What is this thing?
The Isokinator is a personal resistance training device developed by Koelbel, a german company which has been innovating in this space for decades.
It operates with a small spring mechanism and nylon handles. Exercises (a mixture of variants of traditional isotonic movement patterns, and other, more obscure patterns that seem best described as ‘rotating isometrics’) are performed by pulling the handles apart under tension whilst moving the device.
How did I find this?
COVID threw me down a rabbit hole, researching various at-home resistance training solutions. I eventually stumbled upon this.
The novelty factor and compactness of the device are what drew me in. I also saw it as an excuse to learn more about human biomechanics/anatomy and view these matters from an engineer’s perspective.
Remark on the company and ethos
I generally quite like Koelbel’s history of experimentation and unusual (some may say, eccentric, even) product designs. It’s refreshing to see people pushing boundaries in such a stagnant and closed space. Innovation in human health is important! And resistance training is indispensable for that. I love the premise of the isokinator. On paper, it’s exactly what I’d want.
The isokinator promises a lot:
Full-body resistance training (for all but the strongest humans)
Extreme compactness (mass approx. 500g, dimensions approx. 18cm by 8cm x 1.19cm)
Safety. It is based on a combination of self-resistance and unorthodox movement patterns. It seems like it would be far more foolproof than free weights.
There are some more grandiose claims:
superiority to traditional training. Allegedly because the force is ‘always’ perpendicular to the levers your body creates? Koelbel compares the traditional bicep curl to the isokinator. However this seems like a one-off example.
A replacement for a complete gym (think a big-box gym with a dumbbell rack, power racks, benches, and a host of machines). This seems like a REALLY bold claim…
I have been using the isokinator on and off for around 2 years now. I have compared it to traditional resistance machines and free weights, as well as overcoming isometrics.
How did it stack up?
(Personal) Pros:
The build quality is excellent. We cannot fault Koelbel for that.
The device is tiny. Compare to say, lifting an 80+ lb dumbbell. It opens up all manner of training opportunities: in apartments, outdoors. This would be unthinkable with free weights or machines.
Resistance adjustments are a cinch. Just adjust some sliders in a moment and you’re done. Compare to swapping dumbbells or plates. It’s even marginally better than selectorized machines.
The device is definitely capable of creating a ‘burn’ sensation and activating muscles in certain exercises.
Many upper body exercises take advantage of the body’s lever mechanics to apply large forces to muscles with minimal external load on the body (force reading on the scale). This is fairly clever and should further enhance safety.
(Personal) Cons:
Comfort: the nylon straps really begin to dig in and hurt at higher resistances. I began to notice this most during the following exercises:
M2A (Chest circles). For some reason, I was able to get to a pretty high figure (approx 80kg) on this one, and the straps were quite painful against the outer ridge of my hands
M6A (Split squat imitation). This is the exercise with the highest resistance. I was up to 120kg, which, even factoring a discount to 0.7*120=84kg, is still a huge figure. My hands were killing me. I needed to wear extra socks to tolerate it on my feet.
Measurement. Resistance training is a game of diminishing returns. You eventually need to be able to split hairs to make progress. The isokinator has a couple of issues here:
Scale non-linearity, especially at lower resistance values. This makes progress tracking on certain high-leverage exercises (Where one’s arms are fully extended) like the M4 and M5 series very difficult. It seems like you’re constantly stagnant. It seems that measurements in the sub 25kg range can be really confusing. How can a max force output of 0.7*5kg be equal to 0.7*10kg be equal to 0.7*15kg? It isn’t. Something is off there.
The visual feedback with the ‘ball over hole’ approach is problematic. You just can’t see them throughout most exercises. Turning your neck around whilst exercising seems unsustainable (not to mention a little goofy).
Some questionable exercises:
Exercises where resistance is applied in a different direction than the direction of motion (what I would call ‘rotational isometrics’). E.g. M6B, M5D. I’ve had a poor experience with isometrics for fat-loss and hypertrophy (great for general strength though), so this gives me pause.
Exercises with very complex and confusing dynamics. I am especially unsure about M6A, which applies a huge amount of force through one shoulder (without equal force in the other). I think perhaps the erector spinae are doing a mini iso-deadlift to pull the isokinator spring? Anyhow it’s unclear just how much of that isokinator spring tension is actually making its way to your hips, to force your opposite leg to work.
Exercises which don’t seem to activate the target muscle at all: M5A, for instance. The instructions suggest only one’s spine is meant to move? How is this supposed to active my lats?
The exercises are unique and unconventional. Many people will struggle to wrap their heads around them (myself included).
Many exercises are unilateral. This arguably better isolates the muscles but also doubles exercise time. Are you feeling up for calf-raising your legs individually? I’m not.
Only a couple of compound exercises like M6A. The rest are all isolation movements.
Self-resistance is just … tricky at times. I find (purely subjectively) that it requires way more intent and focus to get a similar force out of a self-resistance exercise than with a live load. Perhaps I am psyching myself out after I read about cortical inhibition with overcoming isometrics? TBD, but the perception is very real.
Specificity is a thing. Most of these exercises are unique to this class of device (including the Bullworker Iso-Bow). They may have a ‘cool’/’alien’ factor to them, but they will definitely not transfer as well to performance on traditional exercises. This constrains the audience for this device, just a bit - more for general health and body composition work.
Conclusion
My feelings are quite mixed. I love the idea of this product and really wanted it to be a complete success. A product like this could be revolutionary and greatly improve human health. Compared to many forms of exercise, resistance training suffers from a moat in the form of expensive, problematic training equipment (free weights and machines). The isokinator’s main flaw at this point is force measurement. The comfort issues are solvable with a little thought and/or adjustments (gloves, pads, etc).
The efficacy of the exercises is somewhat contentious. I’ve no doubt the ones that mimic isotonics work. I can definitely feel eccentric action on say, M1A. The ‘rotational isometrics’ will probably build strength, too, but may not burn as much energy as comparable isotonics.
There is also the cost, which is a deterrent for many. If you are curious about this device, try out the Bullworker Iso-Bow first before committing to the Isokinator. Or, better yet, grab a bathroom towel and try out some of the upper-body exercises.You’ll get a sense of whether the exercises are to your liking.
Anyhow, I hope these devices become more popular. We could all benefit from stronger bones, muscles, organs, and higher metabolic rates.
P.S.
Take a look at this video. No comments.