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  • I find it interesting to predict one’s time in an important running race based on a test run, as to know what a good pace is to keep up during that race. I always used a self-conceived rule, which is quite different from the generally accepted rule according to research engineer Peter Riegel, although it took some math to figure that out (see below).

    Self-conceived rule

    I have experienced for myself early on in my running career that my pace increases by a factor of 1.07 when doubling the running distance, under ideal circumstances. For example, a 10 km race tended to be 7 percent slower than a 5 km race. I generalized this idea into a formula.

    1: p2 ÷ p1 = 1.07 n

    2: d2 ÷ d1 = 2 n

    1 & 2 ⇒ n = ²log(d2 ÷ d1)

    p2 ÷ p1 = 1.07 ²log(d2 ÷ d1)

    p2 = p1 × 1.07 ²log(d2 ÷ d1)

    p1 = t1 ÷ d1; p2 = t2 ÷ d2

    ⇒ t2 ÷ d2 = (t1 ÷ d1) × 1.07 ²log(d2 ÷ d1)

    t2 = t1 × (d2 ÷ d1) x 1.07 ²log(d2 ÷ d1)

    Factors for 1.07 ²log(d2 ÷ d1)

    The table below shows some favorite distances from road races. In the rows are the distances from which the pace is known and in the columns the distances from which the corresponding factors can be read as numbers in the table. Multiplying a known pace for a particular distance with this factor gives the corresponding unknown pace for another distance. For example, for a 15 km race (third row in the table) multiply this race’s pace by a factor of 1.1062 to calculate the ideal pace for a marathon (eighth column in the table). A sub-3 hour marathon would require a sub-36 minutes 10 km, according to this table.

    5 km 10 km 15 km 10 mi 20 km ½ mar 30 km mar
    5 km 1.0000 1.0700 1.1132 1.1208 1.1449 1.1509 1.1911 1.2314
    10 km 0.9346 1.0000 1.0404 1.0475 1.0700 1.0756 1.1132 1.1509
    15 km 0.8983 0.9612 1.0000 1.0069 1.0285 1.0339 1.0700 1.1062
    10 mi 0.8922 0.9546 0.9932 1.0000 1.0215 1.0268 1.0627 1.0987
    20 km 0.8734 0.9346 0.9723 0.9790 1.0000 1.0052 1.0404 1.0756
    ½ mar 0.8689 0.9297 0.9673 0.9739 0.9948 1.0000 1.0350 1.0700
    30 km 0.8395 0.8983 0.9346 0.9351 0.9612 0.9662 1.0000 1.0339
    mar 0.8121 0.8689 0.9040 0.9102 0.9298 0.9346 0.9673 1.0000

    Rule according to Riegel

    According to Peter Riegel the increase in pace for a longer distance is radically different:

    t2 = t1 × (d2 ÷ d1) 1.06

    For times between about 3 and 230 minutes.

    t2 = t1 × d2 1.06 ÷ d1 1.06

    t2 ÷ d2 = t1 × (d2 1.06 ÷ d2) ÷ d1 1.06

    t2 ÷ d2 = t1 × d2 1.06 - 1 ÷ d1 1.06

    t2 ÷ d2 = t1 × d2 0.06 ÷ (d1 × (d1 1.06 ÷ d1))

    t2 ÷ d2 = t1 × d2 0.06 ÷ (d1 × (d1 1.06 - 1))

    t2 ÷ d2 = (d2 0.06 ÷ d1 0.06) × (t1 ÷ d1)

    t2 ÷ d2 = (d2 ÷ d1) 0.06 × (t1 ÷ d1)

    p1 = t1 ÷ d1; p2 = t2 ÷ d2

    ⇒ p2 = (d2 ÷ d1) 0.06 × p1

    If the distance doubles, the pace increases by a factor of 2 0.06, or 1.0425. That would mean that as the distance increases, the pace increases drastically less than with the aforementioned calculation method of my own.

    A similar table is shown below, containing factors to be multiplied with known paces to calculate unknown paces, depending on the distances.

    Factors for the Riegel calculation

    The table below shows some favorite distances from road races. In the rows are the distances from which the pace is known and in the columns the distances from which the corresponding factors can be read as numbers in the table. Multiplying a known pace for a particular distance with this factor gives the corresponding unknown pace for another distance. For example, for a 15 km race (third row in the table) you can multiply the pace by a factor of 1.0640 to calculate the ideal pace on a marathon (eighth column in the table). For a sub-3 hour marathon, a time of sub-39 minutes on the 10 km is fast enough, according to this table.

    5 km 10 km 15 km 10 mi 20 km ½ mar 30 km mar
    5 km 1.0000 1.0425 1.0681 1.0726 1.0867 1.0902 1.1135 1.1365
    10 km 0.9593 1.0000 1.0246 1.0289 1.0425 1.0458 1.0681 1.0902
    15 km 0.9362 0.9760 1.0000 1.0042 1.0174 1.0207 1.0425 1.0640
    10 mi 0.9323 0.9719 0.9958 1.0000 1.0131 1.0164 1.0381 1.0596
    20 km 0.9202 0.9593 0.9829 0.9870 1.0000 1.0032 1.0246 1.0458
    ½ mar 0.9172 0.9562 0.9797 0.9839 0.9968 1.0000 1.0213 1.0425
    30 km 0.8981 0.9362 0.9593 0.9633 0.9760 0.9791 1.0000 1.0207
    mar 0.8799 0.9172 0.9398 0.9438 0.9562 0.9593 0.9797 1.0000

    What to use?

    It seems rather obvious to me that a generally accepted rule makes more sense than something you came up with yourself based on your own race results. Other than that, there are strict limits to when the rule according to Riegel applies. For slow runners (e.g. marathon in 4½ hours) or extremely short distances (e.g. 400 m) the rule does not apply, or, at least, the prediction value will be rather low.

    An acquaintance of mine ran a time of 1h01m36s in a “15 km” race (14.87 km according to his GPS). According to my calculation, that would be enough for 3h15m39s on a marathon with certified course (1% longer than 42.195 km). According to Riegel, it would be enough for 3h08m03s on the same certified marathon course. In both cases, the result of the “15 km” race was too slow for an “official marathon” (i.e. with certified course) under 3 hours. A sub-3 hour marathon would have required a time of 56m40s or 58m57s for the “15 km” race (my rule, Riegels rule respectively). This acquaintance has to get faster somehow, either by training and/or good fueling during the race. Ideal circumstances would help too.

    Anyway, I think I can put my home-grown calculation method to rest and start using the much better tested method according to Peter Riegel.

  • In preparation for a half marathon on King’s Day (April 27) I ran and walked 24 km. I’m still suffering through an ankle injury, so I’ll have to be cautious. It was a beautiful day, partially run alongside a canal between two rivers. It was tough, because I did 1.5 times my usual training 🏃

    shadow of runner on a bike path through nature asphalt road with bridge across a canal on the right asphalt road with two signs, one wishing goodbye and the other welcome, marking the border between the provinces of Zeeland and Noord-Brabant beautiful dutch sky, like in an old Dutch painting
  • Someone dug a trench across a footpath, and I stepped right into it, hurting my ankle badly. Who does such a thing, making a trap for pedestrians? The ankle is swollen and hurts, but not enough to go to a doctor. I suppose R.I.C.E. will reduce the swelling, as in Rest, Ice, Compression, Elevation.

  • If everything goes as planned, I will have run around 3300 km (2050 mi) in 2023 when the New Year rolls around. With a little over 5 weeks to go, I’ve already passed 2930 km of running this year, an average of 63 km (39 mi) weekly, 272 km (169 mi) monthly, despite injuries and other mishaps. 🏃‍♂️

  • After doing some research to find out which marathons can be reached in time by public transport, and finding out I already knew those, I’m going for a recovery run, to clear my mind from the realization that a car is still needed for early hours on Sundays, (or late hours in Summer). I’m carless.

  • I need to remind myself that me running competitively is just a mind trick to keep fit. I’m under no illusion that I’m able to win a race, not even in my age class. Keeping fit is already struggle enough. No need for being a target for those after “eternal” fame (i.e. until the next race).

    Crossing of a cycle path and a road
  • I already felt awful when I woke up this morning. After a 24 km run I feel exhausted. It was supposed to be a 32 km long run. I’ll get to bed early tonight, sooo tired 😫

    cycling path alongside the canal between the rivers Rhine and Scheldt
  • Yesterday I did another long run, 26 km with 20 km at marathon tempo. This doesn’t sound all too impressive, until you consider what came before (32 km a week before, 23 km 4 days before). See my training session on Strava. It felt like a race.

    photo of me running, taken by a friend who happened to ride his bike here
  • Yesterday I ran 32 km in 3h46m (see my Strava) as a part of my fall marathon preparation. I was quite exhausted at the end, so I need to do it again to be sure. The marathon is end of October.

    narrow straight dirt road with bike lane alongside asphalt road alongside a waterway year market in the village of Woensdrecht forest path with the sun beating down
  • I ran my first 3+ hours run in my Fall marathon schedule as a run-walk-run. My easy pace for a 4 hour marathon is between 6 and 8 min/km, the slower, the better (since it hurts less and has a similar effect on one’s endurance). The average was around 7 min/km, (11 min/mi).

    bicycle path with heath on the left
  • Yesterday I ran a 10 km “race” in the heat of the day (30℃, 86℉), which is quite hot for traditional Dutch summers (though becoming norm with climate change). I wanted to run a half marathon, and was prepared with a cooling vest, but, apparently, this is a novelty, and I a fool to expect a race 🏃‍♂️

  • I now have a temporary free premium account with Strava, and am even less impressed than with Garmin Connect. Unless you like to flaunt with made up statistics to get some clout within the runner community, I don’t see any point in paying for a premium account.

  • 24 marathons across 24 European countries in 2 months. This guy is just crazy, but in a nice way. He almost died during his first marathon from exposure, separated from his team (words were spoken, improvements discussed). See this YT video.

  • Today’s long run was (from the start) a bit of a bad run (see my result on Strava). It wasn’t so much the temperature, but the fact I wasn’t recovered (enough) from last Sunday’s intensive long run of 32 km. I had to walk the last 6 km. Better luck next time, in three weeks.🏃‍♂️

    Long bike path, mostly in the sun, tough on the body
  • I looked into doing multiple marathons within a year. The best advice I found was:

    • plan the marathon races far in advance, so you know what you’re up to
    • concentrate on post-marathon recovery, especially the first week after a marathon (mostly non-running related activities: walk, cycle, swim)


  • Yesterday I ran a 22 km race as part of a 32 km training session.

    Around 8 o’clock in the morning I jogged 9 km, took a shower, dressed in my race outfit, drank a cup of coffee, grabbed my race gear, and jogged the kilometer between where I live and the track and field club, where the start of the Brabantse Wal Marathon was at 10:45 AM. I did the half marathon event, which actually was 22 km (900 m longer than the half of the 42,195 m marathon distance).

    cat sitting on a race shirt, smug of his action to prevent me from leaving

    The course was mostly off-road, with some steep short climbs and stretches of loose sand, which I had practiced in the past couple of weeks. In the first kilometer there was a single track, and with 270 runners we got stuck now and then, as you would expect. After the field was more spread apart, single tracks were no longer a problem.

    I kept a steady pace, though slower than usual, because of the 10 km pre-race jogging. While I struggled to keep from falling, the inevitable fall happened, giving me bruises on my left shoulder and knee. I couldn’t see that tree root on the heavily shaded path. It didn’t slow me down much (like a few seconds).

    dirt path in forest with a runner 50 m ahead

    In the last five kilometers I ran on familiar territory and could pick up pace. The last 1600 m on the road I could pick up even more speed, sprinting in the last 300 m on the track towards the finish line.

    I put my thumb up after I finished at the track and field club

    The time wasn’t that impressive. But I hadn’t expected that anyway, because of the added distance, and because of the off-road bits that were rather challenging. The 32 km I did in less than 3 hours and 20 minutes I was proud of, especially because of the low average heart rate under warm conditions (21℃). Corrected for temperature (into a result with 8℃), this would have resulted in a 1 hour 50 minutes for a half marathon road race.

    bike path next to lake with a runner coming towards me, taken during the early morning jog

    Now I will take a few days to recover with easy training. Next Sunday will be my next long run, 29 km at a more leisurely pace.


  • I know a physiotherapist who refuses to treat runners, because those are the worst patients. In those runners' minds, running is all about getting fit, so how can that make you sick? There’s no patience and a reluctance to see an injury as a serieus affliction that needs careful treatment. 🏃‍♂️

  • In just 12 days Runalyze dropped my estimated time in the marathon race by 4 minutes, while my marathon shape has reached 99%. By losing some of my excess weight slowly over the next 5 months, I might be able to lose a proportional amount of 15 minutes, provided I slowly speed up my training. 🏃‍♂️

    graph showing time prognosis for the marathon over the past 24 months
  • I decided to do my 15 km run inside the municipality of where I live, and run between two of the three historical windmills. Well, the third is a tidal mill, though no longer operational, if I read correctly. With every flood there was lots of damage. With the Delta Works, no more floods, nor tides.

  • graph showing marathon time prognosis based on training data

    The graph shows what I could expect as a reasonable time on the marathon, based on training data. Two years ago, I could expect 5u30', a year ago 5u15', and now 4u15'. In all cases I was/am preparing for a marathon in October/November. Notice the serious detraining after the 2021 marathon 🏃‍♂️