I smiled when I read markh501’s recollection of the old Duo Squat / Leg Press and “fun” with the infimetric / akinetic bar. I’ve tried to incorporate infimetric training in some of my movements recently and invested in one of these to do it:
Pretty expensive for what it is - but seems to replicate the infimetric movement quite nicely, especially on Chest Press, Rows and Bicep Curls.
Anyone want to know more about what infimetric training is?
Guys, Jeff60 is one of my best-ever trainees. He can supply great answers and guidelines related to infimetrics.
I would caution trainees to not abandon (or supplement) exercises withOUT actual weight. Resistance Exercise must resist weight … not immovable stops. True and Effective inroad must have a constant backloading affect that removes any inclination to stop/hold/pause a hold or motion. A resistive WEIGHT will always keep the muscle active. Unless, of course, one is moving too fast! This means NO Bullworkers, NO Apollo (remember those), NO Hydraulics, NO Pneumatics, NO Motors, NO Bands, NO Pressure Plates, NO Vibrating Rods, NO Springs, NO Bows, etcetera. Additionally there is a Central Nervous System feedback from a weight that involves spatial orientation (implies our head should be above our center mass). This CNS feedback loop has yet to be adequately explained (to my knowledge), but the experience shows it is an issue. I am looking forward to Dr. Darden’s “Backloading” Book as I suspect it will address a major factor of ASSURING A MUSCLE is LOADED throughout an exercise motion/hold. When we use an Exercise Device we must be Resisting Weights from Falling. In my opinion a static or an ultra slow negative is the only way to assure this. Once trainees start moving a weight in a positive direction it is far too easy to unload a muscle, unless to motion is ultra ultra ultra slow.
Much appreciation to Dr. Darden and his progression of the (HIS) science.
Looking forward to hearing of your experiences Jeff.
I’ve been looking into making a homemade device to add on to my (home gym) lat machine for infimetric cable curls and tricep pressdowns.
I’ve would like to learn a lot more about it!
Infimetric training is where you use your own body to provide resistance to your muscles without the need for weights. In an infimetric curl I use the type of “straps” I found to curl one arm up as the other straightens. This means one arm is doing the positive work as the other does the negative. The BIG advantages are: 1. You don’t need weights and 2. You can provide literally ANY AMOUNT of resistance. If it’s too easy - apply more load. Too hard - apply less.
I typically do an infimetric movement at the end of a 30-10-30 set so I would do the set, pick up my “straps” and move infimetrically for about an additional 30 seconds.
A lot of the old Nautilus machines had a bar that you had to keep in place as you worked like this. One - the Rotary Neck - had two handles which you used to apply resistance against each other.
Try it! 
I’ve added a picture from the Bullworker ad to show the curl in action
I could be wrong but from what I remember some Nautilus machines has a bar you could pivot into place at the end of the concentric part of a curl and then you’d push against that for a few seconds and then descend your rep. Is this form of exercise also called infimetric? I’m not clear about this infimetric stuff?
Scott
Yes. You’ve got it! - It’s the same thing except with a strap rather than a bar fixed to a machine
So the strap just slides over the metal turnbuckle, no pulley? I’m surprised that friction doesn’t mess up the feel of the movement, at least to some extent.
As far at the resistance level is concerned, isn’t it a bit like an isometric: the amount of force you can apply is limited by the amount of force you can generate with the muscles being used?
So the infimetric part of the exercise is when you momentarily push or pull against a immovable object or strap or whatever? Like isometrics?
Scott
Friction - Yes. There is a small amount of friction
Isometric - Almost. The difference between isometric and infimetric is that isometric is a static application
So if I remember correctly this guy named Chuck made these machines where one arm was opposing the other. One went up while one went down . Each arm was opposing the other. No weight stack, just tension from each arm in the opposite direction. Is that infimetric ?
Scott
So if I understand this correctly;
You are using your body generated resistance while exercising muscle groups. Is that about right?
That kind of sounds like what I had to do in physical therapy. I take it that this is good basic muscle maintenance, how is it on bone health?
We should recall that the basic concept of “set extenders” has been determined to not work or contribute to strength increases. This was studied and applied in detail by Dr. McGuff when he was attempting to break the inherent stagnation coming from proper application of the (then) Super Slow protocol. His paraphrased words were … “no noticeable or measurable benefit” ,
I summarize the failure of “set extenders” to be related to attempting to get more out of an exercise than is required. There was that craze in the 90’s (pre SuperSlow) to “get one more rep !” aka “C’mon you can do it !”
Yes - that’s infimetric
Sorry - not familiar with how this would affect bone density
That’s ok if you don’t know about the bone density thing. I thought I would ask just in case you did.
This system though is it mostly for muscle maintenance, or am I’m not seeing something?
They’re just another form of inroad. Probably one of the safest. Properly performed they will stimulate muscle growth provided there is sufficient intensity of effort. Actual growth from performing infimetric exercise is dependant upon several additional factors - i.e. rest, nutrition and hydration (and that would be another post entirely). 
I think your mean Charles Spencer. He posted an informative tutorial video on YouTube some years ago. It is still up:
What evidence is there to support muscle growth from infimetric training? It just sounds like another gimmick to be honest, just like the Bullworker was!