Athletic training produces somewhat more damage.
This stress causes many minor internal leaks in the circulatory system. Usually, there are no visible signs of this internal damage, although an extensive leakage may show up as a bruise. Platelets are responsible for sealing off these leaks so that the circulatory system can continue to function. Chang MC, Berkery D, Laychock SG, Schuel H. Reduction of the fertilizing capacity of sea urchin sperm by cannabinoids derived from marihuana. Epidemiological and policy issues in the measurement of the long term health effects of anabolic-androgenic steroids.