T Nation

Impulse-Inertia Machines

Christian, I have been interested for some time in impulse-inertia machines ever since I read about such training in Fred Hatfield’s “Power: A Scientific Approach.” I have also read about such training (with the use of fly-wheels) in Dr. Zatsiorsky’s and Dr. Siff’s respective books. I am aware that Coach Jay Schroeder also uses impulse-inertia machines as part of his evo-sport training. I have only seen one commerically available training gizmo that looked like it used flywheels was the infomercial I saw for some device using Jackie Chan as the spokesperson. I am curious whether you have either trained with impulse-inertia devices and what your experiences (or that of your athletes) have been with improving rate of force development with such training. I am also curious whether you know of any schematics for building a flywheel for training since the odds of finding such a device in a commerical gym are negligable at best (and I have an aversion to any fitness product sold on TV). I am also curious how impulse-intertia training differs in training effect from other forms of high-speed force development training like true plyometric training. Thank you in advance.

I must say that I have not used these machines. There’s a lot on my “to buy” list including the impulse-inertial machine from Impulse Power (3200$) and a NEMES vibration training machine (7800$). But I should get these soon and will probably keep everybody posted on their level of effectiveness.

BTW, you can learn more about impulse inertial machines at:




Thank you for the information Christian. I have actually come across that site before and read it with great interest. Have you or your athletes ever performed any form of flywheel training, whether on a the impulse-inertia machine or not? Also, I am not clear what the benfits to be derived from impusle-inertia training effects are above and beyond what one might expect to receive from shock training. On a side note, since Coach Schroeder’s evo-sport training was mentioned on another thread, Coach schroeder makes use of both the Impulse-Intertia machine and vibration training. I have read that when properly used, EMS can improve maximal strength and rate of force development as well as being used as a form of active recovery. I am also aware that he makes use of EMS, both during the weight training and as a stand-along method of training. I am curious whether you use (or have used) EMS as part of your training or that of your athletes.

Yes, I have used EMS in my own training and my athletes. I used it in only two ways:

  1. Stand alone method (10 contractions of 10 secs. maximal isometric contraction along with max tolerable EMS). Mostly on the quads and hamstrings.

  2. As a potentiator: using a short bout of maximal EMS stimulation 90 seconds before a regular lifting set.

Hey Christian, first off, thanks for all the great articles. On a different thread, I posed the question as to how Archuleta increased is squat so much, do you know? I know the glute ham raises are a big part, but what exercise is akin to the plyometric bench press that we have seen? Thanks.

The squat improvement is likely to come from the same methods as the bench improvement. So:

  1. Heavy loading and high volume of explosive squats

  2. Jump lunges (scissor jumps)

  3. Height landing (droping from a good height and sticking the landing, holding it for 30 seconds)

  4. Glute-ham raises

  5. Vibration training

  6. EMS training

My question to you is why waste your money? If you want to increase rate of force development there is no comparison to Olympic lifts and plyos, plain and simple. Most of these machines are crap and do not accomodate ones strength curve.

hello christian, im interested in know what ems training really is and if you can give me some examples of exercises involving this training tactic, thank you.

EMS means Electromyostimulation. It a machine that sends electricial signals to the muscles making them contract. Kinda like the gizmos they sell on TV (Ab Belt). The cheap versions are not powerful enough to stimulate a maximal contraction and are basically a wate of time and money. But a powerful sports model can be quite effective if the athlete can endure pain.

Geo, T-mag has an entire article on EMS machines written by Charlie Francis. I think it’s called “The Truth About EMS”. Do a search at the main site.

Thanks Christian but I have one more question. On the Evo Sport website, they provide a workout where you do the drops from various heights and hold the position (they also do this for pushups). Should these be done with bodyweight? The reason I ask is because the website says they use a Safety Squat Bar. This leads to another question, if you don’t have the Safety Squat Bar, how do you use weight? Thanks again.

Does anyone know what A.R.P. is? I know it is used for to accelerate recovery and stretch the muscles, but I can’t find any more info about it.


FYI, I asked a question of the Supertraining group regarding impulse-inertia training and Dr. Siff responded. Note that Dr. Siff’s response is in brackets within the text of my question:

I have read through the archives on this subject as well as reading the discussion of such training in Dr. Hatfield’s, Dr. Siff’s and Dr. Zatsiorsky’s respective books. However, I am still a bit confused.

As I understand it, impulse training, either with the use of a flywheel as depicted in Dr. Siff’s and Dr. Zatsiorsky’s respective books, or through use of an expensive low friction machine as described in Dr. Hatfield’s book . . . use high acceleration of low weight as the means by which to produce a high force. In this sense, it seems to me that flywheels and impulse-inertia machines are similar to more well-known (at least to me) shock methods of training. I am curious whether there is some training effect that flywheel/impulse training provides that is not provided by plyometrics. In short, how do plyometrics and impulse training differ in terms of the training effect or is impulse training just another variation on the same theme as more traditional plyometric training?

[The terms “shock training”, “plyometrics”, “stretch-shortening training”, “impulsive training” and “rebound training” are often used to describe much
the same phenomenon. No special apparatus is necessary for any form of impulsive or shock training. Inertial training with a heavy flywheel is not impulsive training, since the action involved is too slow to permit the
storage and utilisation of elastic energy or to enhance neural activation. Mel Siff]

Also, most of us, myself included, do not have access to expensive impulse-inertia machines . . . since commercial gyms certainly would not think of buying such machines. I assume that flywheels will provide an identical training effect, but I am wondering whether there are any commercially available flywheel training devices for home use? The only such device I have ever noticed was a fitness toy sold on an infomercial using martial artist/actor Jackie Chan as its spokesperson. I am normally averse to fitness toys sold on television, but that does not necessarily mean that I should discount the potential usefulness of such a device. Perhaps someone here has used this device and can comment on whether it is useful. If not, does anyone have any schematics to have an impulse machine built?

[It would take me far too long here to illustrate simple exercises and devices that you can use to provide all of that type of training at very low cost, so all I can suggest is that you attend one of our Supertraining Camps one day to learn firsthand about them. Anyway, don’t think of these
devices as offering some special “secret” way to become stronger - it is just one of many different methods which works well if integrated intelligently into an overall conditioning program. Mel Siff]