“It doesn’t always feel good in the moment,” Obama captioned a picture uploaded to the social media site on 20 October.
“But after the fact, I’m always glad I hit the gym. How did you all take care of yourself on this #SelfCareSunday?”
In the post, Obama is pictured wearing a black sports bra and leggings, performing a lunge and holding a medicine ball over her head.
The snap - which has racked up over one million likes - prompted a wave of positive comments from followers - including fellow celebrities.
“Ok Michelle Abs, we see you!” commented model Ashley Graham, while American sports star Tom Brady merely replied with a football emoji.
Other fans shared #SeflCareSunday anecdotes.
“[I] ran the Detroit Marathon with my sister this morning!” responded one user.
Others had a less exercise-focused version of self-care.
“[I] cleaned my house, organised the pantry, took a nap, now beers at the park and ordering a pizza later. Sunday scaries? Don’t know her,” another follower told Obama.
Let’s Move was intended to encourage exercise and healthy eating in children across America, receiving support from the likes of Beyoncé.
Obama regularly credits her own physical activity for its positive impact on her mental wellbeing.
“Exercise is really important to me—it’s therapeutic,” Obama told Marie Claire when her husband was still contesting the presidency in 2008. “So if I’m ever feeling tense or stressed or like I’m about to have a meltdown, I’ll put on my iPod and head to the gym or out on a bike ride along Lake Michigan with the girls.”