I have a COMPEX SP8.0 (it is not cheap, and it is the best EMS on the market) and it can be adjusted based on its measurement of the muscles. I am not taking any half measures when dealing with my SCA3.
I do not go to maximum EMS levels as this can cause later discomfort. However, with regular use I have found it helps with muscle function, coordination, and balance by activating and working the muscles that would not normally function well. If the unit is not used at maximum levels it has reduced the stinging and pain in my feet so I can manage to sleep.
The COMPEX SP8.0 autosenses the condition of the muscles throughout the session so it controls the response within limits. The aim I am trying to achieve is to ensure the muscles do not atrophy due to lack of exercise and to allow the nerves to control the muscles for better control for balance and walking.
I have found that the settings for contraction and recovery show the difference for different muscle groups in my legs. My shins ( which control foot drop) have improved so I can now walkdown slopping footpaths. Normal muscles seem to have low recovery settings and moderate contraction settings. My calves are the problem with recovery signals twice that of the contraction signals and very high settings. So, I suspect this is an issue for me to concentrate on.
I was also on Trelahose IV trial but money ran out and it was ceased after 10 months. My symptoms were stable during the trial but I do not know if I was on a placebo. I have since moved to oral Trelahose sweetener to see if that helps.