DR-HO'S Pain Therapy System PRO (TENS) combines TENS, EMS and proprietary auto-modulating pain relieving wave technology to relieve muscle tension and pain, as well as increase circulation in as little as 20 minutes. It's a drug-free solution that can be used to temporarily relieve pain associated with many conditions like chronic & acute back pain, degenerative or bulging discs, tension headaches, knee and hip pain, arm pain, leg pain, foot and ankle pain, and pain related to sports and activity. The Pain Therapy System PRO comes with a built-in rechargeable lithium-ion battery