Marathon preparation: the real cost of a training disruption

For most amateur and recreational runners, training for a marathon is a bit like a balancing act. On the one hand, more miles and longer, harder training sessions can build the necessary fitness and resilience to complete the distance and complete it in a good time. On the other hand, the higher the training distance and intensity, the greater the chance of a running-related injury or illness. Running related injuries occur when the training load exceeds the recovery capacity of a particular runner, which itself depends on the runner’s training background and his/her unique physiology⁽¹⁾. Novice runners are at particular risk⁽²⁾. Illness, especially upper respiratory tract infections, can occur as a result of the inevitable training-induced immune suppression that occurs when training loads are high and sustained⁽³⁾.

Building in protection

A good marathon training program will not only be individualized to the needs of the runner, it will also include periods when the runner backs off somewhat in his/her training, in order to allow a more complete recovery⁽⁴⁾. This in turn can reduce the risk of sustaining an injury or coming down with a bug. For example, programs will often implement 4-week cycles of training and recovery, with an 3-week period of increasing training load following by a 1-week recovery period with less training intensity before moving on to the next 4-week block. As such, a typical marathon programme might cover 3–4 blocks of training with training load usually peaking around one month before race-day.

Spanner in the works

Despite their best efforts however, many runners fall victim to either injury or illness during a marathon build up⁽⁵⁾, and are therefore forced to take a complete training break. At best, this disrupts training for a relatively short period of time, but in the case of a more serious injury, this disruption may even prevent runners from making it to race-day at all. In short, a massive spanner is thrown into the works.

When an unplanned and extended training disruption does take place, the first thing runners genrally want to know is what impact the disruption will have on the rest of their marathon build up and performance on the big day. “Will I still be able to race?” and “How will my race time be impacted by this layoff” are the two most asked questions. It turns out that’s a tricky question to answer.

While there have been a number of studies on the effect of periods of de-training on running fitness⁽⁶⁾ (see this article on detraining), less is known about the frequency of training disruptions during a marathon training program, and their impact on subsequent marathon performance, especially among recreational runners. That’s because training programs rarely incorporate any extended periods without any training, and instead recommend that runners maintain a consistent training schedule, which almost always recommended for optimal marathon performance ⁽⁷⁾.

The real impact of training disruptions

To try and quantify the real impact of marathon training disruptions, a new study by a team of Irish researchers has investigated the frequency and performance cost of training disruptions, especially among recreational runners⁽⁸⁾. Published in the journal ‘Frontiers in Sport and Active Living’, this study set out to assess the frequency, duration and performance cost of training disruptions, and the importance of training consistency, especially among recreational runners.

This was a retrospective study, which looked back at data gathered from 292,323 recreational runners who completed marathons during the period 2014–2017. These runners were all users of the popular running app, Strava. Although not a direct intervention study, this research makes for compelling reading since it gathered together a huge amount of data from a large number of runners, making it less prone to statistical errors and anomalies.

In total, no less than 15,697,711 individual running activities (ie individual training sessions) were assessed from 292,323 individual runners, who between them completed 509,979 marathons during the period 2014–2017. It should be noted however that the study only looked at runners who participated in at least one marathon event during this period; therefore, was not able to analyse data from runners who may have intended to participate in one or more marathon, but were unable to, because of injury, illness, or for some other reason.