Alex Rodriguez is ''so sore'' after dancing the night away at Jennifer Lopez's birthday bash.

The 43-year-old former professional baseball shortstop is struggling with his muscles and joints after getting down and dirty on the dance floor with his fiancee in the Star Island neighbourhood of Miami Beach, Florida, for her 50th on Wednesday night (24.07.19).

Taking to his Instagram account, Alex said: ''I am so sore from one night of dancing, I don't know how Jennifer does it! Who else hates getting old?!''

He then went on to say he's tried icing his body, having a massage and sitting in the sauna but he's still struggling to get out of bed and function normally.

He explained: ''Jennifer's done 28 shows in about 58 days, she has two more here domestically in Miami. For her birthday, it was a big one, it was 50, I danced for about an hour and seven minutes ... I couldn't get out of my bed tonight.

''I've iced, done cryo [cold therapy], got stretched, got a massage, steamed, sauna. I've been drinking coffee all day. I'm a mess. She went out there [onstage] and destroyed it in Miami [Thursday night]. Killed it. Like if she slept 10 hours. Am I the only one that can't recover anymore? Does it suck to get old or what?''

And it wasn't just his dancing that he went all out on as Alex also splashed out on a bright red sports car - believed to be the 2019 Porsche 911 GT3 - for her birthday.

The brunette beauty's birthday was extra special as her 11-year-old twins, Max and Emme - who she has with ex-husband Marc Anthony - serenaded their mom with a rap and a song.