If you're just starting to get fit, different types of workouts like steady jogging, intense intervals, and all-out sprints all help grow similar numbers of tiny blood vessels per muscle fiber. But...

Lifting weights for three months increases the number of tiny blood vessels in arm muscles of young men, and the growth keeps up with how much the muscle fibers get bigger.

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.

If young adults stop using a limb for two weeks and then do eight weeks of strength training, their muscle fibers get bigger and gain more blood supply.

If you're new to strength training, having more tiny blood vessels around your fast-twitch muscle fibers might help those muscles grow more when you start working out.

When people who aren't very fit start exercising, their muscles grow new blood vessels quickly in the first month, but after that, even if they keep working out, they don’t get many more new blood vessels.