Physical Lethargy

I've read about the existence of mental lethargy, and have experienced it for myself. But, when it comes to physical lethargy, is there any meditative practice that counters it? Also, I'm saying this especially in relationship to willpower (avoiding attachment activities) and effort (practicing aversive activities). Ideally, I'm looking for the best practices to counter these things, and ultimately have more energy, willpower and effort in the day. While we're at it, can anyone give me their opinions on activities which involve attachment but which aren't necessarily so for everyone, e.g. facebook and junk food. These activities, in me, seem to create a strong attachment and consequently I'm trying to rid myself of them, but keep experiencing a failure of willpower and determination. Thanks