Why is the average life expectancy in Africa short and running fast?

Africa's average life expectancy is very short because, first, Africa's medical conditions are poor, only some of the larger cities have medical institutions. Second, the African people are generally very poor, sick only hard to carry on, can not carry on the downfall. Third, Africa has poor hygiene habits, drinking raw water, eating raw meat, and not bathing for a long time, so there are a lot of bacteria and viruses. In the final analysis, it is still poverty. This is what I see.

Africa's black people run fast reason:

Studies have shown that the black athletes of fast muscle fibers in the muscle ratio of up to eighty percent or more, white and yellow people only seventy percent. From the point of view of muscle mechanics analysis, fast muscle fibers are more, the muscle contraction of flexion and extension, and thus explosive force will be stronger. At the same time, muscle fibers are divided into two categories according to the different colors of red and white muscle, red muscle cells in the mitochondria more and supply more energy, so have red muscle or red muscle-based people belong to the explosive players. White muscle cells provide energy evenly and consistently, so people with white muscles or predominantly white muscles have more endurance. Black athletes have predominantly red muscles, making them better suited for sprinting events.

In addition, black runners have hard bones that can withstand greater impacts and have long, slender limbs, narrow hips and less fat, which make them superior to other races in body stretching, coordination and flexion. Bolt's body type can well reflect these characteristics: long limbs, strength, high-speed endurance is good.