Blisters are a fact of life in marathon and ultramarathon runs. Nearly all long distance endurance runners have at some time had blisters. The longer the race, the greater the likelihood runners will get blisters.
What Causes Blisters
The trifecta of blister formation includes:
- Heat
- Moisture
- Friction.
It is difficult to do anything about the heat when running a race, so most blister prevention strategies concentrate on keeping feet dry and reducing friction.
During hot weather, however, dehydration and electrolyte imbalance can make blisters easier to form. Runners should replace fluids and electrolytes to help reduce blisters.
Every runner is different, so runners must try a variety of blister prevention strategies to see what works for them. Runners should never try a new product in a race. Test everything on training runs first.
Tips for Keeping Feet Dry
It doesn't matter whether a runner's feet are wet from sweating or running through water, but feet that stay wet are a major cause of blisters. Feet that stay wet become prune-like and blister very easily. Therefore, one focus for blister prevention strategies is keeping feet dry.
Strategies to keep feet dry include:
- Moisture wicking running socks
- Foot powders and ointments.
Running Socks
The first rule for all runners is to avoid cotton socks. When cotton socks get wet, they stay wet. The runner's feet never have a chance to dry out and therefore blister easily. Runners should wear socks designed for running that are made of moisture wicking fabrics. Modern technical fabrics do a good job of wicking the moisture away from the runner's feet, which then have a chance to dry out. Moisture wicking fabrics for running socks include CoolMax, Olefin, and Capilene. Injinjii toe socks also help prevent blisters on the toes.
In ultramarathon races runners who are prone to blisters from wet socks should regularly change their socks, dry their feet, and reapply any blister prevention preparations they use. Hotspots or small blisters should also be treated so that they do not become major problems.
When racing in very wet conditions, runners may want waterproof oversocks to keep their feet dry. SealSkinz are a popular brand of oversocks that will help keep a runner's feet dry and warm in very cold wet conditions. Oversocks should be worn over inner moisture wicking socks so the runner's feet will not be wet from sweating. Runners should also wear shoes large enough to accommodate the thicker socks.
Foot Powders and Ointments
Foot powders are a common strategy for runners to keep their feet dry. Talcum powder and cornstarch are two inexpensive low-tech foot powders. Zeasorb, Odor-eaters, Bromi-talc, and Gold Bond foot powders are all even more absorbent. Blister Shield Powder both absorbs moisture and reduces friction by combining micronized wax and cornstarch. Runners can pour these products into their socks to help absorb moisture when they start the run and when they change socks.
To reduce sweating, many runners apply antiperspirants to their feet.
There are also ointments that can help runners keep their feet dry. Hydropel Sports Ointment both repels moisture and helps lubricate feet. Gurney Goo and Brave Soldier's Friction Zone are also designed to be waterproof and reduce friction. Runners can rub these ointments on their feet before they start and every time they change socks.
Foot powders or ointments combined with moisture wicking socks can help runners keep their feet dry and reduce the chance of developing painful blisters.
Further Reading
Vonhof, J. Fixing Your Feet, Wilderness Press, 2006. This book is filled with valuable information on blister prevention and is a must read for any runner or walker who has problems with blisters.
Paul A. Heckert - I have a Ph.D. in astrophysics, over 30 years experience teaching physics and astronomy, and over 60 published research articles.
