Picture two lanes side by side, and someone out of their own lane into the next one for a while. That crossing-over can be held as the whole idea of the word. You keep your main lane — the runner is still a runner, the cook is still a cook — but the time spent in the other lane wakes up what your own lane never asks for, and shows you what happens over there.
Wiktionary gives the formation directly: cross- + training.
Wiktionary 直接記下這個字的組成：cross- 加 training。cross- 帶的就是「交叉、跨過去」的意思，所以整個字的畫面從字面上就看得出來。
Wiktionary (kaikki extract) entry 'cross-training', etymology_text: 'From cross- + training.'; source_ref kaikki:3f6f69a190036ae4:2163086891
One branch
跨到別的項目、別的職位
兩個意思是同一個動作，差別只在跑道畫在哪裡——一條是運動項目，一條是公司裡的職位。
noun · B2
Exercise that mixes several different kinds of activity — running one day, swimming or lifting the next — so that the whole body gets used, including the muscles your main sport leaves out.
交叉訓練