Tri Talk Triathlon Podcast, Episode 61

Introducing the decoupling protocol as a method to determine sufficient aerobic base, and how kick drills and circadian rhythms affect your swim performance. Today, on Tri Talk.

Welcome to Tri Talk your podcast source for triathlon tips, training, news and more. New listeners since episode 60 primarily hail from Wisconsin and welcome to our new listeners from Mumbai, India. In Wisconsin, it is a little known fact that Ironman Wisconsin 2009 will take place on my 35th birthday! What better time for me to try and qualify for Kona in the M35-39 division. That is if I can actually get in to the race. In India, I have fond memories of the 2 weeks I spent in Mumbai in 2006. Although, there was a minor episode where a monkey stole my lunch right out of my hands and then taunted me from a nearby tree. That really happened. My goal at Tri Talk is to help you swim, bike, and run faster, to meet your personal triathlon goals. Whether you are an elite or amateur triathlete, we cover sprint distance to Ironman distance. I’m your host, David Warden, and this is Tri Talk Episode 61.

Hey, I know it has been a month, since the last episode but I’ll make it worth your wait. By the end of this episode, you’ll be armed with the information you need to determine if you have a sufficient aerobic base before moving on to higher intensity training. We are going to take out all the guesswork in determining if your aerobic base has been achieved. Absolutely fascinating information. Plus, we have not discussed a swim topic in a long time on Tri Talk, so we will make up for lost time by covering 2 swim-specific research studies. This will allow me to maintain the claim to help you swim, bike and run faster.

Let’s get onto the good stuff! And I do mean good stuff in this episode.

One of the fundamentals of classic periodization training is that the macrocycle, let’s say 6 months, is divided into Base and Build phases. The purpose of the Base phase is to establish an aerobic base prior to introducing higher intensities in the Build period. The Base period is therefore filled with higher volume and lower intensities until that aerobic base is met.

As an athlete, one of the challenges is how to determine when that aerobic base has been met before moving onto higher race-simulation intensities. Yes, in a classic periodization training plan, there are 3 Base mesocycles, or about 12 weeks of aerobic base building before moving into the Build periods. However, what if an athlete is able to achieve their aerobic base after only 10 weeks of training? That would allow 2 more precious weeks of higher intensity training prior to their first A race. Or, conversely, what if an athlete has gone through a full12 weeks of base building, and assumes that they have achieved that aerobic base when in fact they have not.

Also, another risk of classic periodization is that it has a tendency to fit all race distances into one program. How much of an aerobic base do you really need for sprint-distance triathlon? Do you really need to work 12 weeks on the Base periods for sprint-distance racing? What if you just need 8 weeks and can spend the remainder of the time leading up to your A race with more focus on intensity?

Or, on the other extreme, with Ironman training, how do you know that you are ready to stop working on the long, slow rides? Maybe you need more than 12 weeks, even 16-20 weeks of base building without ever even flirting with those Build period intensities.

There is a method to determine if you have a sufficient aerobic base, and I want to thank Joe Friel of TrainingBible coaching for providing me with this information.

This test protocol simply compares your power or speed with heart rate over an endurance ride or run. There is some research to indicate that when aerobic endurance improves there is reduced heart rate drift relative to constant power or constant speed. And, of course, the reverse of this is that when heart rate is held steady during extensive endurance training, output may be expected to drift downward.

For example, the next time you download a workout from your training device, you probably have the ability to graph HR and power or speed on the same chart. In a perfect endurance ride, where there were no intervals or significant intensity, just a nice long Zone 2 ride, these two lines would run relatively parallel to each other.

However, you may have noticed that on some of these long rides, your HR tends to drift up even when output remains the same. Or, if you are trying to maintain a Zone 2 effort, you may notice that when you look at the graph that even though HR remained the same, out (power or speed) went slowly down. In those cases, the lines on the graph representing HR and output no longer run parallel, but begin to drift apart.

The parallel relationship between heart rate and output (power or speed) is referred to as “coupling.” When they are no longer parallel in a workout they have “decoupled.” Excessive decoupling would indicate a lack of aerobic endurance fitness.

But how much is excessive? There is an acceptable amount of decoupling that can take place and still indicate a solid aerobic base. A good indication that a base fitness has been met is less than a 5% decoupling over a Zone 2 workout.

That statement simply generates more questions. How do you calculate that 5%, and how long does the endurance workout need to be? Let’s review.

To determine the % of decoupling that took place in an endurance workout, you will need to be able to get the average HR and output (again output means power or speed) for the first and second half of the endurance workout. You then calculate the ratio of output to HR for each half, and determine the % difference between those two ratios, the ration from the first half and the ratio from the second half. Let me give a specific example. On a flat course, let’s say you performed an hour run in Zone 2. For the first 30 minutes your HR average was 150, and for the second half your average HR was 153. Your average speed for the first half was 7.5 miles per hour, and for the second half it was 7.4 miles per hour. You can already see that there was some drift in that workout. But was it too much?

The power to HR ratio of the first half of the run would be 7.5/150, which equals a ratio of 0.05. For the second half, the ratio is 7.4/153, which is 0.0484. The difference between these two ratios is 3.2%, which is an acceptable amount of decoupling, under that 5% goal.

Another quick example: on a 4 hour Zone 2 bike ride an athletes averages 230 watts for the first 2 hours and 220 for the second half. His HR averaged 141 for the first 2 hours and 149 for the seconds half. His power to HR ratio for the first half was 230/141, or 1.63. For the second half the ratio is 220/149, or 1.48. The difference between those two figures is a 9.3% decoupling. That would be an indication that this athlete’s cycling at that distance has not yet met an appropriate aerobic base.

I gave examples of an hour run and a 4 hour bike ride, but you certainly don’t have to get to a 4-hour aerobic cycling base for Olympic-distance training and racing. Joe Friel also sent me his recommended durations for running and cycling to test for decoupling, for each of the triathlon distances.

Bike decoupling portion of a long ride

Sprint – 1hr

Oly – 2hrs

HIM – 3hrs

IM – 4hrs


Run decoupling portion of a long run

Sprint – 0.75hr

Oly – 1hrs

HIM – 1.5hrs

IM – 2hrs

By the way, Joe is still experimenting with these numbers, and they could change as he refines his decoupling process, but this is what he is using now.

Now, there are a few more points to cover regarding this decoupling protocol.

First, when on the bike, you really have to use power. If you try to use speed as a measure of output on the bike, your numbers, of course, will be totally off. A slight tailwind for the first half and a slight headwind for the second will make your decoupling % artificially soar. Unless you can pull off a flat, windless ride, which we all know the cycling gods would never allow, you have to use power on the bike.

However, recall our discussion on the poor-man’s power meter in episode 54. It would be possible to use speed when on a trainer or set of rollers, where the topography and wind conditions would not be a factor. In that indoor environment, you could take your average “speed” for the first and second half of the ride and get the speed to HR ratios.

On the run, there is a similar problem. You would need to do this endurance run on either a very flat course, or on a two-loop course where the ascent and descent for both halves of the run were identical. What you would need to avoid was an out-and-back run with significant change in total ascent or descent, as this would really mess with your pace data for the first and second half of the run. And although wind does not play as much of a factor on the run as the bike, doing this protocol on an exceptionally windy day could influence the decoupling data. For the shorter endurance run decoupling tests, doing this on a track would be perfect.

But, you could also use some software from called WKO+ which will take the GPS data from your run and calculate your actual output factoring in those ascents or descents. For example, if you did an out and back run that had a total of 300 feet of descent on the way out, and 300 ascent on the way back, WKO+ would know that a pace of let’s say 7:30 on the way out was the same output, or run power, as 7:40 on the way back, factoring in the total grade of that net ascent on the way back. WKO+ will also automatically calculate your decoupling rate for any given workout, and can adjust for topography if it has GPS run data.

Another item that is blatantly missing is swim decoupling figures and durations. Joe Friel did not supply me with any swim decoupling data, but based on the theory of decoupling, and what we do have, I think we can create a rough estimate for the swim. Joe, if you are listening, I hope you’ll allow me some scientific license.

As with the bike and run, you can perform a swim and get both the average HR and average pace for the two halves of the workout. It can be tough to find a HR monitor and strap combo that works well in the water. But, let’s say that you perform the first half of a 30-minute swim with an average HR of 145 and the second half in 149, with an average pace of 1:55 per 100 meters for the first half, and 2:00 even per 100 meters for the second. The two ratios become 0.79 and 0.81, a decoupling rate of 2.5%.

The remaining question becomes what is the endurance swim workout duration to perform the test at? Here are some recommendations which are totally of my own making, simply based on the figures Joe provided on the bike and run.

Swim decoupling portion of a long swim

Sprint 0.5hrs

OLY 0.75hrs

HIM 0.75hrs

IM 1hrs


Of course you’ll note that I have both HIM and Oly distances the same duration for the decoupling test. Since the swim distances of these two events are only a few hundred meters apart, I didn’t see the point of getting anymore granular than that between the two distances.

So there you have it! I would suspect that for Tri Talk listeners in the Northern hemisphere, many of you are just about to start your higher-intensity Build periods since we are into the Spring season. This information is very timely, because doing this test will give you the confidence that your aerobic base is solid before moving onto the Build period.

Moving on! Do you do kick drills regularly? Do you feel like they help you? Let’s talk about a 2007 study published in the International Journal of Sports Science & Coaching that looked to objectively answer that question.

Fifteen male competitive swimmers were randomly assigned to either a control group or an experimental group, 7 in the control group and 8 in the experimental group. Both groups swam 3 times per week for 6 weeks. The experimental group spent 20% of their training distance performing kick drills, while the other group just did kick drills for 4% of weekly training distance, or only 1/5 the amount of kick drills as the experimental group. Before and after the training program, all swimmers performed a 200 m leg-kicking and a 400m freestyle time trial. After the 6 weeks of training, there were improvements in leg-kicking time in the 200m kicking-only time trial by about 6 seconds for the experimental group, or the group that spend 20% of their time with kicking drills. The control group did not see any improvement in their kicking times. But what was interesting was that neither group changed their 400m time trial over those 6 weeks. All the extra kicking, or the lack of kicking, had no effect on their swim times. The researchers concluded that, “These results suggest that normal leg-kicking swimming does not improve middle-distance, full-stroke, swimming performance.”

Based on this study, performing kick drills in your workouts appears to improve your ability to…perform more kick drills.

Seriously, I’m not very objective when it comes to this subject. This may be a case of me searching for the answer I wanted to hear, because I have always felt that kick drills were a waste of time. One could argue that this study really does not apply to triathletes, since our swim distances at any triathlon event would almost always exceed 400 meters. However, the amount of kicking that you do only decreases as the distance increases, so I don’t think this is an applicable argument.

On the flip side, it did not appear that the kick drills harmed performance in any way. If you continued to do kick drills, it looks like it would not hurt your swim performance. However, if you could be spending your time on other swim weaknesses, the risk of kick drills is that even if they do no harm, it takes away from other skills you could be doing that do have an established benefit.

Also from 2007 from the Journal of Applied Physiology, researchers from the University of South Carolina wanted to find out if swim performance was influenced by circadian rhythms, or in other words, if you swim better during different times of the day. To do this, they convinced 25 athletes to spend 50-55 hours in a lab environment.

The researchers were concerned that if they simply allowed the swimmers to sleep on their own schedule, that the variance would be too great between all the swimmers. What time a subject goes to bed, what time they get up, would be significantly different between all 25 participants. So, they kept them in the lab, and moved them all to a 3 hour sleep cycle. 1 hour of sleep and 2 hours awake for 50-55 hours. This way they could control the circadian rhythms of all 25 swimmers. Each swimmer did 6 200-meter time trials separated by 9 hours within that 50-55 hours at different times during the new “day” that had been introduced on them.

The researchers also knew that despite the temporary 3 hour sleep cycle, the subjects bodies were still primarily functioning on a 24-hour cycle. They way they decided to determine where they were in their true 24-hour sleep cycle was to measure the swimmers body temperature before each swim. Body temperature is one way to measure where an individual is in their normal circadian rhythm. Body temperature begins to drop as a person gets closer to their normal sleep time, and rises as they approach their normal wake time

So the 3-hour sleep cycle was only introduced to level the playing field in terms of the amount and timing of sleep between all 25 swimmers, but the ultimate goal was to determine how the swimmers performed in relation to their regular circadian rhythm, and they used body temperature to determine that.

What the researchers found was that the best swim performances took place 5-7 hours before the body reached it’s minimum temperature, and was the worst within the 1 hour before and after minimum body temperature.

Since the average adult reaches their minimum body temperature between 4-5am, this would indicate that the worst swim times for the average adult who sleeps from 10pm-6am, would be either from 3-4am, the hour before minimum body temperature, or 5-6am the hour after. The best times appear to be 9-11pm. The different in swim performance between these two times was 3 seconds per 100 meters, which is a significant amount of time.

I know that this information is interesting, but I’m concerned that it is not very helpful. It is unlikely that you can regularly swim that late in the evening, and the fact is that virtually all triathlons start early in the morning.

What this does assist with is perhaps deciding between morning or evening masters classes, if you have the choice, or even deciding between morning or evening swim sessions. Even then, since your swim racing will take place in the morning, training with evening swimming may not do you much good at all.

I think the real benefit from knowing this potential link between swim performance and time of day is that it is another one of numerous environmental factors you can be familiar with to truly interpret your training and help you understand why you might have completely different results from one training session to the next. Plus, now you know that you can also probably perform your kick drills even better at night, and as a result you’ll get even better at…performing more kick drills! See there I go again.


I want to congratulate Cameron Lasky of Highland, Utah and Jason Crompton of Evanston, Wyoming for their first and second place finishes at the recent 350-participant USAT sanctioned Icebreaker Sprint Triathlon. After guaranteeing an overall 1st place at the event to all my family and friends who came to support me, I was humbled by these two athletes, and I came in a distance third. Ouch.

A final warning to you, the Tri Talk listener! Shaving your legs can be fatal. After nicking myself with a razor while shaving prior to the aforementioned event, I developed a staff infection that spread almost to my groin before successful treatment stopped the spread. Yes, I almost died from shaving my legs. I’ll be back next month with some outstanding wind tunnel data from Colorado Premier Training. Don’t miss episode 62. See you next time!