Power Splits - 20 min TT

woodgab said:

Does anyone else have a hard time producing an even power split (first half / second half)? If so, are your best times when they are about equal? I've been doing ~7-8 mile TT's this summer and just trained yesterday at 332/295. It may not seem it, but even those numbers came with a very deliberate effort at conserving in the first half. I don't have enough data / times to spot whether I'd be better off going even, but I know that's the dogma.
TIA

For me, I just do the first 1/2 mile in upper zone 3, then turn it up.

I usually even-split it, as my last mile or so is upper zone 4...

But then again, I have neither skill nor patience when it comes to doing a TT to perfection...

I am still learning how to put myself right at that line and keep it there for the whole interval. Having to concentrate on a split would require too much mentally... 🙂

Jim

Well, if even splits were paramount, I guess I could just lower overall average power to achieve it. I know my average is going to be +-10 watts from my CP20 (critical power). Since elapsed time is the goal, however, I thought I'd ask. My head is in Joe Friel's terminology, so forgive me when I ask by zone 3 / 4 if you mean sub-threshold?

Riding a TT at a constant power is rarely the fastest pacing strategy, but it's a lot better than the common error of plus/minus splits. The reason most people ride the first half faster than the second half is that they haven't estimated their sustainable power for the given duration by riding for that duration at a constant power. They have estimated their sustainable power based on intervals of a shorter duration and they usually underestimate the falloff in power associated with the longer duration. So, they take it out too hard, die in the middle and then sprint to the finish. The best strategy is to ride a constant power interval at the estimated duration of your TT and then add a few watts for the higher motivation on the day of the event. But, don't be too optimistic about the motivation add-on. It's often a lot less than people think it will be.

woodgab said:

Well, if even splits were paramount, I guess I could just lower overall average power to achieve it. I know my average is going to be +-10 watts from my CP20 (critical power). Since elapsed time is the goal, however, I thought I'd ask. My head is in Joe Friel's terminology, so forgive me when I ask by zone 3 / 4 if you mean sub-threshold?

Yes, right below threshold. All of my races are like this.

For a 40k, I spend the first 5 minutes below threshold.

I find I have much more to give at the end, as well as getting rid of the pre-race adrenaline...

Jim