Perhaps I’m missing what you mean. EMS frequencies between 2-8 Hz can only elicit muscle twitches, but not muscle contractions. I’m not a coach, but when I’ve heard from other coaches taking care of knee pain with EMS, it’s generally about strengthening a weak muscle that was causing an imbalance, thus causing the knee to work incorrectly. Read for instance the blog from coach Dean Hebert, which I’m quoting below with relative links:[ul]
[li]my quads have chronic pain- just above the knee cap. It’s a tendonitis and attachment area pain.
[/li][li]Within only 3 treatments I already felt a reduction in the previous symptoms of peri-knee discomforts due to weak quad muscle group.
[/li][li]Over the past year, my quads have chronic pain- just above the knee cap. It’s a tendonitis and attachment area pain. The initial injury (hill work in the summer of 08) has long been healed but the residual weaknesses are there. Because of this I have compensated and had other niggling injuries.
[/li][li]I no longer have ANY peri-knee tendonitis issues that I had for months. And those very knee tendon (quad insertion points) were the ones that the physical therapist told me that EMS would NOT help
[/li][/ul]
Most effective strengthening programs work at around 75 Hz. If instead your problem is not the knee, but a muscle contracture, my database of EMS programs shows that clinical Globus machines use for that condition a constant twitch at 4 Hz.