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.
But not all lanes are created equal, so knowing how to calculate the distance around a track by lane is helpful. For example, if you run in the outside lane of a standard 400-meter track, you add over 53 meters to the distance of each lap, or about 13 percent. Step 1. Find out the length of the running track. Most outdoor tracks are 400 meters around the innermost lane. However, some tracks are different lengths. Indoor tracks may be one-tenth of a mile or even less. If you aren't sure, ask the facility staff for information about the length of the track.