Final answer:
Lifting heavy weights leads to muscle adaptation known as hypertrophy, which is the increase in muscle mass due to added structural proteins. Atrophy is the loss of muscle mass from decreased activity or use. Effective strength training requires increasing the intensity to promote muscle growth.
Step-by-step explanation:
Lifting heavy weights stresses muscles over time causing an adaptation called hypertrophy. This process involves an increase in muscle mass due to the addition of structural proteins to the muscle fibers, thereby increasing their diameter. Effective strength training requires that the intensity of the exercises be progressively increased to continue challenging the muscles, leading to further hypertrophy. If the weight lifted does not become heavier over time, the muscle size will not increase substantially. The muscle must adapt to the heavier load, and an even heavier load must be utilized for greater muscle mass development.
Conversely, the loss of muscle mass due to the breakdown of structural proteins is known as atrophy. This occurs when there is a lack of use or physical activity, which can happen during prolonged immobilization, malnutrition, or in certain diseases. In contrast, the term myoadaptive response is not commonly used in this context, and kinetic thickening is not an adaptation related to muscle stress from weight lifting.