The true statements are:
Weight lifting does not increase the number of muscle fibers in a particular muscle exercised.
Blood capillary density will increase in slow-twitch fibers in response to training for a marathon.
Long-term resistance training will increase the number of myofibrils in a particular muscle exercised.
Why is this correct?
Weight lifting doesn't lead to the creation of new muscle fibers; instead, it prompts the growth and strengthening of existing fibers, known as hypertrophy.
Endurance training, like marathon preparation, stimulates the growth of new capillaries around slow-twitch muscle fibers. This increase in blood capillary density enhances oxygen delivery to these fibers, crucial for their endurance-based energy needs.
Long-term resistance training contributes to an increase in myofibrils within muscle fibers. These myofibrils are the contractile units responsible for muscle contractions, contributing significantly to muscle growth and enhanced strength.