A cycling criterium requires complex skills that can only be realised after years of targeted training. Not only endurance, strength and speed are required, but also technique, dexterity and bike control are prerequisites for successful criteriums. They usually meet club riders who started cycling as youngsters and have been racing for many years. That's why it's not surprising that you don't finish in the leading group at your first criterium. The opposite would be much more surprising. When building up your training, you have to be patient and dedicate yourself to basic endurance, but especially to technique training. The younger you are as an athlete, the easier it is to put technique training into practice and you can benefit from this in the following years of training and competition.
Ride a lot with high cadences, one-legged and with short sprints. Specific and non-specific strength training should only be integrated into the training programme later, when your basic skills and technique are stable and can be called upon in competition. If you really want to compete, try to train all year round and use mountain bikes and rollers or cycle ergometers for technique training in winter.
During the competition season, you should never neglect basic endurance training. It will ensure that your performance remains stable throughout the season.
Tips for racing newcomers:
1. do not race until you feel technically confident on the bike - otherwise you will endanger yourself and others.
2. join a cycling club. In addition to riding in a group, you will also learn tactical tricks.
3. don't throw in the towel if the first race doesn't go perfectly! It is precisely then that you should continue to practise and gain racing experience. Even professionals use the first races to build up their season.