Training intensity - form, fitness, fatigue

How much an athlete needs to spend training in a certain intensity zone depends on the type of events they are participating in.

The shorter the race, the more they will spend at and above their anaerobic threshold. The longer the race is, the more time they will spend in aerobic zones to build the needed endurance.

Let’s dive into some more interesting topics and physiological states the athlete’s body goes through in today’s blog post.

Training time by intensity zone

Training for a 5k or 10k race is very different from training for a (half/ultra)marathon. The most obvious reason for this is that training for a sprint race requires a lot of work around the anaerobic threshold while any endurance sport requires a lot of work around the aerobic threshold.

How much exactly someone should train is hard to tell because even something as short as a 10k race or sprint triathlon can have large differences between someone who is at the front of the pack compared to someone in the middle or back.

This is something that we need to keep in mind when analyzing proportions of training zones because how much an athlete trains in a particular zone will have a direct impact on how well they will do in a given event.

Training volume for different triathlon races and how much an athletes should spend in a give intensity zone

As you can see from the image above, the longer an event is the more an athlete should spend in zone 1 and zone 2 training to build endurance in order to deal with the prolonged demand on their body.

One of the mistakes most endurance athletes make is to train too often and to long in higher zones than needed. Because of the overall training volume these athletes go through in a give period, the risk of injury and overtraining is great.

Measuring fitness

Let’s now have a quick look at a nice measure that will help us link an athletes heart rate to either power or pace. The concept of cardiac drift helps us determine if the overall work done around the aerobic threshold has been successful.

When training or racing for an extended period of time it’s natural for one of two things to happen. Either the athletes pace or power output will drop while the heart rate will stay the same or they will keep their pace or power output but their heart rate will rise.

This in itself is not a problem if the change is kept within a certain margin.

If the shift is less than 5 percent, the activity is considered coupled. If it’s greater than 5 percent, it is considered decoupled.

Even without calculating the exact percentages (something we will dive deeper into in the near future), athletes can just visually check if both lines stay parallel, as in the first image below, or if they start to drift, as in the second image below.

Coupled workout example. Pw:HR: 3.8%

Decoupled workout example. Pw:HR - 8.9%

There are two ways how athletes can train and try to achieve aerobic coupling.

They can perform an activity by keeping a certain pace and monitor what happens to their heart rate or they can try to keep the heart rate constant and then watch how their pace is changing.

When starting a new training cycle - base period - it’s generally better to focus on keeping the heart rate the same while during later stages - build phase - athletes should aim for keeping the pace or power output close to their racing conditions.

This enables the athlete to train at their target intensity levels while also working on raising their aerobic threshold throughout the season.

Once an athlete can get close to their racing durations and still keep the activity coupled, the athlete’s threshold fitness is fully developed.

Now it’s only a matter of maintaining this level of fitness but the good news is that these type of workouts can now be spread out more while leaving room for more race specific training sessions.

One more thing here to keep in mind is that being aerobically fit for a 10k run or an olympic-distance triathlon doesn’t mean that the athlete is aerobically fit for longer races, while the opposite is always true.

Form, fitness, and fatigue

Just as we talked about the perfect training schedule and it’s components (frequency, intensity, and duration), the perfect season needs to balance three different stats - form, fitness, and fatigue

Balancing these things is based on the premise that the entire training process will lead the athlete to their desired performance goals. The athlete and their coaches trust that putting different workouts in a certain way will result in peak performance on race day.

To be sure that they are on the right track, athletes will perform regular performance test (every 4 to 8 weeks) and the results are then compared with previous data and corrections are then applied if needed.

The problem this entire process has is that improvements in performance for any athlete that hasn’t just started out is quite small when compared to a month or two months ago. It hovers in the 1 to 3 percent range and thus can be just a byproduct of the weather, previous training sessions, or even what the athlete had for breakfast that day.

The good news is that at least for cycling where power meters are now a well established tool, and to some extent running these issues have somewhat been resolved. To establish an athletes form, fitness, and fatigue, a whole new set of variables needs to be taken into account and it will as well be something that we will dive deeper in the near future.

The key point to keep in mind for now is that everything boils down to something called a performance management chart.

Performance management chart sample

The three components we described earlier are all displayed on this graph so let’s explore them a little more.

The blue line represents the athlete’s fitness throughout the training process. It had a sharp decline after the athlete got sick with Covid and so training was stopped for almost 2 months until he fully recovered. Their fitness obviously kept falling because the body wasn’t stimulated at all during that time.

At the same time fatigue, the purple line, was falling at at an even greater rate for the same reason. It represents how fatigued an athlete feels after a few days of training. We can’t push this line to keep climbing forever or the athlete will break at some point and get injured or overtrained. That’s why it’s important to add days of very light training as well as days with no training at all.

On the opposite side from fatigue, form, the yellow line, shot up a great level because they were well rested and, theoretically, race ready.

Once the athlete started feeling better it was time to slowly build up training intensity and duration and we can see a steady rise in fitness. Ideally, the athlete’s fitness will rise until the target race while we keep form in the negative throughout but the athlete had planned vacations with minimal training so we had to adjust their training plan.

Generally, the athlete recovered nicely and had a great race and of May. When we started another cycle of training to prepare him for the second part of the season.

One of the things to keep in mind here is that we have to be deliberate when it comes to rest. Once an athlete is just a few weeks or days away from their target race, we have to start adding more rest and shorter training sessions to allow them to fully recover and have their form rise into the positive.

Their fatigue will fall rapidly while fitness will fall as well but at a very smaller rate. That’s something we have to accept because a well rested athlete with a slightly lower fitness will beat a tired athlete with a lightly higher fitness more often than not.

We will dive into this fascinating topic a lot more in the coming weeks as well as look at different workout types we can perform to improve different parts of an athlete’s fitness.