Train To Race
To start, do hard (close to all-out) 60- to 120-second intervals with complete rest, which is necessary to hit the highs needed to improve. Once you get stronger, and as you get closer to the event, you can decrease the rest time and/or increase the intensity of the rest to make it more race-specific. Start with no more than 15–20 minutes of total interval time.
Hard group rides will force you to surge significantly more than training on your own. The group will also be a bit less predictable, forcing you to go hard at random times, thus changing up the interval duration and recovery parameters.