Muscle growth will be classified as: Sarcoplasmic Hypertrophy and Nitro Mxs Reviews Hypertrophy, this result in a bigger 'puffy' muscle and a harder denser muscle, suppose off season bodybuilder (giant 'puffy') and Olympic gymnast (hard and dense) respectively. Nitro Mxs 2 types of muscle growth are targeted on totally different parts of the muscle thus resulting in a very totally different look.