Recently sloth and torpor has been a huge hindrance in meditation; my biggest hindrance as it happens. I've managed to reduce the bulk of it but I find that it's still hanging around in some sessions. For the most part, I can see sloth and torpor trying to engulf me and thus am able to take evasive action by refocusing my meditative state. Sometimes though, it gets me even to the point of falling asleep. It's been with me now for months on and off. 18 months previous to this it hasn't really effected me like it has now.
Here are some descriptions of the hindrance in question:
Heaviness of mind, like wading through oil. Tiredness when I don't appear to be tired outside of meditation. Falling asleep. Dullness of mind. Sinking into a gloop.
The Buddha compared it to (I'm paraphrasing here) being imprisoned in a cramped, dark cell, unable to move freely in the bright sunshine outside.
The largely recommended antidote by my sangha is to rouse energy by exerting myself outside of meditation. This has not been helpful or perhaps I'm not receiving the message correctly. It seems to be more of a mind thing and that is the route I'd like to take to address it so I've been sitting and watching and trying to evade it. I just can't seem to eliminate it completely. I have some sessions where I am free of it and some sessions that start out with meditative potential only to be confronted some-way through the session with the dealings of sloth and torpor.
Things I've tried: bright light from a light box and also from daylight, light exercise before meditation, opening my eyes in mid-session, water on my face before a session.