Marathon preparation: the real cost of a training disruption

How the analysis was done

The Strava data from all the 292,323 runners was broken down by the researchers to identify the following:

·        Periods of varying durations in the 16 weeks before the marathon where runners experienced a complete cessation of training (a so-called training disruption).

·        Runners who had completed multiple marathons including at least one disrupted marathon with a long training disruption of seven or more days and at least one undisrupted marathon where there were no training disruptions in the 16 weeks previously.

·        The age, sex and ability of all of these runners to explore how these factors might affect the outcome of a training disruption.

Once these parameters had been collated, the researchers went on to calculate the performance cost of long training disruptions. This was determined as the percentage difference between a disrupted marathon (where training had ceased completely for more than seven days) and an undisrupted marathon, where there was a smooth uninterrupted training build up to the event. The analysis also compared the frequency and cost of training disruptions according to the sex, age, and ability of runner. In addition, the researchers looked at whether the disruptions occurred early or late in 16-week training period and how this influenced marathon times.

What they found

·        Training disruptions were more common during the early stages of marathon training (8-12 weeks prior to race day) compared to the later stages (3-7 weeks prior to race day) – see figure 1.

·        Over 50% of runners experienced short training disruptions up to and including 6 days, but longer disruptions were found to be increasingly less frequent among those who made it to race-day.

·        Male runners, younger runners, or faster runners are more likely to experience disruptions of any given duration compared with females, older runners, or slower runners respectively. However, when these disruptions did occur, they were more likely to occur earlier in the training program – implying they were less likely to prevent these runners from completing the marathon.

·        Runners who experienced longer training disruptions of 7 days or more suffered a finish-time cost of 5–8% extra (an extra 9-14 minutes on a 3-hour marathon) compared to when the same runners experienced only short training disruptions of less than 7 days.

·        When they occurred, long (7+ days) training disruptions led to a greater finish-time cost for males than females. Faster runners also tended to experience a greater finish-time cost than slower runners.

Figure 1: Training disruptions early and late in the marathon training period

Blue dots = disruptions close to race day. Orange squares = disruptions earlier in the marathon training program. Short disruptions were far more common than long disruptions. However, disruptions of all lengths were less common later in training program as race day approached.

What do these findings mean for runners?

There’s a lot to unpack here, but the probably the most important finding is that for short (less than 7 days) interruptions to training, there was no significant negative impact on race performance. This is reassuring news because (also from this data) recreational runners are more likely than not to suffer a short training disruption at some point during their marathon training. A practical implication that follows is that when a short disruption occurs, runners should ‘relax’ and not try to ‘catch up’ by packing in extra training to make up for lost time, because this evidence suggests it’s not really needed.

Another key finding is that training disruptions were more likely to occur earlier in the marathon program than later on. This makes sense because this is when novice and recreational runners without an extensive marathon training background are subjecting their muscles, joints and tendons to new and unaccustomed training loads compared to the period before training commenced. Later in the program however, these muscle/tendon systems will have already had 2-3 months to adapt to the increased loading, so new injuries due to the unaccustomed training loads are less likely.

Another practical implication that follows is that runners should take extra care to not overload themselves during the early stages of their marathon training. This involves playing close attention to muscle niggles, aches and stiffness and acting accordingly by backing off a little on the training load rather than following a program blindly because that’s what’s written down in front of you!

When a more prolonged disruption of over 7 days occurs – for example due to an injury that takes time to heal – runners must understand that there will likely be a cost to their race time, especially if they are faster or younger runners. Although this study didn’t explore this aspect further, it’s reasonable to assume that the longer the disruption, the bigger hit to performance – eg, a 14-day disruption will incur a greater performance penalty than a 7-day disruption.

In practical terms, faster runners with previous marathon experience who are seeking a new PB but who suffer a more prolonged layoff during training should accept that their goal is less likely to be achieved. Complete novices and slow runners can take comfort that even a longer training disruption will likely not impair performance on the big day too much.

 Of course, each runner and set of personal circumstances are different, so it’s impossible to be certain of these potentially negative outcome; however, by understanding that training disruptions do tend to have a performance cost, runners are less likely to be disappointed and become disillusioned. When training disruptions are of significant length and getting that PB is your main goal, another alternative is to treat the race in question more as a dedicated training session, and focus instead on getting that PB in a later race!

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