Managing sloth and torpor in meditation? 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.
Mumonkan Case 16: When the Bell Sounds
  
  Unmon said, "The world is vast and wide.  Why do you put on your
  seven-piece robe at the sound of the bell?"  
  
  Mumon's Comment
  
  In studying Zen, you should not be swayed by sounds and forms.  Even
  though you attain insight when hearing a voice or seeing a form, this
  is simply the ordinary way of things. Don't you know that the real Zen
  student commands sounds, controls forms, is clear-sighted at every
  event and free on every occasion?
  
  Granted you are free, just tell me: Does the sound come to the ear or
  does the ear go to the sound? If both sound and silence die away, at
  such a juncture how could you talk of Zen?  While listening with you
  ear, you cannot tell. When hearing with your eye, you are truly
  intimate.
  
  Mumon's Verse
  
  With realization, things make one family;  Without realization,
  things are separated in a thousand ways. Without realization,
  things make one family; With realization, things are separated in
  a thousand ways.


Medhini gives a good gloss of the traditional techniques for overcoming sloth/torpor.  Honestly, I'd try those first before moving into what I'm about to say.

One thing I've noticed in my own practice is that my own sloth and torpor is inversely proportional to my clarity of intention.  What I mean by that is sometimes we take up an object of meditation but don't fully commit to it.  We might focus on the tip of our nose, for instance, but never quite arouse a sense of clear intention.  Our vitaka - our applied thought - is more like someone lazily flopping on a bed.  We just sort of hang out there in a haze of comfortable, quasi-concentration.  And then we promptly fall asleep.

Instead, imagine the intention of a monk putting on his seven piece robe before sitting down for meditation.  Or take a look at this bloke doing some iado:

https://youtu.be/byAgl-b2xFs

That is how you want to approach your concentration object.  Command sound, 
 control form!  Your breath is like a razor sharp sword.  Don't let it escape your attention for even a moment.  Handle it as if your life depended on it!