Metabolic stress is a physiological process that occurs during exercise in response to low energy that leads to metabolite accumulation, such as lactate, phosphate inorganic (Pi), and ions of hydrogen. It is a critical mechanism to achieve an adaptation of hypertrophy, or skeletal muscle enlargement. During resistance training, metabolic stress is created by repeatedly constricting veins through working the muscles, which leads to the accumulation of metabolites. This process is different from mechanical stress, which is the mechanism of converting mechanical energy into chemical signals.

Metabolic stress is one of the primary mechanisms that makes resistance training increase muscle mass, mainly due to the rise of anabolic hormonal release, hypoxia, ROS production, cell swelling, and muscle adaptations. Changes in acute exercise routines, such as intensity, volume, and rest between sets, are determinants for the magnitude of metabolic stress. Different types of training, such as low-intensity resistance training plus blood flow restriction and high-intensity interval training, could be used to maximize metabolic stress during exercise.

In summary, metabolic stress is a physiological process that occurs during exercise in response to low energy that leads to metabolite accumulation. It is a critical mechanism to achieve an adaptation of hypertrophy, or skeletal muscle enlargement, and is created by repeatedly constricting veins through working the muscles, which leads to the accumulation of metabolites.