At times during meditation practice - including loving-kindness meditation, we can experience considerable discomfort, even physical pain without a direct physical cause. The pain may be severe enough to cause profuse sweating & crying, so emotions can definitely be involved. And when the process is over, one feels a sense of relief akin to having worked something to a satisfactory conclusion (rather than mere relief that discomfort has ended). Such experiences can be called physical (vs intellectual) processing of trauma or of psychological problems (karma?). It's a type of catharsis - purification & cleansing of emotions, resulting in renewal & restoration.
At other times, one can experience surprisingly rough, even bumpy shifts of energy through the spinal column area - dismantling of energy blockages / melting of psychological armor. These can simply feel surprising & odd, but no other emotions may arise. These latter energy shifts seem more like physical adjustments to accommodate deeper, non-physical shifts that had recently taken place.
"Sometimes there's an experience of actual heat in the body of burning. It feels uncomfortable. The mind will want to get rid of it, but when we're being anything that is arising, we're not separate from it. We can be the discomfort, we can be the fear. We can be the fire that feels like it's burning in your gut. Because our awareness has no boundaries whatsoever. This is boundless, timeless awareness. It can go anywhere and it is not separate from any experience or any moment. We're just inviting that which we are, this heart of awareness that both is aware but also compassionate into the center of this discomfort or this feeling. It could be a feeling of rage, or jealousy, or fear. It could be lots of things that come up, not to be judged, but they come up to be seen and to be liberated back into the wholeness of our being.
When we're not separating ourselves from them, we'll feel there's a softening that happens. There's a deeper acceptance that what's here is just what's here. It's not a judgment about a self. It's just an expression. We're not the victims of life necessarily, we're its expressions, and so often we feel like a feeling or even bad weather or whatever that we become victims of life. I'm not saying there aren't moments where we truly have felt victimized, but that's on the relative plane. In the deeper dimension, we're not victims of life, we're expressions of it."
Dorothy Hunt "Entering the Heart’s Cave" very fine interview with Tami Simon of Sounds True, Feb 13, 2018. https://www.soundstrue.com/store/weeklywisdom?page=single&category=IATE&episode=12991&utm_source=bronto&utm_medium=email&utm_campaign=N180218-WW&utm_content=This+Week:+Featuring+Dorothy+Hunt+and+Wim+Hof