It is true that a healthy body is able to remove toxins in the bloodstream; however, an athlete who is regularly pushing his/her body to its physical limits will produce large quantities of waste products during workouts (ie: lactic acid), and it is difficult for the body to remove that waste before the next workout. This is particularly true in mature athletes with larger bodies and thicker muscle mass, because there is simply a greater distance for the blood/lymph to travel and more tissue to clean. If a swimmer is also strength training, microtears will be created along with the localized inflammation necessary to heal them. This localized inflammation and “toxin” buildup manifests as a trigger point/”knot”.
In addition, a mature athlete like Adrian or Coughlin, who is attempting to surpass genetic/biological limitations may find that the fascia surrounding their muscles limits their growth in certain areas (try filling a balloon with too much water and see what happens) or “wrinkles” develop in this fascia in areas that experience repeated localized inflammation. The tightness/wrinkles around muscle can inhibit cleansing blood flow to the affected area.
Trigger point treatment or myofascial release by a PT or LMT combined with stretching can improve recovery time (the time necessary to remove waste products) and reduce the effects of fascial limitations in problem areas. My understanding is that cupping is another technique to deal with these problems. The suction probably breaks blockages in blood flow like a flash flood improves the flow of water in a stream when leaves and sticks have clogged it. Plus, by pulling the fascia away from the muscle it must specifically stretch that tissue.
Quoted from a post from http://swimswam.com, User DanJohnRob