Are Ultra Marathons Bad for You? Ask a Doctor Who Knows You¶

Someone at home asks if this is safe. Or you ask yourself, late at night, after another hour of reading race reports you have not told anyone about.

It is a fair question, whether you are looking at a first 50K or a fifth hundred. Here is the straight answer: that is a question for a doctor who knows you, and it is worth asking one before a big block of training. NavRun is not a doctor, and this post is not medical advice.

What a post can do is tell you what researchers have found so far, give you questions to bring, and show you the one thing only you have: your own training record.

Quick Preview: See the weekly and monthly totals you would bring to that visit in NavRun's Analytics Dashboard.

What the research says, and what it does not¶

The evidence is mixed, and the people who study it say so.

Running itself looks good for most people. A 2012 review in Mayo Clinic Proceedings by James O'Keefe and colleagues cited a study with 15 years of follow-up in which runners had a 19% lower risk of dying from any cause than nonrunners. News-Medical's summary of the review also notes the same review found the relationship was U-shaped: the benefit faded at higher weekly distances.

The heart is the open question. The same review describes extreme endurance events temporarily straining the heart, with changes that typically settle about a week after the race. It raises the possibility that, over months to years of repeated strain, some people develop patchy scarring in the heart muscle that can support irregular rhythms. It reports that some studies of veteran marathoners, ultramarathoners and professional cyclists found atrial fibrillation rates about five times those of the general population. The authors add that there are no proven screening methods for detecting these changes.

That is a review of possibilities and associations, not a finding that ultras damage your heart. Most of it is about people who trained and raced for years, and the long-term picture is still being worked out.

Race day has its own risks. In a Trail Runner feature on ultramarathon health risks, the author describes acute kidney injury as one of the most common race-day risks, made worse by heat, dehydration and anti-inflammatory painkillers, and says episodes usually resolve within a few days. Researcher Nick Tiller is quoted there. The article also cites a study finding roughly 90% of ultra-endurance injuries are overuse injuries. Sports medicine physician Mark Harrast is quoted: "running is healthy, more so than not being a runner." The article's bottom line is that most healthy people can do ultramarathons with sensible training, selective racing and enough recovery.

Ultrarunners who answered a survey looked healthy. In a 2014 PLOS ONE study led by Marty Hoffman and Eswar Krishnan, reported by Fox News, 1,200 ultrarunners described their previous 12 months. They reported few serious health problems, and the most common complaints were knee pain, stress fractures and allergy or asthma issues. The authors pointed out that a self-reported survey has limits, since runners may be less likely to report being sick. It is more than a decade old, and the researchers said the long-term effects remain unknown.

So the honest summary: running is good for most people, ultra distances raise real questions about the heart, kidneys and overuse injuries, and nobody has settled how much is too much for a given person. Your age, family history, medications and past health decide a lot here. That is why this is a doctor's call, not a blog's.

What to ask a doctor before training for an ultra¶

If you can only get a short appointment, pick from these. Pick the ones that fit you.

• Given my age, family history and any conditions, is there anything I should be checked for before a long block of training?
• Do I need an ECG or other heart testing, or is a routine physical enough?
• I take (name your medications and supplements). Does anything change on a 6 to 30 hour day on my feet? Ask about anti-inflammatory painkillers in particular.
• What symptoms in training should make me stop and call you? Chest pain, fainting, a racing or uneven heartbeat, unusual shortness of breath.
• How often should I come back while I am training?
• I have had (a past injury, or an old stress fracture). What should I watch?

Write the answers down. Your doctor may say yes, go. Your doctor may ask for tests first. Either way you walk into the start line knowing instead of wondering.

If you are under 18, talk to a doctor and a parent or guardian before any ultra distance. The Trail Runner feature quotes Tiller saying athletes under 16 should not be taking part.

What to bring: your own record¶

A doctor can say more about you with numbers than with "I run a lot." Before the visit, pull together:

1. Your weekly mileage and time on feet for the last few months.
2. How fast that has grown. Did you go from 15 miles a week to 40 in six weeks, or build over a year? Both are real answers. The doctor needs to know which.
3. Your longest runs and how recovery went after them.
4. Any races, DNFs, or time off and why.
5. Anything your body told you: a niggle that kept coming back, nights you could not sleep, a resting heart rate that stayed high.

Your watch or Strava holds most of this already. NavRun's Analytics Dashboard shows weekly and monthly summaries and charts of pace, distance and consistency across the runs you have synced, so you can read the growth for yourself instead of guessing. It does not diagnose anything. It hands you your own record.

Two other posts help you read that record before the visit: ultra training load and preventing injuries explains how to see a sudden jump in training, and ultra overtraining signs lists what a tired body looks like over several weeks.

Is trail running healthy? Is it safe to run 100 miles?¶

Trail running at any distance falls under the same research as above: for most people running is good for you, and the questions start at ultra volumes. If you are asking about 50K, 50 miles or 100 miles, the question for your doctor is the same. The risk depends on you, and training sensibly and recovering well are the parts you control.

Nothing here says a hundred is off limits or that a first 50K needs a cardiology workup. It says to ask, and to ask with your numbers in hand.

What to take from this¶

• Running is good for most people, and ultra distances raise open questions about the heart, kidneys and overuse injuries.
• The long-term research is not settled. Treat anyone who sounds certain with suspicion.
• Ask a doctor who knows you, before a big block, and bring your own record.
• NavRun is not a doctor. If something feels wrong in training, stop and call one.

Start free¶

If you want your weekly totals in one place before that appointment, NavRun reads the running you already logged. Start free. navrun.app