Which aspect of your training you want to work on will determine the length and intensity of the interval. In general, a good block of interval training can be done in an hour or less. This can be a good break from the long hours in the saddle, but shouldn't be done more than a few times a week—and make sure to get plenty of rest in between. Break down your training into macro (yearly) and micro (weekly) segments to ramp up your intervals at the right time during the year.
Yoga is another way to build core strength and become more flexible. It can also improve breathing and help to relax tense muscles on the bike. A flexible, relaxed athlete is a better athlete. Combine this with your resistance/cross-training days and you will be on your way.
Try a Cycling Coach
Find a good coach to develop a personalized training program. This can help a cyclist to set attainable goals and tweak training programs as problems arise. A coach can also help to plan your training around a particular race and offer other services such as nutrition plans or specific drills to improve pedaling technique based on your individual weaknesses. Find a good coach in your area by searching the USAC or USAT websites. Most coaches are set up to help any athlete anywhere in the world through the Internet.Search for a cycling event