For many people on the east coast, they might have a month or more before they even think of racing, but on the west coast, most people have already begun they’re new racing season. In either case, competitive cyclists are trying to ride hard in their workouts or at the races, and a proper warm up can really help with that.
Short and sweet, an ideal warm up would look something like this:
ride steady 15-20m on a trainer, 20-30m on the road
do a few short tempo or threshold intensity efforts
do a handful of short sprints and/or VO2 intensity efforts
ride easy or steady for a few more minutes
line up warm, opened up, and relaxed 5m before the start
Start off with some easy to steady riding. Just ride at a conversational pace until you start to feel warm and loose. If you’re on a trainer or in warm weather, you probably won’t need to ride as long to get warm and loose. If it’s cold, then it’s often easier to get warm on a trainer, because there isn’t an issue with wind chill. If you’re on the road when it’s cooler, then dress accordingly and just drop off extra clothing before the start, and leave extra time for your warm up.
After you’ve broken a bit of a sweat and feel comfortable, do a few short efforts somewhere around your threshold power to get your heart rate up and your lungs breathing more deeply. You could do a few 1-2m efforts at or above threshold power, or 3-4m efforts a little below threshold power, either can be effective, so go with what feels good or comfortable for you.
Once you feel good riding at or around your threshold power or harder, do a few sprints or harder short 20-30s efforts to help get your legs ready for the anaerobic efforts you’ll be doing. Often just a few of these will be fine, but always remember that the aim is to get physically warm during your warm up and to feel good riding hard before the race starts.
For more intense races like crits and time-trials, the warm-up should be longer and more intense. For longer races that aren’t likely to start with much intensity, an easier warm-up will be adequate. For example, before a crit, you could even go out and do an easy hour and finish up with a few hard efforts, whereas for an endurance mountain bike race where you’ll just be riding steady for several hours, you might just ride easy for 15 or 20 minutes to loosen up, but not at all tired.
If you have an evening race, you may even consider doing a pre-race warm-up ride the morning of the race where you just ride at a comfortable pace for an hour or two and get nice and loose, before having a small meal and continuing on with your day. That may allow you to do a shorter warm-up right before the race because you’ll likely feel like your legs and lungs are pretty opened up already.