One day in my early teens, it seemed as if my ability to do chin-ups increased exponentially overnight. The victory was dampened by a cracking voice and acne.

As a man, I take the ability to lift my entire body weight so my chin is above a bar for granted. At my most out of shape, when I was sedentary and tipping the scales toward obesity, I could still do three chin-ups.

But for a woman to do even a single chin-up, she needs to work for it, said Boston strength and conditioning coach Tony Gentilcore. And the work, Gentilcore added, is worth it.

“I consider it an important fitness goal for women,” said Gentilcore, who trains Major League Baseball players as well as many female clients. The latter often have an aesthetic goal in mind, and the chin-up helps them achieve that too. The training helps sculpt muscles in a way many find appealing, and “weight loss can be part of the discussion because it’s less weight to pull up over the bar.”

Once his clients have mastered a chin-up, it’s a skill they don’t want to lose. Instead, they want to go for two chin-ups. Then more.

Lori Andrews, 48, just achieved her first full chin-up, and it was six months in the making.

“I never had the upper body strength to do anything; I couldn’t even climb a tree,” said the interior designer from Calgary, Alberta, who hired a trainer in January to help her do chin-ups.

Why is it women need to work so hard to achieve even a single chin-up?

“It’s not the quality of the muscle, it’s the total amount,” said Cassandra Forsythe, an assistant professor of exercise science at Central Connecticut State University and co-author of “The New Rules of Lifting for Women.”

“With men,” she explained, “puberty provides an enhancement in testosterone, which creates greater muscle mass. There is a large difference in the amount of upper body muscle between men and women.”

There’s a cultural difference too.

“It seems men are always doing upper body work in an effort to build muscle and be stronger,” Forsythe said, “whereas women are often more interested in fat loss and doing cardio.”

So what kind of training does it take?

“You need to train four to five times a week,” Gentilcore said.

“Planks, pushups, core strength. Building total body stability starting on the floor is important, so when they’re hanging from the bar they can hold a good position.”

He then has his clients practice hanging from the bar, adding in flexed arm hangs and hanging leg raises. When they’re ready, he has them “build the pattern” by mimicking the chin-up while having clients stand on elastic bands attached to the bar to take away some of their weight and help lift them up. Over time, those elastic bands get thinner and the clients do more of the work, until they can do the entire exercise on their own.

Andrews’ trainer gave her a well-rounded lifting program with additional chin-up-specific exercises to train the back, core muscles, shoulders and biceps. Biceps help make the chin-up easier than the pull-up — two exercises that are often confused. With a pull-up, the palms face away from the body and hands usually are positioned slightly wider than the shoulders. Chin-ups have the palms facing inward, hands about shoulder-width apart. The body’s configuration with the chin-up allows for more recruitment of the biceps, making it somewhat easier than the traditional pull-up.

The chin-up had long managed to escape Michelle Kania, a 37-year-old athletic trainer in Oswego, Ill., but she made it her mission to learn. She followed Gentilcore’s program via online coaching.

“I got so I could do almost 10,” Kania said. Once she could do it, she was determined not to lose it. She’s currently able to do five chin-ups and plans to increase her training to get back up in the double digits.

Kania said she once impressed a group of Marines with her ability to do chin-ups.

“I like doing it in public, so people look at me,” she said. “I get a kick out of that.”

“Good Fit” spotlights inspiring fitness stories of change, self-discovery and challenge, and other fitness-related topics. Tell us what motivates you and how you stay fit and healthy by calling 529-4803 or emailing features@staradvertiser.com.