This saying has been put to me each day during our physical training and I would like to put it on our plaque when we present it to our instructors. It may also end up becoming a tattoo for a few people as well.
My brother-in-law is from County Claire but admits his Irish is not as strong as it once was.
Thanks to all for helping.

Just for the sake of practicing. More or less a direct translation.

Is cuma le duine ar bith, oibrigh níos deacra.

I'm not sure of the exact nuance of what this phrase means or the relation between the two parts of the sentence. Is it "No one cares, (so) work harder." ". . . (but) work harder."

Wait for comments from others before you decide this is a correct translation or even the right nuance.

Tim

No one cares - Is cuma le haon duine or: Is cuma le duine ar bith
(You may also simply leave out the le-part: Is cuma or make it more intense: is cuma sa tubaiste)

Work hard! - Oibrigh go crua! (or: Oibrigh go dian)
Work harder! - Oibrigh níos crua! (Standard Irish, I don’t know for Clare Irish, perhaps níos cruacha, níosa chruatha)
or: Oibrigh níos déine!

Because you mention "we": If this command is said to more than one person, it is Oibrígí ...

(deacair, comparative níos deacra, is "hard" only in the sense of "difficult")

Thanks to you both.
The meaning behind it is that no one cares if you are sore, tired, or hurt during our running, lifting, and exercising. You have to work harder to be better. We are firefighters and thus sometimes the first and last line to save someone. If we don't do it no one else will.

For simplicity, I would use Labhrás suggestions above in the following form.

Is cuma, oibrigh níos crua.

It's short and concise and slightly alliterative with those "c"s jumping out at you.

As translations here are (or should be) a cooperative effort, please wait for more comments or (re)confirmation.

Tim

Looks nice and pithy to me [being sure to note the fada or accent mark over the "i" in níos].

While the grammatical point about using oibrígí when addressing more than one person is correct, in slogans such as this, it is common to use the singular, perhaps on the theory that one is addressing each reader singularly. If you were standing in front of the group and making a speech to get them aroused, then oibrígí would be the way to go:

Oibrígí nios crua!
"Work harder [you all]!"

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I'm not a native (or entirely fluent) speaker, so be sure to wait for confirmations/corrections, especially for tattoos.