https://physoc.onlinelibrary.wiley.com/doi/10.1113/JP279866
When we perform a stretch we not only stretch the muscles but also all the tissues in the area, including the blood vessels. This study looked at the effect of stretching the quadriceps and the calves on the function of nearby and distant arteries. They found that doing a 12 week stretching program improved both the blood vessels in the local area (leg and calves) and also systemic blood vessels (aorta and arm). Furthermore, they found that stretching just one leg rather than both improved overall blood vessel quality as well.
