Examples:

• My grandmother's 92, but she's as fit as a fiddle.
• She had fallen very ill, but with rest and medication, she is now fit as a fiddle.
• The young bachelor as fit as a fiddle before he got married.
• The team had partied late into the night, but on match day, each of them was as fit as a fiddle.
• I was 47 years old and felt as fit as a fiddle.
• After a refreshing vacation by the sea, I now feel fit as a fiddle.
• I slept so well last night that I feel as fit as a fiddle this morning.
• You may be feeling tired and sleepy now, but with a good night’s rest, you will feel fit as a fiddle in the morning.
• To be a good soccer player one must be as fit as a fiddle.
• A few years back he was as fit as a fiddle, but long work hours and little sleep has wrecked his body.
• In spite of the long trip, Alice arrived looking as fit as a fiddle.
• That woman is 50 years old but she is running like a 20 year old! She is as fit as a fiddle.
• Though Aunt Marge is now in the hospital, she'll soon be fit as a fiddle.
• I have completely recovered from my surgery and climb the stairs to my fifth floor apartment. I feel as fit as a fiddle.