My first 100K vest left a red groove carved into my collarbone.
Not dramatic. Just stupid.
By 40K, the strap was digging. By 70K, the bottles were bouncing like angry pinballs. And somewhere around midnight I realized I was fighting my gear almost as much as the course.
That’s when I learned something simple: in a 100K, your vest isn’t an accessory. It’s a teammate. And if your teammate sucks, you’re carrying that mistake for 15–20 hours.
For 100K, you don’t mess around. You usually want at least 1.5–2.0 liters of fluid capacity. Enough room for nutrition. A layer or two. Mandatory safety gear. But beyond capacity, the truth is this: fit beats features. Every single time.
I don’t care how trendy the brand is. If it rubs your neck, traps heat, or bounces downhill like a drum solo, it’s wrong for you. Snug. No bounce. Breathable. Easy to access while half-asleep at 3 a.m. That’s the real checklist. Because at kilometer 80, you won’t care about logos. You’ll care about whether your vest is helping you… or slowly ruining your day.
The Keys
For a 100K, don’t mess around. You’re usually looking for:
- At least 1.5–2.0 liters of fluid capacity
(front flasks, bladder, or both)
And then space for:
- Nutrition
- A layer or two
- Mandatory gear if the race requires it
But honestly? Fit is everything. I don’t care how “fancy” or expensive the vest is. If it rubs your collarbone or bounces like a drum solo when you’re descending, it’s garbage for you.
Snug. No bounce. Matches your torso and chest size.
That beats features every single time.
Key Features That Actually Matter
- Adjustable front straps (so you can dial it in mid-race)
- Front pockets for flasks, gels, salt tabs, phone
- Breathable mesh and a back panel that doesn’t turn into a sweat swamp
- Option for soft flasks in front (easy sipping) or a bladder in back (more volume between aid stations)
Simple stuff. But when you’re 14 hours in, simple stuff is everything.
SECTION: My 100K Vest Disaster (and What I Wish I’d Known)
Let me tell you how I learned this the hard way.
First 100K. I thought, “It’s just a vest. Any trail vest will do.”
Nope.
By 40K, one strap had basically carved into my collarbone. My bottles were bouncing like angry pinballs. And the bladder? It leaked. Slow drip. So my back felt like a damp sponge for the last 60K.
I still finished. Somehow. But I crossed that line chafed, exhausted, and honestly kind of mad at myself.
I remember thinking, “Why did I wing my gear for something this long?”
In ultras, your vest isn’t just storage. It’s your teammate. And if your teammate sucks, you pay for it for 15 hours.
Over the years – as a runner and as a coach – I’ve tested a stupid number of vests. Cheap ones. High-end ones. Sponsored ones. Ones I bought out of pocket because someone in a Facebook group swore by it.
And here’s what I’ve learned:
For 100K and beyond, your vest is your lifeline.
Not dramatic. Just true.
This isn’t brand marketing. I don’t care about logos. I care about what works when you’re alone at mile 55 and the only thing keeping you moving is stubbornness and a half-melted gel.
SECTION: What Makes 100K Hydration So Tricky?
A 100K isn’t just “double a 50K.” It’s a different animal.
You’re out there 10 to 20+ hours depending on terrain and pace. That’s a full day. Sometimes a full night too.
Aid stations? They might be far apart. Especially in mountain races. I’ve been in ultras where I didn’t see an aid station for 3–4 hours.
Three hours.
If you run dry out there, it gets ugly fast. I’ve stood on a sun-blasted ridge rationing the last sip of warm water and thinking, “This was preventable.”
Here’s what makes hydration tough at this distance:
Staying Hydrated Between Aid Stations
In a marathon or even a 50K, you can sometimes get away with one handheld bottle.
In a hot 100K? That 500 ml bottle disappears quickly.
Running out of water with an hour left to the next checkpoint is not “character building.” It’s miserable.
You need enough capacity to bridge long gaps. That’s why 1.5–2.0 liters minimum starts to make sense.
Bounce & Comfort Over Time
A vest that feels fine for 10K can turn into a medieval torture device at 60K.
Bottles slapping your ribs.
Pack thumping your back.
Weight pulling on your shoulders.
After hours, that small annoyance becomes deep fatigue.
It’s like carrying a squirming toddler piggyback for half a day. Cute at first. Not cute at hour six.
You want minimal movement. Even weight distribution. Because micro-bounce times 100,000 steps adds up.
Chafing and Hot Spots
Tiny seam. Slightly rough fabric. Strap sitting wrong.
Give it 12 hours and it’ll carve you open.
I once finished an ultra with what looked like a red necklace burned into my skin from a strap.
Neck.
Collarbone.
Lower ribs.
Underarms.
Places you didn’t even know could chafe.
And once that skin goes, it’s not coming back mid-race.
Overpacking Temptation
Let’s talk about the rookie mistake.
Packing everything.
Extra jacket.
Extra bottles.
More gels than you could eat in a week.
Three headlamps.
Five battery packs.
I’ve done it.
I’ve literally unpacked a friend’s vest after a race and we joked he could survive lost in the woods for days.
It’s fear packing.
But hauling 6–8 kg for 100K? That’s energy you don’t get back.
You burn more.
You fatigue faster.
You resent your own vest.
Common Misunderstandings
I see these all the time.
“A bigger pack is always better.”
Not true.
A 15–20L vest just means you’ll fill it with stuff you don’t need.
I did that once. Big 15L pack. Used maybe half of what I carried.
You don’t need to carry your fears. You need to carry what keeps you safe and moving.
“Any trail vest will do.”
No.
A 100K vest needs to survive all-day wear.
At 2:00 AM in hour 17, small flaws become huge problems.
Short-race vests might lack capacity. Or strap padding. Or ventilation.
Could you run 100K in a 5L vest? Maybe. If it’s cool and heavily supported.
But usually, that’s asking too much.
“I’ll just use handheld bottles.”
I love handhelds. I train with them. I race shorter stuff with them.
And yes, some ultrarunners go full handheld + waist belt even at 100K.
But think about it.
Lower fluid capacity.
Arms doing extra work.
Almost no room for gear.
In a supported 50K with aid every 5 miles? Sure.
In a 100K with long dry sections and mandatory safety gear?
For most of us, a vest makes more sense.
Bottom Line
For 100K, a well-chosen hydration vest is usually the best middle ground.
Enough water.
Enough fuel.
Enough gear to stay safe.
Without turning you into a hiking backpack.
But it has to fit you. Not the runner on YouTube. Not the elite in the promo photo.
You.
Because at mile 80, you’re not thinking about brand names.
You’re thinking about whether your vest is helping you… or slowly ruining your day.
SECTION: The Science of Hydration, Load & Comfort (Why Your Vest Choice Actually Matters)
Okay. I’m not a lab coat guy. I’m just a runner who hates suffering more than necessary. But over the years I’ve read enough, screwed up enough, and coached enough people to know this stuff isn’t random. There’s real physiology behind why a bad vest decision can wreck your day.
So let’s talk through it. Not textbook style. Real runner style.
- Hydration Needs in Long Ultras
Hydration in a 100K is a balancing act. And honestly, it’s easy to mess up both directions.
Too dehydrated? Performance tanks.
Too much water? You can land yourself in hyponatremia. And that’s not dramatic talk — that’s dangerous.
Research and race data show that once you lose about 3–5% of your body weight from sweat, performance starts dropping in a noticeable way Human Kinetics.
Let’s put that in real numbers.
If you’re 70 kg, 3% is about 2.1 kg. That’s roughly 2 liters of water gone. That’s not nothing. Beyond 5% dehydration, lab testing has shown work capacity can drop by as much as 30% Human Kinetics.
Thirty percent.
You don’t feel “a little tired.” You feel wrecked.
Now — and this matters — losing a little weight in an ultra is normal. A 1–2% drop by the finish? Totally expected. A lot of coaches even consider that fine. You’re out there for 12–20 hours. You’re sweating. You’re burning through fuel. Some weight loss is part of the deal.
But then there’s the other extreme.
Overhydration.
I’ve seen runners get so afraid of dehydration that they just keep drinking. Every aid station. Big gulps. Constant. And then they dilute their blood sodium and end up in hyponatremia territory. Confusion. Headache. Nausea. In extreme cases, it’s life-threatening.
The current thinking in ultra circles is “drink to thirst” rather than forcing a set amount every hour UltraRunning Magazine.
And I’ve found that works better for me.
Do I have a rough number in mind? Sure. On a hot day maybe around 500 ml per hour. But I listen to my body. If I’m not thirsty, I don’t force it. If I’m craving fluid, I drink.
Your vest’s job isn’t to force you to drink. It’s to make sure you have enough fluid available when your body asks for it.
For a 100K, that usually means at least 1.5 liters on you. Two flasks. Or flask plus bladder. Something that buys you time between aid stations.
Because running dry with an hour to go? That’s a lesson you only need once.
- Carrying Weight & Energy Cost
We all know this in our bones: heavier = harder.
But it’s not just “feels harder.” There’s data behind it.
One study showed that even adding 1 kg in a backpack raised runners’ heart rates and oxygen consumption at higher efforts. Add 3 kg, and running economy takes a real hit PubMed.
That means your muscles need more oxygen to do the same job.
Which means you fatigue sooner.
Which means mile 70 feels like mile 90.
I’ve felt this personally.
In one 50K, I packed heavy “just in case.” Extra layers. Extra water. Extra everything. And every climb felt like I had a stubborn dog strapped to my back.
Later race? I stripped it down. Carried only what I truly needed. And the effort felt smoother. Not easy. Just smoother.
The key isn’t zero weight. It’s efficient weight.
A good vest keeps the load close to your center of mass — high and snug on your torso. When the weight sits tight against you, it moves with you.
Loose backpack? It swings. It bounces. And that swinging multiplies forces. Every step becomes slightly more chaotic. Slightly more wasteful.
Over tens of thousands of steps, that adds up.
Your legs are already lifting your body weight over and over again for 100K. Why make them lift more than they have to?
And if you do have to carry it, make sure it’s stable.
- Heat Dissipation & Sweat
If you run in heat — and I train in Bali, so yeah, I know heat — this part matters more than people think.
Your body cools itself by sweating. That sweat evaporates. That evaporation cools you.
Now strap a poorly ventilated vest across your torso and you basically create a mini greenhouse on your back.
I’ve felt this. My back turning into a swamp. Core temperature creeping up. Effort feeling higher than it should.
A vest can absolutely trap heat if it’s poorly designed.
That’s why breathable mesh matters. Thin material. Ventilation cut-outs. Airflow.
Modern vests are better about this. Lots of mesh panels. Quick-dry fabric. You’ll still sweat — don’t get me wrong — but at least the heat can escape.
I’ve looked down after long runs and seen that classic sweat imprint in the shape of my vest. Shirt soaked in a perfect outline. But at least I’m not cooking underneath it.
I even pour water over my back at aid stations sometimes. Soak the vest. As I run, the water evaporates and cools me. It’s a little shocking at first. But it works.
One runner once said on a forum: wearing a vest will make you sweat more underneath it. That’s unavoidable. But a good vest minimizes how much that turns into overheating.
And in brutal sun, that vest can actually protect part of your back from direct exposure. So there’s a trade-off.
Just don’t wear something that feels like a plastic grocery bag strapped to your spine.
- Muscle Fatigue from Poor Fit
This one took me years to figure out.
If your vest is loose, or bouncing, or sitting wrong, your body is constantly stabilizing it.
Your neck.
Your shoulders.
Your core.
Micro-adjustments every step.
It’s like carrying a glass of water that’s sloshing around versus one that’s steady. If it’s sloshing, you tense up to control it.
I used to finish long runs with my traps — those neck-to-shoulder muscles — locked up and burning. I thought it was just mileage.
It wasn’t.
It was me subconsciously bracing against a bouncing pack.
When I finally found a vest that fit me properly — snug, balanced, no weird pressure points — it felt almost weird. My upper body could relax.
I could drop my shoulders. Breathe easier. Run instead of fight.
And that matters over 15 hours.
Poor fit doesn’t just annoy you. It drains you.
Bringing It Together
The physiology lines up with what most of us eventually learn the hard way:
- Stay reasonably hydrated, not flooded or dry.
- Don’t carry more than you need.
- Keep the load tight and stable.
- Don’t cook yourself with bad ventilation.
- Make sure the fit lets your body relax.
Remove those friction points, and you’re not making the race easier exactly — 100K is still 100K — but you’re not sabotaging yourself before the real suffering even begins.
And in ultras, avoiding self-inflicted mistakes is half the game.
SECTION: How to Choose the Right Hydration Vest for 100K
Alright. Enough theory. Let’s talk real life.
You’re standing in a shop. Or scrolling at midnight. Or borrowing your friend’s vest and thinking, “Will this survive 15 hours with me?”
Here’s how I think about it now. After getting it wrong a few times.
- Capacity: How Much Do You Actually Need?
Capacity comes in two buckets:
- How much water you can carry
- How much stuff you can shove in there
Both matter. But they’re not the same thing.
Fluid Capacity
For most 100Ks with reasonable aid spacing (like every 10–15 km), I want at least 1.5 liters available.
That usually means:
- Two 500 ml soft flasks up front (1.0 L total)
- Option to add a 1.0–1.5 L bladder in back
Some runners get away with just 1 liter. Especially if it’s cool. Or they’re fast. Or aid stations are stacked close together.
But I like margin.
Hot race? Remote mountain sections? Long dry climbs? I’ve carried 2.5 liters in desert stretches and drank all of it. Every drop.
Just remember:
1 liter = 1 kilogram.
Water is heavy.
So yes, have the capacity. But don’t carry it full unless you need it for that section.
Research the course. Look at the elevation. Look at the aid gaps. Be honest about how much you drink. Some runners sip constantly. Some barely drink until they’re thirsty.
Know yourself.
Storage Capacity (Liters of Volume)
You’ll see vests labeled 8L, 10L, 12L, 15L.
For most 100Ks? 8–12 liters feels right.
That’s enough for:
- Jacket
- Emergency blanket
- Basic med kit
- Headlamp
- Nutrition
- Maybe poles
Once you get into 15–20L territory, you’re flirting with fastpacking. Great for multi-day or 100-milers. Probably too much for 100K.
And here’s the honest part:
Bigger space invites overpacking.
I coached a runner who showed up to a 100K with a 20L pack stuffed like he was hiking across a continent. After the race we unpacked it. Half of it never got touched.
Next race? 8L vest. Trimmed the fluff. Moved smoother. Finished happier.
Pack for the distance between aid stations. Not for a zombie apocalypse.
Use drop bags for extras.
- Bottles vs. Bladder (Or Both?)
This question never dies.
There’s no one right answer. But there are trade-offs.
Front Soft Flasks (Usually 2 × 500 ml)
These are the modern standard.
Pros:
- Easy to sip from
- You see exactly how much you’ve drunk
- Fast to refill
I like them because I sip constantly. Little drinks every few minutes. That rhythm works for me.
Cons:
- When full, they add front weight
- Can bounce if vest isn’t snug
- Getting them back into tight pockets mid-race can feel like wrestling an octopus
I’ve stood at aid stations trying to shove a full flask into a stubborn pocket while my brain was half asleep. Not elegant.
Still — I prefer bottles for accessibility.
Back Bladder (1.5–2L)
Classic hydration system.
Pros:
- Big capacity
- Weight centered
- Front of vest feels cleaner
Cons:
- Harder to see how much you’ve drunk
- Refilling means vest off, unzip, refill, reseal
- Risk of leaks
I once cross-threaded a bladder cap and slow-leaked sticky sports drink down my back for miles before I noticed. That’s a special kind of frustration.
Bladders are great for long dry sections. Less great for quick pit stops.
Both (My Usual Move)
I often start with:
- Two front bottles (primary drink)
- Bladder mostly empty
Then I fill the bladder only for long remote stretches.
That way I sip bottles first. If I drain them early, I’ve got backup.
Is it overkill? Sometimes.
But in remote or hot 100Ks, redundancy isn’t crazy.
Some runners split fluids too:
- Bottles = water
- Bladder = electrolytes
Play with it in training.
Just don’t test a brand-new system on race day.
- Fit & Sizing (This Is Everything)
If you remember nothing else from this section, remember this:
Fit beats brand. Every time.
Snug, Not Suffocating
A vest should feel like a light hug.
Close to the torso.
No dramatic bouncing.
You can still breathe deeply.
Put it on. Jump. Run in place. If it shifts a lot, that’s a red flag.
No Gaps. No Pinch Points.
Check:
- Shoulders
- Underarms
- Around ribs
Big gaps = movement = chafing.
But if you crank it down so tight that you can’t breathe, you’re just trading bounce for pain.
I’ve done that. Tightened a slightly-too-big vest to stop flopping. Ended up with red strap lines carved across my chest after four hours.
That vest didn’t last long in my rotation.
Strap Placement
Front straps matter more than people think.
They should:
- Be adjustable
- Avoid rubbing your neck
- Sit comfortably across chest
Women especially — try women-specific models. The difference in strap curve and chest shaping can be huge.
I’ve coached female runners who thought vests just “weren’t comfortable” until they switched to a women-specific design. Total change.
Torso Length
Tall? Short? Pay attention.
Too long = bouncing lower back.
Too short = vest rides up and bottles sit awkwardly high.
I’m average height. Most standard sizes work.
But I’ve had taller friends struggle because the vest weight sat too high on their ribcage instead of distributing well.
Try It Loaded
Empty vest in a store means nothing.
Load it with:
- 1.5 liters of water
- Jacket
- Gels
Then move.
I once bought a vest that felt fine empty. Loaded? The bottom sagged and rubbed my lower back.
Returned it.
If possible, test before committing. Or buy from somewhere with a return policy.
- Pockets & Organization (Can You Find Stuff Half-Asleep?)
At 80 km, your brain is not sharp.
You do not want to be digging around trying to find salt tabs while wobbling up a climb in the dark.
Pocket layout matters.
A lot.
Front Bottle Pockets
Standard. Make sure:
- They’re secure
- Bottles don’t launch out
- You can remove and replace easily
Some stretchy pockets grip tight — great for stability, annoying for reinserting a full flask.
Pro tip: a splash of water on the outside of the flask helps it slide in.
Front Stash Pockets
I want:
- Zippered pockets for phone/ID
- Stretch pockets for gels and trash
Yes, trash. I carry used gel wrappers until the next aid. Always.
I usually keep:
- Gels on one side
- Chews or bars on the other
- Salt pills in a small zip pocket
Consistency reduces thinking.
Side or “Kangaroo” Pockets
These are gold.
Reach-around pockets where you can stash:
- Gloves
- Hat
- Arm sleeves
- Poles
I have one vest with a pass-through back pocket. When I overheat, I shove gloves and sleeves back there without stopping.
That kind of access matters at hour 12.
Main Rear Compartment
This is the “don’t need it constantly” zone:
- Jacket
- Thermal layer
- Headlamp
- Emergency blanket
- Med kit
Bladder usually sits here too.
It’s okay if this isn’t super accessible. You’ll usually slow or stop to grab things from here anyway.
High Rear Zipper Pocket
Keys. Cash. Car fob.
Stuff you won’t touch mid-race but want secure.
Create a System
This is underrated.
In training, I always put:
- Gels → right front mesh
- Chews → left front mesh
- Salt tabs → tiny zip pocket
- Phone → right zip pocket
- Headlamp → back kangaroo
I do it the same way every time.
So at 2:00 AM, I don’t think. I just reach.
There is nothing worse than fumbling around for a snack while your balance is questionable and your patience is gone.
Example Loadout (Real 100K Setup)
Here’s what I typically carry:
Front:
- 2 × 500 ml flasks (one water, one sports drink)
- 8–10 gels
- Small baggie of salt tabs + emergency ibuprofen
- Phone
- Couple of bars or chews
Back:
- Lightweight rain jacket
- Long-sleeve layer (if cold expected)
- Headlamp + spare batteries
- Emergency blanket
- Required med kit
Poles folded in back pocket if needed.
Sounds like a lot. But in a 10–12L vest, it fits cleanly. And I can access what matters without stopping.
That’s the point.
You don’t want to fight your vest.
You want it to disappear.
And if you forget you’re wearing it? That’s usually a good sign you chose right.
- Closure Systems & Adjustability
This is the stuff people don’t think about until something snaps at kilometer 70.
Closure just means: how the vest actually stays on you. Chest straps. Side cinches. Buckles. Hooks. All the little bits that you’re going to be adjusting over and over when your body changes through the day.
And it will change. You’ll drink. You’ll sweat. You’ll bloat a little. You’ll shrink a little. It’s a long day.
Chest Straps
Most vests have two straps across the chest. Ideally, those straps can slide up or down along little loops of fabric. That matters more than you think.
You want to position them where they don’t:
- Rub your neck
- Sit awkwardly across the chest
- Press into weird spots when you breathe
Elastic vs non-elastic? I personally like at least some give. When I take a deep breath climbing at altitude, I don’t want to feel like I’m wearing a straightjacket. And when I stuff an extra layer in at night, I want the vest to flex a bit.
In a 100K, your body isn’t static. You’re not the same person at hour 1 and hour 15. A little stretch helps.
Side Straps or Cinches
Some models from Ultimate Direction or Nathan have side bungees or velcro straps that tighten around your ribs.
I love these.
I had an older UD vest where I could fine-tune it perfectly with the side cinches. Once dialed in, it barely moved. That kind of adjustability is gold when bottles empty and weight shifts.
If your vest doesn’t have side adjustment, it better fit really well out of the box.
Buckles, Clips, Magnets
Now we get into the quirky stuff.
Salomon uses those lightweight hooking lanyards for chest straps. Super minimal. Very light. But some runners hate them. They can feel fiddly when your fingers are numb.
Ultraspire has used magnetic clasps or unique buckle systems. Innovative, sure. But here’s the thing: if that fancy mechanism fails mid-race, you’re improvising with safety pins.
I once had an Ultraspire vest with a plastic hook that occasionally decided to unhook itself if I overstuffed the vest. Nothing like feeling your vest start to open while descending rocky trail. Your brain does not enjoy that.
In general, simple is good.
And here’s my rule: try opening and closing it with sweaty hands. Or cold hands. Or tired hands. Because that’s how you’ll actually be doing it.
If it’s complicated in your living room, it’s going to be worse at mile 80 in the dark.
Known Quirks (Because No Vest Is Perfect)
Through community chatter and personal scars, a few patterns pop up:
- Some older Ultraspire buckles had durability complaints. A friend had one snap after heavy use. To be fair, newer models may have improved.
- Salomon’s flask pockets are famously tight. Amazing for stability. Not amazing when you’re in a hurry.
- Nathan sizing can be tricky. I had to size up on one model because my “true size” felt just a little too tight around the ribs. Going up a size and tightening it down worked better.
Bottom line: the closure system needs to be adjustable and reliable. You’ll be tweaking it all day. The last thing you want is a broken buckle halfway through a 100K.
Fixing gear mid-race is not the adventure you signed up for.
- Popular Vest Models: Pros & Cons (Community Favorites)
Let’s talk actual models. The ones I see again and again at ultra start lines. The ones I’ve used. The ones people argue about on forums at 11 PM.
Salomon ADV Skin 12
This vest is everywhere. For good reason.
I’ve used the ADV Skin series in multiple races. The fit is the headline feature. Salomon calls it “Sensifit,” and yeah, it feels like a stretchy hug. When it’s dialed in right, it barely bounces.
Storage? Thoughtful. Front pockets everywhere. That little stretch pocket above the flasks is perfect for gels.
Twelve liters is a sweet spot for mountain 100Ks.
Materials hold up. Mine has taken a beating.
Cons? Those stretch pockets can be tight. When flasks are full, you sometimes have to wrestle them back in. In a calm moment, fine. In a frantic aid station, mildly annoying.
Also, sizing runs snug. If you’re broader or in between sizes, try before committing.
I’ve heard a few runners say high-friction areas can wear thin over time. Mine’s held up, but it’s something to note.
Still, tons of ultrarunners will tell you: “You can’t go wrong with the Salomon 12L.” It’s a standard for a reason.
Ultraspire (Spry, Zygos, etc.)
Ultraspire feels a bit underrated sometimes.
I’ve run with a Spry and tested an Alpha pack. What stood out to me was breathability. The mesh felt airier than my Salomon. On hot days, that matters.
Pocket layout is smart. Easy to access. Bottle pockets feel structured — less wrestling.
Some models use quick-release clips or magnetic clasps. Snaps on easily.
But. There have been durability stories. Older Zygos buckles cracking. Tabs wearing out. One friend broke a tab mid-race.
The Spry is super light, but at around 7L it’s tight for full 100K mandatory gear. The Zygos (~14L) works better for longer or gear-heavy events.
One runner told me: “Ultraspire is underrated. But yeah, I broke a tab once.”
That kind of sums it up.
If you go this route, maybe carry a tiny repair backup. I usually toss a safety pin into my kit regardless of brand. Cheap insurance.
Ultimate Direction Ultra Vest 5.0 (and 4.0 / 6.0)
Ultimate Direction has deep roots in ultra history. Old-school ultra vibes.
I’ve owned multiple UD vests over the years. They are pocket-heavy. Like, Mary Poppins-level pocket situation. Which I actually appreciate.
The build feels tougher than some minimalist brands. Slightly heavier fabric. Slightly more “backpack” feel than second-skin feel.
Pros:
- Tons of organization
- Durable materials
- Side cinch adjustability
Cons:
- Not quite as body-hugging as Salomon
- Slightly heavier (maybe 50–100 grams difference)
- Older models had stiff bottles
The newer versions are more streamlined than the old ones.
If I’m doing a 100K with a long mandatory gear list, I often grab my UD because I know everything will fit without playing Tetris.
Nathan (VaporKrar, VaporHowe, Pinnacle)
Nathan was my first ultra vest brand. The HPL #020 was my gateway drug.
Models like the VaporKrar 12L are popular. Soft materials. Comfortable edges. Less abrasive feel on skin.
They usually include flasks or a bladder, which is nice.
Storage is solid, even if not quite as wild as UD.
They’re often more affordable than Salomon.
Weaknesses? Sizing can be tricky. S/M and L/XL setups sometimes require trial and error. I had one slightly too snug under the arms and paid for it with raw skin after a mountain 50K.
And sweat. Nathan’s fabric absorbs sweat. My back would be soaked and the vest felt heavier when wet. Still comfortable. But definitely damp.
Durability? Mine has lasted years. Nothing broke.
If someone new to ultras asks me for a starter vest, I often mention Nathan. User-friendly. Solid. Reliable.
Other brands worth mentioning:
- Inov-8
- CamelBak
- Osprey
- RaidLight
Plenty of options out there. But the ones above are the ones I see most often at 100K start lines.
- Train With Your Vest (Please Don’t Save It for Race Day)
This is my coach voice now.
Break in your vest like you break in shoes.
Do not debut a vest at a 100K.
Do Long Runs Fully Loaded
If race day means 2 liters and full kit, then train with 2 liters and full kit.
Three to four hour runs.
You need to know:
- Does it chafe at hour three?
- Does it sag when bottles empty?
- Does anything dig into your collarbone?
Find that out in training.
Practice Hydration
If using bottles, practice grabbing, drinking, reinserting while moving.
If using bladder, practice biting the valve and drinking without awkwardly yanking on the hose.
It should feel automatic.
Practice Access
During long runs:
- Grab a gel without stopping
- Pull out salt tabs on a climb
- Remove and put vest back on quickly
I literally time myself sometimes removing vest, grabbing spare batteries, putting it back on. Under 30 seconds is my goal.
Sounds silly.
But when you’re tired, smoothness matters.
Adjust As You Go
Start with full bottles. Then check how it feels 20–30 minutes in.
Weight shifts. Fabric stretches. You warm up.
I often tighten chest straps slightly after the first few miles.
Do that in training so it’s automatic in a race.
I had an athlete who refused to train in his vest. Said it was “just for race day.”
First ultra? Brutal chafing. Hated every minute.
Second ultra? Trained in vest regularly. Adjusted fit. Built familiarity.
Night and day difference.
By the second race, the vest wasn’t some alien thing strapped to him. It was just part of the system.
That’s what you want.
Not something you’re fighting.
Just something that’s there. Quiet. Doing its job.
Coach’s Notebook – Real-World Mistakes & Fixes
I’ve made almost every dumb vest mistake you can make. And I’ve watched athletes repeat the same ones. So this is less “expert advice” and more “scars talking.”
Here’s what I see over and over.
Overpacking the Vest
Oh man. This was me in my early ultras.
My vest looked pregnant. Bulging with “just in case” stuff.
Extra jacket. Extra shirt. Extra food. Stuff I’d never practiced eating. Random items that made sense at 10 PM the night before.
I carried all that weight for hours and didn’t use half of it. And I wondered why my legs felt cooked.
I had a runner show up to his first 100K with an 8 kg pack. Eight. We laid everything out in the parking lot and started trimming. By the time we were done, he was at about 4 kg. He still had every required item. Still had food. Still had water.
He just wasn’t hauling anxiety anymore.
Fix it like this:
Lay everything out. Physically. On the floor.
Make three piles:
- Must-have
- Nice-to-have
- Leave-behind
Must-have = required safety kit, enough hydration for the longest stretch, fuel for between aids, weather gear that actually matches the forecast.
Nice-to-have = backup snacks you don’t really plan to eat, spare shirt, that third headlamp “just in case.”
Leave-behind = fear.
If it’s truly “nice,” put it in a drop bag. Don’t carry it for 10 hours straight.
You’re not moving into the mountains forever. You’re going aid station to aid station.
Pack for the leg. Not the apocalypse.
Vest Bouncing & Sloshing
You take off running and your bottles start punching your ribs in rhythm.
Or the pack thumps your back like a tiny toddler riding piggyback.
I’ve seen runners endure this for miles. Getting more irritated. More sore. Like they’re proving something.
Just stop. Tighten it.
Fifteen seconds.
At the start, get it snug. Then check again after 10–15 minutes once you’ve drunk some fluid. Weight shifts. Fabric settles. Adjust again.
Also balance matters.
One full bottle and one empty bottle? That asymmetry will make one side bounce more. Either even out your drinking or tighten the lighter side slightly.
If you’ve got load lifter straps on the shoulders, use them. Pull the pack closer to your body.
And sloshing noise? That’s just ultra background music. But you can reduce it by squeezing the air out of soft flasks after filling. Get that little vacuum effect.
It’s not glamorous advice. It’s just practical.
Last-Minute Gear Changes
I’m embarrassed to admit this one.
Three days before an ultra, I bought a new vest because I thought it might be “better.” Shiny new toy syndrome.
I ran maybe 20 minutes in it. Declared it fine.
Race day, hour five, I realized the lower strap was rubbing my bottom ribs raw. By hour eight, I had a bleeding abrasion. I ended up stuffing a napkin under the strap to survive.
It was stupid.
Fix:
Do not race in a vest you haven’t trained in for real hours.
Not a jog. Not a shakeout. Hours.
If you get a new vest close to race day, either do a proper long run with it — fully loaded — or stick to the one you know.
In ultras, familiarity beats novelty almost every time.
Not Fueling or Drinking Because of Your Vest
This one is sneaky.
I’ve had runners tell me, “Yeah, I felt low energy, but my gels were in the back pocket and I didn’t want to stop.”
That’s how you bonk.
If it’s hard to access, you won’t use it.
Fix it:
Put regularly used items where you can reach them without thinking.
If during training you realize you’re avoiding a pocket because it’s annoying, change your setup.
I keep gels in front mesh pockets. Salt tabs in a tiny zip pocket I can reach blind. Phone in a front zip.
On long climbs, I eat while power hiking. Grab bar. Rip it open with teeth. Keep moving.
But that only works because I practiced it.
Don’t let bad pocket organization be the reason you’re dehydrated at kilometer 70.
Taking the Vest Off for Every Little Thing
I see this all the time.
Runner needs a gel. Takes vest off.
Needs a phone. Takes vest off.
Needs salt. Takes vest off.
That’s a lot of unnecessary disruption.
Fix:
Back compartment = stuff you don’t need often. Jacket. Emergency kit. Night gear.
Front and side pockets = frequent-use items.
If you do have to take it off — say weather shifts and you need your rain jacket — combine tasks. Refill bottles. Grab next section’s gels. Adjust straps. Make it one stop, not five.
And practice getting it off and back on smoothly. Some vests snag on hats or sunglasses. Figure out your system in training.
The less you break rhythm, the better.
After every race, I jot down vest issues. Chafe spots. Pocket mistakes. Anything that annoyed me.
Over time, you dial it in.
The goal is simple: by race day, your vest should be boring.
Not something you’re fighting.
Just there.
What Ultrarunners Actually Say (Community Voices)
Hang around enough start lines and forums and you’ll hear patterns.
Some of these are almost quotes burned into my brain.
Salomon Love
“You can’t go wrong with the Salomon 12L — it just hugs you.”
That’s about Salomon ADV Skin 12.
People describe it like clothing, not gear. Like it disappears.
It’s often the benchmark other vests get compared to.
Ultraspire Praise
“Ultraspire is underrated. I love the pocket layout. Super breathable. But yeah, I did break a buckle once.”
That sums up Ultraspire pretty well.
Clever design. Great airflow. Some past durability complaints.
If you go this route? Toss a safety pin in your kit. Honestly I do that with any vest. Cheap insurance.
UD Pockets Galore
“My UD vest is like Mary Poppins’ bag. I keep finding more pockets.”
That’s usually about Ultimate Direction.
They give you space. Lots of it. Organization heaven.
Sometimes you forget which pocket you used. But at least there’s a pocket.
Salomon Flask Struggles
“The Salomon pockets hold the bottles so tight, refilling is a wrestling match.”
I’ve watched this at aid stations. Someone trying to jam a full soft flask into a tight pocket while slightly panicked.
I’ve held pockets open for friends mid-race.
It’s a small trade-off for zero bounce. But it’s real.
Overpacking Epiphany
“I thought I needed a 15L pack. Turns out I was just hauling fear.”
That line stuck with me.
First ultra, people pack for worst-case scenario. That’s normal.
Second or third ultra, they realize most of that weight was emotional.
Experience trims the fluff.
Ultralight Humor
“My vest weighed 8 kg. Apparently I was planning to live in the forest for three days.”
Ultra runners laugh about this stuff because if you don’t laugh, you’ll cry halfway up a climb.
The common thread in all these voices?
Fit matters. Bounce matters. Simplicity matters.
And don’t carry your fears on your back.
The right vest feels like part of you.
The wrong one feels like something you’re fighting for 15 hours.
And in a 100K, you already have enough to fight.
Skeptic’s Corner – Do You Even Need a Vest?
Alright. I love vests. You probably noticed.
But let’s be honest for a second.
Do you always need one?
Not necessarily.
I’ve seen some very experienced runners — especially front-of-pack types — go vest-free in certain races. They’ll use handheld bottles and maybe a small waist belt. That’s it.
The logic makes sense.
If aid stations are every 5–10 km — which happens on loop courses or really well-supported races — you might never need to carry more than 500 ml at a time. One handheld. Maybe two. Quick refill. Keep moving.
No shoulder pressure. No chest straps. No chafe risk.
I did a 50-mile road ultra once with just a handheld. Frequent aid. Stable weather. No required gear beyond basics. It felt light. Fast. Kind of liberating.
But look at the conditions:
- Frequent aid
- Predictable weather
- No mandatory heavy kit
- Competitive environment
Would I do that on a mountain 100K with 15 km gaps between aid stations and mandatory jacket, headlamp, emergency blanket?
Absolutely not.
Handheld vs Vest – Is One Faster?
There’s no clear physiological proof that handheld is faster than vest.
If you carry less weight without a vest, sure, you might slightly lower energy cost. Carrying weight does increase oxygen consumption — that’s well documented in load carriage research. Add a kilogram, heart rate and oxygen demand go up. That’s just physics.
But if holding a bottle messes with your arm swing or gives you shoulder tension after four hours? You’ve erased that advantage.
Some runners get hand cramps from gripping bottles for too long. Others don’t care at all.
Personally, I’m fine with one handheld for a few hours. After that, I start really appreciating having my hands free.
Bottle vs Bladder – Any Real Difference?
No magic here.
A bladder doesn’t hydrate you better. It’s just delivery.
Some argue that sipping continuously from a hose keeps hydration steadier versus taking bigger pulls from bottles. Maybe. But that’s habit, not hardware.
I will say this: psychologically, I drink more when there’s a hose near my mouth. It’s right there. I sip mindlessly.
With bottles, sometimes I forget until I consciously grab them.
But I’ve coached runners who are the exact opposite. Bottles in sight remind them. Bladders? They forget.
So again — personal.
There’s no study showing Brand X vest makes you faster than Brand Y.
The vest doesn’t run the race.
You do.
The goal is simple:
- Don’t get dehydrated.
- Don’t carry unnecessary weight.
- Don’t get chafed raw.
If you solve those three things, you’re fine.
I’ve got a friend who hates anything on his shoulders. Runs 100-milers with waist bottles and stuffed pockets. He looks like a moving utility belt. But he’s fast. It works for him.
If my vest advice doesn’t fit you, that’s okay.
But whatever you plan to do — test it in training.
Thinking of going vest-less because aid is frequent? Do a long run with handhelds and all your gear. See what happens.
There are also minimalist harness-style vests. Barely there. Just enough to hold bottles.
There’s no single correct solution.
For most non-elite runners in a typical 100K, though? A vest is the safest and most convenient setup.
Experiment.
Just don’t experiment on race day.
That’s the real mistake.
FAQ
Q: Should I use a bladder or just bottles for a 100K?
Use what you’ve trained with.
There’s no rulebook here.
Bottles are great because you can see exactly how much you’ve drunk. Refills are fast.
Bladders are great for carrying larger volumes and sipping through a hose without thinking.
I personally often use both: two bottles in front for regular sipping, bladder in back as backup for long dry sections.
The key isn’t the system. It’s capacity.
Can you cover the longest gap between aid stations?
If you’ve trained with bottles, don’t suddenly switch to a bladder on race week.
And if you’re unsure? Carry a bit more capacity than you think you’ll need. You don’t have to fill it completely. But having the option is reassuring when weather shifts or aid runs low.
Q: How do I stop my vest from bouncing?
Fit first.
If it’s too big, no amount of tightening will fully fix it.
Tighten chest straps snug. I usually position one high near sternum and one lower near stomach. That locks things down.
Balance load. If front is heavy and back empty, you’ll feel it.
As you drink, adjust again. I tighten mine mid-race sometimes.
Use compression cords if your vest has them.
Pack heavier items closer to your body, not hanging outward.
If it still bounces despite all that? It may not be the right vest for your body.
A properly fitted 100K vest should ride smoothly.
Q: Can I wash my hydration vest?
Yes. Please do.
Unless you enjoy your car smelling like fermented electrolyte mix.
Hand wash in cool water with mild soap. Remove bladder and bottles first.
Rinse well. Air dry. No hot dryer — heat kills elastics and warps plastic.
I’ve machine washed mine in a garment bag on delicate when it was absolutely disgusting after a tropical 100K. It survived. I wouldn’t do that weekly, though.
Clean your bladder too. Mold in the hose is not a personality trait.
Clean gear lasts longer.
Q: How much water do I really need to carry?
Depends on:
- Distance between aid stations
- Weather
- Your sweat rate
- Your pace
In moderate conditions, I drink about 500 ml per hour.
If I expect a 3-hour gap, that’s 1.5 L minimum.
If it’s hot? I might carry 2 L for that stretch.
If aid is every hour? I might carry just 500 ml to 1 L.
Better to finish a section with a little water left than run dry.
Many races require minimum 1.5–2 L capacity. That’s not random. It’s a clue.
In training, pay attention to how much you drink per hour.
I sweat a lot. I often carry 2 L on hot long runs even if I don’t finish it.
And yes, you can “camel up” at aid. Drink a bunch there, leave with full bottles.
Q: What if my vest chafes?
First, find the spot.
Common areas: neck, collarbones, underarms, lower ribs.
Prevention:
- Use anti-chafe balm (BodyGlide, Vaseline)
- Wear a fitted moisture-wicking shirt under the vest
- Tape rough seams if needed
Shirtless + vest in hot weather can be a gamble. Direct skin-on-vest friction plus sweat? Risky.
If you feel a hot spot early, stop and fix it. Lube. Adjust.
Once skin breaks, it’s hard to undo mid-race.
If a vest consistently chafes you no matter what? It might not be your vest.
I’ve had models give me literal red “neck hickeys.” Switched brands. Problem gone.
The goal is to forget your vest exists.
Not wince every time it rubs.
Final Coaching Takeaway
In a 100K, you’re already fighting:
- Fatigue
- Terrain
- Weather
- Your own brain
You don’t need to fight your gear too.
A hydration vest won’t run the race for you.
But it can either quietly support you…
Or annoy you for 16 straight hours.
The best vest is the one you forget about.
Choose one that fits your body. Meets race requirements. Matches how you like to drink.
Then build a relationship with it.
Train in it. Sweat in it. Adjust it. Learn every pocket without looking.
By race day, it should feel boring.
Reliable.
Like an old friend that doesn’t talk much but shows up.
Then you can focus on what actually matters.
The next climb.
The next sip.
The quiet argument in your head at kilometer 82.
Carry what you need.
Carry nothing you don’t.
And go run your 100K.