The sentiment that taking time out of your riding/running/swimming schedule to focus on strength training may deleteriously affect your performance in your chosen discipline is not uncommon.

The importance of strength training cannot be underestimated, and should be incorporated year round.  Focusing on your weaknesses and training to become a well rounded athlete should be the primary goal for most of us.  For cyclists in particular this means that the upper body and core should not be  ignored.

During the off season and base period is a great time to start you strength training if you have never done any before.  This will enable you to substitute a couple of sessions a week for strength training and enable you to start the season feeling stronger and refreshed.

I like to program a mixture of heavy strength sessions and body weight functional and stability sessions for my athletes to help get the best transfer of strength, coordination and balance applicable to their sport.

Single leg and single arm work really challenges most athletes, it can highlight any left/right power discrepancies and also makes the core work really hard without the need for isolated core exercises such as crunches (by the way – there are many more effective core exercises rather than the crunch).  Working up to single arm/leg exercises is a right which needs to be earnt by fully nailing the basic movement pattern before moving on to these more challenging variations.