Need Advice, MTB Energy Levels


Bit about myself first. First time poster, 2nd year in to TR structured trainings. 34 year old male, 60 kgs, currently sitting at 3.63w/kg (ftp 218), coming from 143 last year. Cycling for a lot up til 10 years ago and started again last year. Doing the Speciality MTB Marathon LV at the moment as I’m nearing my A “race” (just there to do well for myself, not wanting to podium or anything alike).

Here is my issue though: about a month ago I did my first event (C race for me), which was 55km (1400m climb). Despite careful food and drink planning (thank you podcast), I ended up not drinking or eating enough and after about 25km the lights went out. I kept going, but the lights only came on again around the 40km marker.
So had my most recent event 65km with 1800m climbing (set as B race as I wanted to test everything for my A race in a couple of weeks). Started carb loading 2 days ahead (± 400g/day) and ate a solid breakfast (800 kcal). On the day I packed 1.5L of SiS Electrolyte, 0.5L of Beta Fuel, 4 Sis Isotonic gels and 4 power bars (±180 kcal each). Ended up consuming roughly 2500 kcal, for an initial intake of 2300 (800 breakfast + 1500 during). However came the 40km marker, the lights went out to come back on around 53km.

So my question is: what can I do more to counter the complete blank? I was sure I had it down this time, but turns out I wasn’t …

Any help is greatly appreciated!

What is your pacing like? Are you going out too hard? With a measured pace over races like that, you shouldn’t bonk like you experienced.

My pacing is fairly conservative (I don’t have a powermeter on the mtb though). I base it on preliminary calculation of pace based on previous events where I felt good (VAM/h, overall avg speed, …). And I set off with that plan and adjust based on the feeling in my legs the first couple of hours.

The wierd thing is my legs feel mostly ok, even during the ‘lights off’ phases. I seem to be drawing a mental blank and concentration goes completely out the window. Which isn’t recommendable on a mtb course :slight_smile:

What’s your breakfast like and how many hours between your breakfast and the race?
It might be something in your breakfast or the time between that’s causing it.

And how much fluid do you have pre-race as you will be dehydrated in the morning,

Breakfast was: 2.5h before the race oats+ full greek yoghurt+handful of blueberries and 1,5h before the race 3 slices of wholegrain bread and peanut butter + 500ml on SiS Energy drink (carbs).

Hydration the day before was about 2.5L of water + whatever water I drink in my tea. The morning off I drunk my 800ml bottle of water with the first breakfast and a coffee. And of course the SiS drink.

Nothing strange there I guess, only other thing I can think of is maybe the time of day your race versus the time of day you train.

Perhaps that’s causing some difficulties for you, I had that when I was playing tennis.
During matches in the evening I was a lot more focused than one’s that I had to play in the morning/early afternoon.

On week days I train early evening but on Sundays for the longer rides I’m of in the morning. So don’t seem to have a big gap there.

What is your intake over race time? Are you leaving it too late to fuel and that’s why you are fading, then when the carbs kick in the lights come back on?
There should be enough carbs in you fuel, assuming you are using the electrolyte powder (with carbs) and not the tablets.

There is a beta fuel thread on the site but for some insight I used it solely for a long event 2 weeks ago, at 84g carbs/500ml/hour I didn’t need bars or gels.

It was my first time using Beta Fuel. For 2 reasons: I wanted a slot where I could get easy energy in without having to twiddle with packaging/wrappers/… and because my CamelBak is only 1.5L and I knew I’d need at least 2L.

My intake is split over time: I eat a bar at every 30 min past the hour and a gel on the hour. And I start my feeding after the first 30 min and continue until about 25-30 min before estimated arrival.
Drinking is 500 ml/h, spread over sips every ±10 min. Indeed, I use the Electrolyte powder, not the tablets.

In this particular case, I ate and drank according to my normal schedule between 0-2h, between 2-3h I drank my bottle of Beta Fuel (no solids), started fading after 3h (which was roughly the 40km point), so started eating bars and gels on a more expedited schedule, ie 3:20 I had my first bar again and kept it going every 30 mins.

Could it be that while even drinking the Beta Fuel I need to keep eating bars and gels? That’s going to be a lot of carbs …

I’d seriously doubt more carbs, you are already taking in over 80g/hr and your strategy seems sound.

If your legs are okay you’re probably not bonking, could it be a mental block?
From my own point of view road racing, I usually can only recall the first and last hours, not much of anything in between. But as you point out, MTB requires focus all the time on the trail.

How is your endurance ride game?
The muscles will get tired even though you keep fueling them.

As I am a father of small children and have a busy job my training have often been short and hard. I fact i rarely have trips exceeding 1,5 hours. My “numbers” have been good but when entering races (XC marathons) I always get one or several seriously dark periods. This does not happen as much when I have got some (2-3) longer endurance rides in the bank in the 6 weeks before the competition.
I am guessing my problem is a combination of (lack of) musculular endurance and carb-dependant body. You cannot refill carbs as fast as you are using it. My theory is that the endurance rides help me with both muscular endurance and switching fuel systems in a way.

What I would do: If your race is 2 weeks away now i would seriously consider doing a 3 hour+ endurance ride this weekend. Keep the efforts low enough so you dont have to fuel it like a race. Just fuel with a bit low GI bars, nuts etc, and maybe a banana. It is probably to late tp learn the body have to utilize only fat, but you can train on the muscular endurance part. When you finish refuel with carbs and protein and make sure you get a good nights sleep. The next day is also an easy day.
If your race is closer than 2 weeks, just dismiss all of the above and do short intense workouts.

My endurance rides have been slightly different this year. Just like yourself I have been rather time constrained and have been working on the LV program with only in the last few weeks a few longer rides (+4h).

I’ve definitely noticed this has an impact on my muscle endurance, but confident in the plan and the podcast discussions, my aim was to up the FTP and work on the 1.5h endurance workouts to be able to ride longer at relative lower intensity. However, this might work great for some such as @Nate_Pearson, but perhaps at my spectrum of the FTP scale, longer endurance rides are more of a requirement. I’m planning on doing a 3h endurance ride this weekend of about 70km with 1100m climb and have a sort of taper week next week to be ready.

My body and muscles are most likely rather carb dependent as (at least according to my scale) I have a 7.1% body fat percentage, so not too much to burn there. Hence also my rather detailed food plans prior to longer endurance rides.