Workout Fanservice

Where a athletic character, usually a man, is shown working out or practicing a new hobby, this opportunity is excellent for Fanservice and eating the Eating the Eye Candy as well.

This is a common method to introduce very stealth fanservice, especially in action movies or Shonen works, plus it's easier for the guy to convince his significant other to join. This does not always require shirtlessness. Also, female characters aren't excluded, but usually the character is male.

When working out, this can be also justified as training for a fight. Needing to for their bodies to be in tip top shapes and to learn the new weapon, honing superhuman abilities (especially newer emerging ones), so to handle the fight's intensity.

All of this boils down to one thing only, the idea of a hot, sweaty, muscly guy or girl sculpting their abs in front of us.

Though having them being nude is optional.

Compare Macho Camp and Training Montage.

Anime and Manga

 * In Bleach, Ichigo Kurosaki has a brief scene in the anime, that scene shows him doing pushups shirtless. That was in the Soul Society arc, the training was to obtain a Bankai.
 * In Magical Girl Lyrical Nanoha ViVid, Victoria Dahlgrïn was shown exercising wearing a sports bra and very short shorts. Whereas the other characters wears more modest outfits.
 * An entire OVA episode of Monster Musume no Ichijirou No was dedicated to this.

Film

 * In Captain America: Civil War, the Steve Rogers and Sam Wilson are jogging around Washington. Up close we can see Steve's abs and biceps, even though he's wearing a shirt.
 * In I Am Legend, Neville usually starts the day with a shirtless workout and the dog joins.
 * The early 1980s workout show, [Aerobicise http://www.aerobicise.com/], it also counts as Poor Man's Porn. In a White Void Room, Two to four hot women "demonstrating" workout techniques and it doesn't help that there's some pretty interesting angles.
 * The Avengers has Captain America has tons of lovely shots of his body and butt, while working his frustrations on numerous punching bags.
 * In the Anchorman, Ron Burgundy attempts to invoke this. Merely by inviting Veronica in his office while he's "sculpting [his] guns." It didn't work, since his body betrays the fact that he's out of shape and he usually refers to his arms as "guns."
 * Gentlemen Prefer Blondes has a number called "Ain't Anyone Here for Love?" where [Jane Russell wanders through a team's workout room https://www.youtube.com/watch?v=q5BQlgDIaBs]
 * In Terminator 2, when we first see Sarah Connor, she's doing some chin-ups off an overturned bed.

Live-Action Television

 * In the CSI: NY's "My Name Is Mac Taylor" episode, in a gym we find Mac doing his lap swim workout.
 * In Supernatural, the episode "The Third Man," Sam begins the day with some push-ups, sit-ups, and pull-ups, merely to keep fit for all the demon, monster, and spirit slaying. The focus is on his back, upper chest, and biceps during this, though we get some shots of his abs above the low-cut jeans in post workout.

Music

 * Olivia Newton-John's "Physical" music video begins with and ends with multiple handsome, muscular men working out, being loaded with Fanservice shots.
 * Eric Prydz's music video remix of "Call on Me" depicts a man who finds himself in an all-female exercise class, who is enjoying the suggestive thrusting and griding of the routine exercise.

Video Games

 * Mass Effect 3's James Vega does a load of pull-ups.