Sunday, November 22, 2009

Stress-Based Training

I've been traveling a lot this month including 10 days vacationing in the Caribbean. I'm now in Norway with some time to kill after speaking to a large group of athletes on Saturday. So I've been thinking a lot. The following is something which grew out of having a lot of uninterrupted thinking time.

Training for racing is all about adapting to stress. Pushing yourself to the limits of your abilities in a race is highly stressful. This stress comes in the form of some combination of intensity, duration and perhaps frequency. For example, the duration of a 20km cycling time trial is relatively brief, but the intensity is quite high. A 5km running race has a similar distribution of intensity and duration. Heart rate and perceived exertion are near their upper-end limits in both types of racing. In an Ironman triathlon, however, the duration is quite high while the intensity is quite low. That's another kind of stress. A cyclist competing in a stage race has a third variable with which to be concerned – frequency. This could take the form of two stages in a day or stages on consecutive days. The combination of intensity, duration and frequency is what makes events such as the Tour de France so challenging.

We can measure and quantify stress if we know duration and intensity (we’ll mostly ignore frequency for now). It’s easy for duration. Just use a stopwatch to determine how many minutes you exercised. Frequency is also simple. Count the number of races or workouts completed in a given number of days.

Intensity is more challenging. Endurance athletes are not very good when it comes to expressing how intense a race or workout was. The most basic way, the one athletes have been using for as long as there has been competition, is perceived exertion. “That was a hard race,” always means the same thing - intensity was high relative to the duration. In a similar way athletes typically use terms such as “easy” or “moderate” to describe intensity when compared with duration. But since this is al somewhat vague, ratings of perceived exertion (RPE) have been used to quantify the intensity-duration combination. The most popular systems were developed by Gunnar Borg. Here is his 10-point scale [1]:

RPE Zone - Level of Exertion
5 - HARD

About 30 years ago the heart rate monitor was invented. By the late 1980s heart rate zones were being used to express intensity. For example, in the system I’ve been using for the last 20 years there are seven zones based on a percentage of your lactate threshold heart rate which can be found with a 30-minute time trial [2]:

HR Zone* - % Lactate Threshold
1 - less than 0.81
2 - 0.81-0.89
3 - 0.90-0.93
4 - 0.94-0.99
5 - 1.0-1.02
6 - 1.03-1.05
7 - more than 1.05
For the purpose of this discussion I've changed my normal normal zone titles for the anaerobic zones: 5a zone to "5," 5b to "6," and 5c to "7." You'll see why shortly.

For cycling, intensity may also be quantified with zones using a power meter in a way which is similar to heart rate zones. In this case the reference point is something called Functional Threshold Power (FTPw) which is very similar to lactate threshold. This also may be found with a 30-minute time trial. Then by using percentages of FTPw power zones are established that are unique to you.

Power Zone - % FTPw
1 - less than 0.56
2 - 0.56-0.75
3 - 0.76-0.90
4 - 0.91-1.05
5 - 1.06-1.20
6 - 1.21-1.50
7 - more than 1.50

Using the idea of FTP, running zones based on pace may also be determined. Only in this case “FTPa” stands for Functional Threshold Pace [4] and found by - you guessed it - a 30-minute time trial.

Pace Zone* - % FTPa
1 - greater than 1.29
2 - 1.29-1.14
3 - 1.15-1.06
4 - 1.05-1.01
5 - 1.00-0.97
6 - 0.98-0.90
7 - less than 0.90

Besides simply expressing intensity of a workout at any given time, these RPE, heart rate, power and pace intensity zones can be used to determine how long and how intense the key “breakthrough” workouts need to be to prepare you for stress of the competition. This is based on what the race will be like in terms of stress. Given some experience in racing you should be able to estimate what the stress of your race will be. For example, if you are doing a 90-minute, steady-state bike race that will be conducted entirely in zone 4 (using whichever system from above you prefer) then the stress of that race could be expressed as a "training stress score" (TSS) of 360 (90 x 4).

Now that you know the stress demand of the race the next step is to determine the key breakthrough workouts to prepare you for the race. In the early to mid-Base periods those workouts would involve low intensities, especially zone 2. So to do a 360 TSS workout in the first half of the Base period you could train for 180 minutes at zone 2 (180 x 2 = 360). This is a grea way to improve aerobic endurance.

By the late Base period you would be training with more zone 3 time so this would require 120 minutes (3 x 120 = 360). But by this stage it is wise to break the workout into intervals since this duration-intensity combination is becoming exceptionaly demanding. So if you did 165 minutes (2:45) including 5 x 20 minutes at zone 3 (300 TSS) with 4 x 5-minute recoveries in zone 1 (20 TSS), a 30-minute warm up with half in zone 1 and half in zone 2 (45 TSS), and a 15-minute cool down (15 TSS) you would again create a 360 TSS workout. Excellent muscular endurance trainng as you normaly should be doing at this time in the season.

In the Build period interval training would again be the way to go. And since we want the workouts to become increasingly like the race these intervals would be done in zone 4. A 367-TSS workout (a little over our 360 but not by much) may then look like this.

30-minute warm-up with half in z1 and half in z2 (45 TSS)
9 x 8-minute work intervals in z4 (288 TSS)
8 x 3-minute recovery intervals in z1 (24 TSS)
10-minute cool down (10 TSS)

You wouldn't want to do a workout like this too often. It's very hard. Probably no more than once every week or two would be best. This would depend on how stressful the workout must be to prepare you for the race and what your fitness is like at the time. Runners would also have to take into consideration the potential of injury from long and intense workout combinations.

This is a lot of work but it may be a way of getting you prepared for the stress of your race. You can do all of this or you can simply use WKO+ software ( with your power meter and/or accelerometer and GPS device. This software automatically determines a Training Stress Score (TSS) for each workout. You can also use this software to estimate the TSS of your races. This is what I do. Much simpler. And very effective.

1. Borg, GAV. Borg’s Rating of Perceived Exertion and Pain Scales. Champaign, IL: Human Kinetics, 1998.
2. Friel, J. The Cyclist’s Training Bible. Boulder, CO: VeloPress, 1996.
3. Allen, H. and A. Coggan. Training and Racing With a Power Meter. Boulder, CO: VeloPress, 2006.
4. Friel, J. The Triathlete’s Training Bible. Boulder, CO: VeloPress, 1998

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At November 22, 2009 5:32 PM , Blogger cavortingEagle said...

Very Nice. Clear and Concise. Thanks.

This weekend, I discovered that my Garmin would express my Heart Rate in "Decimal Zone." So, when I was in the mid to upper part of zone 2 it would say zone 2.6 or 2.7. Is it useful perhaps to further estimate the TSS of a workout by using average HR (expressed as a decimal zone)? Particularly for longer workouts conducted in zones 1-3...
thanks again

At November 22, 2009 6:23 PM , Blogger Jim Dicker said...


This is an interesting way to develop a quantifiable system based on RPE, but I think it is confusing, especially when you refer to WKO+ at the end. Why not just use the 100 TSS per hour at FTP, or zone 5 that WKO+ uses instead of setting up a whole new system. So the TSS for that 90 minute Zone 4 effort would be 1.5 (duration) x 100(TSS at FTP) x .9(percentage of FTP in Zone 4)? At least that way, when an athlete estimating the TSS required for BT workouts gets a coach or starts using WKO+ they will not be confused by TSS scores.

At November 22, 2009 6:54 PM , Blogger Zippy said...

AWESOME! I was just trying to figure out how to modulate my intensity this season to improve upon last season and it's like you read my mind!

At November 22, 2009 11:35 PM , Blogger Joe Friel said...

Hi Jim--Thanks for your comment. You're getting ahead of me. That's my next post with the intensity-duration complex based on estimated TSS. Wanted to start with what most people are aware of (mostly HR and RPE) and then move into normalized power and normalized graded pace as indicators of TSS. Stay tuned. Just need more time (got some?).

At November 22, 2009 11:47 PM , Blogger Joe Friel said...

cavorting--I don't see any big downside to doing that. Altho it may be a bit difficult to be that precise when it comes to what you might expect in a race.

At November 23, 2009 3:46 AM , Blogger Matt said...

Question re: RPE. Should this be graded on purely cardiovascular 'stress'? A run can be 'tough' due to fatigue, injury/discomfort, or even conditions, even though CV intensity is (measurably) low.

At November 23, 2009 4:54 AM , Blogger Joe Friel said...

Matt--Using Borg's RPE scale your 'grade' is based on total body perceived effort.

At November 23, 2009 6:37 AM , Anonymous Anonymous said...

Thanks for a great article! It expands on what is covered on this topic in the cyclist training bible.

It seems that you do consider RPE to be the most optimal way to monitor exertion, since, by necessity, it have to include every physiological aspect and also provides more accurate exertion zones for the current fitness status.

Could you please give some pointers on where the lactate threshold may be found within the RPE scale? Also, since most of your teachings tend to be centered around the same seven HR and power zones, it would be really helpful if you could give some pointers on how to translate these same seven zones for use with the RPE scale.

At November 23, 2009 7:06 AM , Blogger Joe Friel said...

anon--I believe all of that is in the Training Bibles. In the intensity chapter. Traveling so don't have one here now.

At November 23, 2009 9:03 AM , Anonymous Niels said...

I think the idea behind the TSS is pretty good. However, I have a little problem with the calculation. If I increase the load from zone 4 to zone 5 TSS increased with 25 percent. So to ride 10 minutes in zone 4 corresponds to riding 8 minutes in Zone 5. My experience is that the difference is much greater. It is nearly twice as hard.

At December 2, 2009 1:44 PM , Blogger Jeff Winkler said...

Can you clarify what appears to be an inconsistency (or a misunderstanding on my part):

In your Estimating TSS post (Sept. 15), you indicate a Zone 2 effort is 50-60 TSS per hour. Thus, a 360 TSS workout would be 6-7 hrs at high Zone 2. However, in this post you suggest that such a workout only requires 3 hrs at Zone 2.


At December 2, 2009 2:44 PM , Blogger Joe Friel said...

Jeff--I don't recall saying anything about a 360 TSS z2 workout. Can you tell me where that is?

At December 2, 2009 2:49 PM , Anonymous Anonymous said...

During base, I understand that most training should happen in zone 2. Do you prefer higher frequency or longer duration? Does this tradeoff depend on sport? For example, would you advise 3 longer runs or 5 shorter runs, time permitting? Thanks. Christopher

At December 2, 2009 3:21 PM , Blogger Joe Friel said...

anon--good Q. I prefer duration. But frequency is ok at this intensity. Longer runs build aerobic endurance. Shorter runs _can_ improve speed skills. So depends on what your purpose for the workout is.

At December 2, 2009 6:09 PM , Anonymous Anonymous said...

Dear Author !
Excellent idea

At December 6, 2009 3:19 AM , Blogger Bob Turner said...

Incredible info. Thank you!

At December 9, 2009 10:21 AM , Blogger Jeff Winkler said...

Sorry, by "this post", I meant this one from November 22 entitled "Stress-Based Training"

You talk about about "breakthrough" workouts in the second half of the post. You use 360 TSS in your examples of different types of "breakthrough" workouts to simulate goal race workload/intensity.

At December 19, 2009 5:45 AM , Anonymous Gav8 said...

Hi Joe,

Do you have any recommendations on average TSS scores for a total weeks workouts for each period, for example an average TSS for a week in each period:

Transition - TSS 400
Prep - TSS 800
Base 1 - TSS 900
Base 2 - TSS 1000
Base 3 - TSS 1100
Build 1 - TSS 1200
Build 2 - TSS 1300
Peak - TSS 1400

These are just rough figures to give you an idea of what im trying to say.

At present my TSS from week to week, period to period doesn't vary too much, maybe a few 100 difference although intensity varies from alot of longer Zone 2 and zone 3 work in the base periods increasing intensity to zone 4 and zone 5 work in build and peak periods but with less duration.

Would TSS remain roughly the same level throughout the year or would it gradually rise as you approach your race?



At December 19, 2009 6:50 AM , Blogger Joe Friel said...

gav8--I really can't recommend a weekly TSS 'score' as there are too many variables. Everyone is different. usually I've found that TSS increases as the season advances. This is often due to available daylight and weather conditions.

At December 25, 2009 3:58 AM , Anonymous Anonymous said...

I want to quote your post in my blog. It can?
And you et an account on Twitter?

At December 25, 2009 5:48 AM , Blogger Joe Friel said...

Anon--Yes, it's ok to quote my blog in yours. Please provide a link to my Blog if you do. thanks!

At February 3, 2010 9:09 AM , Blogger Rosey said...

Hi Joe, when zone 2 (on a trainer, KK Rock n' roll, Ibike Pro Power meter) feels like RPE 6-7(10 scale), power reading in upper zone three, but HR is in zone 1 which do I go by? I know HR is the focus, but my zone 2/E2 rides seem harder than they should be. Am I falling victim to the dreaded mental beatdown of riding on a trainer 12-17 hours per week? Thanks, Chris.

At February 3, 2010 8:43 PM , Blogger Joe Friel said...

rosey--I have athletes use HR in base 1 and power after that. In the early base period there is often a big discrepancy between HR and power zones. But first, confirm that you have both right. Are you using power zones that you had last season? Or have they recently been determined. How about HR zones. Confirm both are correct.

At February 4, 2010 5:24 AM , Blogger Rosey said...

Thank you Joe, they are both from a 22.5mile TT (50:06 effort) in early Aug 2009. I'm in week 3 of Base 2. When is it appropriate (good training flow) to substitute a test into the plan? Substitute a T2 test for an M1/F1 day, or just wait until the normally scheduled T1 test in Base 2 recovery? Thank you! ~Chris.

At February 4, 2010 9:00 AM , Blogger Joe Friel said...

rosey--HR may be ok from an Aug test, but power is not. It changes rapidly. You need to retest it.

At February 20, 2010 4:22 PM , Anonymous Anonymous said...

Hi Joe,

I've just read the excellent article on training specificity and you wrote:

"...the specificity principle says that if you want to become good at something you need to do that thing..."

"...if your goal is to run a 7-minute pace you need to do a lot of 7-minute-paced running. Not 8 minutes and not 6 minutes..."

I understand the importance of aerobic endurance training early in the season, but the Build period is supposed to be highly (race) specific... and 9x8min intervals are quite different from 90min steady-state work. Shouldn't there be TT-like workouts?

all the best,


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