…Not an entirely new idea, as I’ve road my Saris Cycleops Powertap in MTB races. I’ve trained with one for 7 years now going back to 2004. Most people are familiar with what they are these days. For those that might not be -- it’s a rear wheel hub that’s able to measure the force being applied (in watts) as you pedal the bike. Some would say (myself included) it’s enormously helpful in training at specific levels depending on what part of your endurance energy system you are trying to improve. It keeps you on target from going too hard or too easy for a given workout a bit more specific than heart rate alone.
Why not use it all the time, even when racing? Well, add all those complicated internal workings to a rear bike hub and to a degree it’s gonna be a heavier wheel. Is a heavier wheel a bad thing? Well, think of it in exaggerated terms. Try rolling a 20lb rock, then try rolling a 20olb boulder – or we’ve all made snow man, right? Pretty easy to roll the snowman’s head, but the snowman’s body can be another story once it gets to the proper mass. In either case, it ties in with the law of inertia (as best as I can articulate it) – body at rest stays at rest, body in motion stays in motion. Once you get either the rock/boulder or snowman body part rolling & up to speed it’s about the same effort. It’s the getting started or acceleration part that makes the difference.
Fortunately with bike wheels it’s only fractionally different – moving something that weights 1.5lbs vs. something just under 2lbs. It matters on some level – but what that amounts to on a cumulative basis over a 60minute ‘cross race in terms of added effort, lost acceleration or seconds per lap is subject to debate. And I don’t have that answer but I do have some other interesting data below.
Nonetheless, after having such a good race the day before, I didn’t feel riding the powertap wheel on was going too detrimental to the outcome not to use it. As it turned out, it provide some really insightful numbers and stats to see how real time racing and targets for training intervals collide.
Day 2 of Baycross was alittle more low key, but a closer race than Day 1 – despite Nikoli not showing up (story was he did something we all dread going to an out of town race – forget a race necessary piece of equipment, apparently he forgot his cycling shoes & didn’t realize it til he was half way there – and not enough time to run back and forth). Mason balked on coming for Day 2 as well, whether he was busy, or still a bit upset about the misunderstanding of no “mechanical lap” I’m not sure. He’s a good kid though and getting to be a tough rider so it would have been nice to be there. Even so single speeding Dave Schuneman showed and local MTB strong guys Kelly McKnight and Matt Hudson passed on the bird hunting and whiskey and came for a round of ‘cross.
Not exactly desiring another 75 minute ‘cross race day repeat of Saturday, I opted to take it mellow on the first lap so the laps might be fewer. Dave S. & Scott Nesvold led things out. With Dave setting the first lap pace. I moved up to ride next to Dave in lap 2, trading pulls. He was working pretty hard & looking determined so I offered to help him build up a gap to a chasing Kelly McKnight, followed further back by Scott Nesvold.
By the end of three lap, Kelly was finally warmed up & closing in. Dave was looking winded but kept grinding away shortly behind me. I was about ready to push it to see what kind of numbers I could get on the powertap for the remaining laps of the race. Kelly missed getting Dave’s wheel shortly before I took off and their gap remained throughout the race until Scott Nesvold pulled past Kelly later in the race to settle in for 3rd, Dave rode strong the remainder of the race and took 2nd. I pushed it at the front and came in with just under a 3minute & 1/2 lap lead at the finish.
The interesting part for me was the power tap numbers, heartrate(HR), & lap times of the 11 lap race. The initial 2 laps were at a comfortable cruising speed, my HR was 165-166 beats per minute (BPM) and the average watts were 253 watts and the laps were 5:22. Lap three I picked it up at the end, HR stayed at 166, power was 263 watts & lap time dropped to 5:12.
When I started to drill it on the final 8 laps things changed quite a bit – Lap 4: dropped to 4:48, 309 watts & my HR went towards it’s ceiling 174bpm; Lap 5: 4:54, 298 watts & HR stayed in the mid 170’s the remainder of the race.
After pushing it so hard for those two laps (10 minutes) I was hurting and my power dropped some & lap times went up alittle for the final 6 laps. Hovering around 280 watts and 5min to 5:05 lap times.
Here again is the interesting thing – looking at the power numbers & lap times, you can get a sense of what the different levels of power mean for how much faster or slower a lap will be.
Essentially for a guy my weight/size – a 50+ watt/lap difference is going to create a 35 second difference (when laps are approximately 5minutes long – course length was 1.3miles – however the faster the speed the less difference the power makes due to increased wind resistance)
- a 3owatt difference is 12-17 seconds
- a 15 watt difference is 5-6 seconds
That’s all good assuming smooth riding, no spills, mishaps. As a guy with lower power but a smoother riding could make up those differences - application of power is as important as the raw power itself. Even so, the ability to push out a lot of power is key to racing well. There’s always the contention that it’s actually a Power produced to Weight of a rider that matters most – which is true to a point. It’s most apparent in climbing hills -- but on flats or downhills absolute power matters much more and is only detracted by frontal surface area of a rider – smaller, thinner is better but it’s nominal at ‘cross & MTB racing speeds compared to a road races.
Those two above factors (skill/application of power & weight) play a bigger roll in MTB than in ‘cross. Perhaps that’s why I like the pure simplicity of ‘cross racing. Don’t so much have to worry about dropping weight, it’s only slightly technical (for a MTB’er) and you can just crank on those pedals as hard as you’d like for 60minutes.
The numbers above are interesting but can also paint only part of a picture. What a person is capable of can be very different than what shows up in a race – if a person is overtrained, or sick, or raced the day before vs. being well rested can cause significant differences in power output. My power output Day 1 at Baycross was probably notable better having gapped the same riders (Dave & Scott) by double the time as Day 2, even though I felt I was trying equally hard each day. My body just wasn’t capable of producing the same power.
The following week I raced at Eau Claire in the Carson Park ‘cross race & the same held true there -- only going there I was slightly under the weather and put in more training than rest that week. My power #’s were off even further, an average of 15-20 watts lower than Baycross Day 2. So I guess with high intensity racing never disregard the effect it may have on you. A drop of 3% to 10% of your power output can cost you 5-10 seconds per lap or more. That’s can be a 60-90seconds in a ‘cross race.
Oh well, sorry to bore in case the quantifying side of cycling isn’t up your alley. I just think it’s cool to understand in numbers why the fast guys go so fast and why, well, the many others of us don’t go as fast. I’ll try to do a power to weight posting at some point – as I think that’s even more interesting. You take a small guy with lower absolute power and he’ll still beat larger bigger guys with higher absolute power. I’d love to get somebody like Big Mike Weispfenning on a power tap to see how crazy huge his numbers would have to be – he’d make the numbers put out by pro cyclists Alberto Contedor or the Schleck brothers put out look pretty puny I’d bet…. too bad they only weigh the amount of one of Big Mike’s legs... damn power to weight ratios!
Up next, Carson Park ‘Cross recap and sorry UPCross I might not make it over for the Championship Sat as I’m probably doing a double header in MN this weekend and to see how Faulkner, Reints, Fisher, Lemiux, among others turn up the pain.
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