Don't post a lot any more, though I probably should.
Got on the Marc Pro bandwagon early on. For my 2017 it did as described, flushed soreness, quicker to recover, and was vital to arm care protocol throughout HS, and summer seasons. Definitely worthwhile, in my opinion. Also, while I have not reviewed the other units that are more affordable, mentioned in this thread, my understanding is that Marc Pro uses an electrical wave different from most other units to promote the recovery and healing. Marketing, or true?...who knows, just know our experience with it, and from what I have heard from others.
Having said the above, a cautionary tale: The newer philosophies, training methods (Motus Sleeve), and recovery protocols (Marc Pro) are great, and we are learning more and more every day. They provide added insurance, however it is only "insurance". I would say that I have spent quite a bit of my life in baseball / learning about baseball, and try to keep up with the technology which of the last 10 years has accelerated more than any time in the past.
My lefty son recently underwent TJ surgery late this summer. He is currently living full-time in Seattle training at Driveline Baseball with some of the most progressive minds in baseball, as it relates to training pitchers, and rehab protocols. Nobody could point to any misstep along the way, that would have predicted a near entire rupture of the UCL...in fact his surgeon indicated he likely unknowingly pitched with it torn for over a year. I have my "ideas" of how it happened, mainly high stress innings during 3 consecutive years of Texas HS championship runs.
The surgeon who performed his surgery pretty much echoed most of the medical field, that predicting, and / or preventing injuries is difficult at best. On the day of his surgery, we sat across from a man that struck up a conversation with us, turned out his is an agent for two current pitchers that will likely be in the HOF....he was there because his son (who pitched this past summer for the winning Florida Gators) was having TJ by the same surgeon right after my son. He indicated the same thing, his son was always following the latest & greatest training, and recovery programs...never complained before it happened, and had no obvious mechanical flaws that "should" have caused this.
Yes, Marco Pro is great IMO, but you will find pitchers who throw until their 40's who never took a pitching lesson, or even iced, much less Marc Pro, and you will find pitchers (similar to son) who had TJ at an early age.