Workout x Physical Exercise: Qual a diferença?

Podemos utilizar "workout" como sinônimo para "physical exercise" a qualquer momento ou em apenas determinadas situações?

Definição:
[count] : a period of physical exercise that you do in order to improve your fitness, ability, or performance
(Learner's Dictionary)

Exemplo:
I’ve just had the best workout at the gym!
Her workout includes running on the treadmill and lifting weights.

Thanks in advance!