Getting up to speed from dead start requires a big power input and there is no way around that without bending the laws of physics. As a result your peak power should be in that initial burst as you will have momentum during ever other acceleration in the race. If you feel the need to take longer to get up to speed that's fine which will reduce your 20 sec power. It may also be worth noting that you will accelerate faster at lower speeds given the same power output so peaking at low speed is better than peaking at top speed.

I'm not nearly as experienced as some of the other people here but I'm inclined to say yes, roll out slower. A lot slower.

How did you feel for the rest of the TT? I normally aim to set of at the same RPE as if I was popping to the shops (I kid but I try to start really steady.) Invariably it ends up being quite hard. I generally take 10s standing to spin out the gear, get down in aero, up one gear gradually spin that out in the next 10-15s then up one more to the gear I'll be sat in the bulk of the time. Thats assuming a flat start.

Iain

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i didn't feel unusually bad, but it just made me wonder if it wasn't optimal. i am a pretty good TTer, but i'd like to get better, and this new data point made me think. it can't be good to gun it like that from the start.

A lot of it will depend on the length of the TT and how fit you are.

For a 10mi TT, hard from the start is pretty much the only way to go unless you are reasonably untrained.
For a longer route, i.e. 40+km, measuring your effort in that first minute may pay dividends in the latter stages of the course and lead to a faster time.

To quote a certain, rather well known, physiologist in these parts about 4k pursuit pacing (http://www.slideshare.net/...n1/paso-compressed):


And, imagining your TT events are longer than 4k, this advice is even more important. Honestly, roll into the TT. Your nerves will be more than enough to over-pace it, even if you're thinking "keep it down, keep it down".

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I did a 15k TT wednesday and I checked the first 20s. Nowhere near a 20s PB (but I guess it depends on what kind of riding you do how soft/hard that 20s PB is anyway). The peak was at 1004W at the start, first 20s avg 710. Don't think it hurt me overall, I paced it quite evenly (flat parcours) and didn't really feel like sprinting toward the end ;) I basically took 30s to get up to speed then settled into my pace.

Would you mind sharing the average from the rest so I can put it into perspective ? Thanks!

No problem. The average was 383w, 385np. If i take the average after the 30s burst it would be 379w. My 20s pb as gleaned from my powercurve is 1065w, but 20s max efforts are pretty rare for me so not superuseful in your overall picture maybe (not necessarily saying it would be higher though ;)

When my 40k power was 350-360 watts, and my :05 sprint was 1200, I would hit 600 initially, but just for literally a few pedal strokes. By :05 - :07 I was down below 500 and by :15 I was down below 400. I made a point to NOT be at top speed for about :40 - :50 into the race. This is how I had my highest averages ands fastest times.

Yep, 20 seconds is way too long to go balls out. After 10 seconds punching it you are going into oxygen debt with every pedal stroke which isn't what you want. I did a 10km TT last weekend and looking at the file started at ~600w for 5 seconds, got aero and held 451w for the first 20s to get up to speed. I held 390w NP and 49.1 kmh for the duration and came 2nd overall.

That last bit isn't to brag, just to say I think it was an effective TT effort. If I did 600w for the first 20s I doubt I would have had the punch to negative split and drive it at 500w+ up the small hill in the course. I don't think I lost much time out the gate at all, I was at 51kmh within the first 30s. Just give it a decent punch, get low and get to work-that's what you have to do.

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i try to stay to about 3x ftp

I've tried it both ways, and ^^this^^ is the way that has worked best for me for TTs that last longer than 20 minutes...especially the 40k. My last 40k I held 281 watts, and my first 5 seconds I averaged 489, peaking at 550. The first 33 seconds I was averaging 326, but my real time power was already in the 270-280 range. I let my avg power drop all the way down to 275 the first 3 minutes into the race, and then got into my groove where avg power remained pretty steady at 279-281 the rest of the race.

I've done TT's where I would blow 700+ watts for the first 15 seconds and my HR would just get all jacked up...and I couldn't settle in at my goal avg power. Usually meant riding 10-15 watts below goal avg power for 10-15 minutes before my HR would settle...and by then it was too late to get the avg back up to goal. End result would be either a blow up, or salvaging my race by ending with an AP 6-8 watts below goal average.

I suppose if you're trained to do that explosive burst and still stay in control afterwards to stay at goal AP then you can pull it off. But most interval workouts don't call for that type of effort. Such as a 2x20' where you're supposed to do the first 25" of each 20' interval at 250% of FTP.

That's not possible for me.

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Setting a 20s pb probably isn't a good idea but you gotta give it a shot of gas to get to cruising speed. Just remember that since you are fresh that power feels easy and the first minute will feel easy despite making silly watts. I usually get off the gas after 30s and pedal easy. Usually easy at that point is still over goal wattage.

For shorter TT's my simple rule is to count 10 hard (not all out just hard, peak power is probably 2/3 and the whole acceleration 1/2 of maximum) kicks and immediately settle to aerobars after that. Taking a TT position as soon as possible resists the intuition to pedal hard and over accelerate.


There's much more to lose than win at the start.

What matters is getting upto speed fast, so a big push at the start makes sense, but 20secs sounds like a long time. Have you looked at your speed curve at the start? Assuming your ave speed for the TT is 40kph, do you exceed this after the 20secs push and then fall back to the average as you settle down? If so, then your wasting power accelerating for so long only to lose the speed gained. Just see how long it takes to get up close to your ave speed for the TT and then wind back the power.

 

thanks everyone, lots of helpful info here.

i'll note that the stupid start method seems to have made it harder for me to get up to my TT heart rate, like it blocks up my legs a little. i am pretty sure that in my more successful TT's last year i wasn't starting quite so hard, the last 2 my TT bike has been in the shop so i've gone eddy merckx style, and something about being on my road bike makes me wanna sprint off the start more than usual. the worst example i was 15km/h faster than i needed to be after the start.

i've concluded that if i'm planning on riding at 370 for 20 minutes, the first 20 seconds should probably be 5s 600, 15s 420 then settle down.

when i think about it, if i was gonna do some 5 minute intervals on my trainer at tt pace, if i started with 20s at more than double the wattage i'd never finish the set.

That's more or less my 5s power.

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... and which is why 90% of the advice on ST should be taken with the proverbial grain of salt

You should not go flat out right from the get go, your time will be slower.

Start steady build up to fast and then go to the max spaced out in the first 2.5 minutes.

I am always faster when I ease into top speed.

After climbing up to the start house, or the start line, ensure that you have shifted to a large enough gear that will allow you to start out of the saddle and power up to speed for 10 seconds. I normally hit 200-250+ % of my FTP or more during these first 10 seconds.

http://garytingley.com/2014/08/how-to-prepare-for-a-time-trial/

I start time trials in the small ring usually about 400 or so watts for 20-30 seconds before forcing myself to lower the effort. Taking it out has never worked for me. FYI, I have been racing TTs at 300w this year and have had my best races with very conservative starts relative to my ftp. There is plenty of time on the course to increase power, but it makes for a rough race to go anaerobic out of the gate.

I would say that you should start as easy as you can get away with.
All of the best tt powerfiles that I have looked at include moderate starts.
A hard start never feels hard when you are doing it.
The keys to tt riding are knowing your power, trusting and riding your power, finishing strong, riding the hardest parts of the course with your best power.
Far too many riders try to hold a power level that is not realistic. That coupled with a hard start is a recipe for disappointment.
Other things to consider might be your warmup- maybe you are not ready to go?
Maybe you have warmed up too hard and too long?
These will affect you too.