Final answer:
Muscle ability to lift or support weight is related to hypertrophy or atrophy, which depends on muscle use and resistance training. Increased resistance leads to more muscle fibers contracting, increasing muscle size and strength;
Step-by-step explanation:
When addressing the question of what happens to the ability of the muscle to lift or support a weight, it's important to understand that muscles can either hypertrophy (grow larger) or atrophy (grow smaller), depending on their use. For effective strength training, the intensity, meaning the weight of the load, needs to be progressively increased. This is because muscle strength and the ability to support a heavier load are directly related to the number of myofibrils and sarcomeres in each fiber. When a muscle consistently lifts heavier weights, it adapts by hypertrophying. On the other hand, if the muscle usage decreases, or there is a lack of sufficient resistance, the muscle can experience atrophy, losing muscle mass and strength.
A muscle fiber contracts fully when all of its sarcomeres shorten, but if fewer fibers are engaged, the strength of the contraction is less. Therefore, for a muscle to support or lift a heavier weight, more fibers need to contract at the same time. Over time, with increased frequency of action potentials and greater resistance, these fibers adapt to handle more substantial loads by increasing in strength and size.