I have mixed feelings about the machine.
On the one hand, you can make this motion similar to a punching motion. To a certain extent, being able to mimic a motion you want to do in real life is useful.
On the other hand, this is what is called a "closed chain" exercise. It's similar to deciding that you want to do a bench on a Universal or Nautilus machine rather than using free weights. The only added benefit you get from this device is that you ideally require that you keep a firm torso.
Here's the problem with a closed chain exercise.
an old shoulder injury
Closed chain pushing exercises - whether they be in a machine or doing pushups on the floor - primarily work the larger muscle groups. Those would be the pecs, the triceps, and to some extent the anterior deltoids. Some work is done on the forearms and maybe even fingers if you do Uechi things with your hands (knuckle pushups, Uechi "triad" knuckle exercise, etc.).
The problem however if you do this as your primary pushing exercise is that your large muscle groups get out of balance with your stabilizers. Real-world motions require that you work muscles you aren't aware of (such as the rotator cuff muscle groups) until you actually hurt them. I had a talk with a physical therapist one time about each and every little muscle in the shoulder, and what it does. In so many words, she said "Are you kidding?" All these smaller muscles work in myriad ways to keep that arm in line and the shoulder where it should be when you're punching in free air, get your arm blocked when you are punching, get your shoulder wrenched when you are doing grappling, get your shoulder traumatized when you're meeting the floor in a break fall or roll, etc., etc.
Closed chain exercises also do not teach you coordination useful in a sport or activity.
Closed chain exercises also limit the number of muscles being challenged. The greater anabolic (growth) benefit (release of testosterone, GH, etc.) comes from challenging as many muscles as possible in the same exercise.
And let's not forget that exercises which challenge
you to keep joints stable and in line can also strengthen ligaments - over the long run.
Modern trainers tell you the following:
1) You should start your strength training with open-chain, multiple muscle group exercises. That would be things like a bench press with a bar, or (even more challenging) dumbbells. It would also include squats which work on both balance and strength. And when you are an advanced athlete, you work on things like power cleans, clean-and-jerks, etc. And you go from doing barbells to dumbbells.
2) The machines come second. The machines are there to get at muscles that need extra work (like my damn calves
). They are there to work on muscles that otherwise can't be worked on with free weights such as lats or hamstrings.
Another approach to it all is to go with the circular strength training methods, or the kettle bells. What appears to be "old school" can actually be a fantastic addition to your routine - IF you know what you are doing.
I have no problem with someone who wants to spend a few minutes a day looking a little more fit by having a few machines and devices around the house. A little exercise is better than none at all.
I also have no problem with someone who wants to shock their body a bit now and then by adding one of these exercises in to an otherwise balanced routine.
But closed-chain exercises should NOT be the core exercises for a serious athlete. Otherwise you are a shoulder or back or wrist or knee or hip injury waiting to happen on the playing field or in the dojo.
Furthermore... If you aren't doing advanced exercises which use core muscles (such as the power exercises mentioned above), then you will forever be stuck in the Uechi Robot mode. Your Sanchin will always look like you have a rod stuck up your arse. You'll never "get" the elasticity that needs to be added to advanced kata such as Sanseiryu. You won't be blending your kata movements into natural, whole-body "flinch" moves that your reptilian brain already knows how to do. And you will never learn to tap into that bone-crushing power that some of our advanced Uechi practitioners seem to pull from nowhere.
My 2 cents - and some change.