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?