Why I'll Never Give Up My Power Meter

RapDaddyo

This is an FYI post for the benefit of those who have not yet decided to get a power meter. Although I have been riding with a PM for only ~ 1 month, the benefits are crystal clear. I am a different cyclist with a PM! The post addresses those specific benefits and reasons.

Background: I was a serious cyclist and racer (RRs, TTs and crits) for about 5 years in the early 1970s. I rode ~350 miles/week and raced every weekend from May to September. I rode ~200 miles/week in the off-season. My strength was climbing, and I was only a fair sprinter. Due to life, I had to give it up until this year. I took up running to try to stay in shape, but cycling was always my first love. When I resumed training to race again in March of this year, it was clear that one of the major developments since I rode actively was power meters. After researching them carefully, I bought a PowerTap SL. My logic for choosing the PT is discussed in this post: http://www.cyclingforums.com/t-243111-15-9.html. While I am happy with the PT SL, I’m sure I would also be happy with the SRM Pro, just poorer.

So, why am I a different (better) cyclist with a PM? First, it didn’t take me long to figure out that my intervals were very sloppy and inconsistent using only a HR monitor. I now realize that once I got my HR up to the target level that I would occasionally “cheat” by easing off slightly from time to time during the interval. Due to the HR lag, this never showed up during the ride or on my HR download. But, with a PM, I can instantly see that I have backed off and I pick the pace back up to get into my target zone. My upper zone (5 and above) intervals are much harder now that I am truly staying in the zone for the entire duration, and I think the developmental benefits will be greater as a result.

Second, I also quickly realized that my pacing was really lousy. I now realize that whenever I was trying to maintain a rock-steady pace that I was in fact always easing off my pace on downhill and downwind segments and picking up my pace on uphill and upwind segments, especially in the first 100 yards of a climb. I’m not talking about a couple of watts. I’m talking about 40-50 watts! I believe that a steady pace is the most efficient way to go from A to B, rather than an erratic pace. Whether it’s a TT or a century, I think it’s inefficient to ride with a highly variable intensity of effort. I’m not absolutely sure why this was the case, but I think it is related to the perception of speed versus intensity of effort. I think that when I would go uphill or upwind, my mind would say, “This is too slow. You need to pick it up.” And, when I would go downhill or downwind, my mind would say, “This is nice and fast. Good.” Granted, my HR monitor would eventually reflect the change of intensity of effort, but only after a minute or two. On a rolling course, by then it’s too late. With a PM, I pick up on the change in intensity instantly and make the necessary adjustment. In statistical terms, I think the sum of the squares of the deviations from my target power on long rides will be much less than before.

Third, I never fully realized how much less power is required to draft at high speed compared to pulling from the front. On a recent club ride, I was putting out 350w-375w on front and drafting at about 150w-160w! I mean, one can’t ride a bike more than a week and not appreciate the benefit of drafting. But, at high speeds (>25mph) the difference is huge, much larger than I previously realized. A well-organized paceline with approximately equally fit cyclists could chase down Superman himself on the flat. When you know how much of a rest you’re going to get, you can pull like a banshee when you get to the front. I now realize that I have always held back a bit at front because I wanted to protect my ability to hang on when I moved to the back of the line.

Even though I had carefully researched the benefits of riding with a PM, I was taken aback by these realizations. Bottom line, I’d sell my clothes before I’d give up my power meter.

Woofer

Wow, thanks for sharing. And don't tell any of my competitors.

jws

I'll agree, except for the pacing aspect. For the purpose of training, it may be okay to keep constant power if power is all that matters.

However, if speed matters, as in a race, it's better to apply more power uphill. The reason is simple: uphill, the extra power results in a relatively greater increase in speed. At higher speeds, i.e., downhill, power is better saved because the exponential increase in wind resistance makes it more costly to go faster.

How much to modulate power is a matter of experience and I guess you could say is the art of time trialing.

RapDaddyo

I don't think I agree with your logic. In a TT, one is theoretically going within a few watts of one's maximum sustainable power for that duration. To put out more watts is to put yourself in the position of having to back off later. If that's not the case, then you're not going hard enough. Yet, the reverse is not true. If one puts out, say, 20w less than his target power for a few minutes is not like making a bank deposit, where you can make a withdrawal later. To take it to an extreme, if my maximum sustainable power over 1 hour is 250w, that doesn't mean that if I put out 200w for the first half hour that therefore I can put out 300w the second half hour. If you save it, you never get it back. Do you have any data to back up your assertion, or is this your personal experience.

Woofer

I agree with jws. I thought in your original post you were just referring to intervals. Think of it this way - the only thing that matters in a TT is finishing time. If you spend too much time doing isopower you end up spending too much time in the slow portion of the time trial - either uphill or against the wind. Where ever you go slow your average speed goes down. The trick is balance going as hard as you can go in the hard parts and not going so hard that you blow up or don't have anything left to keep going moderately hard on the easy parts (downhill/tailwind). This is entirely course dependent. If it's possible to go maximum steady state for the entire course *and* maintain constant speed that's the best possible strategy.

http://www.sportsci.org/news/traingain/pacing.html

However, this does not hold true for non flat courses if one can match the model.

http://www.ms-se.com/pt/re/msse/abstract.00005768-199708000-00017.htm;jsessionid=CN1E1OFjQjtg0ag22h8b5K1VtcT4nfD14HxqPJo1UebtFqYMU 9Dq!1707623050!-949856031!9001!-1

Or empirically there's a long wattage discussion here.
http://lists.topica.com/lists/watta...l?mid=907403335

RapDaddyo

Well, if I read the references correctly, the only empirical evidence supports the steady power pacing strategy. Other pacing strategies, specifically "go harder uphill and upwind," seem to be opinion only. Am I reading the references incorrectly?

jws

I certainly understand your logic, and it works great for flat, calm conditions. This is not something I came up with, but there have been many discussions about pacing stategy on variable terrain. The consensus is that it's fastest to apply more power under more resistance(wind or gravity) and recover a bit downhill or downwind. Here's one reference:

http://www.ncbi.nlm.nih.gov/entrez/...9&dopt=Abstract

Here's a post by Andy Coggan at "Wattage":

http://lists.topica.com/lists/watta...l?mid=907401691

Jimmy

RapDaddyo

I think the fundamental question is whether one can ever reclaim "saved" power. I think not. I think that if I put out 20w less than my maximum sustainable 1 hr power for 10 minutes that I'd be lucky to get back 1/2 of that (10w for 10 min) later. Look at how flat the power/duration curve is from 30 min to 1 hr. There is very little difference between one's 1/2 max. power and 1 hr. max power. I say, "use it or lose it."

jws

You are right in that, in terms of average POWER, you never get it back. However, the question of TIME is different.

Jimmy

Woofer

What one needs to consider is that once you go below your average speed, your average speed goes down. The longer one goes below your average speed, the faster one's average speed drops. One wants to minimize the time that you go slow, physiology allowing.

I'm going to make up a scenario as I type. Let's pretend we have an out and back course that goes uphill for four miles and back downhill for four miles. If you can uphill at four miles an hour and downhill at forty miles an hour your time is one hour and six minutes. Now if you go uphill at five miles an hour and downhill at thirty six miles an hour your time is about fifty five minutes.

This is way oversimplified but illustrates the problem space - realistically almost no one wins a time trial on the downhill portions unless technical skills prevail.

jws

Instead of thinking in terms of average power, using normalized power makes more sense in this case (and in most real world situations).

http://www.cyclingpeakssoftware.com/defined.html

btw, CyclingPeaks software is the only way to "fly"

RapDaddyo

Well, that could be. It's an interesting modeling (and race tactic) question. I can buy into the argument of an unequal tradeoff such as I posited -- something like a 2 for 1 tradeoff in watts over time, within limits (e.g., +/- 10% of max sustainable steady state power for the course duration). If used strategically, I suppose one could cover a course faster with such a strategy even though his average power would be less.

Woofer

re:+/-10% - that's something you are going to have to figure out for yourself what those numbers are, and for how long.

Now mass start, that's a different animal. Do the minimum amount of work possible to stay with the pack until you don't want to be with the pack.

RapDaddyo

I agree. In fact, I have never even taken the PT software out of the sleeve. Paul