if you can stand on top of a building and have a lightning bolt pass through through and it does nothing to you i would assume that you are able to store massive amounts of energy and able to control its flow. if you have blood that glows in the dark it probably has huge energy carrying ability. id say the predator can access energy reserves that is far more just muscle strength. i am guessing that the tech they possess allows them huge physically strength if they need it.
so i am guessing that the arm device allows them ways of accessing far more advances energy storing and retrieval that interfaces with their biology.
i mean if you can drop say 5 or 10 stories from a building and land on your feet uninjured then you have a body that is strong enough to wield such power.
if you are asking just their normal bodies themselves i am guessing that they are at least 5 times stronger than human at a purely physical level. i am guessing that come from a world where the gravity is at least 5 times more than ours.
so a predator and a man of same physical dimensions would be a complete mismatch. i am assuming that pred's physical density is accordingly much higher , at least twice. so a man of same dimension as a predator would probably weigh halve of what a predator does.
so a predator of feral's size i would guess with their tech could lift some thing like 2 - 3000 pounds easily. but i also believe their tech can bend gravity and also allow to grip to the ground they are more easily able to be stable when picking stuff up.