On average, men are faster runners than women. This is because testosterone stimulates muscle mass development and increases the concentration of red blood cells and hemoglobin.
Running is a sport that both men and women enjoy, whether they're racing in a 5K or a marathon, or competing for a team or their country while speeding around a track. But no matter the venue, it's pretty common to see men clock faster times than women do.
Given that both men and women train equally hard, why is it that men, on average, are faster runners than women? Even the world's fastest man is about a second speedier on the 100-meter dash than the world's fastest woman: Usain Bolt did it in 9.58 seconds, versus the late Florence Griffith Joyner's time of 10.49 seconds.
The answer to this gender bender is multifold, but it has a lot to do with hormones and body size.
Before girls and boys hit puberty, their bodies are fairly similar. During puberty, however, boys experience a surge of testosterone. By adulthood, some men have up to 20 times more testosterone than women do, according to HealthLine.
Testosterone plays several roles, including telling the body to create new blood cells, keeping bones and muscles strong, and prompting growth spurts, according to the Society of Endocrinology.
"Because [women] produce less testosterone, we are at a disadvantage in terms of muscle," said Dr. Emily Kraus, a primary care sports medicine physician at Stanford Health Care in California. "Males have a greater amount of muscle bulk."