"Muscle exhaustion" means that your muscles have become extremely tired and can no longer continue to work or perform physical activities effectively. Full definition
More muscle exhaustion equals a greater response from your body to rebuild your muscles from the micro damage that occurred during exercise. (muscleandbrawn.com)
Using proper exercise performance to increase muscular contraction in your exercises activates more muscle fibers than normally possible, leading to far more muscle exhaustion. (muscleandbrawn.com)
However, if total volume is an important aspect of your current training regime, make sure to use longer rest periods because they have a better ability to help you achieve your target volume, while short rest periods will lead to a much faster muscle exhaustion. (fitnessandpower.com)