Four months of off-season for the MotoGP riders gave them plenty of time to put some thought into how they wanted to look for the first race of the 2016 season in Qatar.

A motorcycle helmet that filters out harmful emissions from the air is protecting riders in New Delhi and other Indian cities that rank among the most polluted in the world.

A boxer's helmet, for example, must protect against multiple blows, while a horseback rider's headgear has to protect against a single impact, such as a fall. Cyclists' helmets have to be designed ...