Working on endurance: with a power sensor or with cardio?

Following on from our article on the interest of low intensity training to progress, we offer you some tips for managing this type of outing if you are equipped with a heart rate monitor or a power sensor. 

By Guillaume Judas – Photos: depositphotos.com

Contrary to popular belief, it is not enough to pedal like a madman and without thinking to progress, especially in the long term. To build a solid physical condition and see profound changes in metabolism, and then be able to make the necessary efforts to gain power, you have to devote a lot of time to what is called low-intensity training, or "endurance."

But beware, The real work of endurance is not about accumulating hours in the saddle at low speed. Of course, "old-fashioned" outings with a few companions of the same level, doing miles and gradually increasing the mileage each week, produce good results. This is on the condition that youtagto avoid the relays, to avoid remaining hidden in the wheels for three quarters of the outing or to also avoid too frequent racing games.

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Real endurance work is done at a target pace, and the maximum time spent in the target zone allows you to optimize your training. In other words, a well-executed 3-hour outing is more profitable than a 5-hour outing done imprecisely, alternating between moments with too little stress and others in race mode. For endurance, we are talking about an intensity that corresponds to an effort without any muscular pain, which allows easy conversation, which leads to normal fatigue after 3 or 4 hours, and in an effort zone located between 50 to 65% of PMA and 75 to 85% of FC Max. So it means: easy, but “busy”, or “focused”.

For a cyclist with a PMA (Maximum Aerobic Power) of 360 watts and a max HR (Maximum Heart Rate) of 170 beats per minute, the target pace for endurance training is therefore 180 to 230 watts, and approximately 125 to 145 beats per minute. For a cyclist with a PMA of 300 watts and a max HR of 200 beats per minute, we should find values ​​between 150 and 195 watts for power, and between 150 and 170 beats per minute for cardio. This is why This type of session must be individualized or carried out in a small group with cyclists of an equivalent level. Otherwise, the weaker rider may not be working in the right zone and therefore not doing productive work, and the stronger rider may be wasting his time. Getting in the wheels of stronger riders is also not a great solution, because the energy saved on the flat is too high for the session to be profitable, and conversely there is always a risk of going into the red on the uphill sections by following better trained riders.

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Heart rate monitor or power sensor to target the desired intensity?

When the PMA and the max HR are known, it is quite easy to determine the target zone of the training, at least theoretically. However, it is important to know that Power is a direct measure of effort, while heart rate is an indirect measure. On a very short and very intense sprint for example, with maximum power over a short distance, the heart rate is not significant. The heart does not have time to "climb". Conversely, on a small descent or when passing a roundabout, there is little or no power production, and yet the heart takes a certain amount of time to "come down" to a value close to that of rest. And this phenomenon is all the more noticeable as fatigue sets in during a session. On the other hand, the more the physical condition improves, the more quickly the heart comes down after a request. This is what is called cardiac braking.

Ideally, An endurance outing is productive when the power and heart rate curves follow the same trend, and that it is possible to maintain the same power without seeing the cardio curve drift upwards, or conversely without seeing the power curve drop while maintaining the same heart rate values. If this is the case, it means that the session is poorly conducted, or that the athlete is reaching the limits of fatigue in relation to his current physical condition.

Both tools are therefore interesting for carrying out an endurance session. Nevertheless, We can consider that a heart rate monitor is sufficient in winter, or at least when resuming regular activity. Because the max HR is little impacted by the level of training, unlike the power and the values ​​of PMA and FTP (Functional Threshold of Power, or the maximum power that a cyclist can maintain for 1 hour). The ventilatory thresholds linked to the heart rate are also little dependent on the physical condition. Thus, relying on the range 75-85% of max HR during the training resumption period allows you to avoid big mistakes. On flat or slightly hilly courses with few restarts, regularly staying in this target zone by very gradually increasing the duration of the sessions already allows you to progress significantly, even before imposing a painful test of PMA or FTP.

Because in the case of training with power, respecting the right target zone requires knowing the PMA (or FTP), in order to deduce the right intensity values ​​to respect. Power production drops quite quickly after a period of detraining, and of course it takes several sessions before returning to previous values, which are linked to both physical condition and technical mastery of pedaling. The PMA is therefore not a fixed value throughout the year., and it can easily vary by 20 to 30% for the same individual between peak fitness and total detraining. With a power sensor installed on the bike, it is possible to testregularly exercise your PMA to bring it up to speed, making a maximum effort for 5 minutes. But this remains a very demanding effort, and not very reliable when it comes to resuming.

When the condition is more solid and the PMA and FTP values ​​are approaching their best level (or at least they are starting to be stable compared to what we see in the field), the power sensor becomes a more reliable tool for working well in endurance, without taking into account the inertia of the heart rate. With a power sensor, It thus becomes possible to smooth out the effort as much as possible to spend as much time as possible within the desired zone. But pedaling continuously in the 40-50 watt range is not that easy. It involves avoiding power peaks in response to the terrain (small bumps, false flats, accelerations, etc.) but also maintaining constant pressure on the pedals on descents and false flats going down, and limiting any freewheeling moments.

The home trainer for endurance?

Thanks to new devices and applications, practicing home trainers is no longer as daunting as it was a few years ago, whether in terms of sensations or the fun side. As long as you train in a cool and well-ventilated room, it becomes possible to do fairly long sessions on varied virtual courses, whether to compensate for capricious weather or to train during the week despite the night falling very early.

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The home trainer offers the advantagetagand to allow you to ride while controlling a maximum of parameters, which is ideal for endurance work. By avoiding all the risks linked to traffic, and all the situations likely to interrupt pedaling, the practice of the home trainer allows you to pedal very regularly in the target zone, whether in power or heart rate. And since there is no freewheel time, the time spent pedaling is really optimized to train at the desired intensity. No need to chain long sessions to work on endurance. In addition to a single long outing per week, several shorter outings help to progress from the moment the effort zones are respected.

However, it is necessary to take the same precautions as for training on route : heart rate is likely to drift with fatigue, especially if dehydration linked to indoor conditions is added. As for training with power on a home trainer, it is essential to opt for specific references, because the power on route is not necessarily the same as on the home trainer, this depending on the type of device, the software, or even the way in which one pedals on the route and indoors.

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