Examples:

• Despite being in her 70s, Grandma is still as fit as a fiddle.
• After recovering from the flu, John felt as fit as a fiddle.
• The doctor said my test results were excellent, and I’m as fit as a fiddle.
• Lisa’s daily exercise routine keeps her as fit as a fiddle.
• After months of training, the athlete was as fit as a fiddle for the competition.
• My grandfather walks five miles every morning and is as fit as a fiddle.
• Now that I’ve quit smoking, I feel as fit as a fiddle.
• He eats well and exercises regularly, so he's as fit as a fiddle.
• Even after working all day, she seemed as fit as a fiddle.
• Thanks to her healthy diet, she’s as fit as a fiddle in her late 50s.
• After a long vacation, I’m back at work and feeling as fit as a fiddle.
• Despite his age, Mr. Brown is still as fit as a fiddle.
• With his new fitness regime, Mark is getting as fit as a fiddle.
• The doctor was impressed; he said I’m as fit as a fiddle for my age.
• She recovered quickly from surgery and was soon as fit as a fiddle.
• Despite the challenging hike, she remained as fit as a fiddle.
• My dad’s been running marathons for years and is as fit as a fiddle.
• After a few weeks of rest, he was back to being as fit as a fiddle.
• Her routine of yoga and meditation keeps her as fit as a fiddle.
• He might look thin, but he's as fit as a fiddle and very strong.