Fueling Zone 2 Workouts

As a software developer, I can relate so much to this.

The answer is almost always, in most if not all things, it depends…


What we are seeing is that some need to fuel themselves with sugar during 2-3 hour Z2 rides else they feel awful / have to cut the ride short, some take snacks and will have them later on if necessary during a 2-3 hour Z2 ride, others can quite happily ride 2-3 hours of Z2 without needing to snack or fuel during the actual ride as long as they are eating okay outside of their ride.

If you were talking 4-5 or 6-7 hours or 8-9 hours of Z2 it’s likely even the latter group would be taking on calories during such outings.


There was/ is also the misconception that “fasted” is just skipping breakfast.

But regarding nutrition, my experience over the last decade of taking an interest is that a lot of the “science” isn’t actually peer reviewed proven science, it’s “evidence” of potential. The nutrition industry has a lot of people trying to sell you something that leap on this evidence before it’s properly backed up (and then develop cult like followings!).

Like Keto, Paleo, and all the “fasting” diet apps around at the moment.

You’re right that dieting is a real minefield of researched, and non-reaearched products and ideas. All to sell a product to a vulnerable group of people searching for an answer.


This applies both to the people selling you products as well as the people selling you fasted riding. There’s a lot of theory out there about fasted riding; it hasn’t held up well in scientific practice.

Lots of coaching interventions might work that science hasn’t shown as effective yet, so YMMV.


Here’s my 2 cents on the subject which I’ve been internally debating for the past 3 months. This is the 2nd time I’ve done the HVSS base program. The first time was the summer during lockdown 2020 when I first discovered TR and just now, my second time.
Some context about me. I’m in my early 50s, 5’7” 140-150 lbs with a high max heart rate. I’m all fast twitch muscle trying to develop my FTP. I started racing Olympic Triathlons in 2014 and didn’t know how to properly train, so everything was high intensity. I was fueling constantly: gels, bars sports drink. I love carbs and ice cream. During the race season, I dropped my weight to a low of 133lbs. My FTP was probably 180. Since 2020, I’m exclusively biking.
Doing HVSS in 2020, I listened to the fuel the ride and don’t diet on the bike. The rides were extremely tough and I was taking gels and sports drink but I managed to get my FTP to 240 at 138 lbs. However, often my rides would have my heart rate at 85%-90% max rate. After that session, it was hard for me to keep that intensity and my FTP dropped and fluctuated between 210-230.
This year, due to surgery on my hand then a broken foot, I didn’t ride from January to late August. Listening to Dr Peter Attia’s interview with Dr San Millàn changed my training. Since the last week of August, I started riding again, almost exclusively Z2 at 73% max HR. I was up to 151 lbs and the first rides were 90 watts for 45 minutes. Increasing my duration to 75 minutes avg, 127 watts, I started the HVSS in October. Every ride this time has been unfuelled and sometimes fasted. I only have 1 bottle of water. Every time my HR goes over 73%, I lower the intensity to maintain the HR. So all my rides are strictly controlled by my HR. Thankfully I use the AI detection and have avoided the ramp test. Z2 @ 73% max HR is “easy”. I’ve completed virtually every ride. I’m not exhausted and wasted after the workouts. I dropped 15lbs and am back to 136-138 lbs. AI has my FTP at 204 and for fun, I did the Full Frontal 4DP Test the other day and my 20 minute block was 207.
So Z2 rides can be done unfuelled but you have to keep the HR below LTV1.
My two goals are to get my FTP up to 4 w/kg and sprint power back which was greater than 20 w/kg @ 5” from the current 14 w/kg. We’ll see how I have to fuel going forward.

1 Like

This. I’ve been reading along and my particular case, for whatever reason has me struggling to meet calorie needs without post workout shakes with carbs AND carbs during the workout, even just a 1hr z2.

I just can’t seem to get through more food during the day. 600g a day of carbs from food, WTF lol.

A normal day is about 300g, I fill the extra through carbs during and after the ride. 86kg rider.

I am new to cycling, TR and endurance sports so fuelling during workouts it’s new to me. 2hr weightlifting sessions never seemed to require it.

Is there a consideration here to preservation of muscle mass too, where not fuelling IF required cause muscle loss?

Also, in my uneducated endurance brain, wouldn’t fuelling z2 speed up recovery and better prepare you for the next session, be it lifting or riding. A single session unfuelled might be ok but if this is recurring and you struggle to meet daily caloric requirements at the same time, won’t long term progress suffer?

I’m So new to all this I’m finding it confusing. Fuel, don’t fuel, fuel intensity but not z2, etc.

What I do know is calories in vs calories out is the number one determinant of ‘weight’ loss. I’ve played with this and lived it for years.

I normally do Z2 workouts up to 3.5hrs with 2 bottles with 60g of sugar each. As additional fuel I bring one or two packages of ginger bread, with 50g of carbs each.

When I started doing these long rides, I would need to eat the ginger bread towards the second hour. Lately I could even do without the gingerbread and was fine with just the two bottles of sugar water.

This morning I had a different experience. Already 50 min into the ride, my legs were burning as if I was doing a threshold interval, but this was just mid Z2. Then when I ate a slice of ginger bread and flushed it with some sugar water, I was totally fine and all felt normal again!

This has never happened before to be out of juice already within an hour. Looking back, the day before I had done a 1.5hr workout, that consisted of 6 all-out 40s intervals with long rests in between. I had probably eaten at maintenance that day, also with plenty of carbs, but probably not enough given what happened this morning. Anyways, the lesson is, even for Z2 rides, always bring carbs!


I don’t know if it was a recent podcast or one of the snippets on YouTube, but I think Jonathan or Chad said that a rider doing 180w for 1 hour burns 400 calories. For me that’s just below zone 2.

That being the case, having one gel (just using gel because it makes the math easier) every 20 minutes will put me behind by 100 calories per hour. If I use a flask and put 4 gels worth in but consume it in 3 shots (133 cal/28g of carb) I’ll be at brake even and roughly 84g of carb per hour.

In EP 9 of the Science of Getting Faster pod cast Dr. Hearris said that their results indicated that eating once every 20 min was the most efficient. (also that another study indicated rice cakes aren’t as good as gels or liquid carbs for fueling but they were pretty good) Are Gels Really That Bad? w/ Dr. Mark Hearris - The Science of Getting Faster Podcast Ep. 9 - #2 by webdev511

So to avoid deficit at 180w you need 400 calories and roughly 80g of carbs. Oh you’re racing? better turn that up to 11 and your best bet is to still do that every 20 minutes.

180 W is actually more towards 650 kCal per hour ( multiply wattage by 3.6 to get 650 kCal per hour).

But at z2 roughly half is coming from fat, which do not need to be immediately replaced on the bike


So it’s even worse :joy: (outside of z2 if you factor in fat.)

I’ve done enough of intervals like this - 30 to 60 second all-out - to know that it often causes my legs to sting for up to a week.

Also any immediate relief from sugar is purely psychological, there is no way for it to have been absorbed processed in that short of time. A sugar mouth rinse would likely have achieved the same effect


1 Like

1970s. So yeah.


Baffling logic on display again. If you eat regular balanced meals and aren’t jogging around the rest of the day, your muscle and liver glycogen will be full when you workout.

If you’re even relatively well trained- that’s probably to the tune of 2000kcals of glycogen. So no…. you aren’t “behind” on a 180w, 2hour endurance ride where maybe 1200kcals total, ( 6/700 from carbs) have been used - you are well within your body’s capabilities.

You will be behind if you eat like an anorexic rabbit off the bike I suppose….

The more I reflect on the two halves of my season- one riding “fully fuelled” at all times and eating to “hunger”. And the other saving up exercise kcals on the bike with minimal fuelling and then eating real food instead but targeting a measured daily deficit, the more I realise the second approach is far better for my performance as measured in w/kg.

I’m still able to do 8-9000 kj weeks on the bike over 5 rides and never feel depleted.

On Sunday I did a 4h endurance mountainbike race. After a few weeks ‘saving’ fitness, it was fun to ‘spend’ some for a change.
Of course I reverted to fuelling at 100g sugar an hour as I knew the course had plenty of steep climbs and figured I’d be doing a smattering of intensity for 4h straight.
I still ran a calorie deficit for the day.
And I put on 1.5lbs!

Tipping sugar straight into your open glute 4 transporters is potent stuff. My body clearly didn’t need it that day and grabbed hold of it and hasn’t given it up :rofl: It’s taken 6 days to get back to the weight I was that raceday morning.

Needless to say I’m doing the January round on watery squash with a bit of salt. I just don’t need exogenous carbohydrate for sub 3000kj efforts.

1 Like

(post deleted by author)

Thats just 6 WindWarrior sized bowls of Ancient Grains (Kirkland/Costco) :wink:

You’ll need to figure this out for yourself. I eat about 6 times a day. Stable weight. No trouble riding Mon-Wed, Fri/Sat. Last 4 weeks been averaging around 10 hours/week.


Yesterday I did 3.5 hours of endurance riding, but stopped several times and added some extra time for a total of 4 hours.

While pedaling on the main set of 3 hours 20 minutes, I was averaging 193W normalized, and with the stops it was 174W so kJ work was 174 * 3.6 * 3.33 hours = 2085kJ. That is roughly 2085 kcals and matches up with data on TrainingPeaks, the blue bar is a target of 193W:

Fueled that ride with 230g carbs:

  • 60g bottle (28oz/828ml) the first hour
  • 40g Cliff bar the first hour
  • 90g bottle hours 2-4
  • 40g Cliff bar hours 2-4

which averages out to roughly 58g/hour for the 4 hours I was on the bike. But front loaded. Total work for the 3:59:03 on the bike was 2400kJ and I took in 1150 kcals, or roughly replaced 50% on the bike.

It took awhile to eat dinner so post-ride I immediately drank a 60g bottle of carbs and another 28oz of water only on the way to dinner.

Before the ride I had about 250g carbs at breakfast and mid morning meals - coffee, egg sandwich, banana, yogurt, cereal, milk, fresh pineapple, pear, blueberries, and Ancient Grains.

Never faded on that ride, ready to do 2 hours of sweet spot intervals today to end the week at 12.5 hours.

I posted a link to CTS / trainright.com blog post on fueling rides to replace 30-50% calories. That has always worked well for me, but I eat enough carbs in the kitchen. Winning in the kitchen for the win :+1:

I’m in the kitchen right now making WindWarrior fruit plates for my wife and 25 yr old:

My wife and I have rolled this way for 28+ years.