Adding muscle mass (hypertrophy) enhances capillary development, but I doubt it enchances capillary density. The 2 are not the same. While a hypertrophy workout gives muscular endurance I have not seen any research indicating that it enchances aerobic metabolism which requires an extremely high volume (time 45-90 minutes 3-5d/wk) at extremely low intensities 40-60% and that leads to increased capillary density and increased aerobic metabolism enzyme level elevations, because maintaining that intensity consistenly in the weight room is not possible for a duration for any type of track and field athlete. Bodybuilders on the other hand may see increased cappilary density, because they may spend 3-4 hours in the weight room, but I have not seen the research.
