user8162: My upper back muscles are not strong enough yet to support seated meditation, so I use supine/savanana posture sometimes. My mind falls into short dream states, like hypnagogia, very easily in this posture, however.
Any tips for overcoming this laxity while doing supine meditation? I am only doing samatha meditation these days.

user151: The Meditation on Falling to Sleep:
We can be on mindful guard for the arising of the moment we  start to fall asleep. This mindfulness should stop the falling asleep and can give an  initial boost in the meditation faculties like effort and concentration so we  won't fall asleep as much and we can then better practice whatever we want with those improved faculties and wakefulness.
We can know when we are starting to fall asleep by finding and tuning into were  the bodily or mental experiences are that we know always happen right before we start to fall asleep. We then  can easily catch when we will  start to fall asleep.

user295: When you are falling asleep or getting drowsy there is a feeling associated with it (mild uncomfortable heaviness or tightness around your head). Concentrate on this sensation analysing is in terms of Mahābhūta or type of sensation (pleasant, unpleasant, neutral), in this case it is mildly unpleasant. Also you level of awareness is diminishing, so focus on any sensation and actively keeps directing your awareness to any sensation you can feel, continuously evaluating to see if there any lapse of awareness and redirecting your attention to sensations that can be felt.
Also see:

Pacalā Sutta
How to remove dullness of mind, without sitting meditation, in regular activity? 
How is the faculty of persistence developed?
problems with meditation in the morning
Which Hindrances are counteracted or enhance by the 37 and Jhana Factors?


user8196: When using a supine position the trick is to be comfortable without being so comfortable that one falls asleep or enters that subconscious state. I would recommend trying two positions and one form of breathing. First, the way people usually breath without thinking about it is through the chest. Try breathing with the diaphragm, allowing the belly to rise and fall. This type of breathing takes more concentration making one more mindful of the breath regardless of the meditative position assumed. Second, let's consider the two most likely to succeed positions. Lie down on the floor (beds ARE for sleeping) with your legs bent and your toes turned inward toward the center so that your legs do not flop open as you relax. Arms slightly away from the body with palms up. No pillow for the head. Jaw relaxed with tongue resting on the roof of the mouth. Eyes open to discourage sleepiness. Unless this is your normal sleeping position, you should be able to remain mindful during your meditation. The other position is to turn on your side with your arm crooked to rest your head. Your other arm should be resting on your side. Place a small tubular pillow under your shoulder for support. It is alright to move your arm occasionally for comfort, and then resume your meditative position. Again breath from your diaphragm, and jaw/tongue as described above, eyes open. A blanket may be used to lie on if you do not have carpeting. 

8162: <p>My upper back muscles are not strong enough yet to support seated meditation, so I use supine/savanana posture sometimes. My mind falls into short dream states, like hypnagogia, very easily in this posture, however.</p>

<p>Any tips for overcoming this laxity while doing supine meditation? I am only doing samatha meditation these days.</p>
 151: <p>The Meditation on Falling to Sleep:</p>

<p>We can be on mindful guard for the arising of the moment we  start to fall asleep. This mindfulness should stop the falling asleep and can give an  initial boost in the meditation faculties like effort and concentration so we  won't fall asleep as much and we can then better practice whatever we want with those improved faculties and wakefulness.</p>

<p>We can know when we are starting to fall asleep by finding and tuning into were  the bodily or mental experiences are that we know always happen right before we start to fall asleep. We then  can easily catch when we will  start to fall asleep.</p>
 295: <p>When you are falling asleep or getting drowsy there is a feeling associated with it (mild uncomfortable heaviness or tightness around your head). Concentrate on this sensation analysing is in terms of <a href="https://en.wikipedia.org/wiki/Mah%C4%81bh%C5%ABta" rel="nofollow noreferrer">Mahābhūta</a> or type of sensation (pleasant, unpleasant, neutral), in this case it is mildly unpleasant. Also you level of awareness is diminishing, so <a href="https://en.wikipedia.org/wiki/Vitarka" rel="nofollow noreferrer">focus on any sensation</a> and <a href="https://en.wikipedia.org/wiki/Vicara" rel="nofollow noreferrer">actively keeps directing your awareness to any sensation you can feel</a>, continuously evaluating to see if there any lapse of awareness and redirecting your attention to sensations that can be felt.</p>

<p>Also see:</p>

<ul>
<li><a href="http://www.themindingcentre.org/dharmafarer/wp-content/uploads/2009/12/4.11-Pacala-S-a7.58-piya.pdf" rel="nofollow noreferrer">Pacalā Sutta</a></li>
<li><a href="https://buddhism.stackexchange.com/a/13744/295">How to remove dullness of mind, without sitting meditation, in regular activity?</a> </li>
<li><a href="https://buddhism.stackexchange.com/a/14378/295">How is the faculty of persistence developed?</a></li>
<li><a href="https://buddhism.stackexchange.com/a/14444/295">problems with meditation in the morning</a></li>
<li><a href="https://buddhism.stackexchange.com/questions/14258/">Which Hindrances are counteracted or enhance by the 37 and Jhana Factors?</a></li>
</ul>
 8196: <p>When using a supine position the trick is to be comfortable without being so comfortable that one falls asleep or enters that subconscious state. I would recommend trying two positions and one form of breathing. First, the way people usually breath without thinking about it is through the chest. Try breathing with the diaphragm, allowing the belly to rise and fall. This type of breathing takes more concentration making one more mindful of the breath regardless of the meditative position assumed. Second, let's consider the two most likely to succeed positions. Lie down on the floor (beds ARE for sleeping) with your legs bent and your toes turned inward toward the center so that your legs do not flop open as you relax. Arms slightly away from the body with palms up. No pillow for the head. Jaw relaxed with tongue resting on the roof of the mouth. Eyes open to discourage sleepiness. Unless this is your normal sleeping position, you should be able to remain mindful during your meditation. The other position is to turn on your side with your arm crooked to rest your head. Your other arm should be resting on your side. Place a small tubular pillow under your shoulder for support. It is alright to move your arm occasionally for comfort, and then resume your meditative position. Again breath from your diaphragm, and jaw/tongue as described above, eyes open. A blanket may be used to lie on if you do not have carpeting. </p>
