I routinely try to include steady state zone 2 rides as part of my training, but sometimes self sabotage as I do love a good VO2 max effort up a hill.
I was however very disciplined today. 116km at 33.6kph (road), 1367m vert, 4000kj, 139bpm (my zone 2 range is up to 147bpm), 321w, 326w NP. 430g carbs for 3.5hrs
I felt good today, and training has been ramping up the last few week as the snow has started to melt. I don’t train indoors, so the 2 months we had an average of minus 3c (day/night, rarely exceeding 0c and often double digits minus) meant that longer rides were off the table for a while.
The ride was super steady today, and felt incredibly easy until about 75km in when the fatigue started to make itself felt in my legs. I had averaged about 136bpm and 325w up to that point. About 10 minutes later, I noticed a marked heart rate drift developing, and my power started to drop towards 310w, but HR rose a good 5-7bpm. It was fairly sudden - almost as if someone had flipped a switch.
It was obviously no issue to complete the ride, but it just meant that i had to ease off a touch (especially on the hills) to keep in zone. 97% of my time was in zone 2.
My understanding of physiology is reasonable, but if anyone could give me a bit more information on the process that took place today, and the most effective way to push that point of heart rate drift further into the ride, I would be grateful!
My HR monitor had a moment about 5km in, for reference. It’s not the best. Accurate but prone to taking a few minutes to wake up at the start of the ride and can sometimes be a little spikey, which is what some of the 2% of the time I was above zone 2 can be attributed to.
First things first: you can use intervals.icu to show more useful intervals. The clue is in the name.
For that sort of (excellent ) ride I’d create one massive interval covering everything except the warmup and cooldown and then it lets you split it into 5 or 6 (or however many) equal chunks.
Second thing second: HR drift beginning at the same time that RPE decouples is, I think, indicative that you’ve fatigued your smaller motor units and are now additionally having to recruit progressively larger and larger motor units. Those larger motor units are the ones that don’t get recruited as often, and so they’re more likely to be less-well aerobically trained, and so your body is going to need to supply more oxygen to service the ATP demand of the workload. Not sure why it was sudden, but I also tend to see a distinct step up in HR (albeit at much lower power!) after about 90 minutes at my usual endurance pace.
Third thing third: your best bet to move this decoupling point out is good old muscular endurance work. Long endurance rides. Sweetspot work. Threshold work. Although you may also need to pick different parents. I think there’s an underlying natural variation that can’t be trained away. But, if it’s not a limiter on performance, does it matter?
I find drift varies from day to day for me, often on longer z2 rides it goes negative, but not always. One day it can be negative, the next positive. I’m not sure how much it has to do with motor fatigue for me….it feels more related to systematic/adrenal fatigue/stress.
If I am stressing about the ride itself/training/fitting it in around life then it is more likely to be negative split as I calm down once I’m into it. Did you think about something stressful for the second part of the ride?
Wind also has a huge effect for me, being a small person….HR and RPE for the same power is elevated into a headwind, either because I am using more energy or because the noise of the wind stresses me out (still havent worked out which). Did you turn a corner into a headwind/crosswind when the drift happened causing the jump.
If you are sure it was purely down to physiological factors fatiguing fibres causing recruitment of less efficient ones then yup, more endurance training.
Fyi - on the screenshot you shared, you’re on the “timeline” tab. If you click the “power” tab, there is a HR decoupling graph that you may find useful.
Good shout, especially on hydration. I drank about 1.5 litres on the ride, but we have only just transitioned from deep winter to mid spring, with the temperature rising about 30 degrees Celsius in the last three to four weeks.
There are flatter course options for me, but I just like hills!
I think that I was very well prepped for this ride, having done a very easy 2.5 hours the day before. That seems to give me my strongest performances.
Funny you should mention thinking about stressful things! I would say half of the spikes into zone 3 were as a result of visualizing races that I’m going to be doing later this year. It almost immediately results in a 10 bpm increase. But it was no more the case in the second half of the ride than the first.
Thank you for the tips as regards intervals.icu. I will have a look at that when I get back in front of the computer this evening.
As regards my zone 2, I am 100 kilos and 203 centimeters, so my upper end zone 2 (at least for 2 hours or so before heart rate drift) is around 335 to 340w.
I was finding on this ride in the first two hours that even shorter periods of 400 to 420 watts would not result in the straying into zone 3. RPE was very low indeed.
With 4000kj’s ride with 1700calorie intake… Riding at a high zone2 a couple things effecting your ride later in the ride come to mind.
You have a huge engine, eventually even at a solid intake of calories you are going to run glycogen down a bit. You don’t need to get to zero for many things to take place… things like central governor triggering a reduction, push towards more fat as a fuel to limit the gradual reduction of glycogen (increases HR).
At the same time slow twitch fibers are starting to fatigue, recruiting more intermediate fibers that icome with increase metabolic costs(also increasing HR). While also likely increasing your bodies temperature increasing discomfort and also increase HR due to cooling costs.
Very interesting! The lowered glycogen reserves make sense. I recall someone once saying that a human isn’t like a car - with half a tank of fuel, a car still performs normally. For a human, that’s not the case.
I perhaps ought to consider upping my fueling a bit whilst doing these higher output zone 2 rides. 120g/hr is not a challenge for me for a 3-4hr ride. I have done 160-180g before.
I think perhaps, coming back to my original question, that I just haven’t done enough longer rides over winter to challenge my glycogen reserves. Some of this has been out of my control though, with work restricting longer ride days but also sciatic issues around Christmas.
Work is much more flexible now though, and the sciatic issues are 98% gone, so I’m optimistic that I can push this HR decoupling further into my rides.
That will happen to me if I am dehydrated and don’t have enough sodium on board. If you become dehydrated your stroke volume will fall and your heart has to beat faster to circulate blood and it will feel harder.
Loads of brilliant responses and I am grateful for all the help.
I tried to implement some of the tips today and repeated the ride. Carb intake was increased to 150g an hour and fluids increased to 2 litres. It was 9-10c and sunny.
I actually rode it a little more organically this time, allowing myself to stray out of zone 2 on climbs, and the resultant HR average was 147bpm, which is bang on my zone 2 to zone 3 transition.
I loaded up with beetroot through the day (2x12g), which always shifts my HR up by 5-10bpm, but also reduces RPE.
So today’s ride felt easier, despite the higher heart rate, and I went 2.1kph quicker for the extra 17w too.
I’ve switched bikes too, having sold my road bike. So now it’s a Canyon Grail on road tyres. Still plenty of marginal gains to be made though, with faster wheels and tyres enroute.
) ride I’d create one massive interval covering everything except the warmup and cooldown and then it lets you split it into 5 or 6 (or however many) equal chunks.
