In this video, coach Joe Friel examines the relationship between fitness, fatigue, and race readiness. Strike this balance right with your athlete’s training load and you’ll have them arriving at their race with fitness high and fatigue low, which results in favorable form.
CTL (fitness) – ATL (fatigue) = TSB (form)
It’s important to remember that fitness (Chronic Training Load, CTL) improves slowly—over weeks and months—while fatigue (Acute Training Load, ATL) can accumulate rapidly, over days or even hours. Every athlete will be different, and it’s the coach’s job to determine how best to balance this training load, so that race readiness (form or Training Stress Balance, TSB) is optimized. Friel shares his insights into how best to do this, ideally by getting your athlete’s form to within a certain range.
Hi, I’m Joe Friel, I want to talk with you today about a concept that you may already be familiar with. A lot of coaches are familiar with the concept, but they don’t understand the deeper aspects of it. I want to take you through this concept, it’s called the Training Load, and how the training load can be tied into a model (a training model) that gives you some feedback on how your athletes are doing.
The whole idea here is we’re trying to figure out how much training load your athlete is managing at any particular point in time. By doing that, draw conclusions as to how their fitness is doing, how their fatigue is going, and how much they’re ready to race at the given moment.
The Basis of the Training Load Model
So let’s start by looking at this chart see video above (00:50) that has to do with Training Stress Score (TSS). This is a real simple concept. You can see here that we have on the left side of the chart, we’ve got fitness for the athlete, and across the x-axis we have time. As we change the the training load, there are changes taking place in the athletes fitness, simply because we’re changing the amount of training they’re doing. As we can see, as the stress increases, fitness increases over time. That’s an important concept. I know it sounds almost ridiculously easy to even be thinking about. But, that’s the basis of the model.
The Relationship Between Fitness and Fatigue
If you produce a training load for your athlete, the athlete is experiencing stress. We stress them by doing frequent workouts, long workouts, high duration, or high intensity workout. So those are the three things we’re toying with to create stress for your athlete. Because of that, what’s happening is we’re affecting the athlete’s fitness. The other thing that’s producing the same time fitness is being produced is fatigue. The athlete’s becoming tired because of the stress. If we realize that both of these things, if we increase the training load in both of these concepts, both fitness and fatigue increase after we’ve increased the training load. What does that tell us about the relationship between fitness and fatigue? It tells us that they trend in the same direction. If one is increasing, the other is increasing. If fitness is improving, fatigue is increasing at the very same time. We all know one thing about fitness, if it’s improving, it’s improving at a very, very slow rate, it doesn’t improve quickly. Probably, it’s going to be somewhere around six weeks on average, to be able to see changes to take place for your athlete. For example, if the VO2 max for your athlete increases, you’re probably not gonna be able to measure that until about six weeks out. That’s when you’re finally going to get to a point where there’s enough change taking place that you can actually see it with the equipment that we have available to us today.
Fatigue on the other side happens very quickly. Whereas fitness happens slowly over the course of weeks. Fatigue happens in hours, maybe days at the most. So, if an athlete does a hard workout today, that means the athlete is going to be fatigued tomorrow. The language we use to explain that is the Chronic Training Load (CTL), which happens slowly. Chronic means over a long period of time. When we’re talking about fatigue, fatigue happens very quickly, as in hours or days at the very most. Fatigue happens very, very quickly or in a very short period of time. That’s the Acute Training Load (ATL). So, we’ve got CTL, which is referring to fitness, and we’ve got an ATL, which is referring to fatigue.
How to Improve Fitness
So let’s take a look at this model now in a chart form see video above (03:39) to think about these concepts of how we can improve both fitness while we’re dealing with fatigue for our athlete. What we’re looking at here now is simply the measurement of the athletes fitness over the course of time. Again, CTL is simply a way of expressing the more common term we use which is fitness. As the line is rising, that blue line is rising in the chart, we know the athlete’s fitness is increasing over time. As that blue line is dropping, we know just the opposite is happening, the athlete is losing fitness. If we take one spot on this chart, let’s take the spot which is about the first of January. What we’re looking at for that spike, that day is looking at the TSS for that given day. For that day plus the previous 41 days. So, that’s a 42-day rolling average is what we see at that point where that spike takes place right there.That is happening for every day on this entire chart. For one year we’re looking at every day as a 42-day rolling average.
We can see over the course of time that our subject here David Shell see video above (04:45) has seen an improvement in his fitness. His fitness is rising very nicely. We can see it begins to plateau somewhere around about April 1, it begins to plateau. What that’s telling us is that David at that point, as has decided not to increase his training load anymore. He’s flattened out his training load. Because of that, in other words, he’s not adding more stress to the athlete, he is actually monitoring the stress and keeping it at a steady level. Right toward the end of that, right toward the end of May, you look back up at the chart that you see a spike. What that tells us is, because of the plateau is that David was tapering. He was preparing for a race, and the race is that spike. That’s what that spike is telling us. This is the hard very hard day, because all of a sudden, we see a jump in the athlete’s fitness because the training load was increased. The race was very hard. We can see this happens again, later in the season. What does that tell us? David was trying to prepare for a big race right at the end of the season, which is that big spike, he was making sure he was fresh and rested coming into the race. He accomplished the race, which is a big challenge to him, he put a lot of stress into that event. Then he decided to take some time off. We can see the line is dropping almost vertically, that means lots of zeros going on. He’s taking days off, he’s resting, to make sure he comes into the off-season, which is what we’re starting now. Very well rested.
How to Improve Fatigue
Now we’re looking at a slide see video above (06:22) that has to do with what’s called the ATL. Instead of calling it the the ATL, when we refer to this from now on, as is fatigue. This is for the very same period of time, for the very same athlete. You’ve looked now at that fitness, and here we’re looking at fatigue for the very same period of time. Two separate charts, but they’re really over the same year for the same athlete. So, notice this is very spiky compared with the chart we was looking at before. That’s because fatigue happens very quickly. If you do a hard workout, you’re very tired the next day, and this fatigue may last you for several days. Whereas when you do a hard workout, we can’t measure changes in fitness for several weeks. That was the 42-day rolling average.
This now what we’re looking at with fatigue is a seven-day rolling average. I can show you the exact same things that happened here. We talked about on the previous chart, we talked about David preparing for a race that was going to happen some place in late May or so. We can see what David was doing here, he was decreasing his fatigue, as he prepared for that race. In other words, he was tapering or peaking. Then you’ll notice after the race, after that big spike, there’s a drop again. This means he’s simply recovering from the race, he’s not training hard at all. When you’re not training, we know that fatigue is going to go down. But what happens to fitness? It also goes down.
Then we can see somewhere around early June, he starts to train hard again. You can see that fatigue is starting to rise rapidly. Late August, September, you can see he’s backing off on training again, there’s a decrease in fatigue taking place. Then, all of a sudden, there’s a big spike in fatigue. He’s doing the last race of the season, and then if you follow that, to the right of that you can see the vertical drop is taking place in his fatigue. In other words, he is resting. At the bottom, you can see it where it bottoms out about the first of October. Right about there, he decides to start training again to get ready for the coming season. We see the increase taking place and fatigue.
This is fitness and fatigue. We can see the trend the same direction, whenever fitness is increasing, fatigue is increasing, because we’ve increased the training load. We can look just way down to the right end, we can see that begin the big drop is taking place at the end of the season, when David decides to rest and take a break from training. So there we’re seeing changes in fitness and fatigue over the course of an entire year for the athlete.
Race Readiness and Freshness Equal Perfect Form
But this is not all, there’s one more thing here that is critical to understanding your athlete’s readiness to come to a race. This is a thing that we call form. Form is a little bit more vague than either fitness or fatigue. What form is all about is two things. The first thing is race readiness. In other words, the athlete has now gone through all the preparation for the race they need. They’ve developed the fitness they need for the race. They’ve gotten that to a high level that’s part of race readiness. They’ve got other things going for them also such as nutrition (race day nutrition is part of that). Being prepared for the heat and the race, so all these things that go into being ready on race day is a part of this thing called form.
But there’s another part of this which is really critical, and that’s called freshness. Freshness is the opposite of fatigue. Freshness means the absence of fatigue. It means the athlete is rested and is ready to go. That’s what freshness is all about. When both of those things are happening. We need CTL to be high, in other words fitness to be high. Then we need the athlete to be fresh, which means fatigue is going to be low. If we have both of those things happen the same time, the athlete comes to the race ready to go, they are on form.
Formula to Calculate TSB (Form)
Everything else we’ve looked at so far had a mathematical definition. Same thing with with form or TSB, the formula is CTL (fitness), minus ATL (fatigue), equals TSB (form). I know that sounds quite confusing just on the surface, but let’s think about it. If you take the athlete’s fitness, where it is right now, and we remove the fatigue, what we’re left with is form. Therefore, this is the same chart, the same period of time, the same athlete, all the data is the same. But now what I’m looking at is CTL minus ATL. So I’m looking at fitness minus fatigue, which leaves me with TSB. Now there are going to be some points then where you’re going to have positive numbers, and negative numbers. If ATL, in other words, fatigue, if the fatigue number is higher than the fitness level, if ATL is a bigger number than CTL, when you subtract them, you get a negative number. That’s obvious, it’s just math.
What you see on the chart see the video above (11:26), is you see a dotted line, that dotted line represents zero TSB, whenever the athlete is below that line, the athlete is not on form. When the athlete is above that line there, they may be on form. I’ll come back to that maybe here in just a little bit. So, what we can see then if the idea is bringing the athlete into form, we can go back to this chart again and find the same thing as we found before on the other two charts. We can find where David was preparing for his first race, which is some time in June. We can see he’s coming into form, he’s ready, he’s going to be ready to race, perfect – exactly what he wanted to do. Then, we can see that line drop (form line drops), what does it mean when form line drops? That means we’re increasing the training load. Fitness is rising, fatigue is also rising, and the the difference between the two produces a lower training stress balance or lower form. We can follow to the right from that point back in June and we can see again, when he comes to the last race of the season. You can see a spike there somewhere around September 1, or slightly after September 1, you can see a spike followed immediately by a decline in his form. That means he just had a race, and now we’re to the week after, and he’s taking time off.
Deep Dive on the Concept of Form
We’re back to the very same exact spot we talked about for David in terms of fitness and fatigue earlier. There we can see that form begins to go really high. Now this presents a problem to us. We’ve talked about form as being above that dotted line, which is zero. We talked about that as being the athlete being on form. But, you can be too much on form, you can have too much freshness. You can be too rested. What happens when you have too much rest? That simply means that fatigue is going down. If fatigue is going down, what’s happening to fitness? It’s also going down. So we’ve got a concern here that we can wind up with too much form going on for your athlete, that’s risky in terms of having come into a race with too much rest, because you’ve lost too much fitness.
So let’s take the concept of form a little bit deeper. The athlete can have various aspects of form. The athlete can have what I would call strong form, meaning CTL is high, in other words, fitness is high, and TSB or form is also very high, it’s positive. In other words, it’s above the zero line, the dotted zero line. If we have both of those things, the athlete has strong form. However, if it goes too far above that, we’ve now lost that strong form because we’ve gotten too much fatigue, or too much rest going on in the athlete’s training, and we’ve lost some of that fatigue, which means we’ve also lost fitness. I would suggest to you, and this isn’t individualized but what I’ve done with my athletes over the years, is I’ve tried to get on race day I’ve tried to get their form to be somewhere between plus five and plus 25. I found that worked very well for my athletes, but that’s quite a range by the way. But I found that when my athletes got above plus 25, as far as their form is concerned, that they were too well-rested. They’ve lost too much fitness.
Consequently, if you’re trying to make a decision on how high to take your athlete, the only way you can figure out the answer to that question is by trial and error. How does my athlete respond when we reduce their training or increase their training as they come into a race?
Consequences of Weak Form
We can also have weak form. We can have the athlete at a point where their CTL is low and they have positive TSB. Positive TSB could be below that dotted line zero. In other words, the line is trending upward. If the TSB line is trending upward, then the athlete is experiencing positive TSB. But, when the CTL is low, the athlete is not going to come into the race on form with that combination. We’re trying to get CTL high, and come into the same time with a positive TSB. So those two things, we’re trying to balance these things, this is part of the challenge the coach faces in trying to get the balance of this training load right as we move closer and closer to the event for the competition.
Also, we can have TSB trending negative or positive. When your athlete is training hard, TSB form will be trending south, it’s going down. When the athlete is beginning to rest, what’s going to happen is (in other words, trying to come into form) TSB is going to start rising.
Fitness, Fatigue, and Form Blended Together
So when we look at that chart see the video above (16:19), we can see that happening with the athlete. So let’s look at the entire chart now for the athlete. This is all three aspects, all blended together for fitness, fatigue, and form. You can see exactly what’s happened to this athlete over the course of time. I would suggest the most important part of this chart is form. The athlete is typically training for the given event, and you’re trying to make sure that they come to that race with the form they need on race day. You can get overly involved in CTL and ATL. They’re interesting numbers, but quite honestly the bottom line is TSB. That’s the one you should be paying attention to. The others, of course, simply are ways of coming to that final number, that TSB number. So that’s the whole concept, that’s what this chart is all about. Hopefully by studying this, you can see how your athletes are doing in preparation for an event.