Many athletes continue cycling on an indoor trainer, some cross train by running or swimming, or even lift weights. However, I have some recommendations before jumping into an end of season program.
First, get an honest assessment of your physical abilities. This assessment not only includes indentifying your training zones and power levels, but also your range of motion (ROM) in various planes of movement. To have proper ROM in these planes the athlete demonstrates appropriate muscular flexibility and stability. If faulty movemement patterns are identified I recommend implementing a program that helps address these problem areas.
The two assessment protocols I implement are the Functional Movement Screen (FMS) and the other is Postural Restoration (PRI). PRI is not as commonly known to coaches because it is founded from osteopathic manipulative therapy and is typically offered to medical practioners, physical therapists, chiropractors, and athletic trainers.
For endurance athletes I prefer using the PRI assessment. It is very simple and less time consuming and less subjective than FMS. Regardless of approach you adopt, I recommend getting an assessment of your ROM before getting heavily involved in an out of season training program.
Second, use proper techniques in your exercise program. It is vital you are receiving help from a qualified instructor that not only appreciates your sport but who has experience in teaching all the exercises selected for the program. I personally prefer instructing complex strength and conditioning movements versus isolating muscle groups exercises.
Third. Use your time wisely. During out of seaon training I recommend strength and power training before endurance and speed activities. So focus on exercises that incororate squatting, lifting and pressing. Then perform muscle endurance exercises.
Fourth, establish objectives that help you achieve your goals for next season. In as much, your training program should focus on injury prevention as well as performance enhancement. So be careful with high impact activities such as box jumps and other plyometric activities. Although these forms of exercises can ensure stronger joint, tendon, ligaments and muscles, you should ease into them with caution and postural balance.
Lastly, your out of season training program should be customized to your abilities and objectives. Even though group fitness classes can be beneficial they can easily under or over reach your capabilities.