Why does this strength training regime lead to a plateau

Question

I work out at a Kieser Gym, a large franchise in the DACH region with a focus on machine training for health. The standard protocol for almost all exercises is:

• train full range of motion on the specific machine
• do 2s hold - 4s contract - 2s hold - 4s extend reps without dropping the weight
• repeat until failure
• if the time under load is approx. two minutes, add 5% or so the weight next time

On my first day there, they said something along the line: For each muscle (group) there's a certain weight that's your plateu, we advise to work out twice a week until you reached this point, then maintain that level of strength by working out about once a week. Or something similar, it's been a while.

I don't doubt that the plateau thing is basically correct (It seems to hold true for me with certain exercises, more importantly the Kieser guys can look at their clients training data and see if their thesis is wrong), I just don't understand why: In my naive understanding training to failure and adding weight should be a clear signal to the body to induce some form of strength building. Why is this not the case here?

Answer 1

The most notable aspect of the Kieser method, especially in the context of plateauing strength, is that it uses High Intensity Training (HIT), in which a single set, taken to failure, is performed per exercise. I don't have any examples of their programs but from what I understand they usually involve a prescribed list of exercises (based on the different machines available at Keiser gyms) to be completed over two workout sessions per week. This would mean that only one set is performed per week for each exercise.

That is an extremely low volume of training, and would be very likely to lead to relatively early plateaus in progress.

It's generally accepted that as trainees develop more and more muscle, greater training volumes are necessary to make continued progress. Using the definitions developed by Ralston et al 2017, 1-5 sets per exercise per week is low volume, 6-9 sets is medium volume, and 10+ sets is high volume. Anecdotally, "high volume" tends to have an upper limit of 20-25 sets per week. So you can see that the Kieser Method, with its one set per exercise per week, is on the extreme low end of low volume. The fact that they advocate taking this one set to failure would likely make up somewhat for this, but it's still extremely low volume.

It's very likely that when training under this method, you would plateau quite quickly, and if training volume (as opposed to say, nutrition) is indeed the cause of this plateau, then in order to continue making progress you would need to either train more frequently (increasing to three, then four days per week), or perform more sets per training session.

If there's a desire to keep at least vaguely within the style of Kieser, my preference would be to choose heavier weights and halve the time spent on each exercise, i.e. increasing the weight when you can lift for more than 60 seconds, instead of more than 120 seconds. Then you could perform all exercises in the program in a single session instead of two, and repeat that twice per week for double the weekly volume. However it's quite possible (likely, even) that Kieser staff would object to this and tell you to only lift according to their particular scheme.