Here’s How Much A Disruption In Your Training Will Affect Your Marathon Finish Time

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Whether you come down with an injury, illness, or another sort of interruption in your ability to stay consistent with your marathon training, how much will a disruption in your training impact your marathon performance? 

Can you take a couple of weeks off without losing much progress? Can you take several weeks off and still finish the race?

In this article, we will look at what happens when your marathon training isn’t entirely smooth sailing, and you are forced to take some amount of time off. We will examine the impact of various amounts of time missed due to a disruption in your training and how it might impact your marathon performance.

We will cover: 

  • How Much Will A Disruption In Your Training Affect Your Marathon Finish Time?

Let’s dive in! 

A runner keeling down holding their ankle.

How Much Will A Disruption In Your Training Affect Your Marathon Finish Time?

So, what happens when you have to take off multiple days in a row or even a full week during your marathon training? What if you miss a couple of weeks in your marathon training plan because of an illness? 

If you get a minor injury during marathon training and need to spend several weeks cross-training instead of running, how much will this affect your marathon performance? Can you still run a marathon if you have to take several weeks off?

Researchers at University College Dublin aimed to investigate these types of questions to help prospective marathon runners gauge the impact that disruption in their training will have on their ability to run a marathon.

In this massive study, the researchers looked at data gathered from Strava, a popular mobile fitness app used by runners to record running workouts via GPS and input other forms of training or treadmill runs.

A runner holding their ankle.

The data was taken from 292,323 individual runners who logged a sum total of 15,697,711 individual running activities and who completed 509,979 marathons during the period 2014–2017.

One important thing to note about the data that the researchers used in this study is that they only analyzed the Strava training data from runners who participated in at least one marathon between the years of 2014 to 2017. 

Therefore, if runners had potentially been intending to run a marathon but ended up incurring an injury or illness, or another sort of disruption that precluded them from participating in the event, they were not included in the study. 

Although this is a seemingly minor detail and would not really be logistically possible for the researchers to know who was intending to run a marathon but ended up not being able to just by looking at the data (since no interviews or surveys were conducted), it is definitely a limitation to the study. 

If we are trying to examine how much disruption you can experience in your training before you will no longer be able to finish a marathon, we are eliminating all of the runners who were indeed training for a marathon but did not make it to race day or complete a marathon.

A person with a cold on the couch blowing their nose.

With that said, it is still an impressive analysis and certainly the most comprehensive research study to aim to look at this research question.

A much older study found that about 16% of runners who signed up for a marathon were unable to participate for one reason or another.

The researchers also differentiated the group of runners whose training data was included in the study based on whether they were “fast runners” or “slow runners.” 

They chose an arbitrary cut-off time of four hours (240 minutes) for the marathon finish time to separate these two groups; runners who completed a marathon in under four hours were considered “fast“ whereas runners who completed a marathon in over four hours were considered “slow.“

The four-hour cut-off time is a popular target marathon finish time for recreational runners, which is why it was chosen as the distinguishing criterion in this study.

Using this criterion, 157,050 runners were labeled as “fast“ (86.62%:13.38% male: female), and 135,273 runners were “slow” (71.83%:28.17% male: female).

The study also looked at when in the training cycle the disruption occurred:

The training disruption was considered early if it occurred at least 8 to 12 weeks before race day and was categorized as late if it occurred 3 to 7 weeks from race day since this is later in the training cycle.

A person in bed with a cold, blowing their nose.

The researchers did not examine potential disruptions that occurred in the final three weeks before the marathon race for each runner because there is typically a three-week marathon taper, and the way that different runners go about this taper may vary, such that they might take consecutive days off. 

This would make it difficult to know whether the days off were planned or unintended.

Ultimately, the primary aim of the study was to look at the finish time “cost“ of training disruptions. Basically, the research question was how much worse will your marathon finish time be as a result of disruptions in your marathon training?

This is a pretty difficult question to answer for numerous reasons, but the researchers aimed to calculate the resultant finish time change from the expected finish time due to the training disruptions that occurred.

Training was considered to be “disrupted“ if there was a period of at least seven consecutive days off between 3 to 12 weeks before marathon race day and “undisrupted“ if there were fewer than seven consecutive days off during this period.

To help better compare the general finish time cost between disrupted versus and undisrupted training, the researchers looked at a subset of the data that included runners who had at least one disrupted and at least one undisrupted marathon that were separated by anywhere from six months to two years.

This criterion yielded a subset of 43,933 unique runners (83.39% male and 26.61% female) who had 56,735 pairs of disrupted/undisrupted training sets because some runners had more than one disrupted and undisrupted marathon.

A runner kneeling down.

The finish time cost of disruption was estimated based on the relative difference in finish times between the disrupted marathon finish time and the undisrupted marathon finish time.

The researchers looked at the relative difference in finish times rather than the absolute difference.

For example, if a runner completed a disrupted marathon (a marathon that had at least one chunk of seven or more consecutive days off from training within a period of time 3 to 12 weeks before the marathon) in 244 min compared to a time of 235 min for an undisrupted marathon, then the disruption cost is 9 min/235 min = 0.038, or a 3.8% slow down in time.

So, what happens if you need to take a week off while training for a marathon? What about two or three weeks?

Overall, over 50% of runners experienced at least six consecutive days off training, with a slightly greater percentage of men having disruptions in training relative to women.

People running a marathon.

The Results

Results revealed that runners who missed 7-13 days of training during their build-up ran 4.25% slower than when they had not experienced a training disruption of more than six days.

Missing 14-20 days of training resulted in a 6% longer finish time; missing 21-27 days bumped this up to about 7.5%, and after more than 28 days off, finish times were about 8% slower. 

The average relative finish time cost was more significant for males versus females (5% vs 3.4%) and faster runners compared to slower runners (5.4% vs 2.6%). 

It also mattered when the disruption in training occurred. 

When runners had a disruption in training closer to race day, the impact on finish time was worse than those who had a similar disruption earlier in the course of training (5.2% vs 4.4%).

Finally, if the disrupted training marathon occurred after an uninterrupted marathon buildup, the finish cost was not as significant as the inverse.

Overall, although there were limitations to this study, it’s a pretty interesting evaluation of how much a disruption in your training might affect your marathon finish time.

When training for a marathon, it’s almost a guarantee that you will have at least a couple of days that don’t go according to plan but try to stay positive yet honest with yourself about whether you are still in a position to run the marathon.

What have been your own personal experiences? Have you experienced a significant disruption in your training and still finished a marathon? How did it go? Let us know!

For our free marathon training plans, click here!

People finishing a race.
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Amber Sayer is a Fitness, Nutrition, and Wellness Writer and Editor, as well as a NASM-Certified Nutrition Coach and UESCA-certified running, endurance nutrition, and triathlon coach. She holds two Masters Degrees—one in Exercise Science and one in Prosthetics and Orthotics. As a Certified Personal Trainer and running coach for 12 years, Amber enjoys staying active and helping others do so as well. In her free time, she likes running, cycling, cooking, and tackling any type of puzzle.

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