Would you explaing the underlined word in the sentece below? Though I've looked it up, the meaing wasn't clear enough.
This TRX TV workout focuses on the X-factor in endurance training: core endurance. With a more stable core, you can optimize your movements and prevent energy "leakage" during those long runs, rides, or whatever you do.
Thank you,
M
Top answer
Hi, It's not an idiom that I have heard. The meaning seems to be that this factor is very important but not widely known about. Clive
— Clive
Hi, It's not an idiom that I have heard.
The meaning seems to be that this factor is very important but not widely known about.
Clive
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