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The survivorship bias problem

By | | Updated | Mindset

A video of someone finishing a marathon on no training is easy to watch and easy to believe. A Triathlon Magazine piece from June 2025 describes one example: a man signed up by his wife 24 hours before the San Diego Rock 'n' Roll Marathon, who finished in 5:58 in a clip with more than 10 million TikTok views. If you are a new runner, a clip like that can make a training plan look like an optional extra.

This post looks at what those clips leave out, what happens in your body when distance jumps too fast, and what a sensible build-up looks like if 26.2 miles is on your list.

What the videos leave out

The clips you see are the ones people chose to post, and the ones the algorithm chose to show you. That is survivorship bias: you see the finishers who felt fine enough to film a follow-up, and you do not see anyone who dropped out, got hurt, or kept quiet about how the next few weeks went.

A Runner's World article by Alex Predhome, published on the South Africa site on 26 May 2026 and described there as first appearing on the Runner's World USA site, makes the same point. It says survivorship bias can inflate how many people appear to succeed without training. It also notes that many people who say they did "no training" were doing nonspecific work such as gym sessions, walking, or running during the week. So even the finishers on screen may have had more of a base than the caption suggests. Marathon Handbook says something similar about one pair of well-known creators, calling their "zero training" label "a little misleading."

Read: Why Running a Marathon Untrained Isn't Something to Brag About

What a sudden distance jump asks of your body

Aerobic fitness, meaning your heart, lungs and the muscles' ability to use oxygen, improves within weeks. Tendons, ligaments and bone respond to training load more slowly. That gap is the usual reason new runners get hurt: your breathing says you can keep going while the tissue taking the pounding has not had time to get used to it.

Every step is an impact, and a marathon is tens of thousands of them. If your longest run so far is a few miles, a marathon asks for many times that load in one day. Marathon Handbook names a sudden increase in training load as a key predictor of musculoskeletal injury and mentions stress fractures and tendon problems among the risks. Both the Runner's World piece and the Triathlon Magazine piece name stress fractures, and the latter says an overuse injury like that can sideline a runner for months.

Triathlon Magazine also says recovery from an untrained marathon takes at least a week of rest followed by a week of light activity, which is a useful number to keep in mind if you are tempted to treat a long race as a one-off weekend.

Read: Have untrained marathons become social media's newest trend?

Pacing, fueling and heat are separate skills

Injury is only one way a long run goes wrong. Three others show up in almost every long effort.

  • Pacing. Starting at a speed you can hold for twenty minutes is very different from starting at one you can hold for hours. Knowing the difference takes practice runs. Marathon Handbook lists learning a sustainable pace as one of the things long training runs teach you.
  • Fueling. Your body stores a limited amount of carbohydrate for running, and eating and drinking while moving is something your stomach has to get used to. Marathon Handbook says untrained runners tend to hit the wall sooner and that stomach trouble is common.
  • Heat. Running for hours in warm weather raises the demands on your body further, which is one reason to build up on shorter runs first and learn how you respond.

If you have never run for more than an hour, you do not yet know how you handle any of these three. Finding out on race day, in front of a crowd, is a costly way to learn.

Can you finish a marathon with very little training?

Sometimes, yes, and it helps to be exact about how. Marathon Handbook says you might be able to walk a marathon, or jog and walk a six or seven hour one, with little or no training, because walking lowers impact and effort so the problems arrive much later, if at all. The same article states that running a marathon with zero training is not safe or recommended. For beginners it suggests at least six to twelve months of training before starting a marathon plan, ideally with a half marathon first.

That fits the routine most beginner plans follow: build up with run-walk intervals, repeat weeks when you need to, and lengthen one run a week. The shorter races along the way (a 5K, then a 10K, then a half) give you practice with the things a marathon stacks together: pacing, fueling, and recovering afterward.

Read: Running A Marathon Without Training: ALL The Reasons It's A Bad Idea

A starting point you can use this week

If you are not running yet, the first goal is a 5K, not a marathon. Here is a workable version.

  1. Start with short run intervals and generous walks. Something like one minute of easy running and a minute and a half of walking, repeated for twenty to thirty minutes. The runs should feel easy enough that you could talk.
  2. Run three days a week with a rest day between. The rest days are when your body adapts to the work, which is why they count as part of the plan.
  3. Add a little at a time. Lengthen the run intervals or the total time a bit each week, and repeat a week if it felt hard.
  4. Treat pain as information. Muscle tiredness fades. A sharp or localized pain that gets worse as you run, or that is still there the next morning, is a reason to stop and rest, and to see a doctor or physical therapist if it lasts.
  5. Practice the unglamorous parts. On longer runs, rehearse your pace, your drinks and snacks, and what you will wear. Do it before race day.

If you want the intervals called out loud for you, the 5K Run-Walk Interval Trainer from You 2.0 is a free iPhone and Apple Watch app with a nine-week plan of guided walk-run workouts, three a week. It is built for complete beginners and ends with a 30-minute continuous run.

If you have a heart condition, asthma, or any other health concern, check with your doctor before you increase your running. Stop and get help for chest pain, faintness, or severe shortness of breath.

Sources

This article is general information, not medical advice. Talk to a doctor before starting a new exercise or nutrition program, especially if you have a health condition, are pregnant, or are returning from injury. Stop and get checked if you feel chest pain, dizziness, or sharp pain.