Conversely, concentric contractions produce the greatest metabolic stress inside the muscle since muscles rely on anaerobic glycolysis for ATP production, which results in the subsequent buildup of metabolites such as lactate, hydrogen ions, inorganic phosphate, creatine, and others.
So the more mechanical tension we can get during the concentric phase, the more robust the metabolic stress response will be.
With weights, the only time the weight you’re using is a perfect match to your ability to concentrically produce force is when you’re at total muscle failure. That is when you’ve lifted and lowered the weight enough times that you’re unable to complete another repetition.
The problem is, you were underloaded for each rep it took you to get to that point.
ARX’s Adaptive Resistance™ allows you to exert maximally during every concentric, without limitation. This means that metabolic stress is maximized in the process.
But regardless of the tool you’re using, metabolic stress should be a priority of your training for mass.