stevekatalyst

Thanks so much… much appreciated 

Caution - I'm not a doctor so you're getting first hand but non medical advice.  If you are concerned about injury I'd highly recommend that you consult your physician before beginning any sort of workout program.
I've been doing overspeed training of some sort for the past 4 plus years.  I'm currently 65 which means I'm significantly older than you.  I played baseball until my junior year of college.  Mono took me out at that point - I try to work/go to school through it for too long and my spleen became enlarged - Dr. said no contact sports for a year (I was a catcher - hard to avoid contact.)  I switched over to golf at that point and have really never looked back (I played some softball after college but my baseball skill set, strong arm, a few feet of lateral quickness, didn't translate and frankly I found it boring.)
 
I certainly have had injuries, sprained ankles galore, tired arm, back, etc., but nothing that required surgery.  My body hurts like any 65 year old's might.  Overall I'm in pretty good shape and I'm competitive.  If you put a club in my hand and a speed monitor in front of it, I'm going to try and make every swing a personal best.  
 
I gained back and have retained 10 mph's of clubhead speed from using the SuperSpeed sticks.  But those workouts were very hard on my body.  I never injured myself but I was often sore all over the day after especially when I did the kneeling swings.  It's a great program but I really think it needs to be adapted based upon a users age and physical capabilities.
 
The stack does that or at least it claims to - I'm still early on in it so am very anxious to see what program it recommends next and how all of that unfolds.  My goal is to try and pick up another 5 mph.  I'm at 93-96 with the driver now - that would get me back over 100.  My average drive is 224 so another 5 should bring 10 to 12 yards more than enough distance to get back to lower single digits on the tees that I play from in club events.  
 
I would add that it is extremely important to warm up prior to over speed training. 
 
I hope this answer helps some - good luck and let us know what you decide.