waterrockets 

I've always known the "go hard on the hard parts" pacing strategy for a TT, but today I did an impromptu experiment during the hill repeats today. It's amazing what a difference it makes.

I had two pairs of climbs that line up with this experiment. One pair had the same time, and the other pair had the same wattage. The wind was steady and light, not a significant factor in variability. In each pair, one was steady effort, and the other was highly variable, with intentional and defined attacks and recovery (going hard on the steep sections).

In one pair, I got the same time with 15W difference in power (by the same time, I mean the EXACT number of PowerTap samples!). The 15W savings came on the climb where I attacked the steeps and recovered on the shallows. The higher wattage climb was evenly paced.

In the other pair of climbs, I had nearly the same wattage (416W vs 413W), and the variable power ended up being 11 seconds faster (with a 3W lower average).

It's pretty sweet to see how you can save energy and go faster, even when you're solo. The caveat is that some people handle surges better than others, so sprinters can maybe have more variability, but it seems like everyone would benefit from at least some intentional variability.

First pair:
1)
Duration: 4:59
Work: 115 kJ
Min Max Avg
Power: 234 554 384 watts

2)
Duration: 4:59
Work: 110 kJ
Min Max Avg
Power: 40 588 369 watts

==================================================================================

1)
Duration: 4:46
Work: 119 kJ
Min Max Avg
Power: 240 712 415 watts


2)
Duration: 4:35
Work: 113 kJ
Min Max Avg
Power: 157 778 413 watts

==================================================================================

Here are the graphs (pretty easy to see the paced vs. the variable):

wfrogge

Its amazing how you need to train both surges and sustained power outputs. With my 4 weeks off the road I worked nearly 100% on sustained 10-20 minute power intervals and lost all of my surge recovery in the process.

Thinking I would have been better off working on 5-10 minute intervals to balance sustained power with race like surge recovery.

waterrockets 

going for the lowest posts/views ratio on this one. I guess I'll keep the total geek posts in the racing forum then... everybody back to discussing bar tape and electronic shifting

cmh

Interesting data WR. Were you more or less tired at the end of the intervals with lower avg. power but more higher surges? How did the percieved exertion compare?

snoboard2

lol. they just ride their bike out here.

Enthalpic

ElJ already out geeked you by a long shot. Not only did he know about this effect he came up with an impressive optimization algorithm.

https://www.bikeforums.net/showthread...highlight=time


Of course one could have just consulted the literature.

Variable versus constant power strategies during cycling time-trials: prediction of time savings using an up-to-date mathematical model.
https://www.ncbi.nlm.nih.gov/sites/en...ubmed_RVDocSum
Our findings confirm that time savings are possible in cycling time-trials if the rider varies power in parallel with hill gradient and wind direction.

Acceptability of power variation during a simulated hilly time trial.
https://www.ncbi.nlm.nih.gov/sites/en...ubmed_RVDocSum
finish time for the variable power trial (3670 +/- 589 s) was significantly faster than that for the constant power TT (3758 +/- 645 s), the 95 % confidence interval for the percentage improvement being 0.4 to 4.3 %.

Physiological effects of constant versus variable power during endurance cycling.
https://www.ncbi.nlm.nih.gov/sites/en...RVAbstractPlus
No differences were found between the CP and VP trials in mean VO2 (CP 3.33 +/- 0.11 L x min(-1), VP 3.26 +/- 0.12 L x min(-1)), mean heart rate (CP 158 +/- 3 min(-1), VP 159 +/- 3 min(-1)), mean blood lactate concentration (CP 4.2 +/- 0.7 mM, VP 4.3 +/- 0.7 mM), or mean RPE (CP 13.9 +/- 0.4, VP 14.1 +/- 0.4). CONCLUSION: Therefore, during a strenuous 1-h effort (78% of VO2max), subjects experienced no additional physiological stress by varying power +/- 5% compared with that during a constant power effort.

threeoneseven

i have no idea what 1/2 of those numbers in your original post mean...i gauge my riding ability by being able to hang with the cat 3's and 2's in our weekly rides.

waterrockets 

Well, these were 5m intervals, and I did 5 of them, so I was tiring throughout the workout. My varied paces were exaggerated, so that made them feel pretty tough, but the rests were easy too. Perceived exertion was probably flat between the two with the same wattage, but I'd say of the two with the same time, the easier one felt like I was goofing around.

Oh.

That's cool. Essentially, it's "go harder on the hard stuff." When a Cat 4 drops you on the weekly rides, and you know you're stronger, refer back to this thread, or the one quoted by Enthalpic

I'm gaging my ability by racing against Cat 2s. Pacing matters.

waterrockets 

I remember being near a milestone at work and missing that thread. Nice.

Note that I've known about this for a long time. I've just never tested it myself. This thread is just another data point.

In a real TT, your power is likely to be varying nearly 5% even if you're trying to hold an even pace. Maybe they mean varying your target power?

Good articles though

I just liked seeing the impact on the road today, from my own legs.

gr@sshopper

So for those of us sans power meter, hr monitor, or anything else except a desire to crush our buddies' soul, what's the take home message?

Jump hard on the uphills and chill out a bit on the flats?


And more importantly, can anybody explain why this works?

waterrockets 

Yeah, you don't need a PM for this, it was just handy for the experiment. You pretty much want to push harder when there's more resistance (headwind or steeper). Nothing too dramatic (mine were a bit exaggerated). The links enthalpic posted have more info on the specifics.

The reason it works mostly has to do with the physics. On hills, your extra work goes to fighting gravity. The force required goes up linearly with speed. On a descent, with really high wind resistance, the force required goes up with the cube of velocity.

In a strong headwind, your ground speed is much lower than the wind speed, so a large % of ground speed change results in only a small % of wind speed change. Like suffering at 10mph in a 30mph breeze: going 1mph faster is a 10% speed increase, but only fights the wind at an additional 3% (which is cubed to 9% force required -- nearly linear progression in this case, just like a climb).

Also, physiologically, we are able to better control our efforts when there's a lot of resistance to gauge, and it feels better to push against something pushing back.

gr@sshopper

Right. I would have thought of drag, eventually, but it makes sense now. Danke. Soon as the cast comes off, the soul destroying continues!