Get the long rides in
In your first week, you’ll want to ride 1.5 to 2 hours, or about 20 miles, and build from there. If you’re already comfortable with a longer ride than Week 1 prescribes, start with 2.5 to 3 hours and follow the same guidelines for mileage building, topping off at about 85 miles.
Do your long rides at a steady, but not taxing, pace—about 70 to 75 percent of your maximum heart rate. Though most cyclists find that Saturdays or Sundays work best for their long rides, it doesn’t matter which day you choose as long as you get it done.
Nice and Steady
During these 100-mile training plan rides, aim for two to four longer efforts (15 to 30 minutes in length; 15 minutes easy pedaling in between) that increase your breathing and elevate your heart rate to around 80 to 85 percent of your MHR.
Ride at a pace, as if you’re pedaling with someone slightly faster than you. These rides will simulate your goal for your century and train your body to ride more briskly while maintaining comfort, so you can finish 100 miles comfortably.
Distance riders often skip speedwork because they think they need volume, not intensity, to go long. But riding fast improves your endurance by raising your lactate threshold, the point at which your muscles scream “Slow down!” When you raise this ceiling, you can ride faster and farther before your body hits the brakes.
Aim to do four to six very hard or max efforts ranging from 30 seconds to 2 minutes; in between, spin easy for twice the length of the interval. Do these on a challenging stretch of road, such as a hill or into a headwind, during the suggested ride lengths listed in the chart below.
Credit: Cycling Weekly