The second one would sound more natural in conversation. The word order used in the first one is usually only found in writing.

If you're going to say it directly like this, you need quotation marks: Experts say to take a break . . . . etc. OR Experts say, "take a break . . . . "

Both statements convey the same meaning and essentially say that experts recommend taking a movement break every 30 minutes. However, the difference in nuance lies in the emphasis on the action. In the first statement, the emphasis is on the action of taking a movement break. It implies that taking a break every 30 minutes is important and necessary, and experts suggest doing so. In the second statement, the emphasis is on the recommendation from experts. It implies that experts suggest taking a break every 30 minutes, and the listener or reader should follow that advice. Overall, the difference in nuance between the two statements is subtle, and they convey the same message.

I don't think there is any difference in meaning, but there might be a slight difference in emphasis. You could choose one or the other depending on the flow of your thought, and the sentences preceding and following. The first one emphasizes that the reason for taking the break is that experts recommend it. The second one emphasizes that the time interval should be thirty minutes. For example: "Take a movement break every 30 minutes, say experts. Dr. Leslie Jones of the University of Winnemac says 'Our studies have shown a 26% improvement in...'" Or, "Experts say to take a movement break every 30 minutes. The exact interval isn't important, the important thing is to do it."