BEST FOR: Altitude training
WHEN TO GO: April through October
There’s a reason many of the sport’s pros, including Craig Alexander, Matt Reid, and Chrissie Wellington, head to Boulder every year to train. Make that three reasons. First, there’s the altitude. At 5,430 feet above sea level, the athletes who train long-term in Boulder experience the physiological benefits of living high, raising their red blood cell count and lactate threshold. But don’t fret if you don’t have the three to four weeks required to maximize those benefits. There’s always the number two reason to head for the Colorado foothills: outdoor space. More than 99,000 public acres means you’ll never want for a new trail to explore. Finally, there’s the highly concentrated, highly dedicated community of triathletes training at all times, so it’s easy to find a training partner who will push you to your limits—whether you want one or not.