It's tough to train in the off season, but hopefully you were able to maintain a winter training program as a good foundation or base for these early spring rides. A balanced program would have contained both
But it's not unusual to burn out after a hard season of riding, so itís even possible you may have taken a few extra weeks off. If so, put in some easy miles as you build a mileage base before starting those intervals and pushing up the weekly miles.
If you still have a month or two before the weather gets good, you can supplement your road time with an indoor trainer and weights. The stationary bike is really good for speed work. Two or three times a week, after warming up, do eight or ten 20 second sprints with easy spinning for 5 minutes between. Twice a week use your free weights, with more reps (12 to 15,) and lighter weight than you would use for building up muscle bulk. But road work is the key with the bulk of your time on the road building up that mileage base with endurance rides and occasional sprints to keep things interesting.
Before beginning a rigorous training program, it is important to have a base of at least 500 miles of easy rides. If you had a good winter or off season training program, you can pare down this requirement.This is important to allow the muscles and ligaments to respond to the demands of increasing use. If this stage is "pushed" or the miles minimized, the chances of injury during the early season increase.
Once you feel comfortable that youíve put in those long easy miles and have a good base, you can begin to plan a training program that increases total weekly miles by 10 - 15% per week. The 10 to 15% figure has been used for years by marathons runners to minimizes musculoskeletal injuries with training. As bicycling is much easier on the joints and muscles, this figure could be increased with minimal risk of injury.