A few more words on tracking training stress before I get back to bullheaded training.
Turns out my training stress score idea, like most ideas, is not original. "Daniel's Points" is a concept that is very similar to the IF^4 stress score I talked about in the last post. Apparently there was a running coach named Jack Daniels (no relation to the liquor, apparently), probably in the 80's, who made an intensity-to-the-fourth relationship between training stress and, in his case, running speed (which is almost directly proportional to power for runners, since wind resistance doesn't come into account). His runners had a fair amount of success on the collegiate scene.
What I like about it is it builds on the concept of NP in a very natural way, mathematically. Basically, with NP, you are defining a stress function that goes by P^4 (after smoothing to get rid of power peaks). NP is simply the steady state power which results in the average training stress. So, every point in time of the training ride corresponds to a stress that is proportional to P^4. The IF^4 proposal for training stress simply integrates this training stress in time.
Put another way, at every point in time during a workout, your body is exposed to a stressor (proportional to P^4) that it must adapt to. Add up all these stressors and you get an integrated adaptation stress, which is your IF^4 training score. Long, slow endurance rides, necessary to prepare your body for the stress of training, naturally don't score well on this scale - I think this is correct; a long endurance ride will not make you fast, whereas an hour of interval training will. This is in contrast to TSS where a 3 hour ride at endurance pace is given the same or better score as an hour of interval training. Threshold intervals will score equivalently on both scales.
Coggan's TSS is based on TRIMPS (you can google it; stands for "Training Impulse" and was designed for training by HR), which apparently started out as a score directly proportional to the training intensity. When this was found not adequate to describe what athletes were experiencing, another factor of intensity was added, making it an intensity-squared relationship. So, it's a guess with another guess added on. Not the most elegant thing in the world.
This IF^2 relationship makes for a unique problem with TSS; namely, that TSS is a function of overall workout time independent of intensity. If you just add time at zero power to the end of your ride to make it longer, you can manufacture TSS points with obviously no gain in fitness. The IF^4 relationship contains no problem in this respect, because if you run through the math, it quickly becomes apparent that "overall workout time" cancels out of the equation and you just get a straight-up integration of the stress function.
Anyway, like I said, I am keeping track of both this year. I'll watch the IF^4 stress score with the most interest though, because it makes more sense to me than TSS. If training stress can be captured by a single number, it seems the IF^4 has the most theoretical backing and about the same amount of empirical backing as TSS.
At this point in my racing career, I am just curious about these things on an intellectual level. Comes from my engineering background, I am sure. This being my third year, I am just in "watch and learn" mode as far as these metrics are concerned - keeping track of various numbers and correlating them to my race results. I'm sure someone can design a system of training based on any system of keeping track of training stress. The important part, I would imagine, is the athlete's and coach's direct experience in tying training stress metrics to performance.
Sunday, November 29, 2009
Thursday, November 26, 2009
TSS, NP, IF - Thoughts about Training Stress
Having a little information can be a dangerous proposition. Lately I've been reading up on things like TSS (Training Stress Score), NP (Normalized Power), and IF (Intensity Factor). I have a powertap and no coach, so I get to experiment with some stuff.
See, I'm an engineer, which means that I am naturally curious about the equations that come with having a powermeter. In case you didn't get the memo, there's a lot more that you can do with a powermeter than just measure power. The biggest thing that's in vogue at the moment is this thing called WKO+, which is a software program developed by a guy named Hunter Allen which takes all that raw powermeter data, condenses each ride into a single number, then does stuff with that number. The number is the so-called TSS, or Training Stress Score. You can read about this elsewhere, but basically it's a number that quantifies how hard your ride was.
I hate to do stuff with numbers that I don't understand. It drives me up the wall to, say, look at an insurance reimbursement summary because it's got a number added to a bunch of zeros that equal to zero. Not kidding. I can show you the paper. It's even got plus signs and equal signs between all the numbers. Anyway...
So, I hate to do stuff involving numbers that I don't understand. First off, the whole concept of TSS starts with the concept of NP, or Normalized Power. This is your power as a function of time, smoothed out using a smoothing function, raised to the fourth power, averaged, and 4th-rooted. Still following? Basically it means that there is some function, call it the "Stress Function", which is directly proportional to Power raised to the fourth. This is actually supported by some data, so it's not all bullshit here. Basically then, normalized power is the constant power which, if sustained for the time of the workout, results in the average of the stress function. Nobody's following now, but I'll plow ahead anyway. I have no issue with this at all. Makes perfect sense to me.
TSS is basically the amount of energy the rider expends during the ride, "corrected" by an "intensity factor", which is a function of the normalized power described above. I happen to think that the TSS concept is wrong.
The first clue is that a three hour ride at endurance pace will net the same TSS as a one hour ride at time trial pace. Maybe, but consider this: take two identical riders. Set them on an every-other-day training schedule at 100 TSS per workout. So far so good. Now, Rider 1 does his 100 TSS as a three hour endurance ride, every other day while Rider 2 does his 100 TSS sessions as a one hour at threshold interval set. Let them do this for a month, give them a few days off and then set them against each other in a time trail. Which one wins? My money's on the guy who did threshold intervals for a month.
But TSS doesn't reflect this at all. If you look at a plot of their TSS, it is identical. You'd think that they are training identically. But it's been well documented by Friel and others that interval training is much better for training racing efforts than just riding around for a few hours.
So here's what I propose. TSS, when it's normalized to the rider's functional threshold power, becomes the equation: TSS = T*IF^2, where T is time in hours and IF is "intensity factor" which is NP/FTP. Let's go back to the original derivation of NP. NP is the constant power which produces the same average "stress function" value as the raw power function. The whole point of TSS is to incorporate training "volume" with intensity. Andrew Coggan says on the Wattage Forum that "work" (derived by multiplying NP with time) is the volume component and IF is the intensity; he multiplies these together because he can't really think of anything better to do to combine them. The big problem with describing his formula in this manner is that IF and work energy are not independent. They are both dependent on NP. This is sort of a problem if your starting point is assuming that "volume" and "intensity" are independent concepts.
Now imagine a new TSS* formula which simply multiplies the average "stress function" value, which is proportional to NP^4, and time. Normalize it by dividing it by the average stress function value at FTP and you get TSS* = T*IF^4, where T is time in hours. Let's put it to the test:
Rider 1:
TSS* = 3hr*0.6^4 = 39%
Rider 2:
TSS* = 1hr*1^4 = 100%
Isn't this more of what we expect? Rider 1, following his 3 hour, endurance ride schedule, will be vastly undertrained (61% less) compared to Rider 2. This isn't a new concept: Coggan himself considered this formulation briefly after noting that data for time-to-exhaustion vs. power (which is kind of like the TSS concept) followed a near 4th power law form. He dismisses this out of hand though for some reason involving the hypothetical seeming equivalence between the recovery time from a 12 hour ride and a track pursuit effort.
Food for thought anyway. Myself, I am keeping track of both TSS and TSS* and will see how well each correlates to my form through the season.
PS. If you don't know who Andrew Coggan and Hunter Allen are, they wrote a fairly widely read book about training with a powermeter.
See, I'm an engineer, which means that I am naturally curious about the equations that come with having a powermeter. In case you didn't get the memo, there's a lot more that you can do with a powermeter than just measure power. The biggest thing that's in vogue at the moment is this thing called WKO+, which is a software program developed by a guy named Hunter Allen which takes all that raw powermeter data, condenses each ride into a single number, then does stuff with that number. The number is the so-called TSS, or Training Stress Score. You can read about this elsewhere, but basically it's a number that quantifies how hard your ride was.
I hate to do stuff with numbers that I don't understand. It drives me up the wall to, say, look at an insurance reimbursement summary because it's got a number added to a bunch of zeros that equal to zero. Not kidding. I can show you the paper. It's even got plus signs and equal signs between all the numbers. Anyway...
So, I hate to do stuff involving numbers that I don't understand. First off, the whole concept of TSS starts with the concept of NP, or Normalized Power. This is your power as a function of time, smoothed out using a smoothing function, raised to the fourth power, averaged, and 4th-rooted. Still following? Basically it means that there is some function, call it the "Stress Function", which is directly proportional to Power raised to the fourth. This is actually supported by some data, so it's not all bullshit here. Basically then, normalized power is the constant power which, if sustained for the time of the workout, results in the average of the stress function. Nobody's following now, but I'll plow ahead anyway. I have no issue with this at all. Makes perfect sense to me.
TSS is basically the amount of energy the rider expends during the ride, "corrected" by an "intensity factor", which is a function of the normalized power described above. I happen to think that the TSS concept is wrong.
The first clue is that a three hour ride at endurance pace will net the same TSS as a one hour ride at time trial pace. Maybe, but consider this: take two identical riders. Set them on an every-other-day training schedule at 100 TSS per workout. So far so good. Now, Rider 1 does his 100 TSS as a three hour endurance ride, every other day while Rider 2 does his 100 TSS sessions as a one hour at threshold interval set. Let them do this for a month, give them a few days off and then set them against each other in a time trail. Which one wins? My money's on the guy who did threshold intervals for a month.
But TSS doesn't reflect this at all. If you look at a plot of their TSS, it is identical. You'd think that they are training identically. But it's been well documented by Friel and others that interval training is much better for training racing efforts than just riding around for a few hours.
So here's what I propose. TSS, when it's normalized to the rider's functional threshold power, becomes the equation: TSS = T*IF^2, where T is time in hours and IF is "intensity factor" which is NP/FTP. Let's go back to the original derivation of NP. NP is the constant power which produces the same average "stress function" value as the raw power function. The whole point of TSS is to incorporate training "volume" with intensity. Andrew Coggan says on the Wattage Forum that "work" (derived by multiplying NP with time) is the volume component and IF is the intensity; he multiplies these together because he can't really think of anything better to do to combine them. The big problem with describing his formula in this manner is that IF and work energy are not independent. They are both dependent on NP. This is sort of a problem if your starting point is assuming that "volume" and "intensity" are independent concepts.
Now imagine a new TSS* formula which simply multiplies the average "stress function" value, which is proportional to NP^4, and time. Normalize it by dividing it by the average stress function value at FTP and you get TSS* = T*IF^4, where T is time in hours. Let's put it to the test:
Rider 1:
TSS* = 3hr*0.6^4 = 39%
Rider 2:
TSS* = 1hr*1^4 = 100%
Isn't this more of what we expect? Rider 1, following his 3 hour, endurance ride schedule, will be vastly undertrained (61% less) compared to Rider 2. This isn't a new concept: Coggan himself considered this formulation briefly after noting that data for time-to-exhaustion vs. power (which is kind of like the TSS concept) followed a near 4th power law form. He dismisses this out of hand though for some reason involving the hypothetical seeming equivalence between the recovery time from a 12 hour ride and a track pursuit effort.
Food for thought anyway. Myself, I am keeping track of both TSS and TSS* and will see how well each correlates to my form through the season.
PS. If you don't know who Andrew Coggan and Hunter Allen are, they wrote a fairly widely read book about training with a powermeter.
Tuesday, November 24, 2009
The Puzzle Pieces...
...are falling into place. For the last two weeks and change, I've been doing nothing but endurance, low paced rides. A majority has been on the rollers in one or two hour sessions. Team rides of 2.5-3 hours make up the balance. Five rides a week with two days off. I call these "movie intervals". Boring as all hell, but put a good movie on the TV or a good football game (is it coincidence that the Pats/Colts game netted me my best training ride of the year?) and it becomes tolerable.
My weight is coming under control. My off-season high was 184lbs. I am now back down to close to 178 and have hit that zone where my appetite doesn't lead me to pack in the food in response to training. From previous experiences last year and the year before that, this should result in a solid pound a week give or take for the next couple months.
I feel good about this season. I feel strong and now that my weight is dropping again, I am reasonably confident of reaching my weight goal for the season. I am starting with a true base this year, instead of just jumping right into intervals. My plan is to continue the five day a week endurance rides until the first or second week of December. After that and through January, I'll add in, with increasing frequency, threshold intervals and the so-called "sweet spot training" sessions to replace the endurance rides.
Important for this year is to train the intermediate intervals in the 1-5 minute range between sprinting and threshold. I think coaches call this the "anaerobic endurance" range. I did zero training in this power range last year, and I suffered a bit because of it. It's not so much that I am not "good" in that range, but by not training, I don't know how to judge effort during those intervals. Thus, bridging efforts are hard for me because I am afraid of going too hard. I get dropped on the start of climbs because I can't push my limits because I don't know if I can recover. I can't accelerate properly out of corners in a crit to allow me to move up and get out of the yo-yo part of the pack. This kind of training needs to be done closer to the race season. I will work these in starting in February.
Lastly, I am shifting all my training backwards about a month from last year. Last year at this time I started threshold work in November and continued it until racing scuttled those efforts in March. I was burnt out by April instead of being good. This year, I hope to have a much better endurance base going into interval training, and not be in such a rush to get into form. I have to bang it into my head that I don't have to have form until racing season starts, and even then, not until late March and April where the racing really takes off. It's not about flexing muscle in training rides with the crew. It's about being good for races. So patience and faith in training is key. Build up the base and hit the intervals in stride and everything else will fall into place.
My weight is coming under control. My off-season high was 184lbs. I am now back down to close to 178 and have hit that zone where my appetite doesn't lead me to pack in the food in response to training. From previous experiences last year and the year before that, this should result in a solid pound a week give or take for the next couple months.
I feel good about this season. I feel strong and now that my weight is dropping again, I am reasonably confident of reaching my weight goal for the season. I am starting with a true base this year, instead of just jumping right into intervals. My plan is to continue the five day a week endurance rides until the first or second week of December. After that and through January, I'll add in, with increasing frequency, threshold intervals and the so-called "sweet spot training" sessions to replace the endurance rides.
Important for this year is to train the intermediate intervals in the 1-5 minute range between sprinting and threshold. I think coaches call this the "anaerobic endurance" range. I did zero training in this power range last year, and I suffered a bit because of it. It's not so much that I am not "good" in that range, but by not training, I don't know how to judge effort during those intervals. Thus, bridging efforts are hard for me because I am afraid of going too hard. I get dropped on the start of climbs because I can't push my limits because I don't know if I can recover. I can't accelerate properly out of corners in a crit to allow me to move up and get out of the yo-yo part of the pack. This kind of training needs to be done closer to the race season. I will work these in starting in February.
Lastly, I am shifting all my training backwards about a month from last year. Last year at this time I started threshold work in November and continued it until racing scuttled those efforts in March. I was burnt out by April instead of being good. This year, I hope to have a much better endurance base going into interval training, and not be in such a rush to get into form. I have to bang it into my head that I don't have to have form until racing season starts, and even then, not until late March and April where the racing really takes off. It's not about flexing muscle in training rides with the crew. It's about being good for races. So patience and faith in training is key. Build up the base and hit the intervals in stride and everything else will fall into place.
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