Negative splits

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I had a 10 mile timetrial last saturday on a flat 'dragstrip' course. This is a type of event that I ride maybe once or twice a year when there are no road races on, so I have no real 'feel' for how to pace myself over the distance. I do though have a PT, and a recent MAP/VO2max test which suggested that I should be able to sustain around 350W for the distance. (MAP = 449W)

I wasn't too confident in my ability to sustain this power, so planned on a negative splits strategy, aiming to hold around 340 for the first half and then try to get to the full 350 for the second half.

The first bit was *relatively* easy and I averaged almost exactly 340 until the halfway point, but coming back I just couldn't raise the power above this, and was dipping down toward 300 between miles 7 and 9. As it happens, my final time was pretty good (22.09) only a minute off winning the event (not bad on a standard roadbike with clip-ons, spoked wheels etc). The eventual average was down at 330W.

Afterwards though, I really felt that I could have done even better if the pacing had been slightly better. I felt that raising the level from 340 to 350 was too difficult when I was already so close to the limit, almost as though holding the full 350 would actually have been easier. I'm thinking that the difference in pain between 340 and 350 is pretty minimal, but the effort of cranking it up another 10W when you've already been going at 340 for 10minutes is too stressful. Anyone got any thoughts? Next time should I just go for it at 350W and try to hang on?

First off, good ride! Riding at 330W AP for 22mins is no easy task. You actually had your MP dialed in pretty well, although we tend to be more accurate at estimating our MP for shorter durations (because we do high-intensity training rides at or near those durations). Basing a 60min MP on 2x20 efforts is a much different matter, subject to much greater error. And, FWIW, I think your power timeline is the common one: take it too hard in the first part, back off, then finish strong. In my view, the problem is that we often don't ride training rides on a regular basis with constant power efforts equal to the duration of a race. So, on race day we're estimating our max sustainable power based on shorter efforts. The problem is that when we ride a variable power pacing plan unintentionally, we pay a price in terms of a lower AP than if we rode at a constant power. There are compelling arguments for a variable power pacing plan (e.g., if one of the legs had been into a strong wind), but there is a definite price to be paid in the form of a lower AP. My only specific suggestion is to ride training rides at or near the anticipated duration of key target events. For example, I have begun training for a long hillclimb TT in mid-September. I know the race duration will be 1.5-2 hours, so I have begun riding long L4 efforts once a week. By the first week of September, I will be riding L4s at 90-120 mins about once a week. Not necessarily at 100%FT, but definitely in the 91-95%FT range.

Anyone got any thoughts? Next time should I just go for it at 350W and try to hang on? Do you sometimes do long interval training? Such as 2x20 or 2x25 or alike? At which power do you perform them?

For what it's worth, often during TTs, the intention of negative split strategy, end up (in the best cases) in doing an even split.

For example, I have begun training for a long hillclimb TT in mid-September. I know the race duration will be 1.5-2 hours, so I have begun riding long L4 efforts once a week. By the first week of September, I will be riding L4s at 90-120 mins about once a week. Not necessarily at 100%FT, but definitely in the 91-95%FT range.LOL RD, you'll be upsetting Warren again with that post.:D

Next time should I just go for it at 350W and try to hang on?

I'm not a TT expert, nor do I play one on TV, but I'd say go out at 330 and then gradually try to ramp up on the way back. If you went out at 340 and couldn't hold that steady on the return leg, wouldn't you have an even harder time going out at 350? I'd be wanting to pace myself so as to eliminate the dip between miles 7 and 9.

By the first week of September, I will be riding L4s at 90-120 mins about once a week. Not necessarily at 100%FT, but definitely in the 91-95%FT range.

By definition, isn't it impossible to do 90 minutes (much less 120) at 100% of FT?

I'm not a TT expert, nor do I play one on TV, but I'd say go out at 330 and then gradually try to ramp up on the way back. If you went out at 340 and couldn't hold that steady on the return leg, wouldn't you have an even harder time going out at 350? I'd be wanting to pace myself so as to eliminate the dip between miles 7 and 9.

Sure, but the dip came after going up to 350 for a couple of miles - I wondered whether there was a negative impact from increasing the watts when I was already going so hard and whether a constant effort would be less stressful even if that constant was slightly higher.

Do you sometimes do long interval training? Such as 2x20 or 2x25 or alike? At which power do you perform them?

I don't do any specific timetrial training like this, because until now timetrials haven't been high on my priority list and I tend to focus on shorter hill intervals which are more useful for roadracing on the frequent short steep hills we have around here. Having got within a minute of the specialists without any specific training, aero equipment (and that dip between 7 and 9 miles) I'm getting the feeling that I could win an event like this with a few well planned interval sessions. So, I guess the 2x20s start here...

By definition, isn't it impossible to do 90 minutes (much less 120) at 100% of FT?Well, I suppose there are some whose MP/duration curve is flat from 60-120mins, but mine isn't. I plan to do these at ~91%FT.

By definition, isn't it impossible to do 90 minutes (much less 120) at 100% of FT?
In one continuous effort, yes, but not as cumulative work time during intervals.