You can chalk biathlon’s toughness up to one thing: adrenaline management. It’s challenging because it demands stamina and precision. Athletes cross-country ski up to 12-plus miles, stopping intermittently to shoot targets. They use a rifle weighing almost eight pounds, which they carry throughout. It’s not only about speed and endurance, but also the ability to master breathing and slow down your heart rate in order to steady the gun. To try it, find a cross-country ski area with a biathlon shooting range, or go to one of America’s five official biathlon training centers. Biathlon, a staple of the winter Olympics for decades, just added mixed relays—teams of two men and two women—in a brand-new event debuting in Russia this February.