The mitral valve is on the left side of the heart. It lets blood flow from the upper to the lower heart chamber. Mitral valve regurgitation is diagnosed when the mitral valve in the heart does not close well, which causes blood to leak back from the left ventricle into the left atrium. Mitral valve regurgitation forces the heart to work harder to pump extra blood out of the heart.
Measurement of a track. The proper length for a competitive running track is 400 m (1,312.3 ft). Some tracks are not built to this specification, instead some are legacy to imperial distances like 440 yd (402.3 m). Prior to rule changes in 1979, distances in Imperial units were still used in the United States.
100-Meter Specialists. As you might expect, there's a direct relationship between the length of a track event and the amount of aerobic running specialists in that event are advised to do. Therefore, 100-meter runners can get by on very little workaday distance running. UK Athletics coach Brian MacKenzie caps the distance such athletes should run at 3,000 meters -- about 1.88 miles -- and even then advises breaking this running into repeats of 200 meters or longer. He also suggests limiting this type of running mainly to the preseason conditioning period.