UCLA gymnast Frida Esparza has no hesitation when naming her favorite Metallica song.

The bass line of “For Whom the Bell Tolls” rolls along, repeating then shifting then repeating again as a lone bell clangs in the background. The intro lasts about two minutes before the raspy vocals even begin.

Esparza’s journey back to confident gymnastics has a similar pattern. The senior battled confidence issues this year after injury kept her out all of last season. She rehearsed routines over and over and changed choreography before fully re-arriving as a Bruin — and has inspired other UCLA gymnasts in the process.

“I think it’s really lit a confidence within them,” UCLA coach Janelle McDonald told reporters Wednesday. “We’re seeing a lot of those athletes that have been kind of in and out of the lineup just really lock into their consistency and their confidence, which has been exciting to see. And I think Frida’s a big part of that.”

There’s a subset of Bruins this season who are “bubble athletes” that bounce in and out of lineups depending on the team’s needs that week and how consistent each gymnast has been. Lineups have looked different in nearly every meet and could change again today when No. 19 UCLA (5-9) travels to No. 24 Stanford (1-8).

Esparza has been in the uneven bars lineup for six out of eight meets this season, with scores ranging from 9.200 to a 9.950 in the Bruins’ last meet against Cal. She’s competed in the event in the past four meets.

She’s worked her way into balance beam, too, in the last two meets. She scored 9.150 after a routine that included a fall against Utah but bounced back to reach a 9.900 against Cal.

Being on the bubble can give a gymnast mixed emotions, according to Esparza.

“It’s stressful, but exciting,” Esparza said Wednesday. “If you’re there for a hot second, it does get a bit frustrating.

“But in a way, it kind of helps the whole team because they see how much those people on the edge are pushing so hard to get in and it also pushes other people that don’t want to lose their spot. So it just like makes the whole team just like rise up.”

Blasting Metallica’s 1984 album “Ride the Lightning” before 7:30 a.m. training sessions and meets has helped keep her energy and confidence up, too.

UCLA has a lot of depth this season, which has allowed for competition. The absence of Emma Malabuyo, who missed the last two meets due to elite obligations, has also forced the coaching staff to make constant changes. Malabuyo is expected back for the Stanford meet, McDonald said, and will likely compete on bars and beam.

McDonald said that she’s seen bubble gymnasts Alex Irvine and Maddie Anymi in particular feed off of Esparza’s hard work and ability to overcome struggles. Chae Campbell, who competed on beam for the first time since January, also worked alongside Esparza in her return to the event.

“They see like, ‘OK, the opportunity is there,’” McDonald said. “‘And here’s what I’m gonna do to really gain my own confidence and be ready to go for my team.’”

Esparza’s beam choreography has evolved this season, which also boosted her confidence. Some skills have been swapped out and a few leaps have been sprinkled in.

“Ciena (Alipio) reminded me I have so many skills I can choose from that I don’t have to stick with something if I’m not comfortable with it,” Esparza said. “That really changed my perspective on switching skills around and overall it’s been really helpful and it’s taken some stress off.”

Esparza is on the bubble for at least one more event: floor exercise. Her routine, naturally, features music from her favorite metal band. It’s unclear if that routine will make its competitive debut this season, although Esparza seemed excited about the prospect Wednesday.

That’s life on the bubble at UCLA. Routines are repeated countless times to achieve consistency and cut down on deductions, but numbers can be a good thing. After all, Metallica has performed “For Whom The Bell Tolls” live more than 1,500 times.