I started doing more focused training and even did some Z2 Training and not only HighIntensity.
I noticed that some riders can ride like 2-3h in blue Z2 and their heart rate is almost completely constant.
Mine usually very slowly goes up after 1h from 130 to even 160 after 2h (ca 185-190 max). The intensity still feels very easy, but the heart rate is high.
I sweat quite a lot and don’t drink too much and usually don’t eat anything.
Is this a consequence of dehydration or missing glycogen or just missing stamina?
It’s highly variable in different people, but hydration and core body temperature are both significant factors so you can manage drift to some extent with proper hydration and cooling. Better fitness helps as well but you may as well manage it as well as you can with the body you have now.
You can find some more information here:
To execute zone 2 training properly you should reduce power as HR creeps up.
This is a pretty good primer on how to do zone 2 training:
Assuming a normal-sized heart and minimal to no stimulant use, the primary factor influencing HR and performance is overall cardiovascular fitness. Focus on how your resting heart rate evolves over time and track your VO₂max. The key lies more in your resting heart rate than your maximum, as well as how quickly your heart rate recovers after intense efforts.
The way I would put it is that fitness can’t be controlled in the short term. It is whatever it is when you get on the bike. Sort of like cramping problems: better fitness is the best medicine but until that comes you control what you can control. Hydration, cooling, and state of recovery are more manageable in the short term.
Regardless of current level, regardless of trends in levels, regardless of everything - HYDRATE. It’s hard to overhydrate and very hard to affect performance that way, but it’s easy to underhydrate and that’s guaranteed to affect performance.
The only performance cyclists you don’t see drinking and eating during rides are those doing sub-hour events (cycle cross, criterium, track).
Garmin GPS devices can be set to nag you to drink and how much you should have drunk during rides.
[On the scale of sweat glands per square meter, humans are way ahead of most animals. It’s part of our also very high endurance through excellent temperature regulation - but it only works if we keep that cooling system fueled. It’s not a sealed cooling system like on a car.]
This is a dangerous statement not supported by scientific evidence—more of an urban legend. In 2002, a study of marathon runners in the 2000 and 2001 Boston Marathons found that around 13% of participants had hyponatremia, with a small number requiring hospitalization. Since late 70’s, armature athletes in endurance events tend to over-hydrate. However, to each their own when it comes to individual choices. Peace out!
Also don’t forget to ventilate as well as hydrate! Your setup may already be fine, but for example some Zwifters use a shed or other quite confined space, and without a good flow of fresh air the CO2 levels in that sort of environment can go up quite quickly, meaning you have to work a lot harder as time goes on.
A fan is needed for cooling too, but don’t neglect having plenty of air.
Pre and post exercise weighing can provide a pretty decent gauge of whether that is happening or not. I’m well aware of the hyponatremia dangers having seen it result in seizure and a trip to the ICU by a family member (the extra treat was rhabdomyolysis) but I know that for me, under-hydration is a much bigger problem.
Another factor not touched on yet is that when you start your endurance ride you’re mostly using your smaller motor units which are more likely to be your best aerobically trained type 1 fibres.
As those fatigue, you’ll start recruiting larger and larger motor units which are more likely to be less well aerobically trained type 2 fibres. This creates that extra demand on your CV system.
The big idea of long rides is that as you do more of them and make them longer and longer, you’ll be spending more and more time training those larger motor units and they’ll respond to that stimulus by (in time) becoming more aerobically well trained. As a result, you should eventually expect cardiac drift to occur later in rides and to be less significant overall.
If you’re going to quote that Boston marathon study, quote it correctly. The small number you refer to without actually stating the number was 0.6%. The figures for those treated for dehydration at the same event each year are in the 6%-9% range.
One obvious explanation could also simply be that your “Z2” is actually Z3, how wide the zones actually are varies from individual to individual somewhat. The gold standard method for determining the zones involves things like blood lactate tests, but a practical alternative is just reducing the intensity a little bit at a time (say first ride at 125 bpm then next ride at 120 etc. if needed) and see what is sustainable without cardiac drift for 2–3 hours.
Sports drink companies have overstated the necessity for constant hydration to boost sales. The safest approach is to drink according to thirst. For an alternative perspective beyond the marketing hype, I recommend reading Waterlogged: The Serious Problem of Overhydration in Endurance Sports by Tim Noakes, whom I had the privilege of meeting during a training camp. His insights challenge the prevailing narratives about hydration in endurance sports.