Is lethargy due to lack of fresh air or exercise?

[whiskygalore]

Why is it that when I stay indoors all day doing nothing (like today), I feel more tired than normal? My parents always used to push me outdoors, saying that the 'fresh air' would make me sleep better. Is this true, or is it just that by being outdoors, I'm getting exercise and tiring myself out more effectively?

[andy hughes]

Even more today than in the past, with the advent of central heating and air conditioning, we are breathing and re-breathing stale air when indoors, which combined with a warm atmosphere, does lead to a feeling of lethargy, which is enhanced by inactivity. The combination of fresher cleaner air, combined with even the simple exercise of moving around, does freshen your system and probably assists relaxation when you return indoors. Like a lot of our parents' saying, this one is routed in truth.

[LynneMcF]

My mum used to say that if you pull a face and the wind changes direction, your face will stick that way. Any truth in that one?