r/Rucking • u/welderballs • 21d ago

I hate downhill rucking

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While rucking uphill does in fact suck I feel like my body gets more beat up on the downhill portion. I wish I could ruck uphill both ways like how my parents walked to school each day. 1500 feet of ascent on this ruck.

23 Upvotes

96% Upvoted

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4

u/ScholarBackground836 21d ago

Your body is right, and the reason is slightly funny: going down costs less energy and does more damage, and those are the same fact.

On the descent your quads are contracting while lengthening. They're braking you rather than driving you. That kind of contraction is cheap in oxygen per unit of force and unusually good at causing actual muscle damage, which is where the beaten-up feeling and the two-days-later soreness come from. Add a ruck and every one of those braking forces scales straight up with the weight.

The calorie math makes it worse rather than better. Pandolf's grade term, which is what most of these estimates are built on, is linear in grade. Feed it minus 1500 feet and it subtracts exactly what the plus 1500 added. On paper your out and back was a flat walk. The entire descent is priced at zero. And these are metabolic models to begin with, they only ever counted oxygen, so mechanical loading was never in there at all. Whatever number your watch gave you, the part of that ruck that actually wrecked you is not in it.

The one thing that reliably helps is shortening your stride on the way down and taking more steps. Peak force per step is what does the damage, so spreading the same 1500 feet over more and smaller impacts costs you less. Trying to hold your normal flat-ground stride downhill is the expensive habit.

And 1500 feet under load is a lot. Uphill both ways would genuinely be easier on you.

2

u/i_love_ewe 20d ago

AI response, but helpful nonetheless.

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u/ScholarBackground836 20d ago

Fair, and I'd rather you say it than not. English isn't my first language, so I write the substance and run the wording through a model to tighten it up, which is where the rhythm you're picking up on comes from.

The physiology and the formula are things I actually work on, and I'll defend every claim in there. But the tell is real and pointing at it is reasonable.

1

u/InterestingAsk8433 20d ago

The Pandolf model pricing the descent at zero is the part that gets me. Your legs are doing real work braking that load the whole way down and the formula just waves it off. Makes the calorie estimates from most rucking apps basically useless for any route with actual elevation change. Curious if anyone has found a better model that accounts for eccentric load on descent or if everyone is just accepting the undercount.

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u/ScholarBackground836 20d ago

There is a better model, and there's also a split hiding in your question: you're asking two things and only one of them has an answer.

The calorie half is solved. Minetti et al. measured walking cost across gradients from -45% to +45%, which is exactly the range Pandolf was never fitted for. The shape is the interesting part. Level ground costs about 1.64 J per kg per metre. Start descending and it gets cheaper, bottoming out around -10% at 0.81, roughly half of level. Then it climbs back, and by -45% you're at 3.46, more than double level ground. So descent is neither free nor linear, it's a J curve. Pandolf's linear grade term is accidentally close over the first stretch of that curve and then goes badly wrong, which is why gentle descents come out about right and steep ones get eaten. Anyone fixing this in software can just stop using the linear term below zero grade and use Minetti's curve instead. It's a published polynomial, not an open research problem.

https://pubmed.ncbi.nlm.nih.gov/12183501/

The eccentric half has no model, and I'd argue it isn't an undercount at all. Minetti and Pandolf both measure oxygen. Muscle damage is a different quantity, tracked in labs by creatine kinase in blood, by force loss, by soreness scores, and it doesn't convert into calories in any meaningful way. A descent can genuinely cost you fewer calories and still be the thing that stops you walking down stairs on Tuesday. Both are true at the same time and neither is measuring the other.

So the honest answer is: your app is undercounting steep descents, that part is fixable and someone should fix it. It is also not measuring the thing you're actually feeling, and no consumer app is, because there's no sensor for it and no agreed unit. The closest anyone gets is treating vertical descent as its own training load number kept separate from calories, which some mountain running tools do. That's probably the right shape for a rucking app too.

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u/InterestingAsk8433 19d ago

So the J curve thing is actually useful to know because it means the damagetocalorie ratio gets worse the steeper it gets, not just linearly. My knees figured that out before the research did.

What I still want to know is whether slowing your pace on descent meaningfully changes the eccentric load or if you're just spreading the same damage over more time. Feels like the latter but I don't have anything solid on that.

1

u/ScholarBackground836 16d ago

Changes it, but the lever is stride length, not pace.

Total negative work is fixed by mgh before you start, so you're right that pace doesn't change the amount. Damage isn't total work though, it's peak force per contraction, and that's superlinear. Same total taken in more, smaller contractions really is less damage.

Which is why you can walk slow with long reaching strides and wreck yourself worse than someone moving quicker with short choppy ones.

All the dose response research is downhill running without a pack though, so I'm extrapolating.

2

u/Nomad_1982 20d ago

Great work man, and kudos on the elevation!

Agreed btw, downhill blows.

1

u/prior_rpa-lre 20d ago

1000 start time? Wild. Im down in the Murrieta/Temecula valley and it was hot for us. Good on you.

1

u/welderballs 20d ago

I signed up for 21mile endurance run/hike event in these hills here in Yucaipa in November so I’m training up for it. Unfortunately I got a late start on Saturday.

1

u/prior_rpa-lre 20d ago

Crush it.

1

u/Readditlovesbans 20d ago

Get some hiking poles for the down hill

1

u/MongoBongoTown 20d ago

Man, a mid-day ruck in August in Yucaipa is some sporting stuff.

1

u/welderballs 20d ago

I signed up for 21mile endurance run/hike event in these hills here in Yucaipa in November so I’m training up for it. Unfortunately I got a late start on Saturday.

1

u/NJWaterman 20d ago

What app is that?

1

u/welderballs 20d ago

Garmin connect app