The six and a half-minute video, made by Shannon Nadj, who runs the Los Angeles-based studio Hot Pilates showed a workout routine that emphasized strengthening the pectoral muscles in the chest to give the appearance of perkier breasts.

Kardashian has said of her fitness routine in the past: ‘We’re keeping it simple with short rotations and no equipment required (just your body weight for some of the moves)’

Kardashian-approved pilates instructor Shannon Nadj detailed a series of chest and shoulder strengthening exercises that can help make breasts appear perkier as muscles become stronger

Ms Nadj, founder of the LA-based studio Hot Pilates, said: ‘Unfortunately, you can’t push yourself up to bigger, perkier boobs. However, you can strengthen your pectoral muscles right behind and around this area.’

The pectoralis major muscle runs from the sternum up and out to the arms and neck, while the pectoralis minor is underneath the major muscles and helps connect the ribs to the shoulder blades.

Breasts are not muscles and therefore are unable to be toned similar to glutes and abs. They are made up of different types of glandular and fatty tissue, so exercises to improve their appearance targets large muscle groups nearby.

Dr Alyssa Dweck, a New York-based OB/GYN, told Well + Good: ‘There are no exercises for your breasts per se, particularly the glandular tissue inside, but your typical pectoralis muscle exercises can help.

‘Doing these [exercises] can build up enough muscle [to] actually make your breasts a little perkier.’

Fitness experts also agree maintaining good posture can help strengthen the chest and back muscles, translating to perkier and perhaps larger-looking breasts.

Unlike surgery to lift breasts or increase cup size, these exercises are not a quick fix.

Cat Kom, a trainer and founder of Studio SWEAT onDemand, said: ‘You can do exercises to perk up your breasts, but you’d have to do quite a bit to actually see the results.’

Throughout the routine, Ms Nadj wore one-pound weighted bangles on her wrists, though stated that using weights is not necessary to feel the impact of the workouts

Ms Nadj’s movements emphasized opening up the shoulders and the chest while keeping her core abdominal muscles working and engaged.

While demonstrating a half-plank position in which her knees and shins are against her yoga mat, Ms Nadj said: ‘You’re not slouching, your shoulders aren’t rounding forward.’

Throughout the routine, Ms Nadj wore one-pound weighted bangles on her wrists, though she said using weights is not necessary to feel the impact of the workouts.

For another exercise to strengthen the chest and core, she took on a Superman-like position on her stomach with her arms and legs splayed out in opposite directions. The object of the exercise was to keep her legs and chest lifted while doing a swimming and kicking motion. 

She also demonstrated standing shoulder presses and a rowing motion with elbows staying wide, the belly elongated as if being zipped up, while shoulders stayed down and relaxed.

She did each motion 10 times with brief holds before releasing the position.

In addition to highlighting key exercises for strengthening the chest muscles for perkier breasts, Ms Nadj demonstrated the proper way to stretch and lengthen the torso, including the pectoral muscles.

After the exercises, she stood straight up, with her shoulders back and down, her chest raised and one of her arms reaching toward the sky.

One at a time, she lowered each arm while keeping the other lifted. On the inhale, she lifted both arms. On the exhale, she let her right arm fall to her side while the left remained lifted. She then stretched the left side of her torso, the waist, and pectoral muscles.

She repeated that on the other side.

It is important to work the chest from multiple angles, though using weights may not be necessary. Ms Nadj, for instance, wore bracelet weights but also made clear that no added equipment was necessary to feel the benefits of the exercises.

Still, some personal trainers maintain that working with enough weight is necessary to increase strength, and working with sufficiently heavy weights is important.

Jen Comas Keck, a certified personal trainer told Women’s Health magazine you should feel as though you could do about two more reps at the end of each set, but no more: ‘It’s important to challenge yourself with heavier weights for muscle growth to take place.’