A bunch of us locally are into time trials and are masters athletes. Read that as old guys 50-70 years of age.
The warmup that works well for everyone that has tried it is:
10-15 min w/u 50-70% FTP
3:00 ramp working from about 70% FTP to 120% FTP in 30 sec steps
3:00 recovery
3:00 repeat ramp as above
3:00 - 5:00 and get to the start line
20-25 min total is plenty. You want to get warm and open and hit a reasonably high HR but not do a workout before the race.
If it’s 40k you can do just the first ramp but for shorter events the second ramp seems to help get the brain in the right place for the hurt that’s coming.
I warm up on rollers to avoid messing with the wheels. Particularly if using holt on skewers just hopping off the rollers and heading to the start is nice.
Mark