Bulgaria, "looking for ways to get the same results, but with lower intensity and volume of workouts," he says.

Mr. Abadjiev, of course, says that is impossible.

Write to Hannah Karp at hannah.karp@dowjones.com