Researchers took a detailed look at 17 years of training records for Norway's Marit Bjørgen.
The goals of a major push for football helmet safety should bring improvements, but the overall results remain unpredictable.
The vast majority of traumatic brain injuries are concussions. Researchers talk about the problem of these head injuries in sports.
Anything that has mass and moves can give off gravitational waves, but for familiar items they are extremely tiny.
The Coriolis effect has a small but measurable effect on the path of balls and athletes during sporting events.
The numbers suggest that teams tend to both punt and kick field goals too often.