Wearing a surgical mask

2019/ 01/ 07
Baseball players in a junior high school wore white surgical masks when they were practicing.
Do they have a cold?  Are they all  sick?
Why a mark?
It's been cold outside these days, so when we wear a mask, we feel warm because we inhale less cold air than when our mouth is open.  Is this the only reason?   To warm our body?   Doesn't sound scietific.  
Overprotecion!  Are you sports men?