To be honest, I have yet to find a quality mass gainer on the market. The problem with most mass gainers is that they are loaded with cheap sugars as a carb source. Not only can this lead to greater fat gain, it can make drinking them several times a day unhealthy.
Mechanical stress: physical condition which exists within any material because of strain or deformation by external forces or by non-uniform thermal expansion.
Stress: In a medical or biological context stress is a physical, mental, or emotional factor that causes bodily or mental tension. Stresses can be external (from the environment, psychological, or social situations) or internal (illness, or from a medical procedure). Stress can initiate the fight or flight response, a complex reaction of neurologic and endocrinologic systems. Catecholamine hormones, such as adrenaline or noradrenaline, facilitate immediate physical reactions associated with a preparation for violent muscular action.