Let me start with a little history! :)
When we started working with the Olympic and World champions, they faced two general problems. In the preparation period, while they tried to build their form with HIIT workouts for the next season, their endurance was significantly reduced. The other problem was that they couldn't maintain their form during the racing season.
Thanks to our cooperation, we realized that the abilities that they had to improve were defined correctly, but often, the training protocols to improve them were not optimal. Because of the non-optimal training protocols, in the best case, they improved the desired ability but with little efficiency. And, in the worst case, they improved or reduced other abilities.
To achieve the optimal training protocol at each training session, we had to monitor the energy generation systems in real-time during the workout and adjust the predefined protocol's parameters at any moment to make each protocol fit each athlete personally and improve their desired ability with maximal efficiency.
For real-time monitoring, we developed mnsX™, which uses a method to calculate SEP™. Thanks to SEP, the athlete gets real-time feedback about the energy generation systems' status during the training session, and with this information, the athlete can adjust the training protocol at any moment to improve the desired ability with maximal efficiency.
Just a little bit of adjustment for significant improvement!
Before you jump into this topic, I recommend watching our animation video about mnsX in a nutshell and/or reading the
SEP topic (
here) to understand the monitoring topic better. mnsX introduces a new approach to training, which is why the monitoring topic is comprehensive and detailed. I've attempted to explain everything as simply as possible.
I hope you will find it interesting! :)
Aerobic peripheral or anaerobic ability
From the 5 basic parameters, determining intensity for a given (predefined) duration to improve the desired ability is the most challenging.
One of the most important intensity levels is the critical intensity level , which separates the aerobic peripheral ability improvement from the anaerobic. Around the critical level, there is a narrow area (borderland), which is 1-2% of the level (e.g., at 440 watts, it's 5-10 watts). If the intensity is below the critical intensity level (t5-t6), your energy production is aerobic dominant and stable, and you can maintain the effort for a longer period (steady state). If the intensity is above this level (t2-t3), your energy production is anaerobic dominant and unstable, which means you can't maintain the effort for too long.
The improvement of VO2 max is the most effective if you train at the highest intensity while your energy production is aerobic dominant and stable (steady state). In other words, if you train below but as close as possible to the bottom of the borderland.
The improvement of anaerobic capacity is the most effective if you train at the lowest intensity while your energy production is anaerobic dominant (unstable). In other words, if you train above but as close as possible to the top of the borderland, this is how you can spend the most time with anaerobic overload.
In our experience, for a well-trained cyclist with a 3' critical intensity level at 440 watts (t3), the most effective intensity to improve VO2 max is around 435 watts, while the improvement of anaerobic capacity is most effective at around 445 watts (t5-t6). Therefore, even a small 10-watt difference in intensity during a session can result in a significantly different training effect. Using mnsX, which monitors your energy generation systems, allows you to work precisely on the borderland. Without it, you may need to choose intensities further from the momentary borderland.
The continuously changing critical intensity level
Because the momentary energy production capability is continuously changing during a training session, the critical intensity level, which belongs to a given (predefined) duration, is continuously changing, too. If you want to improve your abilities with maximal efficiency, it is crucial to know the momentary critical intensity level and its 1-2% wide borderland.
Most of the time, the 7 power zones are calculated from the last CP20' (FTP20') data, and the critical intensity level is placed somewhere on the border of Z5-Z6, depending on the given (predefined) duration. There is a more accurate method: with 5", 1', 5', and 20' maximal efforts, gets information about the athlete's aerobic capacity, VO2 max, and anaerobic capacity. With this information, the improvement intensity of an ability for a given duration can be defined more accurately.
Thanks to 100,000+ mnsX training records, we have learned that the critical intensity level for a given duration can change by 5-10% between two training sessions and by 3-4% within a single training session. If the critical intensity level is determined using one of the previously mentioned methods, it will be fixed and may deviate by 5-10% from the optimal level. The 1-2% wide area (borderland) around this level is not considered safe, which prompts the need to increase the width of the borderland to approximately ±5-10%. However, the wider the borderland, the lower the training efficiency.
Let's take the previous cyclist and assume the 3' critical intensity level determination was accurate. It was really 440 watts when he did the FTP test. Then, in the next days, when he wants to improve his VO2 max with HIIT, he can use a maximum of 400-410 watts to improve his VO2 max safely. There is a chance that due to fatigue, the actual critical intensity level decreases to the point where VO2 max improvement turns into anaerobic capacity improvement.
The aerobic system's regeneration
In Zone 4 (out of 7) and above, it's crucial to ensure that aerobic energy production (aerobic background) is at its peak throughout the WHOLE training session. Therefore, HIIT's warm-up, regeneration phases during intervals, and cool-down must get special attention. The cool-down is the first step of the next key training. The point of all three things is to ensure your aerobic system works at the highest level.
Using SEP, you can monitor your "available aerobic power" at every moment during your training session. This information helps you evaluate the effectiveness of your warm-up and cool-down routines, but, most importantly, it allows you to monitor and manage the regeneration process after the anaerobic system suppresses the aerobic during high-intensity intervals.
In Figure 3. I will show how the SEP's dynamic changes when the HIIT's intensity increases.
Figure 3. (Click to Open)
In terms of regeneration, the most critical is when the intensity becomes so high that the anaerobic system becomes dominant and starts suppressing the aerobic system (t11-t12, t13-t14). This suppression temporarily reduces your aerobic energy production capability. It's important to note that suppressions are regular in HIIT sessions and are considered normal. However, if you don't handle them properly and you don't regularly regenerate your aerobic system properly (t14-t15), they can lead to a permanent reduction in aerobic energy production capability, resulting in reduced aerobic capacity and potential endurance reduction. SEP indicates (decreases) when the anaerobic system is dominant and suppresses the aerobic, serving as an alert for the importance of regeneration. Additionally, SEP helps you track the regeneration process to determine when your aerobic system is fully recovered after a suppression (t12-13, t14-t16).
SEP may decrease not only due to aerobic suppression but also when the intensity is low (t8-t9, t10-t11), which generally doesn't require concern.
When you train with mnsX, you will learn in no time how to understand and handle SEP, but now I'm sure not everything is clear. That's why I collected some parameters that can speed up or slow the regeneration for easier understanding.
Parameters that can speed up the
regeneration process:
- Larger aerobic capacity leads to faster regeneration. With a larger aerobic capacity, higher intensities require less anaerobic support. The anaerobic system becomes dominant (later) at higher intensities , which means the aerobic suppression is reduced. Consequently, at higher intensities, the decrease in SEP is smaller, and the regeneration time is shortened.
- Weak focus, also known as parasympathetic overload, a.k.a. when your brain is relaxed. The goal is to maximize your focus before the high-intensity phases of your training. This sharpens anaerobic system responses, and when the aerobic energy system requires assistance, anaerobic support comes super fast. After the high-intensity phases, it's advisable to minimize your focus. As your brain relaxes, the aerobic system regenerates faster. Doing the opposite can have adverse effects. If you minimize your focus before the high-intensity phase, anaerobic support will be delayed, and your aerobic energy production may become overwhelmed. Maximizing your focus before the regeneration phase can stress your brain, and the aerobic system will regenerate super slowly.
- Optimal regeneration intensity: Each phase has an optimal intensity for the most effective aerobic system regeneration. Below this intensity, the aerobic system is less engaged, while above it, the system is overwhelmed. Thanks to SEP, finding this optimal intensity is straightforward; it's where the SEP gradient is steepest upward.
Parameters that can slow down the
regeneration process:
- Smaller aerobic capacity leads to slower regeneration. With a smaller aerobic capacity, the anaerobic system becomes dominant earlier (at lower intensities), suppressing the aerobic system more (resulting in a more significant SEP decrease). That means the aerobic system requires more time to regenerate completely.
- Fatigue has a negative effect on the aerobic system too, increasing the regeneration time. In the regeneration phase, the SEP gradient upward is gentler.
- Strong focus means the sympathetic nervous system is more dominant than the parasympathetic. In the regeneration phase, your brain can't relax because of strong focus, and the aerobic system regeneration duration increases. The SEP gradient upward is gentler.
- The aerobic system is less engaged below the optimal regeneration intensity, while the system is overwhelmed above it. Both cases slow the aerobic system regeneration, which you can track with SEP as its gradient upward is gentler.
Regeneration with SEP
Regeneration between intervals is one of the most essential parts of HIIT. Thanks to SEP, you get complete feedback control at HIIT sessions. You can track the regeneration process in real-time and adjust the regeneration intensity and/or duration at any time, aiming for the most effective regeneration between intervals.
Regeneration duration: we can say your aerobic system regenerated completely and it is ready for the next high-intensity phase when your SEP reaches at least the same level as it was at the start of the previous high-intensity phase. With SEP, you can track the regeneration process and see precisely when SEP reaches the optimal level.
Regeneration intensity : because of complete real-time feedback control, you can easily define the optimal regeneration intensity by “playing” with the SEP gradient. Adjust the intensity to make the SEP gradient upward as steep as possible. So, SEP can reach the optimal level faster.
In Figure 4. You can see multiple cases of anaerobic overload and aerobic regeneration after suppression. I will show you how to monitor the regeneration process with SEP and define the optimal regeneration intensity and duration.
Figure 4. (Click to open)
SEP's gradient provides insights into the regeneration of the aerobic system and the extent of aerobic suppression. In the regeneration phases, the upward gradient of SEP indicates the speed of aerobic system recovery. A steeper gradient indicates faster regeneration (t8-t9), while a gentler gradient indicates slower regeneration (t13-t14). During high-intensity phases, the downward gradient of SEP indicates the extent of aerobic suppression. As intensity increases, both anaerobic support (blue) and aerobic suppression also increase (t3-t4). SEP decreases, prolonging the subsequent regeneration phase (t5-t6). With a significant increase in intensity, both anaerobic support and aerobic suppression increase significantly, and SEP decreases significantly (t6-t7). After an exceptionally high-intensity phase, the anaerobic system might continue suppressing the aerobic system for the next 1-2 minutes, further delaying the regeneration (t7-t8).
From Pr1 to Pr2, as regeneration intensity increases, regeneration becomes more efficient, resulting in faster recovery and a rapid increase in SEP (t8-t9).
When you stop after a high-intensity phase (t9-t10), your aerobic system regenerates immediately (t10-t11). However, our observations show that after 90-120 seconds, the regeneration process halts, and aerobic energy production and SEP continuously decrease (t11-t12). This happens because the aerobic system remains active for a brief period after high effort. Then, your body recognizes that the intensity has dropped to a low or zero level (t10-t11), making it seemingly unnecessary to maintain aerobic energy production, and starts decreasing the energy production. Your aerobic system won't regenerate, the energy production will decrease, and SEP too. This can be a serious problem because if you start the next high-intensity phase right after a regeneration phase where you stopped (t12), the aerobic system's energy production and SEP will be way lower than when you started the previous high-intensity phase (t12-t13). The high effort requires bigger anaerobic support, which means the aerobic suppression is more significant (t13), and the regeneration phase duration increases significantly (t13-t14). If this scenario happens regularly in HIIT sessions, it can lead to endurance reduction and a decrease in regeneration ability. After a high-intensity phase, stopping it is okay, but within 1-2 minutes, it is crucial to start regenerating the aerobic system at the optimal recovery intensity and not start the next phase before the aerobic system is completely regenerated.
After the next high-intensity phase (t14-t15), the Pr3 regeneration intensity is too high, slowing the regeneration process. The SEP upward gradient is gentler (t15-t16). Because the regeneration duration is predefined, SEP doesn't have enough time to regenerate. At the next high-intensity phase (t16), SEP is lower than at the start of the previous one, which means the aerobic system needs more anaerobic support, so the aerobic suppression is greater (t16-t17). The result is quite similar to what the complete stop in the regeneration phase causes.
Too high regeneration intensity
One of our achievements in professional kayaking is that we were able to change their training behavior with mnsX. Instead of completely stopping during the regeneration phase, they rest at an optimal regeneration intensity.
Our Garmin™ Connect IQ™ application and datafiled indicate the regeneration process (t20-t21). You can track it on your device, above the SEP graph, when the regeneration starts, how effective it is, and when your aerobic system is completely regenerated, and you are ready for the next high-intensity phase.
(Application is divided into 3 sections. The top is the HR section, bottom is the intensity, and middle is SEP. Right above SEP graph you can see the regeneration process.)
ArguStress Connect IQ™ App
Increasing intensity HIIT test
Figure 5. represents a HIIT session where the intensity of each high-intensity phase increases. The point of this test is to show you how the ratio of aerobic and anaerobic energy production changes according to the intensity change. The training protocol's all high-intensity durations and all regeneration intensities are the same. The intensity increases at each interval, and the regeneration duration is dynamic and depends on the aerobic system.
Figure 5. (Click to open)
The warm-up of the HIIT session is essential because you must “fire up” your aerobic system as high as you can (t0-t4). Higher aerobic energy production requires less anaerobic support at higher intensities, which means the aerobic suppression is smaller, and the regeneration is faster.
When the energy production is aerobic dominant, the SEP's gradient ascends when the intensity increases and descends when the intensity decreases. SEP's gradient follows the intensity change with a 1-2 minute delay. Basically, each intensity has a SEP value if the duration (of the intensity) is long enough (e.g., FTP20' ~ 100% ).
When the energy production is anaerobic dominant, the SEP's gradient behaves in the opposite way (t11-t15). As intensity increases, the gradient descends almost immediately. When the intensity decreases significantly, the gradient ascends almost immediately. The regeneration depends on the intensity.
When the energy production is aerobic dominant (t5-t10), regeneration after the “high-intensity” phase is not critical because there is no direct danger of endurance reduction, and the training is “safe”. However, selecting an intensity where SEP does not decrease significantly is advisable, because it allows you to execute the session with the highest possible aerobic energy production. Above AT, the anaerobic system supports the aerobic (t7-t10), but the energy production is still aerobic dominant. As intensity increases, anaerobic support also increases, causing the ascent of SEP's gradient to slow down.
When the exercise intensity goes above the critical intensity level (t11, t13), the energy production becomes anaerobic dominant. When the energy production is anaerobic dominant, the anaerobic support suppresses the aerobic system, and SEP starts decreasing immediately. You can't hold the intensity for a longer period. The energy production is “unsafe” and can cause endurance reduction. Higher intensity requires greater anaerobic support, which causes greater aerobic suppression and a more significant decrease in SEP (t13-t14). Handling each aerobic suppression properly is crucial. You must regenerate SEP to the same level as it was before the previous high-intensity phase started (t13, t16).
Because the t13-t14 interval intensity is higher than the previous one, the SEP decreases more significantly, and the t14-t15 regeneration duration is not enough for proper regeneration. That's why the regeneration duration is extended to t16 .
If you want to improve one of your abilities with “tc” duration, it is important to know the P1 and P2 intensities. Below P1, you can improve the VO2 max, and above P2, you can improve the anaerobic capacity. With this information, you can define the optimal intensity to improve the desired ability with maximal efficiency (with “tc” duration).