Underwood later incorporated the infant into her workout routine, writing, "Sometimes you have to work your baby into your workout... but that's ok because the the world is your playground! #MonkeyBars #WorkoutAnywhere @caliabycarrie #StayThePath."
The singer and husband Mike Fisher have been together since 2008, and married in July 2010.
She and the 35-year-old NHL player welcomed Isaiah in February, and posted another cute picture of the baby snoozing with his dad in June.
Underwood came to fame after winning the fourth season of "American Idol," and last released Blown Away in May 2012.
She will debut her fifth studio album, Storyteller, on Oct. 23, and released a music video for the lead single, "Smoke Break," this week.
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