Oooky trigger warning! The following post contains some yucky foot pics
Your feet are the only bit of you that actually has to finish an ultra. Your lungs can whinge, your quads can threaten to resign, your mind can spiral into a small existential crisis at 2am, but if your feet go on strike, you are walking a very long, very stupid pilgrimage to the next aid station.
Most ultra foot problems are not mysterious. They are predictable, boring physics. Friction plus moisture plus time, and then your skin turns into wet paper. Add grit, heat, swelling, poor shoe fit, a toenail that looks like it was trimmed with a chainsaw, and suddenly you are doing improvised surgery on a camp chair with a headtorch while someone offers you soup like it solves everything.
This post is basically a love letter to not being that person. A big chunk of it is straight out of the logic in Fixing Your Feet by John Vonhof, which is still the best single resource I know for treating foot carnage like a system instead of a vibe. Read it. Then read it again the week before your race, because apparently humans enjoy forgetting things that would save them pain.
Let’s start with the golden rule. Blisters are friction injuries. Not moisture injuries, not heat injuries, not a curse placed on you by the trail gods. Moisture and heat just lower the skin’s tolerance so friction can do its dirty work faster. If you want fewer blisters, you reduce friction, manage moisture, and control the way your foot moves inside the shoe.
Foot care begins months before race day with the boring stuff: footwear that fits, socks that work, and skin that is accustomed to repetitive stress. It is wild how many runners will do a 12 week training plan but treat their feet like an afterthought, then act shocked when their feet behave like a neglected employee on Friday afternoon.
Shoes first. In an ultra, your feet swell. Sometimes subtly, sometimes like a python swallowing a goat. Swelling is normal. Heat, fluid shifts, repeated impact, and time on feet all contribute. If your shoes are “perfect” at the start, they can be a problem later. A common play is to go up about half a size for ultras, sometimes a full size depending on distance, heat, and your personal swelling tendencies. But sizing is not the only variable. Toe box shape matters, midfoot volume matters, heel lockdown matters, and lacing matters. If your heel is sliding, the front of your foot pays for it. If your forefoot is sloppy, your toes pay for it. Your goal is stable without strangulation, like a firm handshake, not a hostage situation.
Then socks. Socks are not fashion, they are a friction management device. Some people love thin synthetic socks, some swear by merino blends, some go double layer, some use toe socks. The “best” sock is the one that reduces shear forces on your skin in your shoe, for your foot shape, in your climate. If you have never tested your sock system on a long run with heat, sweat, and a bit of grit, you are gambling. And ultras already have enough gambling built in, like nutrition roulette and that one river crossing you convinced yourself will be “fine”.
Blister prevention is basically three levers: reduce friction, reduce moisture, and reduce heat. Lubricants, powders, antiperspirants, tapes, and sock choices all sit under that umbrella.
Lubricant is the simplest and often the most effective tool. The idea is to create a low friction interface so the skin does not get dragged around like it owes someone money. Products vary. Some runners use petroleum based stuff, some use sports specific balms, some use silicone based options. The exact brand matters less than whether it stays put for your duration. A lube that works for two hours is cute. You need the one that still has some integrity at hour nine, when your brain is mashed potato and you have started speaking only in swear words and cave grunts.
Where to lube. Put it where you blister. Heels, the sides of big toes, between toes, the ball of the foot, the top of toes if you get nail rub, the Achilles area if your shoe collar has a personality. The mistake is treating lube like sunscreen and just smearing it vaguely. Be specific. Also, reapply. Aid stations are not just for calories and emotional support, they are for maintenance. Take 60 seconds, top up the lube, and save yourself an hour of hobbling later.
Powders are the opposite strategy. Instead of making things slippery, you try to keep them dry. Powders can work for some runners, especially in hot conditions, but they can also clump when wet and become grit paste. If you use powder, test it properly. Not a 45 minute jog. A long run, sweaty, maybe a bit of water, then see if the powder stays helpful or turns into sandpaper.
Antiperspirant is a contrarian but legit option for heavy sweaters, and Fixing Your Feet talks about this. Some people use a strong antiperspirant on the soles in the days leading into a race to reduce sweating. It does not work for everyone and some skin hates it, so you test well in advance. If you are the kind of person whose socks look like they have been submerged five minutes into a run, this can be worth experimenting with.
Now taping. Taping is awesome when it is done well, and a complete waste of time when it is done badly. Tape is not magic armour. Tape is a sacrificial layer that takes some of the friction instead of your skin, and it can also help hold skin still so it does not shear. The key is preparation and technique.
If you tape onto damp skin, it will peel. If you tape onto oily skin, it will peel. If you tape without rounding corners, it will peel. If you tape and leave wrinkles, the wrinkles become little friction factories. Clean, dry skin, sometimes a skin prep product if you use one, and tape laid smoothly with tension appropriate to the area. Practice at home. Your first attempt should not be at the side of the trail while you are shaking from caffeine and mild despair.
Also, tape choice matters. Some tapes stick better, some are gentler on skin, some become a gooey mess when wet. If you find a tape that works for you, buy enough, and do not “try a new one” because it was on sale. Bargain tape in an ultra is like bargain parachutes.
A good strategy for many runners is pre taping known hot spots, especially if you have repeat blister locations. If your right heel always blisters, do not pretend this time will be different because you are feeling spiritually aligned. Protect it from the start.
Now, the wet feet problem. Wet feet are not automatically doomed feet. They are just more vulnerable feet. Water causes skin maceration, that white wrinkly prune effect, which reduces the skin’s resilience. Then friction does the rest. Wetness can come from sweat, rain, creek crossings, mud, or the joyful surprise of stepping into a bog that tries to steal your shoe.
The wet feet plan is simple: limit time spent wet, limit grit, and keep friction low. If the course is wet, consider carrying spare socks or having a sock change in a drop bag. A dry sock change can feel like a religious experience. But socks alone are not enough if your shoes are full of grit. Empty the shoe, wipe the foot, re lube, then new socks. That two minute pit stop can save your entire day.
Gaiters can also be underrated. They do not make you faster, but they keep debris out, and debris is basically a small army of tiny knives when it gets between sock and skin. If you are racing somewhere sandy, gritty, or muddy, gaiters can be the cheapest performance upgrade you will ever buy.
Toenails. Toenails are small, sharp, and emotionally indifferent to your suffering. They will happily slice adjacent toes, bruise nail beds, and become black souvenirs. The goal is short, smooth, and not recently butchered.
When to cut them. Not the night before. Not on race morning. Cut them several days before, ideally a week out, so any little rough edges or accidental nicks have time to settle. Trim straight across, then gently file edges so there are no corners to catch on socks or neighbouring toes. If you cut nails too short right before a race, you can expose tender tissue and create a new problem. If you leave them long, they can jam into the toe box on descents and you get the classic black nail, or the nail that decides it would rather live somewhere else.
Calluses are another fun one. Calluses are not automatically bad. A little thickening can be protective. But thick, hard callus edges can create shear points that blister underneath. Think of it like building a tough outer wall, but leaving a sharp ridge that cuts the softer stuff below. If you have heavy callus buildup, manage it gradually, not with a dramatic weekend of foot sanding that leaves you with baby skin. Again, do it well before the event.
Now the triage mindset, because prevention is only half the game. Ultras are long enough that problems can start even with a good system. The winners are not the people who never have issues. They are the people who catch issues early and deal with them while they are still small and boring.
The sensation you are hunting is a hot spot. A hot spot is the pre blister warning. It is that specific burning, rubbing, localised irritation that keeps nagging. It is not general fatigue. It is not “my feet are tired”. It is a point that is telling you, loudly, that friction is happening right now.
Your job is to stop at the first hot spot that repeats. Not after it becomes a blister. Not after it becomes a blister the size of a coin. Not after it becomes a blister that has a blister. Early intervention is the whole secret. Ten seconds now or forty minutes later, choose your fighter.
Hot spot protocol. Stop. Take shoe off. Look. Dry if needed. Apply lube or tape, or both. If there is grit, clean it. If the sock is bunched, fix it. If lacing is causing movement, adjust it. Then move on.
If you are already at blister stage, you have decisions. Small blisters that are not painful can often be left alone. The roof is a biological dressing. If you pop it unnecessarily, you create an open wound and increase infection risk and pain. But if it is large, painful, in a high friction spot, or likely to tear on its own, draining it can be smart.
If you drain a blister, do it cleanly. Ideally with a sterile needle or a safety pin that has been cleaned. Puncture at the edge, not the centre, drain, keep the roof intact if possible, then apply an appropriate dressing and tape to reduce friction. There are blister specific dressings that work very well, but they need to be held in place and protected from shear. In real life, tape is often doing the heavy lifting.
If the blister roof has torn and you have raw skin, you need to protect it aggressively. Clean it, dry it, apply a dressing that will not stick painfully, and tape it down so it does not shift. This is where people spiral. They slap something on loosely, it wrinkles, it moves, friction continues, and the raw area becomes a crime scene.
Another common issue is toe bang and bruised nails from descents. This is often a shoe fit and lacing problem. Your foot sliding forward, toes hitting the front. Solutions include better heel lockdown lacing, different shoes, or more space in the toe box. Also, keep toenails managed. If you are doing a lot of steep descending in training, pay attention to which shoes behave well, and which shoes turn your toes into a percussion instrument.
Skin splits and maceration between toes can also happen, especially when wet. Toe socks can help some runners by separating toes, reducing skin on skin friction. Lube between toes can help too, but again, test it. Some people get more sliding and irritation. Others get immediate relief. Feet are annoying like that.
A word on “toughening up”. Yes, your skin adapts. But skin adaptation is not you becoming invincible. It is just you getting a slightly thicker, more resilient surface. You still need good systems. The idea that you can rawdog a 100k with no foot care because you are mentally strong is a personality trait, not a plan. You can be tough and also be smart. These are compatible.
Your training long runs are the lab. Do not waste them. Treat them as experiments in footwear, socks, lube, taping, and lacing. Do the exact thing you plan to do on race day, then observe the outcomes. If you always get a hot spot at kilometre 28, that is data. Solve it in training. Race day is not for collecting new data, it is for cashing in the work.
Build a small foot kit that matches your needs. Nothing fancy, just functional. A bit of lube, your chosen tape, a small needle, a couple of dressings, a tiny pair of nail clippers if you are paranoid, maybe a small wipe or alcohol swab, and a spare pair of socks in a drop bag if the event allows. You do not need to carry a full emergency department. You just need enough to stop small issues from becoming the kind of problem that changes your gait and then sets off a cascade of injuries up the chain.
Finally, remember that foot problems are rarely isolated. If your feet are getting destroyed, it can be a shoe and sock issue, but it can also be a pacing issue. The harder you run, the more shear you create. The sloppier your form gets when you fatigue, the more you scuff and twist inside the shoe. Sometimes the best blister prevention strategy is simply not running like a maniac early. Smooth is fast, and smooth is also kind to your feet.
Your feet do not care about your goal time. They care about friction management, moisture control, and whether you respected the warning signs. Treat them like the primary equipment they are. Because in an ultra, your feet are not along for the ride. They are the ride.
If you want to go deeper, Fixing Your Feet is the bible, and it is full of practical options, product comparisons, and step by step problem solving. But even without it, the principle is simple. Reduce friction. Manage moisture. Catch hot spots early. Be boring and methodical. Finish with feet that look like they’ve done an ultra, not like they’ve been fed through a wood chipper.
