In healthy older adults, doing resistance exercises like weight lifting can lead to an increase in the number of small blood vessels surrounding muscle fibers, even if they have not previously done aerobic exercise.

If you've lifted weights before, it doesn't make a difference in how your muscles rebuild blood vessels during rest and recovery after not using them, compared to someone who hasn't trained before.

In older adults who are healthy, muscle growth from consistent strength training is not affected by how many blood vessels are already present in the muscle before training begins.

In healthy older adults around 71 years old, eight weeks of aerobic exercise increases the number of capillaries surrounding muscle fibers, with greater increases in type II fibers than type I. However, this change does not lead to greater muscle growth when followed by 12 weeks of strength training compared to strength training alone.

Even though the muscles got bigger after the exercise, the number of special repair cells and nuclei inside the muscle fibers didn’t go up — meaning the growth happened without these typical building mechanisms.

In healthy older adults, doing aerobic exercise before resistance training leads to a smaller increase in blood flow to the thigh muscle after lifting weights, which may reflect more efficient energy use by the muscle.