I've got both tube type that top out at 19-20 ( I see now one company sells up to 40#) and flat bands that top out at 20 to 30. My shoulder therapist gave them to me. But, I see a company makes a 65-100 and a 150-200 flat for leg strengthening. Ninja style cross training is getting pretty extreme. They could give you quite a bruise but the carabiner would be too light to cause any substantial force without a bone injury. But, OUCH. That ouch can cause the visual symptoms just like a hard sneeze can.