Anavar is a derivative of DHT (Dihydrotestosterone) which causes it to be highly Anabolic and only mildly Androgenic, this means Anavar is good for building strength but not muscle mass, it also means Anavar is low in side effects. Steroids that are highly Androgenic such as Dianabol or Testosterone cause more side effects. This is an advantage for athletes such as powerlifters or sprinters who are looking to increase their performance without weight gain. A powerlifter who lifts in a certain weight category would want to get as strong as possible without moving up a weight class for obvious reasons.
The Oxandrolone hormone does not carry any estrogenic related side effects. It does not aromatize and cannot lead to gynecomastia or water retention due to increases in estrogen levels. It further carries no progestin related activity, which again supports no estrogenic related side effects. Due to water retention being impossible with this steroid, this will decrease the risk of high blood pressure. Excess water retention can promote high blood pressure. Some steroids that do not aromatize can lead to high blood pressure, such as Trenbolone , but Anavar is rarely associated with this trait.