Hamstring issues when in a five-point-meditation posture Most days when I sit in a five-point meditation posture on a cushion there isn't a problem when sitting for the duration of a meditation session, but for particularly long sessions or on some days, sporadically, my left hamstring will start to feel uncomfortable tight to the point where I will not be able to continue meditating through it. Usually when this happens can't even mindfully adjust to a position where it won't dominate the session from that point onward. 

The pain is sharp and gradually builds until about all I can do is stretch it out and leave it that way. It appears to be muscular in nature. There are no medical conditions that I have that I am aware of that would lead to this problem, and there don't appear to be any circulation issues. 

What are some of the elements I can ensure, adjust, do beforehand, or do regularly to try to keep this from happening or mitigate the problem?
Maybe the desire to adhere to a particular meditation posture is the problem. If someone got it into their head that to meditate properly, one needed to hold a headstand position, then there's sure to be lots of discomfort to get in the way of the meditation.

The purpose of the posture is to reduce bad mental qualities that get in the way of meditation, things like back pain from slumping and not sitting up straight; things like lethargy that comes from lying down.

Yet you need some kind of relaxation to prevent giving the mind food for discursive thought. You can't really meditate while driving because there's too much to be responsible for, not enough room for the mind to calm down.

So how comfortable do you need to be before you can settle down? Is it a distracting thought or a legitimate injury you're doing to yourself? If your legs hurt when you sit down, then just stretch them out and go back to the breath. Yet if you find there's a constant, never-ending stream of uncomfortable things that you need to keep "fixing", then that points to a mental discursiveness that you need to stop following.

The Buddha gives ways of dealing with Distractive Thoughts. If all else fails, press your tongue to the roof of your mouth and batter through your mind's urge to "fix" parts of your posture.

(Re: closing the question, I think there are perfectly Buddhist ways to answer a question like this--these are distractive thoughts, although one needs to discern the difference between a mere thought and an potential injury which is yours to prevent. I've read stories of people injuring their knees because their teacher told them to keep sitting in tight postures, ignoring their pain.)