How tracking devices can make (or break) your marathon

Thursday, March 23, 2017. Author Pleuni Hooijman

In a couple of weeks’ time, some of Europe’s major cities – London, Rotterdam, Hamburg, Rome, Milan, Madrid and Paris - are having their marathon events. So it is not just the spring weather that invites many of us to dress in Lycra and head to the park: There are some serious miles to log and major races to run. As the miles stack up, segment times are challenged, course records are broken, and achievements are recognized on Strava, the biggest social media platform for runners (and cyclists). While Strava can be extremely rewarding, encouraging, and inspiring - e.g. for new routes, motivation between friends, and tracking your own fitness progress - could it also harm your marathon results?

Looking at the data of my befriended athletes and Flyby’s (other Strava users that you crossed during your workout), I’m often impressed with the pace of their long ‘slow’ runs and then surprised with their race results – they are not always as fast as I would assume based on their training pace. Whether it is lack of experience, the ever-tempting segment leader board, PB’s or the kudos-addiction; it seems like many athletes do their slow runs too fast.

The importance of running slowly

Long easy runs are about increasing your ability to use fat for fuel and sparing your glycogen stores so that you won’t hit the wall too early, while maintaining enough energy to accelerate where needed. Also, these runs challenge the body and mind to forge ahead as fatigue sets in. The energy systems used during training depend on your running pace; the faster you go, the faster you deplete your glycogen stores, which when in training for a marathon should be trained to be preserved as long as possible. Running fast also has a higher impact on the muscle fibres, and consequentially, a longer recovery time.

Training at a low intensity stimulates many physiological processes including cardiac muscle efficiency, capillarization, increased myoglobin content (a protein that transports oxygen through the muscles) and mitochondrial development (the oxygen utilising energy power plants of your cells). Your ACE, PGC1A, CKM, AMPD1, AKT1, HIF1A, VEGF and ADRB2 genes impact on your endurance capacity and are fully described in the FitnessGenes reports.

Several studies have shown that a polarized training schedule consisting of 75-80% high-volume / low-intensity runs with 20-25% covering the lactate threshold and high intensity zones and only a few percent in the ‘moderate’ zones, works best for marathon preparation. If you are doing your long runs too fast, you may get rewarded with some extra kudos on Strava, but you’ll end up with a sub-optimal aerobic fat burning capacity. Doing your slow runs too fast also negatively impacts your recovery, impairing your ability to do your hard sessions really hard. There is an unfortunately large group of people spending the majority of their training in the moderate zone and therefore not getting the most out of their training. 

How slow is slow?

I’m often asked at which pace one should be doing their long easy runs. This is really hard to give advice on, but we could roughly say: the right pace is when you can have a conversation easily and you feel you can sustain for hours. It is typically advised to keep your heart rate at about 70% of max. However, having your zones tested while running on a treadmill is a more accurate way of determining what heart rate and pace would be right for your long easy runs. The faster and more experienced you are, the bigger the difference between your race pace and training pace.

There is also a risk of running too slowly; I always feel that I’m running too slowly when it feels uncomfortable and unnatural (e.g. when I start losing correct posture and running technique). One way to prevent yourself from running sloppy towards the end of your long run, is to ‘reset’ your movement pattern every 15min by accelerating a little bit for 30 seconds, then walk 30 seconds, and then resume your easy running pace.

Any prep tips for the final weeks?

If you’re training for one of those European marathons, you’ve reached the final month of your preparation. Now is the time to practice sustained efforts close to marathon race pace, preferably when you’ve been out for a while and starting to get fatigued. I’d recommend including a few weekly ‘long, finish-fast’ runs, alternating with the low-intensity long runs. Personally, I’ve enjoyed great results from these types of sessions, that for example consist of 90 mins slow, followed by 20 mins marathon race pace, then 15 minutes at a fast (say half-marathon) pace, finishing with the final hundred meters nearly sprinting. This session replicates your race-day scenario: battling with someone towards the finish, pushing your limits, and mimicking race circumstances. (If you don’t feel ready for this yet, you could also build in blocks of 10-15 mins at race pace during your long runs).

To get the most out of these sessions, I prep the same as on race day, including breakfast, race gear, race nutrition and hydration. Note that these types of sessions should be done just a few times and only towards the end of your prep phase, as you need to be well-trained in order to recover fully. Earlier in the preparation period, the low intensity long runs are more key, for the reasons mentioned above (to train the low intensity fat burn zones and build a solid aerobic base).


Ignore your tracking device. Train slowly on slow days and intensely on hard days.

While you may aim for a top 10 or QOM/KOM on some Strava segments during the few high intensity interval sessions on your training schedule, just aim at increasing your weekly/monthly/yearly mileage on the long slow runs and don’t be bothered about kudos or achievements. If you are getting nervous about running slower than your marathon pace, just remember: having the majority of your sessions in the aerobic, easy zones will not only improve your endurance, but also will enable you to work harder in your hard sessions.


Dr Pleuni Hooijman PhD is a pro-level triathlete. If you enjoyed this article, please read her other blogs:

Could endurance athletes benefit from a ketogenic diet?

3 easy vegetarian recipes for athletes on the go

Are you genetically more like your mother or your father?

How your muscles work

Tips for effective breathing

The physiology of recovery

The physiology of movement

Foam rolling and genetics

VO2 max-performance and genetics



Sports Med. 1985 Mar-Apr;2(2):83-99. “Applied physiology of marathon running.” Sjödin B, Svedenhag J.

Brooks GA, Fahey TD, White TP. “Exercise Physiology: Human Bioenergetics and Its Applications.” Mountain View (CA): Mayfield Publishing Company; 2000.

Frontiers in Physiology, .” 2014;5 February:1–9 . “Polarized training has greater impact on key endurance variables than threshold, high intensity, or high volume training.” Thomas Stöggl and Billy Sperlich.

International Journal of Sports Physiology and Performance, 2010, 5, 276-291”. What is Best Practice for Training Intensity and Duration Distribution in Endurance Athletes?” Stephen Seiler.

J Strength Cond Res. 2007 Aug;21 (3):943-9. “Impact of training intensity distribution on performance in endurance athletes.” Esteve-Lanao J1, Foster C, Seiler S, Lucia A.

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