It takes twice as long to lose new muscle if you stop working out than it did to gain it.
127
The average sperm cell swims at 8 inches per hour.
76
It takes about 20 seconds for a red blood cell to circle the whole body.
102
Enamel is hardest substance in the human body.
61
Our eyes are always the same size from birth, but our nose and ears never stop growing.
266
Your body is creating and killing about 2.4 million red blood cells per second.
17
An average heart beats 100,000 times a day, pumping some 2,000 gallons of blood through its chambers. Over a 70-year life span, that adds up to more than 2.5 billion heartbeats.
73