carpediemracing 

That's a tough one to call. When the guy that won went you were on his wheel, but it seemed like it was super fast at that point? I didn't realize you were approaching the finish when I first watched it because no one really jumped, it was like a wide drag race until about 100m to go. It seemed everyone was maxed out speed wise. There was a guy to your right in white (seems like he gets 4th or so), I thought for a moment he was in the small ring but then I realized it's probably a combination of a smaller big ring and a long rear derailleur.

Maybe a 54 or 55T, if you're already using a 53x11? Or shift up earlier? You had three shifts I think. I have a hard time accelerating hard at 120 rpm, I'm better at 100-110 rpm; you were at about 120 rpm at some point, dropping down to 110-ish as you shift up a few gears.

Part of the problem is the high heart rate? If you pedal slower your HR will be a bit lower, as long as you're not totally maxed out. Spinning really fast will zing your HR; you use extra energy just spinning your legs, even with little resistance. Think of how hard it is to sprint your 39x21 at 200 rpm. It'll be hard but you're not going anywhere, you might be going 30 mph but you'll be totally blown in 15-30 seconds. Roll your 53x12 at the same speed and, yeah, it's not easy, but you could hold it for much longer and not be totally blown.

When I'm waiting for a sprint I usually put it in a bigger gear, soft pedal, etc, and then as it gets close I shift into an easier gear. I used to look at what gears others were using so I'd intentionally do weird stuff to throw people off (use slightly off chainring sizes, have a custom/weird cog set, etc), but now I don't look and therefore I don't care if someone knows what gear I'm in. The big thing is that basically every jump I make I shift on the downstroke; I'll gear down in preparation for this. If I'm in the 13 I'll shift into the 12 as I jump. If the bike makes a loud shift noise then that's about right. I go in the next gear; the slightly lower rpm, the slightly longer duration that I can apply torque on that first downstroke, it all seems to help my jump. If I'm overgeared then it's not good, fine. I bog down and all that but done right it's a great feeling to rip away as I jump.

On faster downhill finishes (admittedly a weak point for me) I prefer to follow others and do a big jump as late as possible because so much of the lead rider's power/speed gets eaten up by the wind and it's so easy to draft. When I finally do go I have to use a huge gear in the jump because the high speeds mean that just to draw even with the next rider takes a huge effort, forget about passing him. Downhill sprints are more about sustainable speed and therefore some level of aerobic stuff.

I've been okay with leadouts in that same speed range or slightly higher with a 54x11 top gear. I'd jump in the 12T I think, I don't remember, but I'd definitely do most of the sprint in the 11T. My favorite sprints in that situation were actually a long slight downhill followed by a slight uphill sprint, which seems to be the case here. It's a short rise to the finish (?) so it's best to jump early so you only have to maintain speed rather than accelerate on an uphill.