YOU SAID:
they run with swiftness, fast and strong,
INTO JAPANESE
彼らは素早く、速く、力強く走ります。
BACK INTO ENGLISH
They run fast, fast and powerful.
INTO JAPANESE
彼らは速く、速く、そして力強く走ります。
BACK INTO ENGLISH
They run fast, fast and powerful.
That didn't even make that much sense in English.