Sometimes I get a indicated decoupling of 5-10% during warm up. This can last up to 30-40 minutes before I start to feel OK and can push harder. When this happen, I also feel the warm up is hard. Is this the cause of the decoupling? Warm up too hard?
Hi Markku,
I am not an exercise scientist, or a coach, but I can give you some advice from experience. This is going to be a bit of a long post, apologies, you may already understand all of this, but I think it is worth talking about.
There are quite a few things to unpack here, I am going to assume you are warming up for Aerobic / mid - low intensity. If not I can talk a bit more lower down.
Before we start exercising, the body is usually in a relaxed state, and the Aerobic sytem is offline, and the parasympathetic system is ramped up (rest / digest system). Your heartrate is usually low.
What happens when we exercise
Then when you start to exercise, your sympathetic nervous system ramps up and your Aerobic system ramps up, your heart starts beating faster to pump oxygenated blood to your working muscles, your capillaries dialate to allow more blood flow and a bunch of other physiological things happen to bring up your Aerobic system to start producing power for exercise.
What is Decoupling
I think its impotant to talk quickly about what decoupling actually is. Deocupling is comparing the efficiency in the first half of an activity, with the efficiency in the second half.
Efficiency can be defined in a lot of ways, but often it is the ratio of your output, either pace / power, over your avg HR in the first half of an activity, with your pace / power in the second half (activity could be an interval or whatever length of time you want).
Decoupling = Efficiency1 / Efficiency2 = (Pwr1/ HR1) / (Pwr2 / HR2)
It is often used as a percentage change, so calcuated like this:
Deocupling = (Efficiency1 / Efficiency2 - 1) * 100
So, often we we look at decoupling, we are trying to keep our HR constant and see how much slower we get, or hold pace / power constant and see how much our HR rises.
Why do we get a lot of decoupling at the start
So, as you can probably guess, when we warmup and our HR starts to rise for the reasons I stated above, you are going to get a lot of decoupling. This is why Invervals has an option in settings to specify a warmup and cooldown (another topic) length, so it will discount that amount of time for decoupling calculations, we don’t want to use that as it is not indicative of anything, it is just normal human physiology.
How long should a warmup be
The warmup process takes time. The physiological things happening cannot happen instantly, which is why we warmup. The reason we do a warmup slowly, and start at a low intensity and increase the intensity slowly, is that we want to give these systems time to come online. This usually takes around 10-20 minutes depending on a lot of factors. Factors such as recovery state, the intensity you want to get to (are you doing a hard, or easy session?) your training level etc, but around that sort of time.
Why do we care about decoupling (briefly)
Decoupling is very complicated, and seems to happen for a variety of complicated physiological reasons that we dont really need to go into. However, through a lot of testing and study it is believed that once you are warm, i.e. the warmup is 10-20 mins is discounted, if your decoupling is under ~5%, you are operating below your AeT, or Aerobic threshold where you are producing >= 50% of your energy from Fat Metablosim.
Above this threshold, you are pushing into more and more anaeraboic work. Where an increasing amount of energy is coming from glycolytic metabolism. Therefore, decoupling is a useful metric to track your bodies progress in your endurance base / aerobic training, and as an intensity monitor to make sure you are training in the correct zones.
How hard / much warmup?
Since the warmup is used to bring your systems online and get you ready for the training you are about to do, it neccessarily will change in length and intensity depening on the type of training you are about to do. I cannot say without knowing if you are doing an easy base workout, some intervals, some sprints?
However, I can say, the hader the intensity of training you are about to do (mesaured by HR Zones, Pwr zones, etc), the longer the warmup, and the harder you should be workign in the warmup at the end.
E.g. If you are about to do a set of intervals, you want to warmup slowly, bringing yourself over the course of 10-15mins up through Z1 and Z2 (in a 5 Zone hR system) so that your Aerobic system can come online. Then finish with 3-5 mins of Z3 of slightly anaerboic work to bring that system online as well.
You don’t want to fatigue yourself, but you also don’t want to start working out too hard. It is a careful balance measured by feel and experience.
The danger of going to hard in the warmup.
The risk we take when not warming up slowly, easily or long enough is that we bypass or don’t bring the aerobic system up properly. If we come out of the gates too hard with insufficient warmup, and your aerobic system isn’t up to speed to generate enough power, you are going to be making a lot of your power anaerobically. This is going to result in lactate production and an increase in fatigue, you will see more decoupling since you have pushed passed your AeT.
This mistake of pushing too hard to early can make it harder for you body to get your Aerobic system going, since you are relying on glyoclytic metabolism. It will delay your Aerobic system coming online. You will also take a bit of time to clear the lactate that has built up so it can take a bit longer to feel “ready” to go. I think this is most likely what is happening to you.
My final thoughts
I would recommend with what you are seeing, make sure you are warming up sufficiently, and bringing the intensity in the warmup up slowly enough and appropriately for the given workout, more warmup for harder intensity.
Only care about the decoupling from the end of the warmup to the start of the cooldown, outside of these times are not important. I haven’t discussed cooldown here but it is a whole other topic, along the same lines thought, the higher the intensity of the session, the more important a cooldwon is to do at the end. If you are intereseted in why I can write anther reply.
Use decoupling as a metric to track intensity in regard to useful physiological markers, i.e. your aerobic threshold. If you are doing a Z3 or Z4 session or intervals etc, your decoupling will / should be higher than 5%, often much higher, this is expected and normal. If you are doing a base run, you should expect your decoupling to be <5%, if not, it is likely the intensity was too high or you are not recovered enough etc.
Remember the body is one big connetected system, and we have all of these metrics to try describe it and track it, but everything impacts everything else. So don’t take numbers, zones, or any metric as the only truth, zones shift, decoupling is only a proxy. Use what you feel and the metrics together and make informed decisions.
Hope this helped.
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Thanks for you exhaustively and interesting answer!
This decoupling during warm up “problem” I asked of, is something I have seen first time this season. I have cycled and excised for 40+ years (I’m now 70), and I have discovered I now need longer and longer warm up times. 10-20 years ago, 10-20 minutes were enough, now I need 30+ minutes, even when going for Z2-Z3 ride. I shall try and see what happens if I make the warm up less taxing/easier, and not in the same way I did when I was younger.
Hi Markku,
Wow 70 years! Thats amazing, I hope I have your dedication and consistency, very impressive. Just to be clear, I am not a medical professional nor a coach so take what I say with some care.
I’m not that familiar with how athletes adjust as they age, but it could be very possible that you need a longer warmup now to get your aerobic system to come online, but I can’t say for certain. I would say give warming up a bit easier, and for a bit longer, before going into your workout, and see if that improves how you feel during the workout.
Good luck with your training 
Adam
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