I have seen an article regarding whether should we exercise first thing in morning or not and I came across a sentence which seems a little odd to understand.
Early morning exercise can be bad for your health, say researchers.
They claim the body's immune system is not ready to cope with intense exercise first thing in the morning.
A pre-breakfast work-out puts the exerciser at greater risk of infection than the same level of exertion after work, the study by sports scientists suggests.
(Source)
What does "work" mean here?