Why Blisters Form on Long Runs

Ask any runner in the Highlands about their worst blister and you will get a story. Maybe it was the last ten kilometres of a long descent off a Munro, or a sodden section of bog on a trail that looked innocent on the map. Blisters are not a sign of weakness or inexperience. They are a simple physical problem: friction, moisture and heat working together over a long period of time.

When your foot slides inside a shoe, the skin shears against the layers beneath it. Add sweat or water and the skin softens, so it takes far less rubbing to cause damage. Add heat from a long climb, plus grit or a wrinkled sock, and you have a perfect recipe for a hot spot that turns into a blister within a couple of kilometres.

The good news is that almost every blister is preventable. The trick is to sort out the boring details before you set off, not at the halfway point when you are already limping.

Nail Your Shoe Fit Before Anything Else

Most blisters start with footwear that is almost right. Almost is not enough over three hours on a rough hill track.

• Size up. Feet swell during long runs, especially in warm weather or on relentless descents. Many runners need a half or even a full size larger than their everyday shoes.
• Measure late in the day. Pop into a shop in the afternoon or after a walk, when your feet are at their largest.
• Check the width. If the shoe squeezes across the ball of the foot, your toes will not splay naturally and you will get rubbing on the sides.
• Leave a thumb's width. There should be roughly a thumb's width between your longest toe and the end of the shoe. On steep descents your foot will slide forward, and that gap saves your toenails.
• Learn the heel lock. Using the top eyelets to create a loop can hold your heel down and stop the forward slide that causes blisters on the toes and the ends of your toenails.

If a shoe rubs on a short run, it will shred you on a long one. Do not hope it will soften up. Take it back, or keep it for short outings only.

Socks: The Simplest Fix Most Runners Ignore

Socks are cheap, and they are the single easiest change you can make. Cotton holds water next to your skin, goes clammy, and bunches up. It has no place on a long run, particularly in a Scottish climate where rain is always a possibility.

Choose moisture-wicking technical socks, ideally with a blend of merino or synthetic fibres. Merino handles damp conditions beautifully and stays warm even when wet, which matters on a Highland ridge in a sudden haar. Look for:

• A snug, seamless fit with no ridges or bulky toe seams.
• Cushioning in the heel and under the ball of the foot, but not so thick that the shoe becomes tight.
• Two-layer or twin-skin designs, which let the layers slide against each other instead of against your skin.

Change your socks if you can. On a very long run, carrying a spare pair in a dry bag and swapping halfway through can feel like a completely new pair of feet.

Balm, Tape and Hot Spots

Learn where you blister. Most of us have predictable spots: the inside edge of the big toe, the heel, the top of the toes. Treat those areas before they complain.

Anti-chafe balm applied twenty minutes before you set off reduces friction and keeps damp skin from softening. Reapply on any long run over two hours. A petroleum-based balm works well; a sports-specific one is often less greasy and lasts longer.

For areas that blister repeatedly, tape is your friend. Use a smooth, low-friction tape or a hydrocolloid plaster over the hot spot, and make sure it is flat with no wrinkles. Never tape over broken skin without cleaning it first.

The moment you feel warmth or a tingle, stop. Ninety seconds of attention now saves you an hour of misery later. Dry the area, apply balm or tape, and sort out whatever caused it — usually a bit of grit or a rucked-up sock.

Toenails and the Small Habits That Save You

Bruised, black toenails are common, and almost always self-inflicted.

• Keep toenails trimmed straight across, not too short, with the corners filed so they do not catch on the sock.
• Do not cut them the night before a long run. Leave a couple of days so any tenderness settles.
• Look after hard skin gradually with a pumice, but do not remove calluses entirely — they are protective.
• Shake out your shoes before every run. A single grain of Highland grit can cause a blister the size of a fifty-pence piece.
• On boggy routes, consider a light gaiter to keep heather, mud and water out.

Highland Terrain: Wet Feet, Bog and Long Descents

Our local routes are brilliant and they are brutal on feet. Wet ground softens skin faster than sweat does, so river crossings and peat bogs are blister factories. Where you can, step through water rather than tiptoeing around it — a quick soak and a shoe full of water is better than hours of damp socks and grit.

Build your long runs gradually so your feet adapt to the distance, not just your legs. Use club runs and local trails to test your setup on shorter outings before you commit to a big day out. If you are training for a hill race or a long trail route, recce the descents — steep downhill running is where toes and heels suffer most.

Then, if a blister does appear, do not pop it unnecessarily. If it must be drained, use a sterile needle at the edge, leave the roof of the skin intact, clean it, and cover it well. Pack a small foot kit for every long run: balm, tape, a spare pair of socks and a bit of gauze. Your future self on kilometer thirty-five will thank you.