Ultrarunner Podcast Claims Bruce Fordyce better than Kipchoge

yes, I believe Walmsley could challenge for the CR. He can sustain 6-9% grades for more than 1.5km-3km while running 6:00/mi pace.

Is it really a given that you will run out of glycogen in a long ultra though? Would your pace not adjust down enough that you burn a lower percentage of carbohydrates such that you can avoid that? Even at marathon pace you probably aren't burning 100% carbs - as I understand it slowing down 1-2 mins per mile to easy pace can lower your carb usage to 50-70% or so depending on training and genetics. Slower paces I assume would use even less carb.

Someone did a decent rough calculation on this thread already but assuming you're only burning 50% carb at something like 1000 Cals / hr (6 min miles, 100 Cal's per mile, which is probably high for a lightweight elite) that's 500 cals of carbs or 125g. If you can take in something like 60g carbs per hour (gel every 25 mins or so) that means you're losing 65g per hour, giving you a bit less than 8 hrs and 80 miles if you have about 500g carb reserves. A gel every 20 mins and you have 10 hrs or 100 miles. Slow down more (since 6 min miles for 100 miles is way beyond WR pace), maybe decrease carb usage % even lower, math can still work out.

And ya some ingested carbs would likely be diverted for other uses in the body, but it seems to me the numbers are close enough that you could regulate and avoid totally running out of muscle glycogen. I don't think it's a given that you're devoid of muscle glycogen by 60 miles in etc. Of course this is more complicated if you have climbs where you are likely using a higher % of glycogen for some period of time and then less on the downhill since some gravitational energy can be recovered, but I still find it hard to believe that ultra runners are spending multiple hours on course with fully depleted muscle glycogen (unless of course they are napping on the side of the trail or walking it into an aid station).

Comrades Gold Medalist wrote:

yes, I believe Walmsley could challenge for the CR. He can sustain 6-9% grades for more than 1.5km-3km while running 6:00/mi pace.

That is some crazy badplaas talk. You are dreaming if you think Jim runs 6:00 min/mi pace up sustained 6-9% grades.

That being said Jim seems way better suited to road 50mi to 100km races than the mountain stuff he does. I have actually asked him why he does not go do Comrades as he could really be a threat at 'Rades. Jim told me he will go and do it at some point but wants to focus on the trails (granted this was prior to him winning WS, but not he seems obsessed with getting UTMB right)

His 5:21 at JFK is pretty interesting if you look at how peoples times at JFK correspond to their Comrades times.

Sage/Camille:

Relative intensity is what matters.

Would a 5 hour marathoner and a 3 hour marathoner both bonk at mile "21-23" of a marathon?

If you take into account what the highest amount of glycogen a trained athlete can store and then subtract the amount they will burn per hour at their race pace (read: relative intensity), then add in their maximal absorption rate and intake per hour-- you will get a fuel balance. I perform fuel testing on endurance athletes often, and one of the highest fat burning ultrarunners I have seen could theoretically run a flat 50 miles at his aerobic threshold without needing fuel . His utilization of glycogen was that low. For most though, in the back half of a race that is 6+ hours, they will begin depleting glycogen faster than they can take in and absorb. That is where the clock starts ticking, they will either slow down (reduce relative intensity), or make it to the finish before they deplete. With that said, more fuel-efficient runners (ones who burn less glycogen at their race pace intensity) may never bear the risk of bonking as long as they take in their fixed need per hour. Others will be guaranteed to bonk/slow down at some point because they burn glycogen at a faster rate than they can replenish, regardless of their intake. As Camille said, this is all heavily influenced by muscle fiber make-up.

Bonks are certainly not guaranteed (maybe mentally?). But someone getting through a 2 hour race without a bonk, does not mean they have the muscle fiber make-up to sustain a race pace for 50miles or more (as Camille stated).

For the record, one can never fully deplete their glycogen stores. The body shuts it down before that happens, hence bonk.

Everyone is different. It's heavily influenced by genetics and training. At marathon pace, two runners running the exact same pace, at the exact same blood lactate (say 2.5mmol/dL), and relative HR, could be utilizing completely different ratios of fat to glycogen.

For an ultra, as mechanics and subsequent running economy break down, you will be working at a higher relative intensity to run the same pace. Thus increasing glycogen utilization. Fatigue resistance (being able to hold your running economy for longer) is a big factor for that reason. The longer you can put it off, the more fuel you have to work with when things start breaking down.

Yuki Kawauchi has actually run the same 50k race 8 times and a 71k race once. He's won the 50k race 7 times in a row and won the 71k race he did as well. His PR and C.R. of 2:44:07 only 30 seconds off of the 50k world record, this is on a very hilly course in Japan probably similar elevation gain to comrades. In the 71k distance only 6 miles short of the 50 mile total he ran a 4:41:55 a new C.R . This on a course where 25% was gravel and another 15% was grass and dirt, even on the road sections it crests several mountains, so a ton of elevation gain. Yuki is a 2:08 marathoner and I think he would annihilate a lot of people if he ever switched to just doing ultras and ventured for them outside of Japan. I think he could break the 50 mile record and i'm sure he could beat the 50k world record if he went for it on a track or flatter road course.